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Investigating porous concrete with improved strength: Testing at different scales
Abstract
Porous concrete incorporates a high percentage of meso-size air voids that makes its mechanical characteristics remarkably different from normal concrete. A research project was undertaken to design a special type of porous concrete, that fractures into small fragments when exposed to impact loading while having sufficient static strength, to be used in protective structures such as safety walls or storages for explosives. In the concretes designed, while a sufficient static strength was required, high porosity was essential to facilitate the formation of multiple cracks and the subsequent fracturing. Production of porous concretes having improved static compressive strengths was accomplished by modifying the mixture design and the compaction technique; while the design procedure was supported by macro and meso-scale mechanical testing, computed tomography, microscopy and X-ray diffraction analysis.
... Pervious concrete with uniformly distributed or, in other words, consistent cement paste all over the specimen is essential to optimize its performance. Consistency of cement paste relies mainly on the water cement ratio and admixtures, and on the type and amount of binder [29]. ...
... The porosity of pervious concrete is predominantly influenced by the size of aggregates, shape of aggregates, and nature of aggregates [47]. The grading of aggregates may decrease the porosity through better packing of the voids [29]. Li et al. [48] identified the particle size distribution and compaction as the most influencing factors with respect to porosity. ...
... Factors influencing performance of pervious concrete size of aggregates, the incorporation of single sized aggregates resulted in a narrow range of porosity in comparison with graded aggregates [29]. The use of blended aggregates, i.e. the aggregates with varied sizes, resulted in lower porosity due to the filling effect of smaller sized aggregates on the pores of larger sized aggregates [22]. ...
Factors influencing performance of pervious concrete Pervious concrete is an environment friendly solution for eliminating imperviousness-related drawbacks of conventional concrete. Pervious concrete mixes are predominantly composed of cement, coarse aggregate, and water. The partial or complete elimination of fine aggregate results in porous structure, which influences performance of pervious concrete. This article is aimed at reviewing major factors involved in the design of pervious concrete mixes, namely the compaction, aggregate to cementitious material ratio (ACR), sand fraction, water to cementitious material ratio (w/cm), size of coarse aggregate, and void ratio or porosity. The effects of various admixtures, replacement materials, and fibres, are also discussed. The results indicate that pervious concrete acts as an effective medium in promoting the sustainability of urban environments due to its multi-aspectual benefits. Pregled čimbenika koji utječu na svojstva poroznog betona Porozni (propusni) beton je ekološki prihvatljivo rješenje u odnosu na nepropusnosti konvencionalnih betona. Porozni beton najčešće se sastoji od mješavine cementa, krupnijeg agregata i vode. Djelomičnim ili potpunim uklanjanjem sitnog agregata dobiva se porozna struktura koja zatim utječe na svojstva poroznog betona. Cilj je ovog rada opisati glavne čimbenike koji utječu na mješavine poroznog betona, odnosno zbijenost, omjer agregata i cementnog materijala (ACR), udio pijeska, omjer vode i cementnog materijala (v/cm), veličina krupnog agregata i udio šupljina ili poroznost. Također, u radu se raspravlja i o učincima različitih dodataka, zamjenskih materijala i vlakana u mješavinama. Rezultati pokazuju da porozni beton djeluje kao učinkovit medij u promicanju održivosti urbanih sredina zbog svojih višestrukih koristi. Ključne riječi: porozni beton, poroznost, krupniji agregat, veličina agregata, vlakna, zbijanje
... However, the increased strength reduces water permeability of concrete. Researchers [33][34][35] have found that a higher compressive strength of pervious concrete is obtained by using coarse aggregates of different fractions, rather than by a single fraction, because the strength of pervious concrete is dependent on the size of the pores and the pore volume, which is reduced by aggregates of different particle sizes [36]. Various nano-components can be used to increase the compressive strength and durability of concrete, such as nano SiO 2 [37][38][39][40], fly ash [41], pelletized blast furnace slag [42], various types of polymeric fibre [31,34,41], and microfillers [43]. ...
... Researchers [33][34][35] have found that a higher compressive strength of pervious concrete is obtained by using coarse aggregates of different fractions, rather than by a single fraction, because the strength of pervious concrete is dependent on the size of the pores and the pore volume, which is reduced by aggregates of different particle sizes [36]. Various nano-components can be used to increase the compressive strength and durability of concrete, such as nano SiO 2 [37][38][39][40], fly ash [41], pelletized blast furnace slag [42], various types of polymeric fibre [31,34,41], and microfillers [43]. Nano SiO 2 has a big particle surface area and high pozzolanic activity, and thus speeds up the reaction with calcium hydroxide, increases the resulting amount of calcium hydrosilicates (CSH) [44,45], and increases early compressive strength [46][47][48]. ...
... Concrete made with a flowable binder may lose performance characteristics because the binder will concentrate on the bottom of the specimen [59]. The recommended W/C in [34] is from 0.27 to 0.34. The authors of [60] studied the effect of W/C ratio (0.30, 0.35, 0.38) and aggregate size on the properties of pervious concrete. ...
Pervious concrete (PCO) has many advantages and applications, such as water pooling reduction, noise attenuation, replenishment of groundwater reserves, etc. However, the use of pervious concrete is limited due to its low compressive strength and durability, especially as a result of portlandite leaching from concrete exposed to flowing water. The effects of active additives (nano SiO2 (NS) spent catalyst generated at the fluid catalytic cracking unit (FCCCw) and paper sludge waste burned at 700 °C (PSw)) along with particle size distribution of the coarse aggregate on the properties and durability of pervious concrete were determined in the research. Active additives used in the binder were found to reduce portlandite leaching from concrete exposed to flowing water to significantly increase the resistance of concrete to freezing and thawing cycles and to increase sound absorption, compressive strength and infiltration rate. In addition, industrial waste (FCCCw and PSw) used as active additives significantly reduced the use of clinker in concrete applied in the construction of water pervious systems. The coarse aggregate size distribution had the greatest effect on the density, ultrasound pulse velocity (UPV), porosity, compressive strength and infiltration rate of pervious concrete.
... The compaction of the pervious concrete is one of the problems faced during the construction of pervious concrete [8]. The compaction of pervious concrete affects the interlocking of aggregate and the contact area between cement paste and aggregate [9]. ...
... Better quality control under controlled conditions, early open to traffic, reduced laying time and costeffectiveness are some of the major benefits of using Pervious Interlocking Paver Block (PIPB) over conventional pervious concrete [16]. Extensive studies on the mechanical and frictional characteristics of the conventional pervious concrete are conducted in the past [1,3,5,8]. Even though adequate studies have been conducted on the application of conventional pervious concrete in low volume pavements [7,13,16]. ...
... Consequently it strengthens the Interfacial Transition Zone (ITZ) and increases the compressive strength of the mix. [8]. ...
h i g h l i g h t s Developed Pervious Interlocking Paver Blocks. Compared the influence of aggregate gradation. Described the mechanical functional and structural behaviour of PIPB. Concluded the PIPB as a superlative material than the conventional pervious concrete. a b s t r a c t Pervious concrete is one among the evolving sustainable pavement materials due to its unique storm water storage and ground water recharge applications. The present study aims to develop a Pervious Interlocking Paver Block (PIPB) and to study its mechanical, functional and structural performance. In the current explorative research work, the influence of aggregate gradation, and the percentage of fines on mechanical, functional and structural performance of PIPB were evaluated. The mechanical and functional properties such as compressive strength, split tensile strength, flexural strength, and skid resistance are assessed. The structural behaviour of the PIPB pavement section is found using plate load test and large-scale direct shear test. FEM based software, PLAXIS, is used to validate the test results. Infiltration test is conducted on the plate load test section to understand the infiltration rate. Finally, 2D image processing was performed using MATLAB to conclude the test findings. The test results proved that the grade III mix possesses desirable mechanical properties, lower deflection, higher shear strength, and required permeability. The present study affirms that the PIPB can be an effective pavement material for the low volume roads, urban heat island and pavements with drainage problems.
... Pervious concrete, an eco-friendly construction material is an amalgam of cement, water and coarse aggregate, without or with a little fine aggregate content (Aliabdo et al., 2018) which allows permeation of water through its pervious layers. The aggregates used in pervious concrete may be either narrow graded or single sized (Agar-Ozbek et al., 2013;Sonebi et al., 2016). The failure of pervious concrete initiates similar to the ordinary concrete but is highly influenced by the pore structure (Agar-Ozbek et al., 2013;Yeih et al., 2015). ...
... The aggregates used in pervious concrete may be either narrow graded or single sized (Agar-Ozbek et al., 2013;Sonebi et al., 2016). The failure of pervious concrete initiates similar to the ordinary concrete but is highly influenced by the pore structure (Agar-Ozbek et al., 2013;Yeih et al., 2015). The presence of voids in the structure minimises the thickness of cement paste coating all around the aggregates resulting in failure at the interface between aggregate and cement paste (Agar-Ozbek et al., 2013;Ramkrishnan et al., 2018). ...
... The failure of pervious concrete initiates similar to the ordinary concrete but is highly influenced by the pore structure (Agar-Ozbek et al., 2013;Yeih et al., 2015). The presence of voids in the structure minimises the thickness of cement paste coating all around the aggregates resulting in failure at the interface between aggregate and cement paste (Agar-Ozbek et al., 2013;Ramkrishnan et al., 2018). The strength properties of pervious concrete are predominantly defined by the compositional characteristics such as properties of cement (Torres et al., 2015), aggregates and its gradation (Agar-Ozbek et al., 2013;Grubeša et al., 2018). ...
Pervious concrete structure consists of meso-sized pores due to partial or complete elimination of fine aggregates, resulting in decreased mechanical properties in par with conventional concrete. Meanwhile, fibres were pronounced to improve the mechanical properties of concrete without affecting its durability. The main objective of the study is to compare the properties of basalt fibre-reinforced pervious concrete (BFRPC) and carbon fibre-reinforced pervious concrete (CFRPC) with two single-sized aggregates, namely 12.5 and 20 mm. The volume of both the fibres was varied from 0 to 0.4% at intervals of 0.1%. Pervious mix with 12.5 mm sized coarse aggregates and carbon fibre content of 0.2% (12.5CFRPC0.2) was observed as an optimum mix with respect to mechanical strengths as it improved the compressive strength, split tensile strength and flexural strength by 11.59%, 32.70% and 35.32%, respectively, compared with the conventional mix.
... Researchers have reported that the difference in density and porosity between field and laboratory prepared mixtures was as high as 45% [28]. Amongst the different compaction methodologies, hand-steel roller compaction is generally a low-energy efficient method used to compact PC material in the field, which is limited to sidewalks, pathways, and local streets [38,46]. The formation of rod holes is a common occurrence when PC is compacted with hand-steel tamping rod due to low slump of the mixture, resulting in highly inconsistent results [47]. ...
... Test results indicate that compressive strength of PC generally varies from 1 to 28 MPa [6,23,24,26,28,39,40,42,43,60,61,64,67,72,76,77], while higher compressive strength magnitudes have also been reported in some studies [38,46,62]. Studies have reported that the use of smaller sized aggregates augments the strength of PC, minimizes raveling, but compromises on its permeability [58,63]. ...
... It was further observed that compressive strength reduced by almost 50% when pore volume fraction was increased by 10%. Other researchers reported that crack propagation was predominant through the cement paste when fine grained aggregates of 2-4 mm sizes were used whereas crack propagation was principal through the aggregate grains when coarse particles of 4-8 mm sizes were adopted [46]. Similarly, lower cement content (150-250 kg/m 3 ) resulted in PC mixtures with low strength (1.06-6.95 ...
