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Effect of mineral admixtures on fresh, mechanical and durability properties of RAP inclusive concrete
Abstract
This study deals with improvement in the properties of ABTRAP (Beneficiated RAP aggregates by Abrasion & Attrition technique) inclusive concrete by incorporating mineral admixtures such as Silica Fume (SF), Fly ash (FA) and Sugarcane Bagasse Ash (SCBA). 6 mixes were prepared by partially replacing Ordinary Portland Cement (OPC) by SF (5% &10%), FA (10% & 20%) and SCBA (5% & 10%). Maximum improvement in compressive, flexural and split tensile strength of ABTRAPC mix was found when 10% OPC was part replaced by SF followed by 20% replacement by FA and 5% replacement by SCBA. Even SF10 mix showed comparable strength to that of natural aggregate concrete (NAC) mix. Reductions in permeable voids, water absorption, initial rate and coefficient of water absorption and improved abrasion resistance was observed for all the considered mixes. A power regression equation (flexural strength = 0.368 x (compressive strength)0.72) of high co-relation (R2=0.93) was established to predict flexural strength from compressive strength results of ABTRAPC mixes. Based on the finding of the present part of investigation, it is recommended to replace 10% OPC by SF, FA (20% in sulphate free environment) and 5% by SCBA in ABTRAP inclusive concrete mixes.
... Among these SCMs, Micro Silica or Silica Fume has demonstrated significant improvements in the mechanical and durability properties of conventional concrete mixes [23]. The abundance of Silicon Dioxide (SiO2) content (> 80%) and the higher specific surface area of SF particles contribute to densifying the concrete microstructure, enhancing the formation of Interfacial Transition Zone (ITZ), and creating additional Calcium Silicate Hydrate (CSH) gels [24,25]. Moreover, Silica Fume enhances the concrete's resistance to abrasion [25].In a study by Hassani et al. [26] examined the mechanical characteristics of RCC (roller compacted concrete) with silica fume. ...
... The abundance of Silicon Dioxide (SiO2) content (> 80%) and the higher specific surface area of SF particles contribute to densifying the concrete microstructure, enhancing the formation of Interfacial Transition Zone (ITZ), and creating additional Calcium Silicate Hydrate (CSH) gels [24,25]. Moreover, Silica Fume enhances the concrete's resistance to abrasion [25].In a study by Hassani et al. [26] examined the mechanical characteristics of RCC (roller compacted concrete) with silica fume. The addition of 10% silica fume increased compressive strength by 29%, split tensile strength by 22%, and flexural strength by 14%. ...
... Another material fly ash (FA), it is a waste by-product obtained from coal-based thermal power plants and is used as supplementary cementitious material in replacing Portland cement in PCC mixes. FA particles have a lower percentage of SiO 2 and Aluminium Oxide (Al 2 O 3 ) than SF particles, which facilitates in the creation of extra Calcium Silicate Hydrate (CSH) gels [25]. Another study, Atis et al. [28] investigated the mechanical properties like compressive strength, split tensile strength and flexural strength of RCC incorporated with high calcium fly ash by replacing Portland cement by 0%, 15%, 30%, 45% by mass. ...
Roller compacted concrete (RCC) is a zero-slump concrete designed for dams and low traffic pavements like parking lots, yards, storage areas etc. The constituents of RCC are similar to conventional concrete but aggregate content is higher, about 10% by volume. Due to the scarcity of natural aggregates, recycled asphalt pavement aggregates (RAP) are used to replace partially or fully the natural aggregates. Literature suggests that RAP inclusion in concrete leads to reduced mechanical properties due to weak interfacial transition zone (ITZ) but also hints about using measures like supplementary cementitious materials to improve these properties. Most of the studies follow one or the other aggregate gradation and aggregate size which definitely alters the properties from one study to the other. So, in this study, a mix design methodology was developed for roller compacted concrete (RCC) by altering the mix design composition of pavement quality concrete (PQC) conforming to IRC: 44, followed by natural aggregate substitution with 50% RAP aggregates by volume, and addition of fly ash (30%) and silica fume (15%) to improve the interphase of paste-aggregate For suitability of the developed mix proportions for pavement applications, its mechanical properties, abrasion and durability were evaluated. Results showed that addition of RAP reduced the compressive and flexural strength in RCC mixes by 24% and 14%, in comparison to the control RCC due to inferior bonding between asphalt coated RAP aggregates and cement paste. Addition of silica fume improved the compressive and flexural strength of RCC–RAP mix values by 9% (32.8 MPa) and 5.5% (3.9 MPa) but the strength values still remain poorer than control RCC. Durability on the other hand improves with the addition of RAP aggregates and it improves further with the addition of SCMs. Porosity and sorptivity decreased by 5.5% and 36.11% respectively, whereas water absorption increased by 3.36% by incorporation of 50% RAP in RCC. Subsequent SCMs addition to RAP–RCC decreased the porosity, sorptivity and water absorption by 28.92%, 55.55% and 20.5%, respectively with respect to control RCC. Considering a minor decrease in strength (< 10%) and a high improvement in durability and abrasion resistance, it is recommended that such concrete pavements can be used for rural roads. In addition, this article proves that RCC could yield a better correlation between destructive and non-destructive tests, and thus is reliable for casting at site.
... The use of pozzolanic materials like silica fume, steel slag bagasse ash, fly ash, and Rice husk ash results improve the strength and durability characteristics of RAP aggregates in cement concrete mixtures [28,29]. However, few authors suggested that the addition of tadding materials helps to improve the bonding between RAP and cement matrix along with the reduction of porosity, water absorption, and carbonation effect on the strength properties at the densification of ITZ phases [30][31][32]. ...
... The strength was lowered by about 32.6%, 46.2%, and 60% compared to the conventional aggregates corresponding to the 25%, 50%, and 100% replacement of coarse RAP aggregates. Moreover, Singh et al. [31] observed that the compressive strength tends to decrease by about 42% due to the presence of agglomerated particles around the RAP aggregates. Nevertheless, with the incorporation of RAP aggregates, the compressive strength reduces by about 48% as inferred by Debbarma et al. [52] in RCCP mixes. ...
... As with compressive strength, the same pattern was followed in the flexural strength of RAP concrete mixes. The majority of investigations found that the flexural strength of RAP concrete mixes reduces as RAP percentages rise in different curing periods [18,25,31,55,56,67,84]. Singh et al. [11] found that the flexural strength was reduced by about 5-70% when the 50% coarse RAP was added to cement concrete mixes. ...
... Furthermore, RAP aggregate utilisation for the construction of new PC pavements will escalate the vision of sustainability [11,12]. The ban imposed by government agencies on the extraction of conventional natural aggregates through quarrying activities has led to the concept of the use of RAP as much as possible for different construction purposes [13][14][15][16]. Also, various problems such as disposal of RAP, costs associated with the transportation of natural aggregates and release of greenhouse gases in the environment could be solved with the effective on-spot use of RAP aggregates in constructing new pavements [14,[17][18][19][20][21][22][23][24]. ...
... Replacement of Portland cement with up to < 20% fly ash is generally recommended for RAP concrete mixes [22,27]. Addition of a higher dosage of fly ash as Portland cement replacement in concrete mixes containing RAP aggregates results in harmful ettringite formation [13,32,33]. Apart from these industrial wastes, waste originating from the agricultural sector, such as bagasse ash (BGA), can also be used as Portland cement replacement up to 10% for strength improvement of concrete mixes. ...
... BGA was obtained locally from Uttam Sugar Mill, situated in the state of Uttarakhand, India. To increase its pozzolanic activity, the obtained BGA was initially oven-dried for 24 h and later sieved through a 45 µm sieve size [13]. The processed BGA was then used in different proportions of 5, 10, and 15% as a partial replacement (volumetrically) of ordinary Portland cement. ...
The current study examines the strength and transport properties of reclaimed asphalt pavement (RAP) inclusive pervious concrete (PC) pavement mixes containing various industrial and agricultural wastes such as silica fume (SF), fly ash (FA), and bagasse ash (BGA). Apart from a conventional PC mix (containing natural aggregates) and a 100% RAP inclusive PC mix, seven different mixes were developed by mixing 100% RAP aggregates with SF (5 and 10%), FA (10 and 15%), and BGA (5, 10, and 15%) as partial replacements for ordinary Portland cement. The above-mentioned PC pavement mixes were investigated for density, porosity, permeability, compressive strength, modulus of rupture, and abrasion resistance. The interconnected pore structure of conventional PC and RAP-PC pavement mixes was investigated using 2D image analysis and X-Ray microcomputed tomography. Based on the laboratory results, it can be stated that the inclusion of RAP significantly improves the transport properties of PC pavement mixes with increased porosity and permeability values. This was primarily due to a more interconnected pore matrix and lesser isolated voids in the RAP-PC pavement mix. The addition of SF could only improve the strength parameters (compressive strength and modulus of rupture) of the RAP-PC pavement mix. In contrast, BGA inclusion was observed to improve its transport properties (porosity and permeability). Furthermore, the inclusion of SF, FA, and BGA in a 100% RAP-PC mix improved abrasion resistance. When compared to the conventional PC pavement mix, incorporating RAP aggregates blended with SF, FA, and BGA can reduce the production cost of 1 m3 PC by 30–61% and lower CO2 emissions by 13–21%. However, considering the strength and transport property requirements of PC mixes, as well as the economic and environmental viability, the present investigation recommends using 5% SF, 10% FA, and 10% BGA in a 100% RAP-PC pavement mix.
... Additionally, the introduction of ridesourcing services, telecommuting, and the government investments in "smart city program," "National Electric Mobility Mission Plan 2020," Make in India, "Automotive Mission Plan 2026," etc., have been contributing toward the creation of a more dynamic and flexible travel environment which would be more challenging for the transport modeler. Thus, to cope with the changing travel pattern of Indian citizens, there is a need for the development of a comprehensive framework (integrated land use-transportation modeling framework), which would be based on disaggregated activity-based modeling framework including the characteristics of land use and built environment, household and individual socio-economic characteristics, travel attributes, impacts of households interaction, joint tours, modal switching, and multiple activities in one tour [43]. ...
... In recent years, the formulation of ABMs has been studied in different Indian cities, which have been discussed here briefly to understand their scope and limitations. In Mumbai Metropolitan Region, trip chaining behavior has been analyzed with the help of activity-travel survey data [43,44] using NL model based on the random utility theory. This has been used to classify the trip chains into three categories, namely simple (two trips and one activity in-between), complex (all trip chains with at least one activity), and open chains (missing information) for two trip purposes, i.e., work and non-work. ...
... Very limited studies pertaining to the utilization of industrial/agricultural wastes such as silica fume, fly ash, sugarcane bagasse ash, and rice husk ash for enhancing the RAP-PCC properties have been characterized [30,43,44]. In the case of RAP-RCCP, only one such study (as per the authors' knowledge) has been investigated so far [8]. ...
City roads are a highly complex network and comprise several road assets compared to highways. These assets are responsible for providing satisfactory services to road users. Accordingly, it is necessary to list and manage various ancillary road assets along with the pavements. Tools like Road Asset Management System (RAMS) can adhere to these goals. It is challenging to carry out the data collection for many assets simultaneously using conventional methods. The primary objective of this research is to manifest the newfangled tools in the data collection process. This paper is based on the study conducted over around 174 km length of the roads of Aundh-Baner ward of Pune. It covers the automated data collection vehicle (NSV) application, handling about 30 types of road assets, pavement distress, and geometry data, and an in-house developed mobile application with GPS-enabled tablet devices that covered inaccessible assets. The data was also validated using manual methods. Implementation of these tools proved fruitful for the RAMS in providing quality data in the least time.
... Every year an immense volume of aggregates is consumed in the construction of various structures using concrete. Aggregates (natural or crushed) come from the earth, and getting these quantities would have a damaging impact on the ecosystem (Singh et al. 2017). Destroying concrete buildings and discarding the debris would only exacerbate the problem (Dos Reis et al. 2021). ...
... The addition of 40-50% of GGBS as a replacement for cement shows comparable results with the control mixes (Collins et al. 1994). Further, GGBS greatly enhances the strength and durability of the alkali-activated concrete (Singh et al. 2017). ...
The pursuit of sustainable construction practices has led to a growing interest in the utilization of recycled materials in concrete production. To enhance the utilization of recycled aggregate concrete, its performance in terms of mechanical characteristics need to be optimized. This study investigates the effect of fly ash and ground granulated blast furnace slag (GGBS) as cementitious materials on the mechanical characteristics of recycled aggregate concrete. In this research, various combinations of recycled aggregate concrete were prepared with partial replacement cement by GGBS and fly ash. The mechanical characteristics including compressive strength, split tensile strength, and flexural strength tests are conducted on all concrete mixes and the results are compared to the control mix. The results of this study will help advance sustainable concrete technology and serve as a foundation for designing RAC for structural applications that incorporate recycled coarse aggregate, fly ash, and GGBS. The results confirm that the concrete mix with 40% recycled aggregate, 15% fly ash and 15% GGBS as cement replacements is optimum for enhancing the mechanical characteristics of concrete. The enhanced pozzolanic activity and filler effect of these fly ash and GGBS enhances the strength characteristics of recycled aggregate concrete. The findings contribute to sustainable construction practices by promoting the utilization of recycled materials and optimizing the properties of concrete mixtures.
... 53 Brand and Roesler [24] studied the effect of the partial replacement of RAP aggregates by 54 natural aggregates increased the workability but reduced the hardened properties of 55 concrete mixes. Singh et al. [25] cleared that WRAP recycled aggregates processed from 56 washing and abrasion aggregate techniques provide better workability than dirty RAP 57 recycled aggregates (DRAP). In this regard, the RAP recycled aggregate was screened 58 into different methods to segregate into DRAP and WRAP aggregates. ...
