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Recycled asphalt pavement as a base and sub-base material

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Abstract

Laboratory and field investigations were conducted to evaluate the use of recycled asphalt pavement (RAP) in roadway base and sub-base applications. The laboratory resilient modulus test results showed RAP has comparable strength with dense graded aggregate base and sub-base material used in the State of New Jersey. Using the spectral-analysis-of-the-surface-waves method (SASW), the field testing program evaluated the elastic modulus of the RAP base in the field and verified the laboratory results. The field test results showed higher modulus and stiffness for RAP than the dense graded aggregate base normally used in state of New Jersey.

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... Maher et al. [7] was one of the first researchers in late 1990s to characterize RAP on the basis of resilient modulus (M R ) to evaluate the performance of the unbound aggregate based on the mechanistic empirical pavement design guide (MEPDG) parameter. The findings of their research indicated that when RAP is mixed with virgin aggregate (VA), the blend resulted in higher M R than the VA. ...
... Very limited literature is available that evaluates the long term field performance of RAP-VA blends as base course material. Several studies in the past have made attempts to evaluate the performance of RAP as base course but these studies were limited only to in-situ pavement testing (like determination of modulus) and did not study the properties of RAP (Dafoe [5,7]. The conclusions were based primarily on the basis of in-situ modulus values after construction. ...
... The conclusions were based primarily on the basis of in-situ modulus values after construction. Dafoe [5] and Maher et al. [7] suggested that a RAP base course showed higher in-situ resilient modulus than conventional base course. This information may have made the researchers after 1997 to think that RAP performs better than the conventional aggregate. ...
... Therefore, many researchers have evaluated the potential of RAP as an aggregate to reduce the overgrowing problem of waste stockpiles (Debbarma et al., 2019;Hoppe et al., 2015;Seferoğlu et al., 2018;Soleimanbeigi et al., 2015;Stolle et al., 2014;Ullah et al., 2018). Earlier accounts of utilising RAP, as base course material, emerged in the late 1990s and early 2000s which focused in evaluating the performance of RAP, as base course material, based on elastic properties primarily resilient modulus (MR) (Kim et al., 2007;Maher et al., 1997). MR is considered the sole parameter for material characterisation in the design process of pavement structure according to the mechanistic empirical pavement design guideline (MEPDG) (AASHTO, 1993). ...
... That's why earlier studies focused on characterising RAP based on MR. Literature reports that RAP depicts higher MR than virgin aggregates (VA), thus expected to exhibit superior performance than VA (Alam et al., 2010;Kim et al., 2007;Maher et al., 1997). However, latest developments in research have shown that although RAP exhibits higher MR but it accumulates higher permanent deformations (PD) than VA which may become a cause of rutting and excessive deformations in the pavement structure (Bilodeau et al., 2013;Schaertl & Benson, 2010;Soleimanbeigi et al., 2015). ...
Article
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Pavement demolition debris is one of the world’s major waste problems. Each year the United States produces about 100 million tons of reclaimed asphalt pavement (RAP), out of which more than 60% ends up in landfills or asphalt plants. Recent studies have shown that RAP can be considered a viable alternative to natural base course aggregates to resolve the problem of waste accumulation. In this study efforts have been made to develop an artificial neural network (ANN)-based performance predicting model for base course aggregates blended with RAP. Repeated load triaxial (RLT) tests have been employed in this study to evaluate the performance of base course aggregate. Two different RAP samples were blended with virgin aggregates (VA) in proportions of 20%, 40% and 60% and RLT tests were performed on the RAP-VA blends at three different stress conditions. The data from the laboratory test results were used to model the response of the RAP-VA blends in terms of accumulated permanent deformation against loading cycles. The ANN-based model developed in this study predicted the response of the material with an average coefficient of determination of 0.98. The results indicate that the developed ANN-based model is accurate in comparison to previously published regression models, which do not have the room to accommodate complex material properties as in the case of RAP and other recycled materials.