The objective of this review paper was to discuss in detail the various sustainability benefits offered by pervious concrete (PC), while also documenting the current state-of-the-art pertaining to mechanical and hydrological characteristics. The prevailing mix design procedures as well as the impacts of additives and recycled materials on behavior of PC have been discussed. Impact of pore morphology on permeability was examined, and a note was made on current rehabilitation techniques for restoring the infiltration rate of clogged PC surface courses. Field studies that focused on design, construction, and performance monitoring of pervious concrete pavements (PCP), were highlighted. Additionally, the contribution of PCP to reduce the environmental impacts of built infrastructure was summarized. The multiple benefits offered by PCP such as runoff mitigation, heat alleviation, energy conservation, and emissions reduction make it a promising material for construction of environment-friendly PC roadways. However, there still exists a vast scope to enhance the material’s characteristics for development of sustainable pavement systems in the urban built environment.
... This water can either be allowed to infiltrate into the soil gradually or can be transported to a targeted water reservoir through this underground pipe water channel. Permeable concrete is considered to be environment friendly as the surface not only permits water to pass through it and reach groundwater table but also reportedly [1][2][3][4] possesses air permeability. This property enables it to exchange heat with air along with moisture, which balances surrounding temperature. ...
... Investigating a wide range [2][3][4][5][6][7][8][9][10] of experimental studies it is concluded that the optimum water-to-cement ratio of 0.32-0.35 should be considered. ...
Permeable Concrete (PC) is well known for its ability to allow water to pass through it quickly due to its high void ratio. It acts as a feasible solution in controlling runoff water during rain and hence prevents the clogging of water on the surface of road pavement. Normal concrete which is impermeable does not have such interconnected voids due to which water tends to go straight away to the drainage system. Thus in heavy rainfall, the drainage system fails. PC solves this problem significantly by allowing most of the water pass through it which also helps in groundwater recharge. But due to its high porosity, the mechanical properties of concrete including its compressive strength and fatigue life are reported to be lesser than that of the normal concrete. Clogging is also a problem in PC. So, it is necessary to enhance the compressive strength of concrete which eventually will boost its performance. Therefore, to provide consolidated and precise guidelines, numerous experimental studies were investigated in this study to obtain solutions to avoid confusion. It was found that there are several ways to increase the performance of concrete as; using polymer, maintaining proper w/c ratio, adding 1% Superplasticizer (SP), using single-sized uniform aggregates, and using 0.8% silica fume. Also, clogging can be prevented by proving vertical channels while making PC blocks.
... Mechanical strength parameters namely compressive strength, split tensile strength, and flexural strength pertaining to pervious concrete mixes were found to improve with the inclusion of metakaolin in its matrix irrespective of the size of the aggregates used. During mechanical strength testing, the specimen failure line occurs through the interfacial zone due to the presence of lean bonding between aggregates [34,35]. ...
... The cracks initiates at the thin interface between the aggregates and cement paste followed by progress through the pores present in the mix (Fig. 10). Similar observations were recorded by Brake et al. [5], Agar-Ozbek et al. [34], and Ibrahim and Razak [40] for pervious mixes irrespective of the sizes of aggregates. Fig. 11 shows the load versus displacement curve of elements with 12.5 mm and 20 mm sized coarse aggregates respectively. ...
Pervious concrete paves way for the reduction of storm water runoff on the urban road surfaces with the aid of its porous nature. The impact of metakaolin as partial replacement for cement in pervious concrete was investigated in this study along with the impact of aggregate sizes. The ratio of aggregate to cementitious material and water to cementitious material were maintained at 3.54 and 0.35, respectively, in all the investigated mixes. Two single sized coarse aggregates with maximum nominal size of 12.5 mm and 20 mm were used. The replacement level of cement in pervious mixes by metakaolin was varied from 0 to 20% at 5% interval. Mechanical properties namely the compressive strength, tensile strength and flexural strength were experimented. The optimum replacement of cement by metakaolin was 15% due to the maximum increase in the mechanical properties. Inclusion of metakaolin at optimum level was found to improve the performance of pervious mixes subjected to static, cyclic and impact loads for both the aggregate sizes.
... (Deo e Neithalath, 2010) Concreto especial que possui poros de tamanho considerável (2-8mm) e um elevado índice de vazios. -Ozbek et al., 2013;Chen et al., 2013;Lian, Zhuge e Beecham, 2011). ...
... Referências Bibliográficas Compressão (MPa) Ano (Yang e Jiang, 2003) 7,1 -13,8 2002 (Yang et al., 2008) 5,22 -6,71 2008 (Chindaprasirt et al., 2008) 13 -22 2008 (Mahboub et al., 2009) 6 -19 2009 (Huang et al., 2010) 5 -11 2010 (Neptune e Putman, 2010) 11 -20 2010 (Kim e Lee, 2010) 1,5 -15 2010 14 -25 2011 15 -50 2011 (Sumanasooriya e Neithalath, 2011) 6,9 -20,6 2011 (Lian, Zhuge e Beecham, 2011) 11,5 -49 2011 (Bhutta et al., 2012) 10 -25 2012 5,4 -11,4 2012 (Sata, Wongsa e Chindaprasirt, 2013) 11,9 -13,6 2013(Chen et al., 2013 > 32 2013 (Agar-Ozbek et al., 2013) 24 -50 2013 (Dong et al., 2012) 8 -15 2013 (Bhutta et al., 2012) 7,5 -16 2013 (Zaetang et al., 2013) 2,47 -5,99 2013 (Kuo, Liu e Su, 2013) 4 -12 2013 (Nguyen et al., 2013) 10,5 -16,3 2013 (Gaedicke, Marines e Miankodila, 2014) 5 -26 2014 (Hesami, Ahmadi e Nematzadeh, 2014) 14 -21 2014 (Ibrahim et al., 2014) 6,95 2014 (Gupta, 2014) 15 2014 ((Soto-Pérez e Hwang, 2016) 15,2 2016 (Wu, M. H. et al., 2016) 18 2016 (Zhang et al., 2017) 24,2 2017 (Nguyen, Boutouil, Sebaibi, Baraud e Leleyter, 2017) 18,6 2017 (Kim et al., ) 9,9 2017 Fonte: (Sandoval, 2014) ...
Os resultados encontrados indicam que existe uma influência direta do tipo de sedimento e da velocidade de adição do mesmo no fenômeno da colmatação do CoPe, sendo os sedimentos finos (argila) os mais prejudiciais na perda da permeabilidade do material. Com base nesses resultados, um modelo analítico de colmatação foi proposto, o qual permitiu determinar o potencial de colmatação (c) dado por cada tipo de sedimento e para cada velocidade de colmatação simulada, resultando em uma ferramenta útil na previsão da perda da permeabilidade. Em termos de recuperação de permeabilidade, a hidrolavagem mostrou-se mais efetiva para os sedimentos finos (argila) e o ar para os sedimentos grossos (areia). A recuperação de permeabilidade apresentou um comportamento inverso à colmatação, visto que a maior recuperação de permeabilidade aconteceu com o sedimento de argila e a menor recuperação com o sedimento de areia. No estudo da periodicidade de manutenção, ficou evidente que não existe uma diferença significativa em termos de recuperação de permeabilidade com as duas periodicidades estudadas, sendo as duas igualmente efetivas. Com os resultados de colmatação e os resultados de limpeza foi proposto um modelo de vida útil hidráulica para o concreto permeável, o qual correlaciona as condições do local (erosão, regime de chuvas e topografia) com a perda de permeabilidade ao longo do tempo. Finalmente, o modelo proposto permitiu prever o tempo necessário para o material atingir a permeabilidade mínima de norma em função das condições de manutenção.
... Figure 7 shows that there are other factors that influence the mechanical strength of pervious concrete. Indeed, a number of studies show that this strength decreases with increasing size of aggregate (Agar-Ozbek et al., 2013;Elango & Revathi, 2017;Jing Yang, 2019;Sun et al., 2018;Xie et al., 2020;Zhong & Wille, 2016a). In order to properly study the effect of aggregate size on the mechanical strength of pervious concrete, the only variable in the samples in each of these studies is the aggregate size; other factors, such as the degree of compaction, the W/B and aggregate/binder (A/B) ratios, and are kept constant. ...
... A given particle size does not always result in identical compressive strengths. For example, the mechanical strengths of the pervious concrete from the study by Aagar-Ozbek et al. (Agar-Ozbek et al., 2013) were higher than those found by Sun et al. (2018) (Figure 8) with respect to the samples with particle sizes 2-4 mm and 4-8 mm. The difference in strength between the two studies is related to the condition of each experiment and to other factors such as the cement paste content, the degree Moreover, a different result was found by Yu et al. (2019b) who studied the effect of aggregate size on the compressive strength of pervious concrete. ...
Pervious concrete can be described as porous concrete that allows water to penetrate through the interconnected network of pores. Over the past century, the construction industry has shown increasing interest in pervious concrete, which is an environmentally friendly material. This paper sets out to present the composition and method for formulating pervious concrete; identify the different factors influencing porosity; and establish a relation between the porosity and density of pervious concrete based on cement and natural aggregates resulting from various works of research. In addition, a relation is established between the compressive strength of conventional pervious concrete and its porosity. The equation of the resulting curve shows that such strength is influenced by other parameters that have not been widely studied in the literature. Thus, this study focuses on the relation between compressive strength and other parameters such as type, size and shape of aggregates, cement paste content, water/cement ratios and aggregate/cement ratio. The study also presents the different equations for predicting tensile strength on the basis of the compressive strength of pervious concrete. The results show that the equation for conventional concrete is not suitable for accurately predicting the tensile strength of pervious concrete. In addition, an equation is established to correlate the flexural and compressive strength of pervious concrete, since the existing literature provides no models that correlate these two properties. The findings show that the equation for the flexural strength of conventional concrete is suitable for predicting that of pervious concrete.
• HIGHLIGHTS
• This paper presents the composition and method for making up pervious concrete based on cement and natural aggregates.
• It lists the factors affecting the porosity of pervious concrete.
• A relation is established between density and porosity and between compressive strength and porosity.
• The factors that influence the compressive strength of pervious concrete are studied.
• The equation for predicting the tensile strength of conventional concrete is not suitable for pervious concrete.
• The equation for predicting the flexural strength of conventional concrete is suitable for pervious concrete.
... Based on the size of aggregates and the porosity of the pervious concrete, permeability of pervious concrete ranges from 1.35 to 12.2 mm/s (ACI 522R 2010, Nguyen et al. 2013). The permeability of pervious concrete can be improved with the use of single-sized aggregates (Agar-Ozbek et al. 2013). Use of larger sized aggregates increases the porosity of the concrete (Sonebi et al. 2016), whereas the smaller sized aggregates increase, the mechanical strengths due to fall in porosity values (Crouch et al. 2007). ...
... Further, the inclusion of fibres in pervious concrete matrix improved the mechanical performance of pervious mixes with both 12.5 and 20 mm aggregates (Table 5). Due to the presence of thin bonding between aggregates, most of the failure occurs along the interfacial zone (Agar-Ozbek et al. 2013, Ibrahim and Razak 2016, Lori et al. 2019b. Moreover, factors which affect compressive strength also cause similar effects on the split tensile strength and flexural strength of pervious concrete (Yeih et al. 2015). ...
This study focuses on determining the performance of carbon fibre-reinforced pervious concrete (CFRPC) mixes subjected to static, cyclic and impact loadings. Two single-sized coarse aggregates, namely, 12.5 and 20 mm were used with aggregate to cement ratio and water to cement ratio of 3.54 and 0.35, respectively. The volume fraction of carbon fibre (CF) was varied from 0 to 0.4% at 0.1% intervals. The optimum volume fraction of CF was determined as 0.2% for both aggregate sizes. Slab specimen with 0.2% of CF was found to outperform the conventional pervious concrete slab under static, cyclic and impact loading.