... Similarly, ASTM (American Society for Testing and 143 Materials, 2016) recommended that a minimum of 25% finer particles be used as fine 144 aggregates in cement concrete mixes. 145 The RAP is classified into different ways of characterization in terms of washed RAP, 146 dirty RAP, Abrasion and Attrition treated RAP, surface treated RAP, dust RAP, smooth 147 textured RAP, and contaminated RAP [8, 25,55,56]. The specific gravity of RAP usually 148 ranges between 2.26-2.63 ...
Reclaimed Asphalt Pavement (RAP) as recycled aggregates is a relatively a new construction process of rigid pavements due to the scarcity and degradation of natural aggregates. This study aims at sequential characterization of RAP aggregate to obtain an optimized proportions for strength. For this purpose, RAP aggregates were used for replacement of natural aggregates (NA) in concrete mix which was achieved by varying from 0 -100% . Furthermore, zirconia silica fume (ZSF) were used as an partial replacement of the cement in the concrete mix, replacing Ordinary Portland Cement (OPC). Experimental studies have shown that the incorporation of washed RAP (WRAP) slightly reduces the compressive strength of concrete by 2.7- 37.35% as compare to the reference control concrete mix. Although the 7-days, 28-days and 56-days compressive strength of WRAP recycled aggregate based concrete are slightly better than 7-days, 28-days and 56-days compressive strength of dirty RAP (DRAP) recycled aggregate based concrete. Similar trend was observed in the flexural strength and split tensile strength of WRAP recycled aggregate based. Overall, the results show that 40% WRAP recycled aggregates with 10% ZSF as a replacement of cement outperform DRAP aggregates in concrete mixes. According to the ANOVA results, the combination of ZSF and WRAP aggregates met the cement concrete pavement strength standard, thereby contributing to sustainable development. Reclaimed Asphalt Concrete Pavements (RACP) are now seen as a potential and long-term answer to the present environmental and economic crisis.
... Replacement of conventional coarse aggregates with crumb rubber resulted in reduced optimal moisture content and maximum dry density compared to natural aggregates. Decreased water absorption has been observed due to the less previous nature of crumb rubber, and this resulted in have concentrated on how this drawback can be addressed [59]. One of the alternatives arrived through research was to incorporate supplementary cementitious materials in RAP-based RCC to make it mechanically compatible without compromising on mechanical properties and make its way for use in RCC for surface courses of pavements [62]. ...
... According to the literature, SA particles can increase the strength characteristics of PCC mixes by up to 10% when replaced with Portland Cement [60,61,63]. Due to the hydrophilic character of Sugarcane ash particles, it has been reported that RAP-included PCC mixtures are advantageous for up to 5% only, after which it has a negative influence on PCC characteristics [59]. ...
In the recent past, emphasis was given roller-compacted concrete in the field of pavement construction owing to its proven advantages like fast construction method, high density, and economical when compared with conventional concrete. Roller compacted cement concrete is the name given to stiff concrete that can be compacted by a roller which is generally used in surface and base courses of pavements. Many marginal materials were used for developing sustainable roller-compacted concrete. In this paper, an effort has been made to consolidate the research done to date to make roller-compacted concrete a sustainable material for pavement construction. The feasibility of using various materials like reclaimed asphalt pavement wastes, recycled concrete aggregate, electric arc furnace slag, cross-linked polyethylene waste, silica fume, bagasse ash, ground granulated blast furnace slag, jarosite, crumb rubber, rice husk ash, fly ash, sugarcane ash, coal waste ash and coal waste powder explored by various researchers in the past were consolidated under one roof in this study. The effect of all the materials on different mechanical, durability and fresh properties of Roller-compacted concrete was reported in the study. Many of these materials yielded satisfactory results when partially replaced or partially added to various constituents of roller-compacted concrete. In essence use of these materials not only have environmental benefits like reduction of carbon footprints but also saves the cost of construction.
... • Tensile strength and durability properties enhanced by SF [61]. • At 50% replacement level, the tensile strength was enhanced by SF and FA mixtures [62]. ...
... People are using more and more cement every day, and the release of CO2 causes irreparable damage to the environment. It is possible to reduce part of the environmental pollution by replacing pozzolanic materials such as silica fume (SF) instead of ordinary Portland cement (OPC) [22][23][24]. SF is made of silica that has no definite shape or structure, which comes from the industry that makes ferrosilicon [25]. This material is a gray-white powder that is formed when industrial silicon and ferrosilicon alloys are melted [26,27]. ...
Concrete, as one of the most widely applied materials in buildings, has high environmental impacts. Researchers are continually seeking solutions to mitigate these environmental issues while enhancing the mechanical strength and durability of concrete. However, there is a lack of studies on the effect of combining silica fume (SF) as pozzolanic materials and shape memory alloy (SMA) fibers on the mechanical properties of concrete. Moreover, there is very limited research on the influence of these materials on concrete mixtures after primary failure cracks using the secondary compressive strength test. In this research, 0.1, 0.2, and 0.3% SMA and 5, 7.5, and 10% SF were applied and then subjected to compressive strength, splitting tensile strength, flexural strength, secondary compressive strength, and ultrasonic pulse velocity tests. According to the results, 10% SF is more economical, which increases the compressive, splitting tensile, and flexural strength by 14%, 7%, and 10%, respectively. Also, using 0.3% SMA improves the compressive, splitting tensile, and flexural strength by 2%, 5%, and 8%, respectively. Furthermore, SMA has the ability to reduce the secondary compressive strength compared to other samples, indicating the quality of this material in controlling stress after cracking. Finally, it was indicated that the combined use of these two materials increases the strength parameters.
... Concrete will continue to be widely used worldwide due to its good compressive strength, high plasticity, and flow ability when in a fresh condition, durability and fire resistance when hardened, and even relatively low cost [4,5]. Research on the mechanical properties of newly developed concrete construction materials is necessary for characterizing their performance for field execution [6][7][8]. Fiber-reinforced concrete (FRC) is not a new concept. Since biblical times, fibers have been used in cementing construction materials in the form of straw and horsehair. ...
The compressive strength and splitting tensile strength of concrete reinforced with nylon fiber are examined in this work. Tests were done on concrete mixtures including different quantities of nylon fibers to see how they affected the mixtures compressive and splitting tensile strengths. The results show that adding nylon fibers to concrete usually improves its compressive strength and splitting tensile strength, with the highest performing concentrations. The use of nylon fiber-reinforced concrete (NFRC) has drawn interest as a possible way to improve both the durability and strength of regular concrete. The purpose of this study was to investigate how the performance of concrete is affected by the addition of nylon fiber. The addition of various percentages of nylon fibers to the concrete mix is 1%, 1.5%, 2% and 2.5% by volume. The mixtures were made with common ingredients for concrete, including water, fine and coarse aggregate, and cement. The greatest gains were mechanical qualities and durability was noted at 2.5% by volume, which was determined to be the ideal dosage of nylon fibers. The results of the study showed that the A5 mould with the highest proportion of nylon fiber (2.5%) used in water curing for 28 days had compressive strengths of about 36.62 MPa, 10.41 MPa in H2SO4 curing and 30.33 MPa in NaCl curing and splitting tensile strength 5.10 MPa in water curing, 1 MPa in H2SO4 curing and 4.96 MPa in NaCl curing.
... The effects of RAP aggregates beneficiated by AB & AT with admixtures on the mechanical, fresh, and durability properties are investigated, and the amount of admixture needed to improve performance is determined. The admixtures are Silica fume (SF), Sugarcane bagasse ash (SCBA), and Fly ash (FA) [29] [41]. RAP can also be used as an alternative material which can be used in place of natural aggregates for preparing a sustainable PCP mix [30]. ...
New materials are continuously made available to meet the modern need for various applications in civil engineering. This book consists of eight chapters describing the advanced materials in civil engineering. The various chapters includes the use of construction and demolition waste material for soil stabilization;review on application and performance of RAP in highway construction; static load response of laminated composite stiffened cylindrical shell using finite element analysis; review on the importance of coarse recycled concrete aggregates as alternative construction materials; performance evaluation of light transmitting concrete made with plastic optical fibers; effect of water to geopolymer solids ratio on properties of fly ash and slag-based one-part geopolymer binders; impact response of laminated composite simply- supported stiffened conoidal shell with cut-out and finally statistical review of bamboo's mechanical properties for building applications.
... Fig. 13 (b) indicates SEM images of MD results under SC conditions (5S) indicate less uniform distribution of hydration products or gapped/porous structure/high micro-cracking along with excessive C-S-H gel formation. Accelerated hydration of cement under steam curing and the early generation of CH provides a medium for extended pozzolanic reactions (EPR), the gel generated by EPR of CFA not only filled the pores but cross-bond with C-S-H and C-A-S-H which increase the overall strength of gel system and improves the microstructure solidity [50,54]. This in turn decreases the thermal damage caused by steam curing. ...
This study investigates the substitution of traditional burnt clay bricks (BCB), used since 7000
BCE, with environmentally friendly Fly Ash-Cement and Sand Composite Bricks (FCBs), utilizing
industrial waste like Coal Fly Ash (CFA) from thermal power plants. The research encompasses
two phases: the first involves experimental production of FCBs, while the second focuses on
optimizing FCBs by varying CFA (50%, 60%, 70%), Ordinary Portland Cement (OPC) content
(9%–21%), and incorporating stone dust (SD) and fine sand. Comprehensive tests under normal
and steam curing conditions, adhering to ASTM C 67-05 standards, include X-Ray Diffraction
(XRD), Energy Dispersive X-Ray (EDX), and Scanning Electron Microscopy (SEM) analyses. Results indicate that steam curing enhances early strength, with an optimized mix (MD: 5S)
achieving a compressive strength of 15.57 MPa, flexural strength of 0.67 MPa, water absorption
rate of 20.08%, and initial rate of water absorption of 4.64 g/min per 30 in2, devoid of efflorescence. Notably, a 9% OPC and 50% CFA mix (MD: 1S) shows improved early strength of 4.95
MPa at 28 days. However, excessive CFA replacement (70%) with lesser cement content negatively impacts physio-mechanical properties. This research underscores the potential of FCBs as a
sustainable and economically viable alternative to BCBs in the construction industry.
... Environmental stresses and landfill levies have thus prompted the use of RAP aggregates in structural concrete and road construction (Hassan et al., 2012;Kant Sahdeo et al., 2020;Sahdeo et al., 2021Sahdeo et al., , 2019. Furthermore, incorporating RAP aggregates as a partial replacement of natural aggregates will also help to reduce a project's total cost (Abraham and Ransinchung, 2018a;Singh et al., 2017aSingh et al., , 2018aSingh et al., , 2018b. Abraham and Ransinchung (2018b) and Debbarma et al. (2020bDebbarma et al. ( , 2019 the fine fraction of RAP as a partial substitution for fine aggregate in cement mortar mixes and concluded that the required 28-day characteristic compressive strength could be achieved with up to 25% replacement. ...
The cement mortar mixes were developed with the intent of testing the suitability of fine graded reclaimed asphalt pavement aggregates as a replacement for naturally fine materials. The natural fine aggregates were replaced in multiple percent levels of 25%, 50%, 75%, and 100% by weight. The results demonstrate that the mechanical qualities of the mortar mix are deteriorating. To address this, zinc industry waste - jarosite was used as a part replacement for cement in proportions of 5%, 10%, and 15%. Jarosite improved the microstructural, mechanical, and shrinkage properties. For instance, when comparing with the control mix, the mix containing 25% fine reclaimed asphalt pavement aggregates shows a reduction of 5.5% in hardened density and 14% in compressive strength. On the other hand, when 10% jarosite is included in the 25% fine reclaimed asphalt pavement mix, there is an observed increase of 4.85% in hardened density and 7% in compressive strength with respect to the mix containing 25% fine reclaimed asphalt pavement aggregates. As a result, the current study proposes using 10% jarosite when fine reclaimed asphalt pavement aggregates are used to make cement mortar mixes. Furthermore, a cost analysis is performed to determine the difference in construction costs. These findings are expected to inspire rational mix design recommendations for mortar mixes including fine reclaimed asphalt pavement aggregates, as well as bring environmental and economic benefits by lowering carbon footprints.
... Concrete will continue to be widely used worldwide due to its good compressive strength, high plasticity, and flowability when in a fresh condition, durability and fire resistance when hardened, and even relatively low cost [4,5]. Research on the mechanical properties of newly developed concrete construction materials is necessary for characterizing their performance for field execution [6][7][8]. ...
The initiation of micro-cracks in concrete is primarily due to its brittleness, which causes severe impacts on the overall behavior of the concrete. However, incorporating fibers in concrete could significantly improve its mechanical properties. The current study demonstrates the influence of two types of fibers on the mechanical properties of concrete. Nylon Fiber Threads (NFT) and Ny-lon Fiber Strands (NFS) at a fiber content of 2.5 kg/m3 were incorporated in the concrete mix. Concrete with a compressive strength of 30 MPa and a water-cement ratio of 0.4 was produced to investigate the fresh and mechanical properties of conventional and nylon-fiber reinforced con-crete (NFRC). The concrete prims and cylinders were tested for compressive, splitting, and flexur-al strength using ASTM standards (ASTM C-39, C-496, and D-790, respectively). It was found that NFT-reinforced samples achieved higher mechanical properties of concrete (13.05%) com-pared to NFS-reinforced samples. Test results showed that incorporation of nylon fibers (NF) in concrete decreased the compressive strength of cylindrical and cubical specimens by 0–10% and 5–15%, respectively. However, it increased the splitting tensile and flexural strengths by 0-15%, and 5-15% respectively. Furthermore, the incorporation of NF in concrete significantly improved the ductility and delayed the crack initiation in concrete.