... Bennert et al. (2000) reported higher resilient modulus of RAP to crushed aggregates with similar gradations, while other studies reported lower California Bearing Ratio (CBR) values (Garg and Thompson 1996) and resilient modulus (Taha et al. 1999) of RAP. Maher et al. (1997) evaluated field performance of three base materials using a seismic pavement analyzer (SPA). The results indicated that bases with 100% RAP and 25% RAP content exhibited higher degrees of damping than the dense-graded aggregate base. ...
... This indicated that after equivalent compaction work, RAP was the most difficult to be compacted among the three types of materials. This may also be the cause of high damping and deformation of RAP based observed in previous field studies (Maher et al. 1997;Puppala et al. 2012). At low temperature such as 5°C, according to the creep behavior of RAP at different temperatures (Fig. 5), less viscous behavior of RAP would be expected. ...
Article
Full-text available
Laboratory tests were conducted to evaluate the resilient modulus and rate dependencies of unbound reclaimed asphalt pavement (RAP), crushed limestone, and crushed gravel prepared with the same gradation and equivalent compaction work. Resilient modulus, permanent deformation, and strain energy loss were studied through repeated triaxial and creep testing at different temperatures. The results from this study indicated that RAP tended to have higher resilient modulus when tested as unbound aggregates. However, the permanent deformation of RAP tended to be higher than the crushed stones at ambient temperature. Due to viscoelasticity, the strain (load) rate and temperature dependency of unbound RAP base material was significantly higher than those of crushed limestone and gravel. The temperature dependency of unbound RAP base could significantly affect the performance of asphalt pavements.
... The utilization of RAP can reduce construction costs and prevent environmental pollution [7]. However, often low strength and stiffness are in the way of an enormous quantity of RAP to be taken by the construction industry [4,[8][9][10][11][12]. ...
Article
Concern exists regarding the performance of concrete containing a higher percentage of recycled aggregates. There is an ongoing effort to improve the strength and durability characteristics of such concrete in various ways. As part of that effort, this study investigated the laboratory performance of geopolymer concrete containing a higher dosage of reclaimed asphalt pavement (RAP) as a pavement construction material. A series of laboratory investigations were performed to evaluate the mechanical, durability, and morphological characteristics of RAP-geopolymer concrete (GPC). The mechanical properties of RAP-geopolymer concrete were also compared with RAP-Portland cement concrete (PCC) produced using ordinary Portland cement (OPC). Results indicated that RAP-geopolymer concrete exhibited higher compressive, flexural, split tensile strength as compared to RAP-cement concrete. Further, RAP-geopolymer concrete revealed satisfactory results in terms of durability regarding wet-dry cycles and water absorption (sorptivity). Morphological and microstructural investigation using scanning electron microscopy (SEM), X-Ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) also discovered the formation of geopolymer compounds in RAP-geopolymer concrete which explains the better mechanical and durability properties of such concrete mixtures.
... The main privilege of FDR is reusing the reclaimed asphalt pavement (RAP) and aggregates. The use of RAP in pavement layers, especially the base course, results in decreased waste and provision of useful materials for maintenance, rehabilitation, and reconstruction in road construction [6,[33][34][35][36]. ...
Article
One method for improvement of distressed pavements is full-depth reclamation (FDR). In this technology, the present asphalt layer is pulverized and mixed with the aggregate layer beneath it and then the mixture is stabilized using a stabilizer agents such as Portland cement in order to increase the strength parameters of the mixture. The aim of this study is to evaluate the laboratory results of stabilizing the blend of reclaimed asphalt pavement (RAP) and aggregates with cement in order to be used as a treated base coarse in full-depth reclamation (FDR) method. The present study was conducted using two different types of aggregate soils. Compaction and unconfined compressive strength (UCS) tests were carried out on different ratios of RAP to aggregates of 0/100, 20/80, 40/60, and 60/40. Four cement contents of 3, 4, 5, and 6 percent were added and the samples were cured for 7 and 28 days after compaction. Results show that by assuming a constant percentage of RAP, by increasing one percent of the Portland cement, the UCS value for the stabilized layer including SP-SC and GW-GC increased by an average of 376 and 410 kPa, respectively. According to this research, the elastic modulus of FDR layers can be assumed between 9000 and 40,000 kPa with respect to soil type and dosage of RAP in FDR layers. Results also show that the optimum content of Portland cement for construction of FDR layers is between 3 and 4% for SP-SC soil and between 3 and 5% for GW-GC, respectively.