... Porous concrete, sometimes referred as pervious concrete or Enhanced Porosity Concrete (EPC) is a macro-porous concrete that is rapidly gaining fame around the world because of its beneficial applications in sustainable construction considering cost and application. [1] It is lucid, evident fact that, mechanical behaviour of a building material solely depends on the properties of its composted structure. The presence of voids can contribute adversely to the material's mechanical properties such as strength at failure, elasticity and creep strains. ...
... Consistency was found to be 33% with the initial setting time 38 and final setting time 613 minutes respectively. [1] Coarse aggregate occupies 70 to 80percent of the volume of concrete. The crushed stone aggregates were poised from the native quarry. ...
Porous concrete has its application in many fields. Mainly for drainage purpose porous concrete can be used as a covering as well as to drain the liquid. Strength is only drawback in the porous concrete as the surface area contact between the coarse aggregates is less. In order to enhance the strength properties, poly propylene was used in layers. Various no of layers was introduced in the prism as well as for cube to determine the strength enhancement properties. Through experimental study it was found that strength due compressive force of the pervious concrete increases up to placing 3 layers of polypropylene geo textile fabric and get decreased after that. Similar to the compression test, the flexural strength also showed similar behaviour in the increase in strength up to the 3no of layers. Similarly, porosity test was carried to find the effect of porosity due to PP layers. It was found that 18.5% reduction in porosity was noted when 3 layers of PP were incorporated.
... Table 5 shows the summary of results obtained from the tests discussed in previous section. Observation from the crack pattern, as shown in Figure 6, reveals that under loading, failure propagates predominantly on the interface layer between the aggregates and the cement paste for both the aggregate sizes due to the thin bonding between aggregates (Agar-Ozbek et al. 2013, Ibrahim and Razak 2016, Lori et al. 2019b). Thus, it can be understood that the surface roughness of the aggregate surface and the bonding between aggregates and cement paste plays a crucial role. ...
... 8 proves the finding ofLi et al. (2019) andAgar-ozbek et al. (2013) which indicated that the gradation or particle size distribution of aggregates has major impact on n values.Figure 8shows the porosity of pervious concrete mixes with 12.5 and 20 mm aggregates. It can be understood that the mixes with 12.5 mm aggregates possess lower porosity values than mixes with 20 mm aggregates. ...
Pervious concrete remains a sustainable solution for effective water management in urban scenarios. Owing to the absence of fine aggregates, properties of pervious concrete rely much on the properties of aggregates and porosity. This article is aimed at determining the effect of aggregate size on the performance of pervious concrete mixes using 12.5 and 20 mm nominal-sized aggregates. In addition to that, the effects of polypropylene and glass fibre were experimented by varying their proportion in volumetric increments of 0.1% up to 0.4%. The aggregate to cement ratio and water to cement ratio were retained constant at 3.54 and 0.35, respectively. Results indicated that the fall in aggregate size improves mechanical properties but decreases porosity and permeability values. The presence of fibres in pervious concrete mixes was observed to improve flexural and split tensile strength but has no significant effect on the compressive strength, porosity and permeability.
... A mixture of cement and silica was found to contribute to the mechanical properties by forming a dense Interfacial Transition Zone (ITZ). However, in a study on replacing 15% of cement with silica fume, X-ray CT analysis reveals the formation of an ITZ layer but no improvement in tensile and compressive strength (Agar-Ozbek et al., 2013). In contrast, Yang and Jiang (2003) report that 6% replacement with silica fume, 0.8% superplasticizer, and 20% fine aggregate achieve a higher maximum flexural strength than the control mix. ...
Pervious concrete has gained research interest due to its eco-friendly system and hydrological benefits. With sustainability in view, several researchers tried to employ alternatives such as Supplementary Cementitious Materials (SCMs) in concrete. However, studies on employing high-volume SCMs as cement replacement in pervious concrete are scanty. Thus, the present study is initiated to evaluate the properties of pervious concrete by incorporating a high-volume of fly ash, silica fume, and Granulated Blast-Furnace Slag (GGBS) as a partial replacement for cement. The high-volume replacement accounts for a replacement percentage of 20%, 35%, and 50%. Further, at a high-volume replacement of SCMs, it is hypothesized that the unreacted SCMs in the concrete mixture will act as fine aggregate and induce positive effects on the mix. The study evaluates the properties of pervious concrete, including compressive strength, flexural strength, porosity, permeability, Young's modulus, and Poisson’s ratio. With increasing the SCMs’ content in the pervious concrete, the compressive strength is observed to decrease significantly compared to the strength of the control mix. However, at all replacement percentages, the compressive strength of pervious concrete is observed to be higher than the desired strength. The influence of unreacted SCMs at high-volume replacement is evident in all the properties evaluated. Further empirical models are also developed for the properties assessed in the study to understand the quantitative comparisons between different design conditions of Pervious Concrete (PC).
... The strength and durability properties depend on the rough aggregate texture, angularity, and size. Studies were carried out on cementing wood composite panels based on permeable concrete (Agar-Ozbek et al., 2013;Brake et al., 2016). ...
When designing reinforced concrete structures, the main tasks are to ensure the required strength and operational reliability, which are closely related to the technology of their construction. Composite cement-particle boards are a promising alternative for the development of a lightweight retained formwork system. Despite the technical and economic efficiency of the construction of monolithic buildings, it is not possible to eliminate the formation of industrial defects. The purpose of the study is to identify cause-and-effect relationships of defects in building structures erected from blocks of retained formwork made of cement-particle boards. The research was carried out on construction sites in industrial conditions on the territory of a residential area, including eight residential buildings of various storeys (12–16 floors). During the research, a probabilistic mathematical model for assessing the reliability of a construction technological system by structure quality parameters was developed and verified. The use of assessment of the reliability of retained formwork is an unconventional and new approach in research in the field of construction technologies. The value of the developed probabilistic approach lies in the possibility of using it to evaluate management strategies and improve technological systems.
... Prismatic samples of 400 mm length and width and 100 mm height were prepared. The plates were compacted in a single layer (100 mm) with a 55 kg metal roller, as compaction with a metal roller has been successfully used in permeable pavements for use in roadways for light traffic and people [40][41][42]. The specimens were demolded after 48 hours and cured submerged in a water reservoir for 28 days. ...
The use of permeable concrete pavements can mitigate flooding in densely populated areas by serving as a functional and sustainable mechanism for surface water absorption and drainage. However, it is found that the performance of the pavement is often limited to low and moderate flows and that the absorption capacity of the concrete matrix decreases as the flow rate increases. Therefore, the present study was developed aiming to evaluate the potential to reduce runoff in permeable concrete pavements subjected to simulations of successive events of heavy rainfall. For this purpose, 2 binary combinations of coarse aggregates were used, varying the cement consumption and the water/cement (w/c) ratio. The samples were submitted to simulations of heavy and sequential rainfall, with evaluation of the volume of water absorbed and the runoff. The mechanical and hydraulical properties of the permeable pavements were evaluated, as well as the characteristics of the area and volume of the internal and superficial pores. Among the results, specific weight stands out as the parameter that showed the highest linear correlation with the mechanical and hydraulic behavior of the specimens. It was also found that the runoff coefficient had a moderate negative linear correlation with the average pore size of the surface of the pavement. Finally, the permeable concrete pavements investigated were found to have the potential to reduce surface runoff in densely populated areas that are prone to frequent flooding, thus playing a critical role in mitigating the problems associated with stormwater runoff.
Keywords
Permeable concrete; Heavy rainfall simulations; Permeability coefficient; Porosity; Runoff coefficient
... A smaller aggregate size or a lower proportion of aggregates increases the strength of pervious concrete but also significantly decreases permeability [1]. Agar-Ozbek et al. [2] investigated the influence of different aggregate particle sizes on specimen cracks using microtomography. When aggregate particle size was small, the cracks mainly appeared in the paste, but when the aggregate was large, cracks appeared mainly at the ITZ. ...
Pervious concrete has good water permeability and, if used in construction, it can alleviate the heat island effect. However, its low strength and poor durability are major obstacles to its use. This study shows that nano-reinforced pervious concrete created by incorporating cellulose nanofibrils (CNFs) can improve the physical properties and increase the durability of pervious concrete. CNFs were added to the concrete mix in proportions ranging from 0.05% to 0.2% by weight of binder. The additions were found to alter matrix rheology. The hydration kinetics of matrix with differing CNF contents were compared and analyzed. The experimental results show the addition of CNFs delayed peak heat flow and maximum cumulative heat. The 28 d compressive strength of pervious concrete increased by up to 26.5% and 28 d flexural strength by up to 25.8% with the addition of 0.05–0.2% CNFs. Addition of 0.1% and 0.2% CNFs increased water permeability. Addition of 0.05–0.15% CNFs decreased mass loss by 73.2–83.7% after 150 freeze–thaw cycles, which corresponded to an increase in frost resistance. Denser matrices and stronger interfacial transition zones were observed using scanning electron microscopy when 0.05–0.2% CNFs were added.
... Figure 2.1 displays a saw-cut cross section of a pervious concrete made with aggregates of size ranging from 6-10 mm with paste thickness varying from 0.2 to 1 mm. Pervious concrete is also refered to by no fines concretes (e.g., Tittarelli et al. [2014]), porous concretes (e.g., Arifi et al. [2017], Agar-Ozbek et al. [2013], Lian et al. [2011]) and permeable concretes (e.g., Kia et al. [2017], Lian and Zhuge [2010]) in the literature. ...
In this study, we aim to gain insight into the damage mechanisms of pervious concrete subject to frost attacks in the presence of salt. We perform numerical simulations using a poroelastic model on system geometries representing pervious concrete at the scale of one or a few aggregates: (1) one aggregate coated with cement paste, (2) one aggregated coated with a cracked layer of cement paste, and (3) two aggregates coated and bonded with cement paste. The numerical simulations indicate that the damage is more likely to occur at the contact between aggregates. Furthermore, we observe significant shear stress at the vicinity of the paste/aggregate interface. We undertake a thorough parametric study to evaluate the impact of various boundary conditions, initial conditions, and materials parameters on the stresses generated during one or several freeze–thaw cycles. The insights can provide guidelines to design pervious concretes with enhanced freeze–thaw durability.
... Agar-Ozbek et al., have investigated porous wood-concrete with improved strength with testing at different scales [16]. Belytschko and Black have studied the elastic crack growth in finite elements of wood concrete [17]. ...
Utilizing solid wastes and industrial by-products as a partial replacement for raw materials has become an acceptable practice among researchers and scientists in the civil engineering field. Sawdust and wood shavings are not an exception; they are being used in concrete as a partial or total replacement for some of its constituents. The main goal of this research is to establish a relation between destructive and non-destructive testing for concrete containing wood shavings as a partial replacement of sand (woodcrete). With this type of material existing, thus the need to understand the behavior of such material becomes urgent and evokes the need to ease the process of the assessment and the evaluation of such materials and therefore provide more understanding of its behavior. In addition to the conventional concrete mix, five mixes of woodcrete were made by replacing fine aggregate by volume with wood shavings at different replacement levels varied from 5 to 50%. Cubic samples were tested at the age of 90 days using nondestructive tests (NDT), namely, rebound hammer test and ultrasonic pulse velocity test. Then, the specimens were tested using a conventional compressive test using a universal compression testing machine. Statistical analysis was performed to establish empirical relations between destructive and non-destructive results. The dynamic modulus of elasticity was calculated, and some formulas to estimate the (compressive) strength of woodcrete using NDT results were proposed and tested against experimental results and showed acceptable results.