... Concrete will continue to be widely used worldwide due to its good compressive strength, high plasticity and flowability when in a fresh condition, durability and fire resistance when hardened, and even relatively low cost [4,5]. Research on the hardened properties of newly developed concrete construction materials is necessary for characterizing their performance for field execution [6][7][8]. ...
The initiation of micro-cracks in concrete is primarily due to its brittleness, which causes severe impacts on the overall behaviour of the concrete. However, incorporating fibers in concrete can increase its strength and performance. The nylon fibers used in this study were of two types: Ny-lon Fiber Threads (NFT) and Nylon Fiber Strands (NFS). This research aims to examine the effect of nylon fiber on the mechanical properties of plain cement concrete (PCC). The potential strength of nylon-fiber reinforced concrete (NFRC) was determined versus that of PCC, at fiber content of 2.5 kg/m3. The compressive strength of concrete 30 MPa with a water-cement ratio of 0.4 was produced to investigate the workability and density tests of conventional and fiber-reinforced concrete (FRC). The concrete beams and cylinder samples were tested for compressive, splitting, and flexural strength using ASTM standards (ASTM C-39, C-496, and D-790). It was found that NFT-reinforced samples achieved higher hardened properties of concrete (13.05%) compared to that NFS-reinforced samples. Test results showed that the incorporation of fiber in the concrete decreased the compressive strength of the concrete of cylinder and cube by 0–10% and 5–15%, respectively, however, it increased the splitting tensile and flexural strengths by 0-15%, and 5-15% respectively. Furthermore, the incorporation of nylon fibers (NF) in PCC significantly enhanced the ductility and delayed the cracks initiation in concrete.
... The results are in line with compressive strength. Studies [87][88][89][90] show that flexural strength closely follows compressive strength outcomes. The flexural strength of the mixture improved at 28 days to the same replacement levels (as elaborated for compressive strength) due to the combined influence of factors such as steel slag's higher angularity and irregularity, high roughness, which resulted in high water absorption and reasonable cohesive force, which strengthened ITZ. ...
Continuous consumption of natural resources such as river sand and coarse aggregates due to increased industrialization and urbanization has impeded the movement towards green concrete in construction, i.e., utilizing waste materials in its production, steel slag waste being one of them. Accumulation of Linz-Donawitz slag (LD slag) has become cumbersome in India, posing a problem of landfills and environmental degradation, i.e., abating soil and water quality due to the leaching of toxic metals. Fewer experimental studies have examined whether weathered fine LD Slag can substitute for fine aggregates in concrete. Additionally, the research has yet to compare the behavior of concrete comprising weathered fine LD slag in Normal Strength Concrete (NSC) and High Strength Concrete (HSC) containing Metakaolin. The current study aims to establish an optimum replacement quantity for fine aggregates with fine LD slag. The slag replaced fine aggregates by volume at 25, 50, 75 and 100%. The findings that examined the effects of using LD slag on the mechanical behaviour, durability and microstructure of concrete are presented in this study. Furthermore, taking a total of 180 experimental data points, the compressive strength of concrete was predicted using artificial intelligence (AI) methods such as Artificial Neural Networks (ANNs), Decision Trees (DT) and Random Forests (RF). Coefficient of determination R², Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) were computed to assess the performance of generated models. Besides, a sensitivity analysis technique was employed to determine the most influential parameter among cement, Metakaolin, Fine Aggregate, Coarse Aggregate, LD slag, Superplasticizer, water content and testing age on the compressive strength results. Experimental investigation showed that adding LD slag up to 50% for NSC and 25% for HSC was optimal and showed better results for tested properties than conventional concrete mixes. Among proposed AI techniques, the DT technique was the best-performing model with an R² value of 0.973 and the least for MAE (3.534 MPa) and RMSE (4.409 MPa). Sensitivity analysis performed on the DT model showed that testing age was the most critical parameter for the prediction of compressive strength.
... These waste materials are in the form of aggregate, which is coated with a layer of asphalt around its periphery. These materials are known as reclaimed asphalt pavement (RAP) aggregates (27)(28)(29)(30)(31)(32)(33)(34). The use of RAP in cement concrete pavements is a novel concept that has attracted much interest because of its underutilization in asphalt pavements (27,35,36). ...
Pervious concrete (PC) is emerging as a novel pavement material for its unique characteristics of reducing storm-water runoff and mitigating urban heat islands. This makes it well suited for low-volume pavement applications. It is also expected that reclaimed asphalt pavement (RAP) aggregates as a replacement for natural aggregates will improve the porosity and permeability of PC pavement mixtures. As a result, this study checks the feasibility of using RAP-based PC mixes in a parking space. The construction process will offer a guide to the field engineer on how to push this technology further when recycled materials are used. The PC parking space, with a capacity of 5 tonnes laden weight, was developed by replacing natural aggregate with 25% RAP aggregate (30% of 10 mm and 70% of 4.75 mm). Field mixtures were found to have higher porosity and lower density when compared with laboratory-prepared mixes. The field infiltration capacity was observed to be in the range of 0.50–1.75 cm/s while maintaining a flexural capacity of 2.36 MPa to 3.17 MPa (342.28 pounds per square inch (psi) to 460 psi). This suggests that using binary-graded RAP aggregates helps create an interconnected pore network, enhancing PC mixtures’ transport capabilities. The present study illustrates the step-by-step construction process of PC pavements for field applications. Based on the findings, it is recommended that 50% could be the maximum feasible limit for the usage of RAP aggregates in PC field mixes.
... Along with the mechanical performance, paving concrete shall be durable enough in different environmental conditions for enhanced serviceability (Singh et al. 2017). The extent of intrusion and transport of the fluids and ions from the environment into the matrix determines the durability of the concrete system (Shankaramurthy et al. 2021). ...
Extraction of recycled concrete aggregates (RCA) from construction and demolition waste is an effective way to induce sustainability in the highway sector. However, inclusions of these inferior materials could significantly deteriorate the performance of paving quality concrete (PQC) due to the presence of old adhered mortar (AM) around the RCA. Numerous techniques are available in the literature that primarily address the issues with AM for increasing the potential of RCA for concrete applications. However, the energy demand and associated emissions are higher in most of these techniques, whereas carbonation and slurry impregnation (SM) techniques are regarded as the best ways to economically enhance the characteristic of RCA for large-scale applications. The present study is the first of its kind to optimize the SM process for carbonated RCA for PQC roads; RCA was stockpiled in the natural environment in loose condition for around 12-14 months for fully carbonating the Portlandite phase. The parameters optimized are slurry material type (silica fume, fly ash, and cement), their concentrations (20% − 60%), exposure duration (4-12 h), and RCA sizes (20 mm and 10 mm), whereas the porosity, toughness, absorption, and dry density were considered for process optimization. Finally, for process validation, various PQC performance parameters (fresh, mechanical, and durability) were determined. The findings suggest soaking the RCA sizes in any of the considered cementitious/waste material slurry at 40% concentration for 6 h for enhanced performance of both RCA and PQC made with treated RCA.
... Shi et al. [23] found that the interfacial transition zone (ITZ)'s porosity and a preferential asphalt cohesion failure together had a significant impact on the reductions in strengths of PCC containing RAP (RAP-PCC). This view is supported by other researchers, who also reported that RAP material typically fails in asphalt cohesion, which means that the asphalt layer arrests cracks through the asphalt layer surrounding the RAP particles [24][25][26]. Based on their laboratory findings, Senff et al. [20] reported that as a nano-filler, SiO 2 nanoparticles could better understand the mechanism of nano silica and the effect of nano-silica on fresh cement paste properties and mortar covering various pores between gel of calcium silicate hydrate (C -S -H) particle. ...
... The minimum water absorption was reported for rigid payments (Pandey and Kumar 2020a), which may be owing to the formation of densely packed structure with the inclusion of smaller RSA and MS as compared to the OPC. Moreover, interconnectivity of the pores in OPC have also been rendered with the inclusion of RSA and MS (Duan et al. 2013;Singh et al. 2017). This also results in a decrease in water absorption capacity of the concrete mixture. ...
With the growing demand, a large amount of paddy has been harvested by growers leaving behind the stubble (left over rice straw), which is being a big burden on the farmers for its management. For the easy access, the burning of stubble has been opted which in turn results in the deterioration of the environment. To mitigate this problem, rice straw utilization strategies should be opted. Therefore, in this review article, the strategies of utilizing rice straw in fiber or ash form to manufacture construction materials have been summarized. The manuscript also considers the method of productions, variability in raw materials, and various mechanical/physical properties of construction materials targeted. Further, the financial aspects related to utilization of rice straw and rice straw ash are also encoded at last. This review will be helpful to expedite the research in this field and may also be used for startups related to various product development using straw in the local areas, which may depreciate the burning of straw in the field and its environmental effects.
... The Flexural strength (or the modulus of reuptur) is usually taken as a ratio of the UCS, as mentioned in the study by Thompson 1986. Another study that investigated the relationship between flexural strength and compressive strength of concrete using RAP as course aggregate was conducted by Singh et al. 2017. As a result of this study, a power regression model (Flexural Strength = 0.368 × (compressive strength) 0.72 ) was established. ...
This laboratory study investigates the feasibility of using geopolymer-based stabilization of base soil and reclaimed asphalt pavements (RAP) to fully replace cement in road rehabilitation projects. Geopolymer is an environment-friendly material that is based on the alkaline activation of aluminosilicate precursors. The performance of Portland cement as a chemical stabilizer for the full depth reclamation (FDR) of asphalt pavements is well established. However, Portland cement manufacturing has a high carbon footprint and other significant environmental impacts. Furthermore, there is a shortage of cement available for FDR projects across many country regions. Simultaneously, there is a strong motivation to explore various industrial wastes such as ponded ash, slag, ground glass fibers, etc., as replacements for Portland cement in construction. Therefore, a geopolymer based on ground glass fibers (GGF), either separately or combined with ponded fly ash (PFA) or slag (S), was studied to replace cement in FDR. All mixtures were tested for unconfined compressive strength (UCS), flexural strength, and drying shrinkage, wetting/drying, freezing/thawing, and tube suction tests. The results showed promising performance of geopolymer-based stabilized mixtures as compared to control. However, some test methods related to FDR with cement need to be modified to suit the mixtures of FDR with geopolymer.
... BOF and KR have a crystalline structure as well as GBFS since it was cooled under atmospheric conditions [6]. The content of silica and alumina in the slag react with Ca(OH)2 to form a compound calcium silica hydrate (CSH) [7]- [9]. The reaction results in the form of CSH, which is equal to the hydration reaction of C3S and C2S in cement. ...
Slag is a waste from steelmaking industries that was released into the environment. Slag was used as reinforced material in mortar. Different types of slag, including Air Cooled Slag (ACS), Granulated Blast Furnace Slag (GBFS), Basic Oxygen Furnace Slag (BOFS), and Kanbara Reactor Slag (KRS), were used as a reinforcing material in this study. The composition of slag in the mixture on mortar was 10%, 20%, 30%, 40%, and 50%. The sample was made with a water-cement ratio (w/c) of 0.35, with the ratio of sand and cement being 1:1.5, respectively. Treatment of mortar sample at ambient temperature was applied. The mortar samples were left to cure until 3, 7, and 28 days, which performed a compression test. The results show that adding slag to the mortar enhanced the compressive strength of the pristine mortar. The highest strength was obtained by adding 10% slag at 28 days. The compressive strength of GBFS, BOFS, KRS, and ACS was 23.76 MPa, 23.28 MPa, 19.68 MPa and 17.48 MPa, respectively. Based on the XRD result, it was discovered that the mixture has more Calcium Silicate Hydrate Peak than Pristine mortar.
... Extensive research has been developed on the reutilization of unreinforced RAP, for flexible pavement surface course [12][13][14]; flexible pavement base courses [15][16][17][18][19]; flexible pavement base layers [20][21][22][23][24][25][26][27][28]; rigid pavement in concrete mix, as course and fine aggregates [29,30]; and even airfield pavements [31,32]. Promising, although scarce, research has been carried out on the influence of fiber inclusion on the mechanical behavior of cemented/stabilized RAP mixtures, with most studies mainly focusing on concrete applications [8][9][10][11]. ...
The milling of asphalt pavements has been extensively applied as a restoration technique, however, a large quantity of reclaimed asphalt pavement (RAP) waste is generated during this process. Numerous applications have been developed for the reutilization RAP, yet, these approaches are still not based on a rational criterion methodology for cemented soils, especially for fiber-reinforced ones. The goal of this research was to analyze the effect of fiber reinforcement on the mechanical behavior of reclaimed asphalt pavement-powdered rock-Port-land cement mixtures, while proposing a rational dosage methodology through the porosity/cement content index (η/C iv). Resilient modulus, split tensile strength, and durability tests were conducted in non-reinforced and fiber-reinforced mixtures. Results have shown that non-reinforced mixtures depicted higher resilient modulus, split tensile strength, and durability when compared to fiber-reinforced ones, implying that fiber addition only hindered the mechanical properties of the specimens. This was associated with the length and diameter of the fiber along with the grain size and particle shape of the reclaimed asphalt pavement. Finally, the η/C iv index was shown to be an appropriate dosage methodology to predict the mechanical behavior of both non-reinforced and fiber-reinforced mixtures.