... In recent years, efforts have been made to incorporate RAP into pavement base or subbase applications (e.g. Maher and Jr., 1997, Taha et al., 2002, Park, 2003, Taha, 2003, Blankenagel and Guthrie, 2006, Poon and Chan, 2006, Cho et al., 2011, Hoyos et al., 2011, Puppala et al., 2011, Piratheepan et al., 2013. RAP stabilized with cement binders has been reported to perform satisfactorily in pavement base and subbase layers (Hoyos et al., 2011, Puppala et al., 2011. ...
Article
Full-text available
In recent years, efforts have been made to incorporate reclaimed asphalt pavement (RAP) into pavement base or subbase applications by means of cement binder stabilization. This approach, however, may not be an environmentally friendly solution due to the high carbon footprint involved in the production of Portland cement. Recycled concrete aggregate (RCA), on the other hand, has been widely accepted in pavement applications. The sustainable solution of blending RAP with RCA was investigated in this research in an attempt to facilitate the usage of this blend as an alternative pavement subbase material. An extensive suite of geotechnical laboratory tests was undertaken on RAP with contents of 100, 50, 30 and 15% in blends with RCA. Results of the research study indicated that RAP/RCA blends with a low 15% RAP content meet the repeated load triaxial requirements for use in pavement subbase layers. Results of field performance of a pavement subbase constructed with untreated 100% RAP, at a private haul road field-demonstration site, confirmed that it had insufficient strength requirements to meet local road-authority pavement-subbase requirements. RAP and RAP/RCA blends, although found in this study to be not fully compliant with the local road-authorities requirements, could be potentially considered for lower traffic usage, such as haul roads and footpaths. (C) 2014 American Society of Civil Engineers.
... The M R value obtained from unreinforced RCA was 330 MPa, which is consistent with the results reported previously by others (Maher et al. 1997;MacGregor et al. 1999;Gnanendran and Woodburn 2003). The M R value of RCA+biaxial increased by 24% and of RCA+triaxial increased by 34% when compared with unreinforced RCA at a maximum confining stress of 137.9 kPa. ...
Article
Full-text available
Extensive amounts of natural quarry aggregates are currently being used in road and pavement applications. The use of construction and demolition (C&D) materials such as recycled concrete aggregate (RCA), crushed brick (CB), and reclaimed asphalt pavement (RAP) as an alternative to quarry aggregates has generated interest in recent years, particularly as a pavement base or subbase material. However, the resilient moduli responses and performance of these C&D materials reinforced with geogrids under repeated loads have yet to be established. This research investigates the resilient moduli (MR) and permanent deformation characteristics of C&D materials reinforced with biaxial and triaxial geogrids with the use of repeated load triaxial (RLT) equipment. The effects of varying deviatoric stress on the resilient modulus of unreinforced and geogrid-reinforced C&D materials were also investigated. Regression analyses of resilient modulus test results were performed using the two- and three-parameter models. The MR properties of the geogrid-reinforced RCA and CB were found to be higher than that of the respective unreinforced material. The MR value of RCA+biaxial increased by 24% and of RCA+triaxial increased by 34% when compared with unreinforced RCA. The permanent deformation value obtained from RCA+biaxial decreased by 29% and of RCA+triaxial decreased by 36% when compared with unreinforced RCA. The MR value of CB+biaxial increased by 16% and of CB+triaxial increased by 55% when compared with unreinforced CB. The permanent deformation value decreased by 29 and 37% for CB+biaxial and CB+triaxial, respectively, when compared with unreinforced CB material. The incorporation of geogrids had significant effects on the resilient modulus and permanent deformation characteristics of C&D materials. The three-parameter resilient moduli model was found to provide a good fit for the geogrid-reinforced C&D materials.