... Figure 2.1 displays a saw-cut cross section of a pervious concrete made with aggregates of size ranging from 6-10 mm with paste thickness varying from 0.2 to 1 mm. Pervious concrete is also refered to by no fines concretes (e.g., Tittarelli et al. [2014]), porous concretes (e.g., Arifi et al. [2017], Agar-Ozbek et al. [2013], Lian et al. [2011]) and permeable concretes (e.g., Kia et al. [2017], Lian and Zhuge [2010]) in the literature. ...
Pervious concrete is a type of concrete that allows to drain water easily from the surface to the soil. It is characterized by a high permeability (~150-1000 L/min/m²), which is a consequence of its large connected inter-aggregates porosity. This structure is obtained by using single-sized aggregates and by limiting the use of fine aggregates. Even though pervious concrete presents substantial benefits, it is subject to various durability challenges such as freeze-thaw and clogging. In fact, in cold regions, pervious concrete structures are subjected to freeze-thaw cycles which deteriorate the material. The aim of the Ph.D. is first to understand the damage behavior of pervious concrete subjected to freeze-thaw in saturated conditions and in the presence of deicing salts, and second to optimize the mix design to increase the number of freeze-thaw cycles the pervious concrete can sustain before damage. In order to reach these goals, experimental and modeling approaches are considered. First, an experimental assessment of the freeze-thaw resistance of various formulations of decimeter-sized cubic samples of pervious concrete is performed. Every mix design contains an additive that potentially enhances the resistance to freeze-thaw. In terms of modeling, to understand why pervious concrete gets damaged when subjected to freeze-thaw cycles and the relevant physical processes that might be involved, we develop a poromechanical model relevant for freeze-thaw in saturated conditions and perform poromechanical finite-volumes/elements simulations on cemented aggregates subjected to freeze-thaw. We simulate the response of one aggregate coated with cement paste and two aggregates coated and bonded with cement paste.
... Pervious concrete properties, which are modulus of elasticity, density, infiltration rate, compressive and tensile strengths, are proved to be functions of porosity [52,209,[213][214][215][216][217][218][219]. The porosity depends on many factors such as compaction method, ratio of water to cement, ratio of aggregate to cement, aggregate sizes, additional admixtures, fibers, etc. ...
... Hệ số thoát nước của bê tông rỗng thường từ 0,1 -3,3 cm/s và phù hợp để làm lớp bê tông bề mặt hoặc block bê tông thoát nước [20]. Trong bê tông rỗng, số lượng lỗ rỗng có khả năng liên kết với nhau tạo thành hệ thống lỗ rỗng thông nhau tối đa đạt được là 30%, lỗ rỗng này quyết định khả năng thoát nước của bê tông rỗng [21]. Trong tổng độ rỗng, ngoài các lỗ rỗng thông nhau còn có các lỗ rỗng đóng kín và lỗ rỗng trong các hạt cốt liệu (rỗng trong hạt). ...
Bài báo này trình bày các đặc tính của gạch bê tông rỗng thoát nước sử dụng hỗn hợp cốt liệu tái chế (cốt liệu gạch đỏ và cốt liệu bê tông), trong đó, đặc tính lỗ rỗng và hệ số thoát nước được tập trung phân tích. Các đặc tính cơ học bao gồm cường độ nén, cường độ uốn cũng được trình bày trong nghiên cứu này, đây là thông số xác định ứng dụng của sản phẩm. Trong nghiên cứu sử dụng 10% hạt bê tông khí chưng áp (AAC) kích thước 2,5 – 5 mm để làm tăng độ rỗng trong hạt và tổng độ rỗng của gạch bê tông rỗng. Hỗn hợp cốt liệu có hàm lượng gạch đỏ từ 0%, 20%, 40%, 60%, 80%, 100% làm thay đổi đáng kể tổng độ rỗng của gạch bê tông. Khi thiết kế độ rỗng 20%, tổng độ rỗng tăng từ 32,6% lên 44,4% khi sử dụng 0% và 100% gạch đỏ. Tuy nhiên, cường độ nén của mẫu giảm đáng kể từ 10,6 MPa còn 5,3 MPa. Các cấp phối thiết kế có hệ số thoát nước từ 2,4 – 9,8 mm/s, tương ứng với tổng độ rỗng từ 28,5% đến 48,4%, trong khi đó cường độ nén giảm từ 14,8 MPa xuống 4,5 MPa. Mối quan hệ giữa hệ số thoát nước, độ rỗng và đặc tính cơ học được trình bày trong nghiên cứu.
... It is important to highlight that it is well known that the aggregate size influences the Young's modulus of concrete more than its compressive strength [24], although compressive strength might also be related to concrete pore size composition-distribution and spacing [25]. Decreasing the coarse aggregate size can also increase the concrete compressive strength [26][27][28], mainly due to the increase in adherence generated by the effect of aggregate size reduction [27][28][29]. ...
The work presents the results of an experimental campaign carried out on concrete elements in order to investigate the potential of using artificial neural networks (ANNs) to estimate the compressive strength based on relevant parameters, such as the water-cement ratio, aggregate-cement ratio, age of testing, and percentage cement/metakaolin ratios (5% and 10%). We prepared 162 cylindrical concrete specimens with dimensions of 10 cm in diameter and 20 cm in height and 27 prismatic specimens with cross sections measuring 25 and 50 cm in length, with 9 different concrete mixture proportions. A longitudinal transducer with a frequency of 54 kHz was used to measure the ultrasonic velocities. An ANN model was developed, different ANN configurations were tested and compared to identify the best ANN model. Using this model, it was possible to assess the contribution of each input variable to the compressive strength of the tested concretes. The results indicate an excellent performance of the ANN model developed to predict compressive strength from the input parameters studied, with an average error less than 5%. Together, the water-cement ratio and the percentage of metakaolin were shown to be the most influential factors for the compressive strength value predicted by the developed ANN model.
... The addition of SBR latex exerted positive effects on the mid-span deflection of specimens, as illustrated in Fig. 6. The SBR polymers interpenetrated in cement hydrates produced a commingling network of films, which enhanced the ductility and flexibility of pervious concrete [49]. The flexural strength of reference mix A-350-S-5% was lower than mixtures produced with metakaolin (D-MK-10%) and both silica fume and metakaolin (E-MK-SF-10%) except silica fume mixture (C-SF-10%), which had almost identical flexural strength to reference mixture. ...
This study evaluates the performance of pervious concrete subjected to rapid freeze–thaw (F-T) cycling, calcium leaching and the combined attack of calcium leaching and F-T cycling. Silica fume, metakaolin and SBR polymer emulsion were incorporated at different levels into pervious concrete mixes to improve strength and durability performances. The results indicated that the addition of 5% fine sand and proper compaction had a positive influence on improving the resistance of pervious concrete to F-T cycling. The increase of supplementary cementitious materials (SCMs) from 5% to 10% significantly improved the resistance to rapid F-T cycling and to the combined attack of calcium leaching and F-T cycling. The optimum content of SCMs was 10% based on the mechanical and durability performance of pervious concrete with acceptable permeability. Calcium leaching in 6 M NH4NO3 solution combined with F-T cycling induced severe surface deterioration and internal damage compared to individual attacks of F-T cycling or leaching. Compared with control and polymer-modified mixes, pervious concrete incorporated SCMs possessed better resistance of calcium leaching and frost. The morphological changes caused by calcium leaching exhibits the decreased volume fraction of solid phases in a cement matrix and consequently increased the porosity, which ultimately degraded strength and durability performance of pervious concrete.
... Therefore, at this level a replacement of 20% of concrete block by recycled concrete allows obtaining a lower porosity of the material comparable to the one of the reference concrete. Literature values for porosity measurements of a concrete comprising a composition of recycled milled materials with a variable dimension from 2 to 8 mm have showed higher porosity values than the one of this study [35]. It can be concluded that the samples in this study are as compact as the reference concrete and even more compact at longer times. ...
The construction sector generates thousands of tons of construction and demolition waste annually, which encourages us to move towards recycling this waste. In view of obtaining a circular economy, recycled concrete from Morocco has been used as filler. In Morocco only the 5% of construction waste is valued, therefore, the aim of this paper is to show that beyond 5% valued interesting results can be obtained. Because of the growing awareness of the importance of recycling construction and demolition waste in the context of “Sustainable Development", percentages between 5% and 20% of construction waste have been introduced into the concrete replacing the sand. The porosity, the compressive strength and the chloride diffusion of concrete with 0-20 wt% of recycled aggregate have been studied. In the end, it has been concluded that the C20% presents interesting values of these three properties taking into account their current values. The compressive strength increases up to 18%; porosity decreases to 4.2% and chloride diffusion decreases up to 50%. The importance of the recycled aggregates obtained from construction and demolition waste should be considered as a sustainable material which is economic end environmentally.
... Given that pervious concrete has a reduced cement paste content and thus a smaller ITZ phase, the effect of SF on ITZ in pervious concrete may not contribute to the strength. For instance, Agar-ozbek et al. (2013) found minor contributions from SF replacement of 15% of OPC to the tensile and compressive strength of pervious concrete with 4e8 mm size coarse aggregate. However, X-ray CT analysis showed some effects of using SF in densifying ITZ of smaller aggregate sizes (2e4 mm), due to the larger ITZ phase than 4e8 mm aggregates. ...
Pervious concrete has made a comeback as a green infrastructure solution for urban areas. The fast adoption of the permeable pavement practice by many cities worldwide warrants an urgent response from researchers to address the lack of standards for mixture optimization, pavement design, and characterization methods, which results in field placements with insufficient strength and durability. These critical issues are the topic of this review paper. Laboratory test results relevant to the mechanical and hydrological performance of pervious concrete, e.g., compressive and flexural strength, impact and abrasion resistance, porosity and permeability, and their interrelationships are discussed in great detail. The use of additives, alternative binders, fillers, and fibers from natural sources and waste streams and their impact on pervious concrete performance parameters is reviewed. Efforts in computational modeling of mechanical, structural, and hydrological behavior of pervious concrete materials and pervious concrete pavements are also presented. Based on this extensive review of state of the art on these important matters, the areas of need for future research are identified.
... In line with the compressive strength, Nur Hidayah et al. [23] reported that the elimination of fine aggregates from conventional composite reduces the compressive strength by approximately 60%. Few studies have been done to improve the strength and durability of pervious concrete [11,[24][25][26]. ...
This study describes an investigation into the assessment of performance and suitability of pervious paver blocks (PPB) using reclaimed asphalt pavement (RAP) aggregates. Virgin aggregates (VA) and RAP were mixed in three different proportions (0–100, 50–50 and 100–0) using two different aggregate gradations (G1-coarser and G2-finer) to fabricate chamfered PPBs using a standard factory method. Three different water-cement ratio (w-c ratio) (0.25, 0.30 and 0.35) were used for the production of the specimens. The properties of PPBs was characterized by measuring porosity, density, dynamic modulus of elasticity using UPV, compressive strength and abrasion by Cantabro loss (CL).
Porosity and density measurements had higher variability with no strong inferences on the effect of mix attributes. The G1 gradation takes an edge over G2 as indicated by the UPV and dynamic modulus of elasticity (DME) results at the w-c ratio of 0.25 and 0.30. G1 gradation resisted deformation better than small-sized binary gradation (G2). G1 gradation depicted strength reduction of 4.23%, 14.3% and 23.6% and in the case of G2 gradation, 10%, 27% and 43% strength reduction was observed on an average for 10, 30, and 50% RAP addition, respectively. A strong correlation of CS was found with UPV and CL measurements. ANOVA results comprehended that using RAP in pervious concrete had significant effect on different properties of pervious concrete. The overall results indicate that up to 50% RAP can be used in pervious concrete paver block with G1 gradation, which will increase the sustainability aspect of pervious concrete.