... Tolmachov et al. [4] added water reducer, mineral admixture, and fiber into concrete to increase its flexural strength by 25.7%. Singh et al. [5] found that the flexural strength of RAP concrete could be increased by 10% by adding 10% (mass fraction) silica fume. Zhang et al. [6] found that when the fly ash content was 20% (mass fraction, the same below), the flexural strength of recycled concrete could be increased by 29.9%. ...
The residual compressive stress of concrete members can offset the tensile stress caused by some external load and hinder the generation and expansion of surface cracks to enhance the flexural strength of concrete. In order to carry out this strengthening method, the single-layer and double-layer gradient coatings mixed by sulphate aluminium cement with different amounts of expansion agent on the surface of concrete specimens were discussed, and the theoretical calculation formula of surface compressive stress caused by this was deduced. Combined with experimental data, the influence of surface compressive stress on flexural strength of concrete was studied. The results demonstrate that the greater the surface compressive stress generated in the coating, the better the effect of improving the flexural strength of concrete. To obtain sufficient surface compressive stress, it is recommended that the cross-sectional product ratio of the substrate to the coating is more than 80; the higher the elastic modulus of the coating, the greater the surface compressive stress; the smaller the shrinkage rate of the coating, the greater the surface compressive stress. The improvement effect of double-layer gradient coating on the flexural strength of concrete is better than that of single-layer coating. Compared with the reference specimen without coating, the improvement rates of double-layer gradient coating on the early and late flexural strength of concrete are 57.7% and 45.7%, respectively.
... Researchers have investigated the effect of RAP in mechanical properties like compressive and flexural strength, effect of gradation on concrete mix properties with coarse RAP aggregates [14][15][16] and with fine RAP aggregates [14,17]. Effect of coarse fraction of RAP in concrete mixes in non-ideal environment was also studied [18]. Any pavement mixture to be feasible, it is imperative to study all aspects of the same which includes mechanical, durability, permeation since the life of the pavement structure depends on them. ...
The effect of fine fraction of Reclaimed Asphalt Pavement (RAP) aggregates on durability characteristics of mortar and concrete were assessed. The natural fine aggregates were replaced by finer fraction of RAP at 25%, 50%, 75% and 100% by volume. Resistance to sulfate and acid attack, drying shrinkage, alkalinity, chloride content and presence of carbonation of the mixes were analyzed. Increase or equivalent strength was observed for both mortar and concrete specimens with 50% or lower RAP replacement level under sulfate attack in sodium sulfate solution in comparison to decrease in strength under sulfate attack in sulfuric acid and acid attack in hydrochloric acid solutions. This is due to difference in formation and filling of pores and microcracks by salt—crystallization products in mortar and concrete. The pore distribution characteristics such as threshold diameter supports this observation as well. The threshold diameter decreases from control mix to 50% RAP mix and then increases. Similar pattern of observation was seen in concrete mixes as well. The drying shrinkage of RAP inclusive cementitious mixes were within the stipulated limits. The RAP inclusive concrete mixes do not pose any threat to the reinforcement due to absence of carbonation, chloride content being lower than the maximum limits and pH content between 12 and 13. From the study, it may be concluded that fine RAP inclusive cementitious mixes have durability life and has the potential to be used as pavement quality concrete.
... The obtained results are in line with the literature reported. 67,74,75 However, cRAP aggregates with varying service life, storing history, and bitumen concentration study at the advanced replacement level should also be accomplished. ...
Pervious concrete (PC) is a new type of concrete that is gaining popularity because of its low-impact development capabilities and ability to reduce stormwater runoff. The current study focuses on the potential use of waste from the sugarcane industry and on flexible pavement, specifically sugarcane bagasse ash (SBGA) and reclaimed asphalt pavement (RAP), to create PC mixes. Furthermore, an unconventional method was used to extract the benefits of RAP without compromising the structural integrity of PC: designing the mixture based on hydrological properties rather than mechanical parameters and then improving structural integrity through the use of SBGA without compromising the hydrological capacity of the designed PC mixture. Six PC mix combinations were developed by substituting recycled asphalt pavement for natural coarse aggregate in varying proportions of 0, 50, and 100 %. Following that, three RAP-incorporated PC mixes were created using 5, 10, and 15 % SBGA as a partial replacement for cement. It was discovered that using SBGA as a partial replacement for cement reduces mechanical properties while increasing functional properties such as permeability. Surprisingly, no significant differences were observed in the percentage voids of PC mixes containing RAP aggregates. The addition of 10 % SBGA significantly improves the mechanical properties of 100 % coarse RAP (cRAP)-inclusive PC mixes. When the total cost of 1 m3 concrete was calculated, the addition of cRAP aggregates and SBGA in pervious concrete pavements mixes resulted in a 44 % reduction. Furthermore, the current study suggests replacing 10 % of ordinary Portland cement with SBGA in cRAP inclusive PC mixes, as this increases the strength of cRAP–PC mixes while also providing environmental and economic benefits.
... Realizar combinaciones con agregados RAP está siendo una novedosa técnica de incorporar el aditivo mineral con muestras recicladas del pavimento (Singh, et al., 2017) estudiaron a 3 aditivos minerales diferentes HS, CV y ceniza de bagazo de caña (CBC), actuando como remplazo del peso de cemento mostrando mejoras con porcentajes de 10, 20 y 5% respectivamente en sus propiedades mecánicas y exceder el 5% más en CBC aumenta la absorción de agua en tanto a los vacíos permeables totales. Otros tipos de agregados de concreto reciclados o denominados RCA con adiciones de MK y HS de un 10% al diseño de mezcla de SCC son capaces de compensar las pérdidas de las propiedades de durabilidad del concreto de manera óptima cuando son reemplazadas parcialmente del agregado natural en un 50% que cuando se reemplaza en un 100% (Kapoor, et al., 2016); cabe decir que la utilizacion del RCA no son frecuentes y eso debido a su alta porosidad y capacidad de absorción de agua (Bouarroudj, et al., 2021). ...
El presente artículo recopila e identifica la adición de ciertos aditivos minerales de uso más frecuente en la industria de la construcción como modificadores del concreto durante su estado fresco y endurecido, los cuales en su mayoría son usados como remplazo parcial del cemento. Actualmente los investigadores buscan optimizar las propiedades del diseño de mezclas dependiendo al uso por el cual son concebidas, así mismo que sea factible económicamente y respetuoso con el medio ambiente. Se revisaron 50 artículos indexados entre los años 2010 y 2021 distribuidos en las siguientes bases de datos: 37 artículos de Scopus, 10 artículos de ScienceDirect, 2 artículos de Springer y 1 artículo de SciELO. Los aditivos en estudio son escoria de alto horno granulada (EAHG), cenizas volantes (CV), humo de sílice (HS), ceniza de cascarilla de arroz (CCA). En su mayoría presentan una mejora considerable en sus características mecánicas de tracción, resistencia a la compresión y módulo de elasticidad. La adición de CV mejora en la mezcla del diseño durante su estado fresco, la CCA durante su estado endurecido y las mejores resistencias para el HS; sin embargo, la EAHG resulta cumplir con casi todas las expectativas en mayor porcentaje y así mismo junto con la CCA, son potencialmente competitivos.
... Shi et al. [23] found that the interfacial transition zone (ITZ)'s porosity and a preferential asphalt cohesion failure together had a significant impact on the reductions in strengths of PCC containing RAP (RAP-PCC). This view is supported by other researchers, who also reported that RAP material typically fails in asphalt cohesion, which means that the asphalt layer arrests cracks through the asphalt layer surrounding the RAP particles [24][25][26]. Based on their laboratory findings, Senff et al. [20] reported that as a nano-filler, SiO 2 nanoparticles could better understand the mechanism of nano silica and the effect of nano-silica on fresh cement paste properties and mortar covering various pores between gel of calcium silicate hydrate (C -S -H) particle. ...
... Replacing RAP for aggregates in concrete mixtures is another application of RAP. There have been several studies, all of which have two general results in common, firstly, using RAP as a replacement for aggregates causes the mechanical properties of the mixture to drop, and, secondly, replacing coarse aggregates leads to lower strength drops compared with replacing fine aggregates (Abdel-Mohti et al., 2016;Erdem and Blankson, 2014;Huang et al., 2005;Khodair and Luqman, 2017;Khodair and Raza, 2017;Shi et al., 2017;Singh et al., 2017;Singh et al., 2018). ...
The feasibility of utilizing Reclaimed Asphalt Pavement (RAP) as a replacement for coarse aggregates in Roller Compacted Concretes (RCCs) was assessed. This replacement was performed in different volumetric percentages (25%, 50%, 75%, and 100%). During this process, RAP materials were subject to abrasion and impact in the Los Angeles drum and mixer before being added to the mixture. Compressive strength, splitting tensile strength, flexural strength, crack propagation, Ultrasonic Pulse Velocity (UPV), electrical resistivity, density, and water absorption (in 7, 28, and 90 days of age) tests were done on all mixtures. Results show that utilizing RAP in RCC can cause a drop in the mechanical properties, but it has positive effects on crack propagation of the specimens due to their increased toughness. Increasing the amount of RAP in the mixtures has increased their electrical resistivity, likely owing to the hydrophobic properties of RAP, which causes prevention from connecting pores to each other. The relationship between the mechanical properties and UPV of the mixtures was analysed using regression models. Moreover, one- and two-way ANOVA (analysis of variance) tests were performed on the results at a 95% confidence level. Finally, replacing the coarse aggregates with RAP only up to 75% is suggested if pre-processing is performed.
... Screening and washing of RAP are necessary to remove the dust film and agglomerate to some extent. The bonding property of the RAP inclusive concrete mixture is highly affected by the thick layer of coated asphalt aggregates which hinders the adhesion between concrete paste and RAP aggregates [24,27]. ...
This paper focuses on developing sustainable self-compacting concrete (SCC) through the optimization process by incorporating Reclaimed Asphalt Pavement (RAP) as coarse and fine aggregates and also utilizing Cashew Nutshell Ash (CNA) as a cementitious material. To achieve this optimization technique is implemented in four stages, which are the RAP aggregate treatment process, gradation selection process, RAP replacement percentage, and considering the CNA replacement percentage. RAP has been treated by a novel freeze-thaw cyclic procedure followed by the abrasion treatment method. Bailey's Aggregate Grading Technique (BAGT) has been implemented to line up the aggregate packing gradation. Mechanical and rheological properties have been conducted and analyzed based on compliance requirements of SCC at ambient temperature. Paste properties are analyzed through Field Emission Scanning Electron Microscopy, X-ray diffraction, Energy-Dispersive-Spectroscopy, and Thermo Gravimetric Analysis. Further, quality assessment of SCC has been performed through X-ray μCT (Xradia, XCT-500) and Ultrasonic Pulse velocity tests. In addition, compressive and flexural strength of selected SCC mixes have been performed at 50°C, 100°C, and 150°C. Based on the results, with the incorporation of 75% coarse RAP, 50% fine RAP along 15% CNA as a binder constituent it becomes possible to achieve a sustainable SCC and it was found to be most suitable for real-time practices.
... Partial replacement of SF upto 10% does not reduce the workability and also upto 20 percent SF content the maximum strength is obtained [12]. The cement was replaced by Silica fume in proportion of 5% & 10% and it is observed that maximum compressive strength obtained at 10% replacement of SF [13]. Scope of the present investigation is limited to determine the effect of different mineral admixtures like RHA (10%,15%,20%), SF (10%,15%,20%) & GGBFS (10%,20%,40%) on performance based M40 grade of concrete and compare the test results with control mix for 7,14 & 28 days of curing. ...
This investigation exhibits a study on the effect of silica fume, Rice husk ash and Ground granulated blast furnace slag on mechanical property of Performance based concrete. The Performance based concrete with various proportion of different mineral admixtures were tested including compressive strength at 7,14 & 28 days of curing. The ordinary Portland cement by weight was partially replaced with Rice Husk Ash (10%, 15%, 20%), Silica Fume (10%, 15%, 20%) and Ground granulated blast furnace slag (10%, 20%,40%). Estimations were completed subsequent to restoring at 20°C and 65% relative humidity. Total 90 cubes were casted for different mixes for compressive strength of concrete. The test results reported that optimum % of Rice Husk Ash is for the Mix(C90RHA10) and the compressive strength increases by 6.62% compare to control mix at 28 days. Also, the optimum % of Silica Fume is for the Mix (C80SF20) and the compressive strength increases by 13.4%. Similarly, the optimum % of GGBFS is for the Mix (C60GGBFS40) and the compressive strength increases by 6.81%.
While several research studies considered the utilization of reclaimed asphalt pavement (RAP) aggregates for asphalt and concrete pavements, very few attempted its possible utilization for precast concrete applications like concrete paver blocks (CPBs). Moreover, few attempts made in the recent past to improve the strength properties of RAP inclusive concrete mixes by incorporating certain supplementary cementitious materials (SCMs) have reported an insignificant or marginal effect. The present study attempts to comprehensively investigate the utilization potential of some locally and abundantly available materials having suitable physicochemical properties to improve the performance of a zero-slump CPB mix containing 50% RAP aggregates. The studied filler materials, namely, wollastonite (naturally occurring calcium metasilicate mineral) and jarosite (hazardous zinc industry waste), were used to replace 5–15% and 10–20% by volume of Portland cement in the 50% RAP CPB mix. Apart from their individual effects, the efficacy of wollastonite-jarosite blends was also investigated. Considering the lack of indoor storage facilities and economic aspects of CPBs, the influence of water spray curing regime on the performance of the RAP CPB mixes was studied and compared to that of continuous water curing regime. Inclusion of the considered fillers was found to statistically and significantly enhance the flexural strength, tensile splitting strength, and abrasion resistance of the 50% RAP CPB mix; however, the compressive strength (in most cases), permeable voids, water absorption, and water permeability properties showed an insignificant improvement. Results of thermogravimetric analysis confirmed the occurrence of pozzolanic reactivity, and microstructure analysis revealed improvements in packing of concrete matrix and ITZ with filler inclusion qualitatively substantiating the improvements in strength and durability characteristics. The toxicity characteristics of heavy metals that may leach from the hazardous jarosite-based RAP CPB mixes were found to be within permissible limits. Based on the performance requirements specified by IS, IRC, and ASTM standards, all the RAP CPB mixes with filler inclusions fulfilled the acceptance criteria for heavy traffic applications, and water spray curing can enact as an alternate method for curing these mixes. However, to avail maximum performance benefits, it is recommended to use 5% wollastonite, 15% jarosite, and a combination of 10% wollastonite and 10% jarosite as a Portland cement substitute to produce sustainable eco-friendly RAP CPB mixes.
Here performance evaluation of Self Compacting Alkali Activated Slag Concrete incorporating Reclaimed Asphalt Pavement as fine aggregate was carried out. Investigation on mechanical properties by replacing the fine aggregate by Reclaimed Asphalt Pavement in different proportions were also evaluated. Development of Self Compacting Alkali Activated Concrete mixes (SCAAC) was made with GGBFS and Lime are used binders, with binder content varying between 550 to 650 kg/m ³ of fresh concrete and lime content varying from 10% to 20% of binder content. The net W/B ratio of the mixes was kept around 0.57. The fine aggregate was replaced by Reclaimed Asphalt Pavement with percentage replacement from 50 to 100% of Crushed Stone Sand. The alkaline solutions had Na 2 O dosage percentages in the range 5-6% with a constant activator modulus maintained at 1. By using Minitab Statistical Software nine mixes were produced with 4 factors and 3 levels. In this study the TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) optimization technique was carried out to know the effectiveness. Results showed the slump flow greater than 650 mm, with their L–Box, U-box and V-Funnel values ranging between 0.85,20mm and10s respectively, results showed enhanced mechanical properties as compared to control OPCC mix.
Recycling flexible pavement generates huge quantities of Reclaimed Asphalt Pavement (RAP) aggregates, which are sometimes deserted in landfills or open dump yards. Use of this otherwise waste material in concrete may be a viable option to reduce both the ever-increasing demand for natural aggregates and minimize the landfill area utilization due to the dumping of RAP. Many researchers studied the influence of RAP aggregates on concrete performance and suggested various pre-treatment methods for the processing of RAP aggregates. A comprehensive review on the influence of RAP aggregates on concrete performance is needed to raise awareness among engineers and contractors. This paper presents an extensive review on various properties of concrete which vary with the use of RAP aggregates in concrete. Also, reviewed the process for the preparation of RAP to utilize as aggregate in concrete. The addition of pre-treated RAP aggregates increases the workability of concrete. The use of RAP aggregates diminishes the mechanical and durability characteristics of concrete. Literature shows that the use of processed RAP aggregates along with supplementary cementitious materials or fibers can improve the performance of RAP concrete.
Sugarcane bagasse was variously treated by three different processing protocols to improve the pozzolanic activity of the resulting sugarcane bagasse ash (SCBA). Three parameters were examined namely, the particle size, the calcination temperature and the duration of calcination. The resulting SCBA was blended with Portland cement to examine potential benefits upon the strength and chloride resistance of mortar specimens. As expected, the particle sizing and re-calcination, together imparted greater pozzolanic activity to SCBA. The results demonstrate that the optimal SCBA, possessing an acidic oxide (SiO2+Fe2O3+Al2O3) content over 70% and LOI can be reduced to 4.3%, resulted from grinding the boiler residue to 35μm, followed by calcination for 90 min at 600°C (P3-T90). In addition, the XRD test reveals that increasing the calcination temperature up to 600°C could remove the residual carbon and other volatile compounds effectively. However, any further increase was noted to convert amorphous silica to cristobalite in SCBA itself and, also to enlarge the microcrack at ITZ in the hardened mortar. Furthermore, the optimal SCBA was found as P3-T90 in this study to produce the best blended mortar, as evident from an 18% increase in compressive strength, a 15% increase in flexural strength and a 43% decrease in chloride diffusion coefficient. This is firstly attributed to the improved pozzolanic activity and in turn, to the increasing C-S-H phase. Besides, the associated porosity and mean pore size were minimized to 15.78% and 36 nm, respectively.
In the recent period, major importance has been given for the development of concrete pavements rather than flexible pavements. These flexible pavements consist of more than 30–40% high quality aggregates which may be reused in the construction of new roads. Furthermore, due to the paucity of natural aggregates (NA) and environmentally friendly materials, reclaimed asphalt pavement (RAP) is frequently used as a substitute material for the construction of road. In this context, the aim of this study is also to define the optimum range of these RAPs as an alternative of the natural aggregate (NA) for sustainable pavement structures. In the present research, the different proportions of RAP content (coarse and fine) are about 25–50%of the natural aggregate that has been used in the concrete mix. Also, zirconia silica fume (ZSF) is used as an admixture that partially replaced the ordinary Portland cement (OPC) in the concrete mix. In this study, various proportions of ZSF (10, 20, 30 and 40%) were added for the improvement of the mechanical properties of rigid pavement. . This experimental study investigated the performance of high RAP content and ZSF on compressive strength (CS), tensile strength (TS), flexural strength (FS), and water permeability of rigid pavement (RP). The experimental results indicate that the presence of ZSF improves the workability of the wet concrete mixes. However, excessive (more than 40% of the natural aggregate) use of RAP reduces the CS and TS of concrete. The overall result indicates that the performance of 30% fine RAP with admixtures (ZSF) is better as compared to the virgin aggregate in the concrete mixes. The final results were statistically evaluated by two-way factor variance analysis (ANOVA).
Reduce, reuse and recycle are treated as the thumb rule for achieving sustainability, and this formula rightly applies to construction materials as they are depleting at an incredible pace. Reclaimed asphalt pavement (RAP) is a sustainable alternative for construction aggregates. Several researchers have identified RAP as inferior material over natural coarse aggregates and proposed incorporating materials like superplasticizers, admixtures, fibers, and pozzolanic materials to compensate for the decrease in mechanical properties. Thus, the present study aims to evaluate the mechanical and durability characteristics of RAP-based roller-compacted concrete with red mud as part addition to cement. The present study considers a constant replacement percentage of 50% by weight of natural aggregates with RAP to evaluate mechanical and durability properties. Upon comparing the fresh properties of RAP-based roller-compacted concrete with red mud over roller-compacted concrete with only natural aggregates, a 3–15% increase in optimum moisture content is observed. Further, the mechanical properties like compressive, flexural, and tensile strengths, which showed a downtrend due to RAP inclusion, have significantly improved by incorporating red mud. However, a 15% red mud by cement weight is observed to be an optimum dosage based on the mechanical properties. Red mud-inclusive mixes outperformed RAP and control mixes in terms of durability characteristics such as water absorption, abrasion loss, and resistance to the aggressive environment. Further, incorporating 15% red mud in RAP-based roller-compacted concrete liberates a lower calcium silica ratio, which ascertains the dense microstructure formation.
Rapid road infrastructure developments in recent years have led to a depletion of conventional road construction materials owing to its excessive exploitation. As a result, government agencies across the globe are compelled to opt for alternative road construction aggregates. In lieu of above, incorporations of reclaimed asphalt pavement (RAP) aggregates have found its way alternative aggregates for productions of bituminous and concrete roads without much modifying the aforesaid materials. Several studies pertaining to the utilization of RAP in flexible and conventional concrete pavements have been studied in detail; however, the same for Indian conditions is scanty; furthermore, its application in roller-compacted concrete pavements (RCCP) is also meager due to hesitation among the engineers since there exist no codal guidelines on the use of RAP for concrete roads. Utilization of RAP for constructions of RCCP has acquired global attention owing to several economic and environmental aspects. Studies recommended that 50% of conventional natural aggregates could be replaced by RAP for productions of RCCP mixes, without much hampering its strength and durability properties. The overall objective of this paper is to bring out the issues related to the effective utilization of RAP in RCCP. In the same line, the efficacy of various pozzolanic-rich waste materials alongside RAP has also been addressed. It is concluded that RAP with or without admixtures can be used in roller-compacted concrete pavements after thoroughly investigating its respective properties making RCCP a sustainable road.
Over the years, supplementary cementitious materials (SCM) have been successfully utilized in concrete buildings, but they have been rarely exploited in concrete pavements. In recent years, due to the growing importance of concrete pavements, researchers have begun studying the performance of various types of SCMs from pavement perspective. The overview herein assesses the existing research associated with utilizing different kinds of silica-rich waste as SCM. For this purpose, five agricultural waste (AW) comprising rice husk ash (RHA), rice straw ash (RSA), corn cob ash (CCA), palm oil fuel ash (POFA), sugarcane bagasse ash (SBA) and three industrial by-products (IB), i.e., fly ash (FA), ground granulated blast furnace slag (GGBFS) and microsilica (MS), were selected. Their effects on various properties of concrete were exhaustively reviewed. This study also furnishes reasons for limited literature on SCMs utilization in concrete pavements. Moreover, this review accentuates the previous studies’ gaps, which require further research, such as the need for dedicated standard codes for AW utilization in concrete pavements. The guidance for future research to further enhance the properties of pavement quality concrete is also given.
Concrete is one of the world's second-largest consumable materials. This leads to more consumption of natural nonrenewable raw materials like aggregates, sand etc. To overcome the problem, it is important to use various waste material in concrete manufacturing. This chapter attempts to review the present literature on in-depth studies that have been undertaken in an attempt to investigate reasonable applications and capability of bagasse ash for building construction materials. In the chapter various fresh, harden, and durability aspects of bagasse ash concrete were described.
Stepping in the 21st century, the materials used in pavement construction have diversified and progressed with time. Due to an increase in the cost of materials, depletion of natural resources, and accentuation on environmental sustainability, the usage of recycled asphalt pavement material has become popular worldwide. However, there appears to be inadequate works and a gap in understanding the method of recycling and its concomitant economic and environmental benefits at a commercial level in India. The majority of studies have focused on base and sub-base courses, whereas few works have been conducted for the surface course. Furthermore, India is a growing powerhouse in South Asia, and the pavement industry constitutes a vital sector. Thus, the reuse and recycling of reclaimed asphalt pavement in India is an emerging domain, but their usage is in low amount as compared to the United States, Europe and Japan. Hence, the objective of this review paper is to provide information on the suitability and utilization of reclaimed asphalt pavement in various areas of pavements that will eventually contribute to creating a balanced system in solving the environmental and material scarcity, economic benefit and consequently transform the construction industry to sustainable and eco-convivial.
The utilization of Ordinary Portland Cement (OPC) cause hazard due to emission of CO2. To avoid this, Pozzolanic material is used as a substituted for OPC. These are activated by alkaline to form a gel known as aluminosilicate which acts as a binder in concrete. In this study cement is partially replaced by Silica fume (SF). The torsional behaviour of the conventional concrete and SF based geo-polymer concrete is tested with varying percentage of longitudinal reinforcement. The results were compared in terms of torque, twist, stiffness degradation, curvature ductility, torsional toughness and crack width.
The feasibility of using concrete containing recycled asphalt pavement (RAP) in concrete pavement applications was evaluated. Concrete containing 0, 10, 20, and 40% of RAP were produced in the laboratory and evaluated for their properties that are relevant to performance of concrete pavements. Results of the laboratory testing program indicate that compressive strength, splitting tensile strength, flexural strength, and elastic modulus of the concrete decreased as the percentage of RAP increased. The coefficient of thermal expansion and drying shrinkage did not appear to be significantly affected by RAP content. When a finite element analysis was performed to determine the maximum stresses in typical concrete pavements in Florida under critical temperature and load conditions, the maximum stresses in the pavement were found to decrease as the RAP content of the concrete increased, due to a decrease in the elastic modulus of the concrete. Though the flexural strength of the concrete decreased as RAP was incorporated in the concrete, the resulting maximum stress to flexural strength ratio for the concrete was reduced as compared with that of a reference concrete with no RAP. This indicates that using a concrete containing RAP could possibly result in improvement in the performance of concrete pavements.
Reclaimed Asphalt Pavement (RAP) is the result of removing old asphalt pavement material. RAP consists of high quality well-graded aggregate coated with asphalt cement. The removal of asphalt concrete is done for reconstruction purposes, resurfacing, or to obtain access to buried utilities. The disposal of RAP represents a large loss of valuable source of high quality aggregate. This research investigates the properties of concrete utilizing recycled reclaimed asphalt pavement (RAP). Two control mixes with normal aggregate were designed with water cement ratios of 0.45 and 0.5. The control mixes resulted in compressive strengths of 50 and 33 MPa after 28 days of curing. The coarse fraction of RAP was used to replace the coarse aggregate with 25, 50, 75, and 100% for both mixtures. In addition to the control mix (0%), the mixes containing RAP were evaluated for slump, compressive strength, flexural strength, and modulus of elasticity. Durability was evaluated using surface absorption test.