... Paving block banyak digunakan sebagai lapis perkerasan jalan, parkiran, halaman rumah dan gang-gang kecil yang berada di desa maupun perkotaan [2] [3] keunggulan paving block yaitu memiliki daya serap yang baik. [4] Dengan manfaat paving block yang mampu menunjang fasilitas masyarakat maka dituntut pula kualitas paving block yang kuat dan mempunyai daya serap air serta kualitas yang baik yang sesuai dengan kriteria standar yang diperlukan [5] [6]. Kualitas paving block dipengaruhi oleh campuran serta proporsi material penyusunnya. ...
The main objective of this study was to find out and analyze how much the influence of the coconut shell charcoal had on changes in compressive strength and water absorption in the K-175 paving block. This research method is experimental research, which is a research of making paving block specimens, by conducting activities or experiments using coconut shell waste as a mixture of paving blocks, with a mix design mix referring to the comparison of concrete mix with K-175 quality (SNI 03-2834-2000). The conversion value of compressive strength of specimens at the age of 7 days to 28 days from specimens N, 5%, 10%, 15% and 20% is 271,80 kg/cm², 205,12 kg/cm², 102,57 kg/cm²,76,92 kg/cm² and 64,11 kg/cm² respectively. In the normal test code, the paving block is classified as class B quality, while the 5% specimen code is classified as class B quality, for the test object code 10%, 15%, and 20% do not meet the paving block quality standards. The results of the water absorption test increased in paving blocks with a combination of coconut shell charcoal. All of them have increased water infiltration on paving blocks.
... Equations (18) and (19) are used to determine the ideal solution and the negative ideal solution, respectively. Where K is the beneficial criteria set index (when maximum value is wanted), and K' is the non-beneficial criteria set index (when minimum value is wanted). ...
Despite the number of environmental advantages that porous concrete (PC) pavements can provide, they are mainly used in light-traffic roads, parking lots and sidewalks due to their low mechanical strength. This research focuses on the common additives employed in PC pavements, according to a literature review, with the aim of increasing their mechanical strength while maintaining an acceptable infiltration capacity. The results demonstrated that the combination of superplasticizers and air-entraining additives can provide indirect tensile strength values over 2.50 MPa, with an infiltration capacity over 0.40 cm/s. In addition, polypropylene fibers were seen to provide very good safety properties, preserving some structural integrity in the case of failure. All mixtures studied obtained outstanding skid resistance results under both dry and wet conditions.
... Pervious concrete properties, which are modulus of elasticity, density, infiltration rate, compressive and tensile strength, are proved to be functions of porosity (Deo and Neithalath, 2010a;Agar-Ozbek et al., 2013;Xu et al., 2018;Shi and Chen, 2018;Alam and Haselbach, 2014b) (Fig. 2). The porosity depends on many factors such as compaction method, ratio of water to cement, ratio of aggregate to cement, aggregate sizes, etc. ...
In this study, we propose a new design of prefabricated hollow blocks, which are made of pervious concrete. The effects of thickness of block walls are studied to optimize an adequate size. The comparison of performance of porous and solid blocks is studied through fluid-solid interaction models. A polyhedral finite element formulation (PFEM) is employed to analyse responses of the structure under equivalent static and dynamic wave load conditions. The effectiveness of PFEM is verified by comparing the obtained results with those of standard finite element method (FEM) using the commercial software ANSYS. Their accuracy is also proved via the validation model of a step-beam, in which the natural frequencies are used for comparison. In static analysis, the maximum displacement of block increases rapidly when porosity of concrete changes from 5% to 35%. The optimum porosity is found to be around 20%. The variable thickness of the block walls reasonably affects the displacement resistance. However, compared to porosity, the influence of thickness is not significant. The change of Poisson's ratio slightly affects the responses of the block. For dynamic analysis, the vibration of pervious concrete block types under the impact of wave load with small duration (<20 ms) lasts longer than the case attacked by long duration shock (around 50 ms). However, the amplitudes of displacement responses by long duration impact wave are greater than that of short impact. Study also showed that the porous concrete block could significantly reduce the run-down pressure acting on the structure compared to solid block.
The present work is intended to provide worthful information about the structure and half-metallicity of Co-based Heusler alloy. The first principle density functional theory was used to analyze Co2TiN. First, the structure of an alloy was optimized through the consideration of Cu2MnAl and Hg2CuTi, two structure types along with different magnetic phases. The resulting stable structure Hg2CuTi showed the metallic nature of an alloy in both spin configurations with GGA potential. However, an implication of Hubbard parameter (U) considerably affected the electronic structure and therefore bands got shifted with 100% polarization at Fermi level which increases the efficiency of spintronics. Under the effect of U, spin-up configuration showed semiconducting nature with 0.21 eV that revealed the half-metallicity in Co2TiN full-Heusler alloy.
This paper investigated the mechanical and permeability performances of pervious concrete mixtures produced using different aggregates and fibers. Basalt, limestone, travertine, and pumice aggregates were used at two fractions (5–12 mm and 12–19 mm) with steel and polypropylene fibers. In the scope of experimental program, slump, rheology, unit weight, compressive strength, flexural strength, splitting tensile strength, abrasion resistance, porosity, and permeability tests were performed on pervious concretes. As a result of this comprehensive laboratory investigation, pervious concrete specimens exhibited adequate mechanical performance for structural applications by achieving 8.8 MPa compressive strength, 3.0 MPa flexural strength, and 2.2 MPa splitting tensile strength. Besides, the fiber-reinforced mixtures reached a high deflection capacity, which was a significant parameter for pavements constantly exposed to fatigue-originated tensions. In addition to superior strength performance, the highest porosity and infiltration rate results were obtained as 29.5 % and 13.91 mm/s, respectively. Steel fiber inclusion notably increased the abrasion resistance, while the polypropylene fiber remarkably enhanced the permeability performance. It was revealed that pervious concrete specimens could achieve an excellent infiltration rate (>10 mm/s) using polypropylene fiber, regardless of the aggregate type. Limestone, basalt, and travertine generally achieved similar results, while pumice exhibited poor performance compared to other aggregates. Also, it was determined that using smaller-sized and more uniform aggregates generally increased the total performance of pervious concrete specimens.
The Economy of all countries is developing at a rapid pace and to maintain equilibrium between nature and growth, it needs to conserve all its natural resources. Full progress can be achieved by any country if it uses all the natural resources equitably including the most important water. This investigation was mainly focused on two criteria, in the first criteria was to eliminate the fine aggregate from concrete and the other was to allow water to pass through the concrete. Due to the consideration of these two criteria, this type of concrete is known as pervious concrete (PC). The purpose of this investigation was to develop mixture design and mixture proportioning charts for PC. The main properties studied include compressive strength, density, and permeability and void ratio. To measure the permeability of the PC, a test setup was created in the laboratory. The falling head test method was used to evaluate the permeability coefficient for PC. PC was produced using two sizes of natural coarse aggregates. The first group is 4.75–10 mm i.e., size A (passing from 10 mm and retaining on 4.75 mm IS sieve) and the second group is 10–20 mm i.e., size B (passing from 20 mm and retaining on 10 mm IS sieve). The cement content was used in the range 250–400 kg/m3 for the experimental investigation work. The aggregate/cement ratio was used 4:1. Three w/c ratio were used i.e., 0.3, 0.35 and 0.4, respectively. It has been observed that for 4.75–10 mm size aggregates, the compressive strength is more as compared to 10–20 mm size aggregates. Other PC properties such as void ratio, permeability were not much affected by changing coarse aggregate size. Based on the PC property results, PC mixture design charts were developed. The step-by-step process of PC mixture design was developed with the help of PC mixture design charts. This mixture proportioning method may be useful for the development of the preliminary mixture design of PC.
Pervious concrete (PC) increases infiltration of stormwater runoff, absorbs sound energy and resists heat transfer. Compaction is not applied to PC to ensure connected porosity. Inconsistency in porosity distribution and uncertainty in mechanical properties of mass-produced PC lead to limited industrial applications. Studies have involved laboratory experiments, only to find greater variation in mechanical properties. Optimizing design parameters remains a challenge in PC mass production in the absence of compaction. This study aims to mass-produce PC with uniform characteristics by optimizing compaction energy and design parameters. A total of 1400 samples were cast varying aggregate-to-cement (AC) ratios and compaction energy. Density, porosity and compressive strength of the samples were analysed. Compressive strength and porosity varied extensively from 4.0 to 36 MPa and from 0.05 to 0.45, respectively. A semi-theoretical approach was adopted to optimize the AC ratio and compaction energy. The empirical model incorporated mean aggregate size and shape factor obtained. Experimental and theoretical optimum AC ratios were comparable, 3.3 and 2.45, respectively, while a compaction energy equivalent to 25 blows is required to ensure consistency, without compromising porosity and porosity distribution. The model developed in the study could be used to optimize the mix design in particular to compressive strength and porosity envisaged for specific field-scale application.
Use of pervious concrete (PC) for permeable pavements can help avoid urban waterlogging and urban heat islands. However, PC typically has low strength and poor durability owing to its special porous structure. The purpose of this study was to understand the influence of aggregate size and water–cement ratio (w/c) on PC under different environmental conditions (freeze–thaw and thermal cycles). The experiment designed a PC made with five aggregate sizes (3–5 mm, 5–7 mm, 7–9 mm, 9–11 mm, 11–13 mm) and five w/c values (0.21, 0.25, 0.29, 0.33, 0.37). The mass loss, compressive strength and life of all mixtures were tested under freeze–thaw and thermal cycles. Results indicated that aggregate size and w/c were identified as important factors determining the properties of PC and were evaluated using survival analysis to determine the optimal mixture. As the number of freeze–thaw cycles increased, mass loss and risk of damage increased while compressive strength decreased. As the number of thermal cycles increased, mass loss increased and compressive strength first increased and then decreased. After thermal cycling, high w/c had better frost resistance, contrary to the results for direct freezing–thawing.
The need for porous concrete has become increased due its ability to control surface water, increase the rate of recharging groundwater, and reduce pollution of the ecosystem. Granite is a coarse aggregate that is quite expensive when compared with gravel in Nigeria. Therefore, this research is aimed at optimizing blended granite and gravel in the production of porous concrete. Samples of blended granite-gravel porous concrete of varying mix proportions were produced using cement to aggregate mix ratio of 1:4. The samples were tested for their porosity, workability and compressive strengths. The data collected were analyzed with the aid of Design Expert 10.0. It was observed that the optimal combination for the granite-gravel blended porous concrete is 12% granite, 88% gravel, and a water-cement ratio of 0.66%. This combination gave a porous concrete with a compressive strength of 48.4 N/mm ² , percentage porosity of 6% and a compacting factor of 0.91. These values when compared to that of the control specimen revealed that the optimal mix gave a porous concrete with higher porosity, higher workability and a better compressive strength.
Geopolymer is green cementitious material that can be produced from industry waste or abundant earth materials through alkali-activated reaction. This study aims to conduct microscale characterization of geopolymer paste and mechanical properties of pervious concrete. Metakaolin (MK) and fly ash (FA) were used to synthesize geopolymer with granulated blast furnace slag (GBFS) as admixture. The experimental results showed that the room temperature curing was sufficient for strength formation of MK based geopolymer paste as compared to high temperature. The microscale characterization indicated that GBFS had introduced new crystal phases and better surface integrity was realized with the optimum content of GBFS. The GBFS had prominent effect on mechanical strength enhancement, and the optimum content was 10% and 30% for MK and FA based geopolymer paste and pervious concrete, respectively. In addition, mechanical strength of geopolymer pervious concrete was inversely proportional to the porosity caused by different aggregate gradations. However, when the porosity was similar, the smaller aggregate size induced the higher compressive but the lower splitting tensile strength.