The use of sustainable technologies such as supplementary cementitious materials (SCMs), and/or recycled materials is expected to positively affect the performance of concrete mixtures. However, it is imperative to qualify and implement such mixtures in practice, if the required specifications of their intended application are met. This paper presents the results of a laboratory investigation of self-consolidating concrete (SCC) containing sustainable technologies. Twelve mixes were prepared with different combinations of fly ash, slag, and recycled asphalt pavement (RAP). Fresh and hardened concrete properties were measured, as expected the inclusion of the sustainable technologies affected both fresh and hardened concrete properties. Analysis of the experimental data indicated that inclusion of RAP not only reduces the ultimate strength, but it also affected the compressive strength development rate. The addition of RAP to mixes showed a consistent effect, with a drop in strength after 3, 14, and 28 days as the RAP content increased from 0 to 50 %. However, most of the mixes satisfied SCC fresh properties requirements, including mixes with up to 50 % RAP. Moreover, several mixes satisfied compressive strength requirement for pavements and bridges, those mixes included relatively high percentages of SCMs and RAP.
Reclaimed Asphalt Pavement (RAP) recycling in pavement engineering can be actually carried out by means of hot recycling and cold recycling. An additional option arise from mixing with natural aggregates to build the sub-base layer. This paper shows the first results of a research activity undertaken on a test track specifically constructed with the aim to analyze the effect on pavement performance of a sub-base layer mixture with 50% of natural aggregates and 50% of RAP. The investigation is based on LWD and FWD analysis, comparing results with those obtained on the subsequent section of the test track made by only natural aggregates.
This article intends to quantify the reaction extents of cement grains and fly-ash (FA) particles in blended cement pastes during their hardening process. To this aim, a synthetic model for cement hydration extent in blended pastes is established taking into account the dilution effect, local w/c augmentation effect as well as heterogeneous nucleation effect of FA particles. Then the cement hydration and FA reaction extents of blended cement pastes with two w/b ratios (0.3, 0.5) and four FA contents (0%, 20%, 40%, 60%) are investigated. The non evaporable water content (Wn) and calcium hydroxide content (CH) were measured by thermal gravity analysis (TGA) and the FA reaction extent was quantified by the selective dissolution method. On the basis of these experimental data, the cement hydration extent and FA pozzolanic reaction extent are determined from both experimental approach and model-based approach. From the results, it is observed that local w/c, heterogeneous nucleation effects and FA hydration have comparable contribution to the total Wn content in blended pastes while the FA hydration dominates in CH content. Furthermore, the good agreement between the experimental hydration extents and model-based extents validates the established synthetic model for cement hydration extent in blended pastes.
Recycled asphalt pavement (RAP) is the removed and/or reprocessed pavement material containing asphalt and aggregate. The use of RAP in asphalt pavement has become common practice in the construction of new, and reconstruction of old, hot-mix asphalt (HMA) pavements. However, little research has been done to examine the potential of incorporating RAP into Portland cement concrete (PCC) to replace virgin aggregate. In a previous study by the first two of the current authors, laboratory-prepared RAP was used to investigate the potential use of RAP in PCC. The present study focused on the evaluation of mechanical properties of PCC made with real RAP materials through laboratory experiments. Two types of RAP materials (coarse and fine RAP) were used to replace an equal amount of virgin coarse and/or fine aggregate. Silica fume and high-range water-reducing agent (HRWRA) were also added into concrete mixtures to minimise the strength loss resulting from the incorporation of RAP. A total of 17 concrete batches were cast and evaluated for compressive and split tensile strengths, static compressive modulus of elasticity and toughness index. Test results indicated that there was a systematic reduction in the
strengths and elastic modulus as well as an increase in the toughness index with the increase in RAP content. While the addition of HRWRA into the matrix improved the mechanical properties of concretes containing RAP, addition of silica fume did not.
Sugar cane bagasse ash, a byproduct of sugar and alcohol production, is a potential pozzolanic material. However, its effective application in mortar and concrete requires first the controlled use of grinding and classification processes to allow it to achieve the fineness and homogeneity that are required to meet industry standards. The present paper investigates the role of mill type and grinding circuit configuration in grinding in laboratory- and pilot plant-scale on the particle size, specific surface area and pozzolanic activity of the produced ashes. It was observed that, although different size distributions were produced by the different mills and milling configurations, the pozzolanic activity of the ground ash was directly correlated to its fineness, characterized by its 80% passing size or Blaine specific surface area. From a low pozzolanic activity of less than 50% of the as-received ash, values above 100% could be reached after prolonged grinding times. Electric power requirements to reach the minimum pozzolanic activity were estimated to be in the order of 42 kWh/t in an industrial ball mill. Incorporation of an ultrafinely-ground ash in a high-performance concrete in partial replacement of Portland cement (10, 15 and 20% by mass) resulted in no measurable change in mechanical behavior, but improved rheology and resistance to penetration of chloride ions.
It is necessary to establish the material design system for the utilization of large amounts of fly ash as blended cement instead of disposing of it as a waste. Cement blended with fly ash is also required as a countermeasure to reduce the amount of CO 2 generation. In this study, the influences of the glass content and the basicity of glass phase on the hydration of fly ash cement were clarified and hydration over a long curing time was characterized. Two kinds of fly ash with different glass content, one with 38.2% and another with 76.6%, were used. The hydration ratio of fly ash was increased by increasing the glass content in fly ash in the specimens cured for 270 days. When the glass content of fly ash is low, the basicity of glass phase tends to decrease. Reactivity of fly ash is controlled by the basicity of the glass phase in fly ash during a period from 28 to 270 days. However, at an age of 360 days, the reaction ratios of fly ash show almost identical values with different glass contents. Fly ash also affected the hydration of cement clinker minerals in fly ash cement. While the hydration of alite was accelerated, that of belite was retarded at a late stage.
Recycled asphalt pavement (RAP) is the removed and/or reprocessed pavement material containing asphalt and aggregate. The use of RAP in asphalt pavement has become a common practice in the construction of new, and reconstruction of old, hot mix asphalt (HMA) pavements. But little research has been done to examine the potential of incorporating RAP into concrete. Since RAP contains asphalt, it is very likely that the toughness of concrete made with RAP could be improved. In the present study, the mechanical properties of RAP-incorporated Portland cement concrete were investigated through laboratory experiments. Two types of RAP (coarse and fine RAP) materials were considered. The results from this study indicated that RAP could be incorporated into Portland cement concrete without any modification to the conventional equipment or procedures. Without any treatment, there was a systematic reduction in the compressive and split tensile strengths with the incorporation RAP in concrete. Notably, the energy absorbing toughness for the RAP incorporated concrete has been significantly improved.
Recycled asphalt pavement (RAP) is the reclaimed and reprocessed pavement material containing asphalt and aggregate. Most RAP is recycled back into pavements, and as a result there is a general lack of data pertaining to the mechanical properties for RAP in other possible applications such as Portland cement concrete. In the present study, some mechanical properties of Portland cement concrete containing RAP as coarse aggregate were investigated in the laboratory. Six concrete mixes of widely differing water/cement ratios and mix proportions were made using RAP as coarse aggregate. The properties tested include the physical properties of the RAP aggregate, the compressive and flexural strengths of the concrete. These properties were compared with those of similar concretes made with natural gravel aggregate. Results of the tests suggest that the strength of concrete made from RAP is dependent on the bond strength of the asphalt-mortar (asphalt binder-sand-filler matrix) coatings on the aggregates and may not produce concrete with compressive strength above 25 MPa. However, for middle and low strength concrete, the material was found to compare favorably with natural gravel aggregate.
Poor affinity of asphalt toward mortar paste has been testified as the primary reason for reducing the reclaimed asphalt pavement (RAP)–inclusive concrete properties, although the effect of dust present in RAP aggregates due to extraction of RAP using demolition techniques has not been investigated so far. The present paper discusses the effect of different extraction methods on the mechanical properties of fine RAP aggregates. Also, the effect of incorporation of fine RAP aggregates on fresh, mechanical, and durability properties of concrete
has been investigated. It was found that as the substitution level of fine natural aggregates (NA) by fine RAP (0, 25, 50, 75, and 100%) increases, the properties of concrete tend to decrease gradually. From the present laboratory investigation, it is learnt that 50% fine RAP (extraction made using demolition technique) can be used for construction of major highways, whereas 100% fine RAP may be suggested for less important roads and in lower layers of pavement.
The presence of asphalt film around Reclaimed Asphalt Pavement (RAP) aggregates has been reported as the main factor lowering the properties of RAP inclusive concrete. A novel Abrasion and Attrition (AB&AT) technique to improve the quality of RAP by removing the contaminant layers of dust and punching the asphalt film adhering to RAP aggregates is introduced in this paper. The effect of incorporating Dirty RAP (DRAP), Washed RAP (WRAP) and AB&AT treated RAP, on the fresh, mechanical and durability properties of concrete are also investigated and compared with each other. The mechanical properties of RAP aggregates were found to be increased significantly on processing with AB&AT method. Beneficiation of RAP by AB&AT method increased the compressive strength of concrete by 9.74% &12.71%, split tensile by 2.66% &12.21% and flexural strength by 6.05% & 8.55% as compared to WRAP and DRAP inclusive concrete. Incorporation of RAP into concrete mix improved workability & cohesiveness. Durability properties of concrete such as water absorption, initial rate of water absorption, total permeable voids and coefficient of water absorption were observed to be reduced for RAP inclusive concrete.
This paper intends to evaluate the real influence of a commercial densified silica fume (SF) and of recycled concrete aggregates (RA) on the behaviour of high-performance concrete (HPC). For that purpose, three families of concrete with 0%, 5% and 10% silica fume (SF) of the binder’s mass were produced. In addition to the commercial silica fume, fly ash (FA) and superplasticizer (SP) were also incorporated in the concrete mixes. Each type of concrete comprises a reference concrete (RC) and three recycled aggregates concrete (RAC) mixes with replacement percentages (in volume) of fine natural aggregates (FNA) with fine recycled aggregates (FRA) and of coarse natural aggregates (CNA) with coarse recycled aggregates (CRA) of 50/50, 0/100 and 100/100, respectively. Considering the mechanical performance and durability of the concrete mixes, results show that it is possible to incorporate significant amounts of FRA and CRA. Regarding the silica fume, the densification process used in its manufacture seems to lead to the formation of agglomerates that change the real particle size of the SF, originating a loss of performance of the concrete made with them.
Influence of bacteria on strength and permeation characteristics concrete incorporating silica fume (SF) as a substitution of cement has been investigated in this study. The cement was partially substituted with 5, 10 and 15% SF and with constant concentration of bacterial culture, 105 cfu/mL of water. Cement was substituted with silica fume in concrete by weight. At 28 d, nearly 10–12% increase in compressive strength was observed on incorporation of bacteria in SF concrete. At 28 d, the compressive strength of concrete increased from 32.9 to 36.5 MPa for SF, 34.8 to 38.4 MPa for SF5, 38.7 to 43.0 MPa for SF10 and 36.6 to 40.2 MPa for SF15 on addition of bacteria. Water absorption, porosity and capillary water rise reduced in the range of 42–48%, 52–56% and 54–78%, respectively, in bacterial concrete compared to corresponding nonbacterial samples at 28 days. Reduction in chloride permeability of bacterial concrete was observed and the total charge passed through bacterial concrete samples reduced by nearly 10% compared to nonbacterial concrete samples at 56 d of age. At 28 d, total charge passed through concrete reduced from 2525 to 1993 C for SF, 1537 to 1338 C for SF5, 961 to 912 C for SF10 and 1186 to 1174 C for SF15 on addition of bacteria. Calcite precipitation on addition bacteria and confirmed by SEM and XRD analysis is considered as the reason for improvement in properties of concrete. Economic study of bacterial SF concrete has also been carried out in the present work. The Benefit/Cost Ratio of bacterial SF concrete got reduced with the increase in SF quantity. Compared to control concrete, bacterial SF concrete containing 10% silica fume demonstrated highest benefit in improvement in its properties and corresponding highest Benefit/Cost Ratio.
This paper first addresses the effect of steel and forta-ferro fibers on the mechanical properties of high-strength concrete, and then, investigates the effect of silica fume and nano-silica on the mechanical properties of the fiber-reinforced concrete. In total, 230 concrete specimens were produced in two stages and subsequently tested; in the first stage of specimen production, hooked-end steel fibers with Vf of 0.5%, 0.75%, 1%, 1.25%, and 1.5%, and forta-ferro fibers with Vf of 0.2%, 0.35%, 0.5%, 0.65%, and 0.8% were added to concrete mixture, and in the second stage, silica fume with the weight percentage of 8%, 10%, and 12%, and nano-silica with that of 1%, 2%, and 3% were replaced the cement in mixtures with a fixed volume fraction of both fibers. The aim was to study the mechanical properties of the fiber-reinforced concrete including compressive strength, tensile strength, modulus of elasticity, water absorption, and density, and to propose equations for predicting the compressive and tensile strength and the modulus of elasticity of the fiber-reinforced concrete with no pozzolan.
Accelerated carbonation of plain cement concrete and concrete with fly-ash replacing cement partially, is discussed in the present paper. Mechanical properties such as compressive strength, flexural strength, modulus of elasticity, durability aspects such as depth of carbonation and porosity of carbonated concrete are studied. To study the influence of water binder ratio on the above-mentioned properties, water-binder ratios of 0.35, 0.50 and 0.65 are used. It is observed that the mechanical properties of carbonated concrete have increased with the duration of carbon dioxide exposure. So did the depth of carbonation, whereas the volume of permeable voids has reduced leading to the decrease in porosity. An expression to predict the depth of carbonation of fly-ash concrete has also been developed.
The effect of substitution the slag with silica fume on compressive strength and permeability of alkali activated slag concrete has been examined and analyzed in this study. The use of alkali activated slag concrete is one of the strategies for production of environmentally friendly concrete which is produced through activation of adhesion feature of blast furnace slag in an alkaline solution. Alkali activated slag concrete with a proper mixture shows superior mechanical properties and durability compared to traditional normal Portland cement concrete. For cases in which AAS concrete with higher performance and durability is needed, AAS concrete with silica fume can be considered as a possible alternative. Since the permeability plays an effective role in concrete durability, this research was carried out to examine the effect of using silica fume on permeability of alkali activated slag concrete by substitution of three levels of silica fume including 5 wt%, 10 wt% and 15 wt% of slag. The effects of two types of curing conditions including water curing and curing under plastic cover were also examined. Short-term and final water absorption, penetration of chloride ion and depth of penetration of water were measured to examine the permeability. The effect of these factors on compressive strength was examined and the relation between compressive strength and passing electrical charges and depth of water penetration was also evaluated. To contrast the use of silica fume on internal characteristics of concrete, samples were observed by scanning electron microscopy (SEM). The results showed that the application of silica fume could increase compressive strength and reduce the permeability of alkali activated slag concrete and water curing was the most appropriate type of curing.
Based on its high content in amorphous silica (SiO2 > 70 wt.%), waste glass is an excellent material for valorization into pozzolanic nanoparticles or the so-called “glass fume” (GF). GF, produced using a scalable radiofrequency induction-coupled-plasma (RF ICP) spheroidization technology, mainly consists in an emulation of silica fume (SF) composed of spherical and amorphous silica-based nanoparticles (dia. of 30–200 nm). To test the impact of GF on the mechanical and durability properties of cement-based materials, compressive strength and rapid chloride ion penetration tests (RCPT) were conducted on high-performance concrete (HPC). Meanwhile, measurements of the resistances to alkali-silica reaction (ASR) and to sulfate attack were performed on mortar bars.
As SF, GF increased the compressive strength of HPC at early age (<7 days) by its nucleation and filler effects, but also its high alkali content (11–12 wt.%). At late age (>28 days), GF is characterized by a slower pozzolanic reactivity than SF. However, GF-contained HPC achieve similar compressive strength than SF-contained HPC after 91 days of curing.
At early age, GF-contained HPC and mortars yielded lower durability properties (RCPT, ASR and sulfate attack) than SF-contained HPC and mortars due to the slower pozzolanic reactivity of GF. In fact, they yielded similar durability properties compared to the plain cement HPC and mortars (control mixtures). At late age, the alkalinity of the pore solution is reduced and the cement paste is densified by the pozzolanic calcium silicates hydrates (C-S-H) and the durability properties are greatly improved with respect to a control HPC.
In order to make our environment green, a lightweight inorganic aluminosilicate polymer uses waste fly ash as source material instead of cement in concrete. Source material in combination with sodium-based alkaline liquid form a cement free material called geopolymer. This paper briefly presents the thermal performance of fly ash-based geopolymer mortar such as heat resistance behavior, thermal conductivity, compressive strength and dry density under different curing regime such as ambient temperature, heat chamber, hot air oven and autoclave. Here the silicate to hydroxide ratio was fixed as 2.5 and liquid to flyash ratio was taken as 0.4 throughout the process. From the results it was found that among all curing conditions, hot air oven curing shows best outcome. On further study it was found that specimen placed in hot air oven at 80°C for 6 hours gives higher compressive strength of 27.20MPa with the dry density of 1875kg/m³ and also thermal conductivity of 0.340W/mK than 24 hours curing for 1 day which make geopolymer as more energy efficient material.
This study presents the results of laboratory investigation of fresh, hardened and durability characteristics of self-consolidating concrete (SCC) containing high volume of supplementary cementitious materials (SCMs) including class C fly-ash (FA) and slag (S) with recycled asphalt pavement (RAP) aggregate. Sixteen mixtures were prepared with different percentages of FA, S, and RAP. SCC mixtures were divided into four groups where each group had a different percentage of RAP replacing NCA (0%, 15%, 30%, 50%) and Portland cement being replaced by different percentages of SCMs (0%, 75% FA, 75% S and combination of 37.5% FA and 37.5% S). The water to cementitious material (w/cm) ratio for SCC mixtures in this study was maintained to be 0.4 with a target slump flow higher than 500 mm. The fresh concrete properties such as: flowability, deformability, filling capacity and resistance to segregation were measured. Moreover, hardened properties such as compressive strength at 3, 14 and 28 days and split tensile strength at 28 days were measured and durability characteristics including unrestrained shrinkage up to 90 days and chloride permeability resistance at 45 and 90 days were tested. The use of SCMs and RAP affected both the fresh and hardened properties of SCC. Analysis of experimental data showed that all the mixtures satisfied the SCC fresh properties requirements. The addition of RAP and SCMs had an adverse effect on both the compressive and tensile strength of concrete mixtures. However the use of SCMs has positive effects on the unrestrained shrinkage and permeability.
The abrasion erosion characteristics of concrete made from moderate heat Portland cement, fly ash, and silica fume were investigated via sandblasting test. In this study, the influences of fly ash, silica fume, impinging velocity and impinging angle on abrasion erosion resistance were taken into account. The test results indicated that the concrete fabricated with moderate heat Portland cement, fly ash and silica fume was applicable to the mass construction in need of either low hydration heat or high abrasion erosion resistance. The abrasion mass loss rate of concrete increased with the increasing of the impinging angle, and showed an exponential relation with the impinging velocity. Furthermore, the proposed method by Bitter and Neilson et al. was applied to analyze the abrasion erosion characteristics of concrete. The characteristics of each concrete mixture could be featured by four parameters ( , and n) according to this method, and they could be used for preliminarily predicting the abrasion erosion resistance of concrete.
The environmental footprint of agricultural production can vary significantly both between countries and within a country based on regional conditions and agricultural practices. A life cycle assessment approach was used to model fossil fuel energy inputs and greenhouse gas emissions associated with the production of sugarcane in South Africa. Results were calculated for sugarcane produced in two distinct regions, the irrigated North and the non-irrigated North Coast. Regional differences also include terrain, soil, and use of mechanization. Models were adapted to estimate the impacts of burning prior to harvest, leaving a biomass mulch blanket with green cane harvesting, and increasing the level of mechanization for harvest and other field operations. Irrigation contributes to a higher energy input in the irrigated North but differences are mitigated by the lower fertilizer, agro-chemical, and diesel use per ton of sugarcane produced there. Despite higher energy inputs in the irrigated North, greenhouse gas emissions are similar for sugarcane produced in each region. Green cane harvesting reduces energy inputs and greenhouse gas emissions by 4% and 16%, respectively, in both regions. Impacts of mechanization on soil compaction and stool damage result in lower yields and proportionally higher energy inputs and greenhouse gas emissions. Results demonstrate the potential for variability in LCA results based on regional differences in production practices within a country.
Expansion of sugarcane production for satisfying food and bioenergy demands along with decreasing availability of agricultural workers brings about the concerns on changing the traditional sugarcane cultivation and harvesting practice to mechanization. The study aims to assess the effect on climate change impact via life cycle greenhouse gas emissions along with harvesting costs from 5 current sugarcane harvesting practices in the central region of Thailand. The results show that harvested green cane using cutting machines has moderate greenhouse gas (GHG) emissions as compared to the other options but it has the highest harvesting cost due to the need for hiring cutting machines which can be quite expensive. Moreover, the insufficient availability of cutting machines in some areas has created a problem of system management. This has led farmers to choose the burning of cane as per the past practice due to the ease of finding labor. Therefore, it could be recommended that the actual cost of mechanized harvesting and good management of cutting machine services should be considered if we need to increase mechanical harvesting. There is no significant difference in the greenhouse gas emissions of various harvesting practices as the largest greenhouse gas emissions are actually from the land preparation stage. Even though the harvesting stage does not contribute much to the greenhouse gas emissions, there is still an opportunity for improvement of both GHG and cost performance for which measures are recommended. In addition, there is a need for further study on its contribution to other impacts such as microbiological properties of the soil and local air pollution from sugarcane trash burning.
The main objective of this research is to investigate the potential use of reclaimed asphalt pavement (RAP) as an aggregate in portland cement concrete (PCC). RAP aggregate finer than #4 (4.75 mm) sieve was treated as fine materials while those particles passing 3/4 inch (19.05 mm) and retained on #4 sieve were treated as coarse aggregate. One set of concrete cylinders was prepared using 100, 75, 50, 25, and 0 percent RAP as coarse aggregate while fine aggregate was 100 percent RAP. Another set of samples was made using 100, 75, 50, 25, and 0 percent RAP as fine aggregate while coarse aggregate was 100 percent RAP. Samples were prepared using water-cement ratios of 0.40 and 0.50. In addition, control mixtures containing 100 percent conventional aggregate (gravel and sand) were made for comparison purposes. Higher compressive strength was obtained as the percentage of RAP aggregate was decreased for all mixtures. Tne control specimens yielded the highest compressive strength. However, the strength was sufficient to qualify the use of RAP aggregate in concrete applications such as barriers, sidewalks, driveways, curbs, pipes, and gutters. Furthermore, mixtures containing RAP aggregate had enhanced ductility and showed excellent shatter resistance properties. Additional studies should investigate the use of additives and admixtures with RAP aggregate.
This study was focused on evaluating the feasibility of using minimally processed reclaimed asphalt pavement (RAP) as aggregate replacement in concrete pavements. A statistical experimental design procedure (response surface methodology) was used to investigate the effects of key mixture parameters on concrete responses. The response surfaces generated from this analysis adequately characterized the behavior of these concrete mixtures, and were ultimately used to develop optimum mixtures to meet varying performance criteria. In laboratory tests, the optimum mixtures performed well and as predicted, thus validating the feasibility of using RAP in this application and this mixture design methodology.
Steel furnace slag (SFS) is an industrial by-product that is used as an abrasion-resistant aggregate in asphalt pavement surfaces. However, SFS has found limited application in concrete pavements because of its potential for expansion from hydration of the free calcium and magnesium oxides present in the slag. This study investigated the application of asphalt-coated SFS aggregates, i.e., coarse fractionated reclaimed asphalt pavement (FRAP), as an aggregate in concrete. Autoclave expansion testing of SFS FRAP samples and chemical analyses revealed that the SFS FRAP contains residual free calcium oxide and therefore has the potential to expand, although the presence of the asphalt coating reduced the overall expansion magnitude. The performance of SFS FRAP in concrete at 20% and 50% replacements was similar to concrete with unexpansive dolomite FRAP in terms of strength and fracture properties, though the SFS FRAP may cause higher shrinkage strains and reduced freeze/thaw durability. Therefore, application of SFS FRAP with low autoclave expansion, but available free oxides should be limited for use in concrete but may be suitable for nonstructural applications or temporary roads. With further standardized expansion testing, SFS FRAP may be suitable for use as an unbound foundation material or again as an aggregate in a bound asphalt layer.
Steel furnace slag (SFS) is an industrial by-product that is not commonly utilized in bound applications because of its potential to contain high contents of free calcium and magnesium oxides, which expand when hydrated. In this study, a process was developed to quickly screen SFS aggregates for free oxide contents and expansion potential using complexometric titration, thermogravimetric analysis, and an autoclave expansion test. Two of the three SFS aggregate sources (high and low expansion) were selected for testing as a coarse aggregate in concrete. It was confirmed that SFS aggregates in concrete can produce acceptable strength properties, suitable freeze/thaw durability, and exceptional fracture properties. However, these SFS aggregates produced greater free drying shrinkage than concrete with dolomite aggregates. For SFS aggregates having low expansion potential, the hardened property tests indicate that SFS may be a suitable aggregate for concrete.
By-products from a number of industrial processes are used as alternative supplementary cementitious materials in concrete. Sugarcane bagasse ash is mainly composed of amorphous silica and can be used as a pozzolanic material in concrete. Production of sugarcane bagasse ash (SCBA) based blended cements with different replacement levels of SCBA, and the performance of concrete with these cements in terms of compressive strength, heat of hydration, drying shrinkage and durability are discussed in this paper. Durability performance was investigated by five different methods in this study, namely Oxygen permeability test, Rapid chloride penetration test, Chloride conductivity test, Water sorptivity test, DIN water permeability test and Torrent air permeability test. The results from this study show that use of sugarcane bagasse ash in concrete prominently enhances its performance. Low heat of hydration, additional strength gain due to pozzolanic reaction, significant reduction in permeability because of pore refinement and similar drying shrinkage behavior were observed for bagasse ash blended concrete compared to control concrete.
Construction and Demolition (C&D) materials are increasingly used as construction materials in engineering applications. Their usage currently includes applications such as pavements, ground improvement, engineered fills, pipe bedding, backfill and aggregates in concrete. A comprehensive laboratory evaluation of physical and shear strength characteristics of recycled C&D materials was undertaken using gradation, Los Angeles Abrasion, unconfined compression, California Bearing Ratio (CBR), direct shear and consolidated drained triaxial tests. The recycled C&D materials evaluated were recycled concrete aggregate (RCA), crushed brick (CB), reclaimed asphalt pavement (RAP), waste excavation rock (WR), fine recycled glass (FRG) and medium recycled glass (MRG). All the recycled C&D materials are classified as well-graded materials and their compaction curves are controlled by water absorption and surface characteristics. RAP, FRG and MRG exhibit flat compaction curves while RCA, WR and CB exhibit bell-shaped compaction curves. The shear responses of the recycled C&D materials are classified into two groups: dilatancy induced peak strength and dilatancy associated strain-hardening behaviors. RCA, WR and CB are dilatancy induced peak strength materials in that their peak strength is clearly observed after the maximum dilataiicy ratio occurs. Higher dilatancy ratios in these materials are associated with higher peak friction angles. RAP, FRG and MRG on the other hand are dilatancy associated strain-hardening materials, which exhibit strain-hardening behavior even with a relatively high magnitude of dilatancy. Based on the evaluation of the shear strength characteristics, it is ascertained that the compacted C&D materials have the potential to be used in pavement base/subbase applications as they have the required minimum effective friction angles. RCA, CB and WR in particular are found to also meet the physical and shear strength requirements for aggregates in pavement base/subbase applications.