With the rapid development of society and industry, novel technologies and materials related to pavement engineering are constantly emerging. However, with the continuous improvement of people’s demands, pavement engineering also faces more and more enormous challenges that the pavement materials must have excellent engineering properties and environmental benefits. Meanwhile, the intelligence is the mainstream development direction of modern society, and the development trend of future transportation infrastructure. Materials Genome Initiative, a program for the development of new materials that materials design is conducted by up-front simulations and predictions, followed by key validation experiments, the rapid development of science and technology and AI toolset (big data and machine learning) provide new opportunities and strong technical supports for pavement materials development that shorten the development-application cycle of new material, reduce cost and promote the application of new carriers such as intelligent sensing components in transportation engineering, to achieve the intelligence of transportation engineering. However, traditional pavement materials possess several unavoidable shortcomings, indicating that it is exceedingly difficult for them to meet the above requirements for future pavement materials. Therefore, the development of future new pavement materials, which can be designed on-demand as well as possessing enough mechanical properties, high durability, practical functionality, and high environmental protection, is urgent. In recent years, as a “designable” polymer material with various excellent engineering performances, polyurethane (PU) has been widely applied in pavement practices by changing the chemical structures of raw materials and their mix proportions, for instance pavement repairing material, permeable pavement material, tunnel paving material and bridge deck paving materials, etc. Although PU material has been widely applied in practices, a systematically summarization is still quite necessary for further understanding the working mechanism of PU materials and optimization it’s engineering applications. To fill the gap, this article puts forward the special requirements for future transportation infrastructure materials, and introduces the basic properties and working mechanism of PU materials in order to make up for the defects of conventional road materials. Based on this, this article also summarizes the engineering performances and environmental benefits of applying PU as the binder for different road infrastructure materials in recent years. Considering the gene-editable nature of polyurethane, further research of the on-demand design principles of PU pavement materials is recommended. The establishment of raw material gene database, material terminal performance database and their structure-activity relationship are highlighted. The current research is essential to the practice guidance and further optimization of the PU materials for road infrastructures, which in line with the future Carbon neutral policy.
This paper presents an experimental investigation on the shear response of strain-hardening cement-based composites (SHCC) using X-Ray microtomography (microCT). For the developed composites, PVA and micro steel fibers were used in a constant fiber volume fraction of 2.0 %. The hybrid composites were produced replacing PVA by steel fibers in 25 %, 50 % and 75 % fractions. The shear behavior of the composites was studied by performing Iosipescu shear tests. The crack pattern evolution along the tests and the displacement field in the notch region were analyzed using the Digital Image Correlation (DIC) technique. Information about the porosity, fiber distribution and alignment were obtained using microCT for each specimen tested. The results show that the hybridization increases the crack opening but has little effect on the shear strength. The results also show that PVA fibers affect the alignment of the steel fibers and increase the porosity of the composites.
Pervious concrete (PC) appears as a special type of concrete in the search to better manage surface runoff. Its main characteristics are its high porosity and consequently its high permeability, which allows water to infiltrate quickly and safely. The research on the material has evolved a lot in recent years, but the lack of standardization in the productive process has made its diffusion and application in the field very difficult, since it does not have enough parameters to verify in the field at least the compacting of the material (unit weight). Compaction has great influence on pervious concrete (PC) properties: porosity, permeability and in consequence mechanical strength. Thus, this study aims to propose a standardization of procedure for molding cylindrical and prismatic specimens of PC (in laboratory conditions) using the unit weight like control parameter. The standard procedure chosen was the proctor hummer (2.5 kg), due to its ease and good results (low variability), both in the cylindrical specimens and in the prismatic ones where the point of application of the compaction blows was also defined. Finally, an experimental campaign was carried out to verify the hydraulic and mechanical properties of the produced PC and the compliance of the NBR 16416 was verified. Then it was verified that the proposed molding procedure produces PC within the standard parameters, in addition a control abacus was proposed that allows by means of the unit weight and the porosity to determine the number of blows to compacting the material, giving the opportunity to choose a more or less pervious material, and more or less resistant.
The purpose of this study is to produce recycled concrete from the most common environmental pollutants, which are plastic waste and recycle concrete. Where plastic bottles were cut and used as fibers to reinforce concrete besides using the recycle concrete as an aggregate. also, it can be used in improving the various properties of concrete in terms of improving compressive strength, bending, thermal insulation, etc., because it is considered one of the most influencing disadvantages of concrete. Five mixes of concrete free of fine aggregate were poured with various volumetric proportions (0.6, 0.8, 1.0, 1.2 and 1.4) % of plastic fibers were added to them. The natural aggregate was completely replaced by a carefully graded product according to the specifications of crushed concrete residue. A comparative mix of recycled fiber-free concrete was poured. The results showed that with an increase in the fiber content, the thermal conductivity of the concrete samples decreases, the compressive and bending resistance increases at the age of (28) days, as well as, the density of concrete decreased. Besides, the results showed a slight improvement in the resistance to the impact of the slabs at the age of (90) days.
This work presents an experimental campaign with 162 specimens of cylindrical specimens of 10 × 20 cm2 and 27 prismatic specimens with 25 × 25 × 50 cm3, in order to analyse the influence of nine different concrete mixtures on compressive strength and the propagation profile of longitudinal ultrasonic waves. A neural network is best defined as a set of simple, highly interconnected processing elements that are capable of learning information presented to them and its ability to learn and process information classifies it as a form of artificial intelligence. In this work, neural networks models were used to find out the influence of several parameters used in fabrication of concrete on the material compressive strength. The results obtained showed that the simulation with neural networks associated with ultrasound tests are important tools to evaluate the compressive strength of concrete.
A crescente impermeabilização dos espaços urbanos traz consigo problemas e desastres ambientais como as inundações, em decorrência da alteração na dinâmica da água da chuva que infiltrava e passa a escoar, exigindo a maior capacidade dos sistemas de micro e macrodrenagem. O concreto permeável (CPER), composto por cimento Portland e agregado graúdo, ganha espaço como forma de mitigar os efeitos da redução das áreas permeáveis. Nesse contexto, o presente trabalho busca investigar a influência da sequência de mistura no comportamento hidráulico e mecânico do CPER produzido com seixo rolado, dada a existência de lacunas na literatura sobre o impacto desse parâmetro sobre material. Para tal, foram estudadas três sequências de misturas a partir da produção de placas de CPER de dimensões 40cmx40cmx10cm. Foram analisados os resultados de resistência à tração na flexão, porosidade, tortuosidade e permeabilidade. Estatisticamente, não foram verificadas diferenças entre os resultados, entretanto, observou-se o crescimento do volume e da área de poros, alterando-se as sequencias, quando utilizado na produção dos concretos um misturador de eixo inclinado.
Steel slag pervious concrete (SSPC) is a promising sustainable pavement material for sponge city construction. The influence of aggregate size and notch depth ratio on fracture performance of SSPC was studied in this work. Considering two kinds of aggregate size (4–6 mm and 10–20 mm) and four kinds of notch depth ratio (0.2, 0.3, 0.4, 0.5), the three-point bending test of a rectangular beam with a single side notch was carried out, and the whole fracture process was monitored by acoustic emission. The experimental results show that the fracture behavior of SSPC has obvious boundary effect. Meanwhile, large-size aggregates can improve the fracture strength and fracture energy of SSPC, which is related to the stronger mechanical interlocking and bonding between aggregates caused by thicker slurry layer on the surface of large-size aggregates. In addition, the acoustic emission monitoring results show that the internal wave source activity and strength are higher in the fracture process of large-size aggregate specimens, and there are more shear cracks. Finally, the PFC3D numerical model established by the discrete element theory was used to simulate the fracture behavior of SSPC. The results show that the particle flow code is an effective method to study the fracture behavior of pervious concrete.
Although pervious concrete (PC) has many positive contributions such as reducing noise pollution, recharge groundwater, reducing urban heat island effect, it has not been used at the desired level due to its limited strength properties and lack of standards to be used on high volume roads yet. The purpose of the study was to develop optimum pervious concrete mixtures that can be used as road paving material on high volume roads. For this reason, the Technical Specification for Concrete Road Pavements of General Directorate of Turkish Highways was taken into considered. The effect of aggregate/binder (A/B) ratio on the strength of pervious concrete with different aggregate sizes was investigated. The amount of water that gave the least clogging at the bottom of the samples was chosen as the optimum amount of water. Porosity, compressive strength, tensile strength, bending strength, and abrasion resistance tests of silica fume added pervious concrete with different aggregate sizes (2–4 mm, 4–8 mm and 8–16 mm) and different (A/B) ratios (2, 2.5 and 3) were performed. The results showed that the pervious concrete produced with the appropriate (A/B) ratio and aggregate size provides the required strength requirement even for concrete roads and can be used as a concrete road pavement material. The results also showed that both the (A/B) ratio and the aggregate size significantly affect the strength properties of pervious concrete mixtures. In particular, (A/B) ratio was found to be more effective than other mixtures for 2–4 mm aggregate size mixtures.
In this study, experiments on pre-cracked push-off specimens without stirrups were conducted to analyze the aggregate interlock behavior of recycled aggregate concrete (RAC). The major variables considered in this study were the surface roughness, recycled coarse aggregate (RCA) replacement ratio, concrete strength, aggregate particle size and loading rate. Experimental results indicate that the roughness of the fracture surface relating to the ratio of aggregate fracture significantly affects the shear stress of pre-cracked push-off specimens. The findings reveal that the RCA replacement ratio has adverse effects on the macro-roughness and the aggregate interlock behavior of RAC. The increasing concrete strength leads to a decrease in the surface roughness and the aggregate interlock capacity of RAC. The inferior properties of RCA contribute to decreasing the aggregate interlock behavior of RAC specimens with larger RCA particles. The influence of the loading rate on the aggregate interlock is insignificant with the increase from 0.06 mm/min to 0.6 mm/min.
A novel design of a drainage coverslab in pedestrian walking areas has been developed as a composite section of reinforced concrete and a porous concrete layer. Porous concrete exhibits a reduction in permeability due to clogging by particulates, which severely limits the functional level of the coverslab. Slabs were tested for sever clogging mechanism in the laboratory. Samples of new coverslabs with various sizes of aggregates were cast using various compaction methods. Strength was tested using 3 point load test and clogging potential of cover slab was determined by infiltration test (ASTM C1701). Infiltration was tested on a series of coverslab samples which were clogged with top soil mixture collected from the field, landscape fine compost and silt clay slurry to simulate worse case clogging in the field. Comparison of surface textures of the porous surface was made based on sand patch test and proposed clay patch test. This paper focuses on discussing the design of porous concrete layer of coverslab, construction methods and practical issues related to application and mitigation techniques.
Steel slag (SS) was used to replace natural aggregate (NA) in pervious concretes (PCs) and important properties of the concretes were investigated in this work. The replacement levels of SS were 25%, 50%, 75% and 100%, respectively. The properties of the PCs, including the compressive strength, the splitting tensile strength and the flexural strength as well as the bulk density, the connected porosity and the water permeability coefficient, were studied. Additionally, the carbonation resistance and the abrasion resistance of the PCs were also evaluated. It is found that the bulk density, the connected porosity and the water permeability coefficient of the PCs increase with SS replacement level overall. Incorporating SS shows positive effects on the development of compressive strength, splitting tensile strength and flexural strength of the PCs. All the PCs show excellent carbonation resistance. Moreover, the PCs incorporating SS exhibit better abrasion resistance than the control mix. SEM images reveal that the hydrates of cement develop well in the PCs incorporating SS and rather tightly link with SS, compared with the PCs incorporating NA. The formation of a significant amount of CaCO3 is observed after carbonation. In general, steel slag can be used as alternative aggregate to replace natural aggregate in preparing PCs.
Research has been done to obtain a Porous Concrete (PC) mixture capable of bearing heavy traffic loads while maintaining sufficient air voids (AV) to percolate water into the ground. This research aims to establish several design parameters in PC mixture dosage in order to generate a multi-criteria methodology that helps to obtain a final product, which is beneficial for both citizens and environment. Compression strength, indirect tensile strength, permeability, skid resistance, and stiffness modulus were evaluated, employing different aggregate gradations (AG), water to cement (w/c) and sand to cement (s/c) ratios, designing with the Porous Concrete that the right addition of sand and AG can improve mechanical capacity Design (PCD) methodology. Results demonstrated by around 10% and permeability rates by around 25%. This investigation provides a starting point for the use of additives in PC mixtures that helps to bring multifunctional properties such as heat island mitigation, air purification (photo-catalysis) and noise reduction, among others.
Interlocking paver blocks are used widely at low speed traffics road especially surrounding building complexes. Interlocking paver blocks are easy to install and provide aesthetic finishing to the landscape. However, usage of interlocking blocks in large areas reduce ground permeability that lead to higher runoff. New interlocking paver blocks were investigated to reduce runoff and the effect on its mechanical performance. Two types of paver block produced which is paver block with permeable concrete and paver block with void in the center. The results show that the compressive strength for paver block with permeable concrete is averagely higher than paver block with void by 31.5% while the flexural strength of all samples were between 1.0 to 1.7 MPa. Paver block with void recorded highest reduction of runoff compared to paver block with permeable concrete which is 25.5%. This is in line with water infiltration test result. It was concluded that the water retaining performance of paver block increase with increment of void volume and increase in void volume caused reduction on compressive strength of interlocking blocks.
Porous concrete is an environmentally friendly material. To evaluate the damage and discuss the failure mechanism of porous concrete, a uniaxial compression test was carried out in this study. Based on acoustic emission (AE) technology, the changes in AE ringing counts and energy were recorded, and the b-value was analysed. In this research, the evolution of cracks and stress-strain curves of specimens under uniaxial compression were also analysed by the discrete element method (DEM). The results showed that the failure process of porous concrete could be divided into an initial stage, crack propagation stage and failure stage. The mechanical properties and failure characteristics of porous concrete are different from those of conventional concrete. The main failure mode of porous concrete under compression is the failure of the bonding layer between the aggregates, whereas the aggregate failure of conventional concrete rarely occurs. There are many connected or unconnected pores in porous concrete. During the failure process of porous concrete, cracks propagate into the pores until penetrating cracks occur. This paper provides a basis for further study on the microscopic mechanism of porous concrete failure.
This paper describes the results of studies to develop pervious concrete for use as an overlay material over traditional concrete to reduce noise, minimize splash and spray, and improve friction as a surface wearing course. Workability and compaction density testing methods were developed to ensure constructibility and placement consistency. The mixture testing matrix consisted of evaluating aggregate type and gradation, cementitious material amounts and composition, and various admixtures. Selected mixtures were tested for permeability, strength, workability, overlay bond strength, and freezing-and-thawing durability. The selected mixture was self-consolidating and slip-formable and was placed at the MnROAD testing facility during late October 2008. The test results indicate that pervious concrete mixtures can be designed to be highly workable, sufficiently strong, permeable, and have excellent freezing-and-thawing durability, thus being suitable for pavement overlays.
The shape of aggregates used in concrete is an important parameter that helps determine many concrete properties, especially the rheology of fresh concrete and early-age mechanical properties. This paper discusses the sample preparation and image analysis techniques necessary for obtaining an aggregate particle image in 3-D, using X-ray computed tomography, which is then suitable for spherical harmonic analysis. The shapes of three reference rocks are analyzed for uncertainty determination via direct comparison to the geometry of their reconstructed images. A Virtual Reality Modeling Language technique is demonstrated that can give quick and accurate 3-D views of aggregates. Shape data on several different kinds of coarse aggregates are compared and used to illustrate potential mathematical shape analyses made possible by the spherical harmonic information.
Portland cement pervious concrete (PCPC) is increasingly used across the United States, and this has prompted various entities to begin the process of developing standardized test techniques. A major issue with placing PCPC is the inconsistencies in concrete workability between mixtures developed in the laboratory and in the field. It is therefore urgent to properly determine workability of pervious concrete and to ensure that the designed concrete mixtures are suitable for particular compaction methods and field conditions. This paper describes a new test method for characterizing PCPC workability-the gyratory compaction test method. A modified Superpave gyratory compactor (SGC) is employed in the present study. Two PCPC workability parameters are defined from the gyration compaction curve: (1) workability energy index, which describes initial concrete workability and (2) compaction densification index, which describes the resistance of the tested mixture to further compaction. The effects of binder content and water-to-cement ratio as well as effect of concrete mixing time on PCPC workability are studied. Based on the test results, values of the workability parameters for concrete with various degrees of workability are specified.
This paper presents results from an investigation aimed at identifying whether enhanced porosity concrete (EPC) may have the potential to be used for sound mitigation purposes. Toward this end, EPC mixtures were prepared using single sized aggregates as well as blends consisting of two different aggregate sizes. In addition, mixtures were prepared to determine the influence of sand content and silica fume on the measured acoustic characteristics and mechanical properties of EPC. All mixtures were tested for sound absorption using an acoustic impedance tube and flexural strength using three-point bending. An image analysis procedure was used to characterize the total porosity and size of the pores for each mixture. Differences in aggregate grading were observed to result in variations in both the acoustic absorption and flexural strength. These variations are directly related to both total porosity and pore size. The results of this research indicate that EPC mixtures with single sized aggregates provide substantial improvement to sound absorption as compared to conventional concrete. Blending aggregates in correct proportions enables the pore size and overall porosity to be controlled resulting in an improvement in the acoustic absorption. The influence of specimen length on the frequency at which maximum absorption is achieved is discussed and a simple conceptual model is used to illustrate the influence of pore structure on the sound absorption properties.
The interfacial transition zone (ITZ) is regarded as a key feature for the transport properties and the durability of concrete. In this study one self-compacting concrete (SCC) mixture and two conventionally vibrated concrete (CVC) mixtures are studied in order to determine the influence of compaction on the porosity of the ITZ. Additionally oxygen permeability and water conductivity were measured in vertical and horizontal direction. The quantitative analysis of images made with an optical microscope and an environmental scanning electron microscope shows a significantly increased porosity and width of the ITZ in CVC compared to SCC. At the same time oxygen permeability and water conductivity of CVC are increased in comparison to SCC. Moreover, considerable differences in the porosity of the lower, lateral and upper ITZ are observed in both types of concrete. The anisotropic distribution of pores in the ITZ does not necessarily cause anisotropy in oxygen permeability and water conductivity though.
Not available Civil, Architectural, and Environmental Engineering
Controversy exists as to why silica fume increases the strength of concrete when it is used as a partial replacement for cement. Some evidence supports the view that the increase in strength is due to an increase in the strength of the cement paste constituent of concrete. However, contradictory evidence shows no increase in the strength of cement paste, but substantial increases in concrete strength, when silica fume is used. The latter evidence is used to support the theory that silica fume strengthens concrete by strengthening the bond between cement paste and aggregate. This study is designed to explain the contradictory evidence and establish the role played by silica fume in controlling the strength of concrete and its constituent materials. These goals are accomplished using cement pastes, mortars, and concretes with water-cementitious material ratios ranging from 0.30 to 0.39. Mixes incorporate 1) no admixtures, 2) a superplasticizer only, or 3) silica fume and a superplasticizer. The research demonstrates that replacement of cement by silica fume and the addition of a superplasticizer increase the strength of cement paste. It also demonstrates that cement paste specimens, with or without silica fume, can exhibit reduced strength compared to other specimens with the same water-cementitious material ratio if the material segregates during fabrication, thus explaining some earlier experimental observations. The segregation of cement paste is caused by high superplasticizer dosages that do not cause segregation of concrete with the same water-cementitious material ratio. Concrete containing silica fume as a partial replacement for cement exhibits an increased compressive strength in large part because of the improved strength of its cement paste constituent. Changes in the paste-aggregate interface caused by silica fume appear to have little effect on the uniaxial compressive strength of concrete.
Due to its excellent air and water permeability, pervious concrete has become an environmental friendly material in paving application, providing its benefits in reducing the runoff water, enhancing pavement skid resistance by rapid drainage of water, and reducing pavement noise. However, its high porosity and low strength limit its popularity. Based on the concept of pervious concrete, a mix design approach especially for pervious concrete was proposed and an experimental study was undertaken to produce high performance pervious concrete by using gap-graded coarse aggregates and adjusting cement content. The results indicated that pervious concrete with compressive strength up to 33.5 MPa and permeability coefficient of 6 ml/min can be obtained by using this mix design approach. The results also showed that for pervious concrete made with gap-graded aggregates, the strength increases, and the permeability coefficient decreases with the decrease of the aggregate size. There is an optimum content of cement used to coat the coarse aggregates, enhancing the cement-aggregate interface bonding and overall performance of pervious concrete.
In this study, an experimental configuration that reveals the dynamic response of porous concretes in a drop weight impact test was introduced. Through the measurement of particle velocity at the interface, between the impactor and the concrete target, the dynamic response was obtained in an easily applicable way. Laser Doppler velocimetry (LDV) was used in monitoring the time history of the particle velocity at the interface, which was subsequently analyzed to determine the dynamic strengths of the concrete specimens tested. The velocity measurements were analyzed using a special reverberation application of the impedance mismatch method. The test results showed that the experimental configuration was sufficient to measure the dynamic strengths of porous concretes and a normal concrete with moderate strength. The method was validated by using impactors having different dynamic impedances in testing the same material and was also verified to be precise enough to distinguish between different types of porous concrete mixtures. DOI: 10.1061/(ASCE)MT.1943-5533.0000511. (C) 2012 American Society of Civil Engineers.
The interfacial transition zone (ITZ) has a great influence on the properties of cement-based materials. The ITZ characteristics of marble and sandstone aggregates were compared in terms of the following aspects and methods: morphology of hydration products by scanning electron microscopy (SEM), element ratio of calcium (Ca) and silicon (Si) by energy dispersion X-ray spectrometry (EDX), calcium hydroxide (Ca(OH)(2)) crystalline orientation index by X-ray diffraction (XRD), and pore structure by backscattered electron imaging and stereo microscope. An attempt had been made to compare the mechanical properties and transport properties of ITZ by two methods bending strength and chloride ion permeability. The results showed that a richer calcium hydroxide and a higher crystalline orientation were found in the ITZ of marble-cement paste because of the acidic difference of the aggregates. However, a more porous structure appeared in the interface of sandstone-cement paste, which was attributed to the porous structure of sandstone itself. Also the sandstone-cement ITZ was found to exhibit poor mechanical properties and high permeability.