A ternary-blend concrete (65% cement, 25% slag, and 10% fly ash) containing fractionated reclaimed asphalt pavement (FRAP) as a partial replacement (0, 20, 35, and 50%) for coarse aggregate was investigated through a comprehensive laboratory testing program. With increasing FRAP replacement, the concrete workability increased, unit weight decreased, and air content was mainly unaffected. The source of the measured strength and modulus reductions was linked to the interface between the FRAP particle and the paste. The incorporation of FRAP did not significantly impact the concrete free drying shrinkage but did reduce the restrained ring shrinkage strains. The freezing-and-thawing durability was acceptable for all tested FRAP contents. Fracture results indicated that FRAP addition did not statistically affect the initial or total fracture energy of the concrete. Mixtures containing up to 50% coarse FRAP may be used in concrete pavement and still produce acceptable fresh and hardened properties.
Sugarcane bagasse ash is obtained as a by-product from cogeneration combustion boilers in sugar industries. Previous studies have reported that the use of sugarcane bagasse ash as supplementary cementitious material in the concrete can improve its properties. The utilization of bagasse ash has been
constrained because of inadequate understanding of the material and lack of suitable processing methodology for use in a large scale. Processing methods significantly influence the pozzolanic activity of
any supplementary cementitious material. Proper assessment of pozzolanic activity and processing
methodology of bagasse ash were not investigated in earlier research studies. This paper describes a
study that involves pozzolanic performance evaluation and microstructural characterization of sugarcane
bagasse ash for use as pozzolanic material in concrete. A comprehensive evaluation of pozzolanic activity
of sugarcane bagasse ash based on different processing methods including burning, grinding, complete
removal of coarse fibrous particles by sieving and combinations of these methods were examined in this
study. Suitable processing methodology to attain maximum pozzolanic activity of sugarcane bagasse ash
with minimum level of processing is described in this paper
Sugarcane bagasse ash is obtained as a by-product from cogeneration combustion boilers in sugar industries. Previous studies have reported that the use of sugarcane bagasse ash as supplementary cementitious material in the concrete can improve its properties. The utilization of bagasse ash has been constrained because of inadequate understanding of the material and lack of suitable processing methodology for use in a large scale. Processing methods significantly influence the pozzolanic activity of any supplementary cementitious material. Proper assessment of pozzolanic activity and processing methodology of bagasse ash were not investigated in earlier research studies. This paper describes a study that involves pozzolanic performance evaluation and microstructural characterization of sugarcane bagasse ash for use as pozzolanic material in concrete. A comprehensive evaluation of pozzolanic activity of sugarcane bagasse ash based on different processing methods including burning, grinding, complete removal of coarse fibrous particles by sieving and combinations of these methods were examined in this study. Suitable processing methodology to attain maximum pozzolanic activity of sugarcane bagasse ash with minimum level of processing is described in this paper.
An experimental study investigated the California bearing ratio (CBR), shear strength, stiffness, and cyclic creep properties of crushed, reclaimed asphalt concrete pavement (RAP) — natural aggregate blends for granular base and subbase. The CBR was found to depend on the properties of the constituent materials and the compactive effort used to prepare the specimens. It was concluded that the CBR test may not be appropriate for evaluating the suitability of blended material for granular base construction. Based on the triaxial tests, it was observed that the addition of RAP to natural aggregate (Ontario Granular A) reduces the shear strength slightly and tends to increase the accumulated strain (deformation) that develops due to repetitive loading. The influence of RAP on the mechanical properties, including ‘elastic’ modulus, was sensitive to specimen preparation and preconditioning. For certain combinations of RAP and Granular A, the mechanical properties were similar to those of Granular A. The key to a stable blend was found to be compactive effort.
Nowadays, environmentally friendly building is becoming a crucial issue in construction industry. The course towards sustainable concrete involves mainly minimizing the environmental impact of concrete production by substituting virgin mineral materials by recycled ones as well as reducing the global CO2 emissions. The approach adopted here includes a large substitution of natural coarse aggregates (NA) by recycled concrete aggregates (RCA) obtained from crushed concrete debris, as well as the use of 30% fly ash (FA) as a partial substitute of Portland cement for FA concrete production.Previous study by the authors has revealed the potential of using coarse RCA to produce concrete with a similar 28-day design strength to that obtained when using natural aggregates. This paper discusses the effect of both partial and full replacement of natural coarse aggregates by coarse RCA in a fly ash concrete. Engineering properties and durability performance have been examined on both concrete types (Portland cement and fly ash) for mixes designed with various proportions of the RCA (0%, 30%, 50% and 100%) by mass. The results obtained showed that while embedding high amount of the RCA could lower the resistance to chloride penetration and carbonation of concrete still comparable design strength to that of the control mix might be achieved.
This paper summarizes the research carried out to compare the performance of foamed asphalt pavement mixes with conventional crushed aggregate for the construction of road bases. The research work focused on the investigation and evaluation of the feasible use of foamed asphalt technology for Saudi roads using marginal quality construction materials, marl, and reclaimed asphalt pavement (RAP) materials for local applications. Materials included the Ministry of Transport (MOT) granular base class A and B, subbase material class B, and reclaimed asphalt pavement (RAP) material. Foamed asphalt mixes were designed for subbase class B (foamed SB) and RAP (foamed RAP) material utilizing low percentage of Portland cement. Foamed asphalt mixes were optimized to meet dry and wet indirect tensile strength (ITS) requirements. Designed mixes in addition to granular base class A and B were evaluated for CBR, dynamic resilient modulus at 25 °C and wheel tracking test dry at 50 °C and soaked at 22 °C.Results indicate that base class A has the lowest rutting followed by base class B then foamed SB and finally foamed RAP for dry condition at 50 °C, while foamed RAP has the lowest rutting followed by foamed SB then base class B and finally class A for soaked condition at 22 °C. Portland cement was effective in reducing ITS loss of foamed asphalt mixes. Resilient modulus testing indicated that SB mix has behavior comparable to base class A. Foamed RAP mix has shown the best behavior. Saturation has reduced resilient modulus of all mixes significantly. Foamed asphalt technology can be used successfully to construct road bases from locally available marginal or recycled materials.
The pore structure of cement pastes incorporating fly-ash was evaluated during their hydration process through gravimetry method, mercury intrusion porosimetry (MIP) and nitrogen adsorption/desorption (NAD) methods. The pore structure of samples is characterized by the total porosity, pore size distribution (PSD), pore internal surface area as well as characteristic pore sizes. The correlation between the hydration process and the formed pore structure is investigated. The results indicate that: (i) w/b ratios have determinant impact on all characteristics of pore structure; (ii) fly-ash replacement ratio can influence the pore structure significantly at early age but this influence becomes less important with sample age by fly-ash hydration process; (iii) the total porosity and specific surface area are well correlated with the chemical kinetics of hydration through hydration degree or the formed gel/space ratio but the critical pore size is rather independent on the chemical kinetics.
Although fly ash has been widely used in concrete as a cement replacement, little work has been done on determining the degree of hydration of high-volume fly ash/cement (FC) systems. In the present study, the degree of hydration of the cement in Portland cement (PC) paste was obtained by determining the non-evaporable water (Wn) content. The degree of reaction of the fly ash in FC pastes was determined using a selective dissolution method. Based on the relation between the degree of cement hydration and effective water-to-cement (w/c) ratio, the degree of hydration of the cement in FC pastes was also estimated. It was found that high-volume fly ash pastes underwent a lower degree of fly ash reaction, and in the pastes with 45% to 55% fly ash, more than 80% of the fly ash still remained unreacted after 90 days of curing while the hydration of the cement in high-volume fly ash pastes was enhanced because of the higher effective w/c ratio for the paste. This effect was more significant for the pastes with lower water-to-binder (w/b) ratios. Thus, preparing high-volume fly ash concrete at lower w/b ratios can result in less strength losses. This paper also introduces a model to describe the relationship between the w/c ratio and the degree of cement hydration and gel/space ratio. The gel/space ratios of the FC pastes, evaluated based on the proposed model, were found to be consistent with the gel/space ratio of PC pastes in terms of the relationship with compressive strength. The gel/space ratio data correlated (inversely) linearly with mercury intruded porosity, but the former correlated more with compressive strength than the latter.
In many countries there is a trend to recycle wastes obtained during pavement maintenance or reconstruction, and to forbid the landfill of these products. Thus, in some circumstances it can be tempting to use reclaimed asphalt pavement (RAP) in new hydraulic concrete mixtures. This paper presents experimental data and modelling about the effect of RAP incorporation on cement concrete mechanical properties (compressive strength, tensile strengths and E-modulus). All these properties tend to decrease with the rate of RAP dosage, and with temperature. Then attempts are made to adapt LCPC mix-design models to these innovative concretes. Two alternative hypotheses are evaluated. In the first one, RAP aggregate is viewed as composite particles playing the role of an homogenous aggregate having lower bond, strength and E-modulus as compared to normal aggregate. In the second one, the bitumen phase is assumed to be finely dispersed within the cement paste, acting as a supplementary dosage of water (or air). According to the simulations, the second hypothesis is the best one. This finding extends the scope of application of modern mix-design methods, and will help in using RAP in cement concrete, for the technical, economical and environmental benefit of the road community.
Effect of lime:silica ratio on the kinetics of the reaction of silica with saturated lime has been investigated. Below C/S=0.65 the reaction does not proceed to completion and even in the presence of a large excess of silica only 90% lime is consumed. A parameter, lime reactivity index, has been defined to quantity the reactive silica present in rice husk ash. The product of the reaction between rice husk ash and saturated lime is a calcium hydrosilicate, CSH(I)∗∗. The fibrilar structure and the hollow tubular morphology of the fibres of CSH, have been explained by a growth mechanism, where the driving force is osmotic pressure.
The utilization of waste materials in concrete manufacture provides a satisfactory solution to some of the environmental concerns and problems associated with waste management. Agro wastes such as rice husk ash, wheat straw ash, hazel nutshell and sugarcane bagasse ash are used as pozzolanic materials for the development of blended cements. Few studies have been reported on the use of bagasse ash (BA) as partial cement replacement material in respect of cement mortars. In this study, the effects of BA content as partial replacement of cement on physical and mechanical properties of hardened concrete are reported. The properties of concrete investigated include compressive strength, splitting tensile strength, water absorption, permeability characteristics, chloride diffusion and resistance to chloride ion penetration. The test results indicate that BA is an effective mineral admixture, with 20% as optimal replacement ratio of cement.
This paper presents the results of experimental work on short- and long-term mechanical properties of high-strength concrete containing different levels of silica fume. The aim of the study was to investigate the effects of binder systems containing different levels of silica fume on fresh and mechanical properties of concrete. The work focused on concrete mixes having a fixed water/binder ratio of 0.35 and a constant total binder content of 500 kg/m3. The percentages of silica fume that replaced cement in this research were: 0%, 6%, 10% and 15%. Apart from measuring the workability of fresh concrete, the mechanical properties evaluated were: development of compressive strength; secant modulus of elasticity; strain due to creep, shrinkage, swelling and moisture movement. The results of this research indicate that as the proportion of silica fume increased, the workability of concrete decreased but its short-term mechanical properties such as 28-day compressive strength and secant modulus improved. Also the percentages of silica fume replacement did not have a significant influence on total shrinkage; however, the autogenous shrinkage of concrete increased as the amount of silica fume increased. Moreover, the basic creep of concrete decreased at higher silica fume replacement levels. Drying creep (total creep − basic creep) of specimens was negligible in this investigation. The results of swelling tests after shrinkage and creep indicate that increasing the proportion of silica fume lowered the amount of expansion. Because the existing models for predicting creep and shrinkage were inaccurate for high-strength concrete containing silica fume, alternative prediction models are presented here.
Various combinations of a local natural pozzolan and silica fume were used to produce workable high to very high strength mortars and concretes with a compressive strength in the range of 69–110 MPa. The mixtures were tested for workability, density, compressive strength, splitting tensile strength, and modulus of elasticity. The results of this study suggest that certain natural pozzolan–silica fume combinations can improve the compressive and splitting tensile strengths, workability, and elastic modulus of concretes, more than natural pozzolan and silica fume alone. Furthermore, the use of silica fume at 15% of the weight of cement was able to produce relatively the highest strength increase in the presence of about 15% pozzolan than without pozzolan. This study recommends the use of natural pozzolan in combination with silica fume in the production of high strength concrete, and for providing technical and economical advantages in specific local uses in the concrete industry.
Geopolymer materials based on natural zeolite
- A Nikoliv
- I Rostovsky
- H Nugteren
A. Nikoliv, I. Rostovsky, H. Nugteren, Geopolymer materials based on natural
zeolite, Case Study Constr. Mater. 6 (2017) 198-205.
Tentative guidelines for cement concrete mix design for pavements
IRC: 44, Tentative guidelines for cement concrete mix design for pavements.
Indian Road Congress (2008).
Method of Tests for Strength of Concrete
IS 516, Method of Tests for Strength of Concrete, Bureau of Indian Standards,
1959.