In this paper, cement paste characteristics and porous concrete properties are studied. The results indicate that cement paste characteristics are dependent on the water to cement ratio (W/C), admixture and mixing time. Cement paste with high viscosity and high flow suitable for making porous concrete is obtained with the use of low W/C of 0.20–0.25, an incorporation of 1% superplasticizer, and sufficient mixing.Porous concretes having suitable void ratios are produced with appropriate paste content and flow, and sufficient compaction. Good porous concretes with void ratio of 15–25% and strength of 22–39MPa are produced using paste with flow of 150–230mm and top surface vibration of 10s with vibrating energy of 90kNm/m2. For low void ratio, high strength porous concrete of 39MPa is obtained using paste with low flow. For high void ratio, porous concrete of 22MPa is obtained using paste with high flow. Furthermore, the results indicate that the strength of porous concrete could be estimated from strength equation of porous brittle material.
Most silica fume currently used in concrete is in the dry densified form and consists of agglomerates of sizes between 10 μm and several millimeters. Many of these agglomerates may break down only partially in normal concrete mixing. Examination of various mature silica-fume-bearing concretes using backscatter mode scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis shows that such agglomerates have reacted in situ and given rise to recognizable types of reaction products filling the space within the original outline of the agglomerate. One type is “quiescent,” and usually shows no evidence of volume instability. EDX spectra indicate that the product formed within such grains is C-S-H of very low Ca/Si ratio, with modest alkali contents. Other silica fume agglomerates may undergo a distinct alkali–silica-type reaction (ASR), with the reaction product found within the original outline of the agglomerate having significantly less calcium and usually much higher alkali contents than the quiescent type. Such reacted agglomerates show evidence of local expansion, shrinkage cracking (on drying), and other features common to ASR. Both types may be found within the same concrete, sometimes in close proximity. It further appears that exposure to seawater may convert previously formed reaction products of silica fume agglomerates to magnesium silicate hydrates.
The influence of silica fume on mechanical properties of concrete remains an important technical and research topic. The objective of this paper is to report some preliminary results of an experimental program aimed at separating the two possible mechanisms above transition zone modification and bulk paste modification.
Research on the structure and bond between cement stone and aggregates shows that the structure of the contact zone clearly differs from that of the plain cement stone. The main constituent of the contact zone seems to be calcium hydroxide which is also mainly responsible for the cement-aggregate bond.
The effects of aggregate gradation, amount, and size on pervious portland cement concrete (PCC) static modulus of elasticity were compared using four different mixtures. A standard mix and three variable mixes using a uniform gradation, increased aggregate amount, and increased aggregate size were used. The effective air void content was determined for each mixture. The compressive strengths and static elastic moduli were determined and compared at equal void contents. For a uniform gradation, the compressive strengths and static elastic moduli appeared to be higher within an optimal range of voids; however, there was no statistically significant difference between the results from the different gradations. An increased aggregate amount resulted in a statistically significant decrease in both compressive strength and static elastic moduli due to the subsequent decrease in paste amount. While the compressive strengths were higher for mixtures containing smaller aggregate sizes, there was no significant difference between the static elastic moduli when different aggregate sizes were used. Further research is needed to understand. the effects of aggregate size on the static modulus of elasticity of pervious PCC.
No-fines concrete is defined as a type of concrete from which the fine aggregate component of the matrix is entirely omitted. The aggregate is of a single size and the finished product is a cellular concrete of comparatively low strength and specific weight. The cellular nature eliminates capillary attraction and provides greater thermal insulation and water permeability than exists in conventional concrete. The advantages of no-fines concrete for different construction purposes have long been recognized. The post-World War II era has experienced the extensive use of no-fines concrete for load-bearing walls in single and multistory buildings, retaining walls, and ground-drainage slab systems. This paper traces the development and applications of no-fines concrete for building and other nonpavement purposes. The pavement applications are introduced in a companion article published in the ASCE Journal of Transportation Engineering.
No-fines concrete is a type of concrete from which the fine aggregate is totally omitted and singlesized coarse aggregates are held together by a binder consisting of a paste of hydraulic cement and water. The earliest application of no-fines concrete dates back to 1852 when two houses and a seagroin of 61 m (200 ft) long and 2.15 m (7 ft) high were constructed in the United Kingdom. Its extensive use came about after World War II when nearly the whole of Europe was in vast housing need. The unprecedented demand for bricks. and the subsequent inability of the brick-making industry to provide bricks in sufficient quantity. led to the adoption of no-fines concrete as a construction material since it required considerably less cement per volume than conventional concrete. Earlier use of no-fines concrete was confined to building construction and other nonpavement applications. The present paper cites the use of no-fines concrete for pavement applications in the United States and Europe.
An understanding of the mechanical response of pervious concretes as a function of material design and pore structure parameters is essential for effective utilization of this material. A methodology to proportion pervious concrete mixtures of desired porosity using high or low cement paste contents is provided in this paper along with the compressive response of these mixtures. The compressive stress–strain relationships demonstrate: (i) a consistent trend of decreasing peak stresses and strains at peak stress with increasing porosity, (ii) a reduction in strains at peak stresses with reducing paste contents, and (iii) a rapid drop in the post-peak response with reducing porosity. The compressive energy absorbed by the pervious concrete specimens is found to scale linearly with compressive strength and can be related to the porosity and critical pore sizes in the material.Highlights► Porosity-based mixture design methodology for pervious concretes. ► Compressive stress-strain response of high- and low-paste content pervious concrete mixtures. ► Analysis of the dependence of compressive strength on porosity and paste volume fraction. ► Compressive energy absorption of pervious concretes and the influence of porosity and critical pore size on energy absorption.
This paper describes the so called interfacial transition zone—ITZ—in concrete. This is the region of the cement paste around the aggregate particles, which is perturbed by the presence of the aggregate. Its origin lies in the packing of the cement grains against the much larger aggregate, which leads to a local increase in porosity and predominance of smaller cement particles in this region. The ITZ is region of gradual transition and is highly heterogeneous, nevertheless the average microstructural features may be measured by analysis of a large numbers of backscattered electron images of polished concrete samples. Such measurements show that the higher porosity present initially is significantly diminished by the migration of ions during hydration.
Dry densified silica fume is by far the most common form of silica fume used in current concrete practice; the alternative,
slurried silica fume has become unavailable in many places. Densified silica fume as commonly supplied consists of particles
of sizes up to several millimeters, which are generally not dispersable into individual silica fume spheres. Densified silica
fumes from some sources can be dispersed by moderate ultrasonic treatment into small clusters or chains of spheres; others
resist such treatment and mostly remain as large agglomerates. Under conventional concrete mixing, substantial contents of
agglomerates almost always remain in the concrete. Thus the assumption that the densification process is somehow ‘reversible’
is not generally warranted. The sizes of undispersed agglomerates remaining in concrete after mixing often exceed the sizes
of Portland cement particles, thus limiting any potential benefits attributed to the fine particle filler effect. Large undispersed
grains appear to always undergo chemical reaction in concrete, but such reactions may induce ASR damage only under especially
unfavorable circumstances.
The compressive strengths of silica fume cement paste and mortar were evaluated at various water-cementitious ratios. Five different water-cementitious ratios were used including, 0.22, 0.25, 0.28, 0.31, and 0.34 and two contents of silica fume, 16% and 25% by weight of cement. Superplasiticizer content was adjusted for each mix to ensure that no segregation would occur.The results show that the increase in compressive strength of mortar containing silica fume, as a partial replacement for cement, greatly contributes to strengthening the bond between the cement paste and aggregate. Partial replacement of cement by silica fume and the addition of superplasticizer increases the strength of mortar but has no influence on the strength of cement paste. Results were verified by statistical analysis using hypothesis testing at a 95% confidence level.It was also demonstrated that superplasticizer in combination with silica fume plays a more effective role in mortar mixes than in paste mixes. This can be attributed to a more efficient utilization of superplasticizer in the mortar mixes due to the better dispersion of the silica fume particles. The paper also reviews some of the available literature on the influence of silica fume on cementitious composites and unsettled questions associated with this topic.
In fresh concrete a watercement (W:C) ratio gradient develops around the aggregate particles during casting, resulting in a different microstructure of the surrounding hydrated cement paste. This zone around the aggregate is called the interfacial transition zone (ITZ). This review describes the formation mechanisms and the microstructure of the ITZ. The higher W:C implies a diffusion process during hydration, and this zone may be consequently described as a heterogeneous area with a porosity gradient and a complementary gradient of anhydrous and hydrated phases. By using very fine and well-dispersed mineral additions, the initial W:C gradient around the aggregates is lowered and the ITZ is densified. The microstructure of the ITZ may be improved in the vacinity of calcereous aggregate, which reacts with calcium aluminates of Portland cement paste, forming calcium carboaluminates. The overall engineering properties of concrete in relation to the ITZ are beyond the scope of this review. Nevertheless, the local properties of the interfacial zone are reviewed: the mechanical and the transport characteristics of the ITZ are discussed in relation to the porosity and connectivity of pores.
Since concrete is a composite material, the interfaces between components can be expected to have major effects on physical properties. In ordinary portland cement concrete, the interfacial zone between cement paste and aggregate has been shown to exhibit characteristics greatly differing from those of the bulk paste. The addition of mineral admixtures to the mix has been shown to significantly alter this interfacial zone microstructure and enhance physical properties of the composite. In this paper, a direct comparison is made between results obtained using a three-dimensional microstructural model and those obtained experimentally on a similar set of mixes containing various amounts of silica fume. Quantitative measurements of backscattered electron images of the interfacial zone in the real materials are compared to model results. The model reproduces the experimentally-observed characteristics of the interfacial zone, which are quite different with and without the presence of silica fume. Based on the model and experimental results, it is suggested that the presence of silica fume produces a more homogeneous microstructure by balancing the Ca/Si molar ratio in the interfacial zone relative to that in the bulk paste, unlike ordinary portland cement concrete where this ratio increases dramatically as the aggregate surface is approached.
Stereo pair imaging in a scanning electron microscope was used to document details of the topography of fracture surfaces at various degrees of magnification. The fracture surfaces investigated had been produced by fracture testing of chevron notched beam specimens according to ISRM Method 1. The procedure involved loading in a very stiff machine to the point of initial deviation from lineariry, unloading, and reloading repetitively until failure. Specimens were prepared and examined from dolomite and andesite rock used commercially for concrete aggregates, and from cement paste with and without silica fume. Various topographic features of the fracture surfaces are described.
In this paper, a pervious concrete pavement material used for roadway is introduced. Using the common material and method, the strength of the pervious concrete is low. Using smaller sized aggregate, silica fume (SF), and superplasticizer (SP) in the pervious concrete can enhance the strength of pervious concrete greatly. The pervious pavement materials that composed of a surface layer and a base layer were made. The compressive strength of the composite can reach 50 MPa and the flexural strength 6 MPa. The water penetration, abrasion resistance, and freezing and thawing durability of the materials are also very good. It can be applied to both the footpath and the vehicle road. It is an environment-friendly pavement material.
Two experimental techniques have been developed to determine mechanical properties of the interfacial zone between cement paste and rock. The first technique is based on ISRM Method I, and involves measuring bond fracture properties from chevron notched specimens of rock, paste, or rock/paste. The second technique uses composite compression cylinders to determine the influence of interfaces on the stiffness of composite materials. The techniques are described, and some preliminary results are presented.
ASTM special technical publication: significance of tests and properties of concrete and concrete-making. Philadelphia: ASTM; 1994. Fig. 9. Summary of the factors affecting porous concrete strength
- P Klieger
- Lamond
- Jf
Klieger P, Lamond JF. ASTM special technical publication: significance of tests and properties of concrete and concrete-making. Philadelphia: ASTM; 1994. Fig. 9. Summary of the factors affecting porous concrete strength.
Concrete petrography
- St Da John
- Ab Poole
- Sims
St John DA, Poole AB, Sims I. Concrete petrography. New York: John Wiley and Sons; 1998.
Experimental study on properties of pervious concrete
- Yang