... Based on laboratory and field evaluations, the resilient modulus of unbound granular base and subbase material has been reported to increase as the percentage of RAP increases (Highter et al. 1997;Maher and Popp 1997;MacGregor et al. 1999;Bejarano 2001;Sondag et al. 2002;Bennert and Maher 2005). Mokwa and Peebles (2005) found that the addition of asphalt concrete millings to a granular material results in a more ductile response to loading and a decrease in the low-strain secant modulus when compared to the mechanical behaviour of conventional aggregate. ...
Article
An experimental study investigated the California bearing ratio (CBR), shear strength, stiffness, and cyclic creep properties of crushed, reclaimed asphalt concrete pavement (RAP) — natural aggregate blends for granular base and subbase. The CBR was found to depend on the properties of the constituent materials and the compactive effort used to prepare the specimens. It was concluded that the CBR test may not be appropriate for evaluating the suitability of blended material for granular base construction. Based on the triaxial tests, it was observed that the addition of RAP to natural aggregate (Ontario Granular A) reduces the shear strength slightly and tends to increase the accumulated strain (deformation) that develops due to repetitive loading. The influence of RAP on the mechanical properties, including ‘elastic’ modulus, was sensitive to specimen preparation and preconditioning. For certain combinations of RAP and Granular A, the mechanical properties were similar to those of Granular A. The key to a stable blend was found to be compactive effort.
... The sustainable usage of RAP also leads to significant economical savings for the construction of new highway pavements [6]. Large quantities of RAP are however not taken up whole-heartedly by industry, due to their often low strength and stiffness characteristics [3,[7][8][9][10][11]. Though some efforts have been made to blend RAP with other higher quality natural or recycled materials in pavement base/subbase applications, these RAP blends often do not meet the minimum local road authorities specified requirements [4,8]. ...
Article
This paper investigates the strength development of Recycled Asphalt Pavement (RAP)-Fly Ash (FA) geopolymer as a road construction material. A mixture of sodium hydroxide solution (NaOH) and sodium silicate solution (Na2SiO3) is used as a liquid alkaline activator (L). Unconfined Compression Strength (UCS) is used as an indicator to measure the strength development of RAP-FA geopolymer and RAP-FA blend (without L). The UCS development is analyzed via Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD) analyses. Test results show that the compacted RAP-FA blend can be used as a base course material as its UCS values meet the specified strength requirements. The UCS of RAP-FA blends increases with time due to the formation of Calcium Silicate Hydrate (C-S-H) and Calcium Aluminate Hydrate (C-A-H), as detected from XRD and SEM analyses. The UCS of RAP-FA geopolymer increases as the NaOH/Na2SiO3 ratio decreases and is higher than those of compacted RAP-FA blends. When the NaOH/Na2SiO3 ratios are less than 90:10. At an early stage of 7 days and room temperature curing, XRD and SEM analyses indicate that low geopolymerization products (N-A-S-H) in RAP-FA geopolymer are detected when only NaOH (NaOH/Na2SiO3 = 100:0) is used as L, hence the UCS of RAP-FA geopolymer at NaOH/Na2SiO3 = 100:0 is lower than that of RAP-FA blends. With increasing curing time and temperature, NaOH solution dissolves more silica and alumina from FA in the geopolymerization reaction, hence the UCS developed with time and temperature. The highly soluble silica from Na2SiO3 incorporates with leached silica and alumina from FA into a N-A-S-H gel which co-exists with C-S-H and C-A-H from RAP and FA reaction. Therefore, the 7-day UCS values of RAP-FA geopolymer increase with decreasing NaOH/Na2SiO3 ratios for both room temperature and 40 °C curing. This research study confirms the potential of RAP-FA blends and RAP-FA geopolymers as an alternative stabilized pavement material.
... According to the National Asphalt Pavement Association (NAPA, 2009), asphalt pavement is the most recycled material used in U.S. and highway construction industry annually produces more than 100 million ton of RAP that is recycled into new pavements. RAP has been used as base, sub-base, and subgrade material in pavement construction in recent years but the inadequate strength and stiffness characteristics limit their use in the pavement (Mulheron and O'Mahony, 1990;Maher et al., 1997;Rana, 2004). The characteristics of the RAP is influenced by the asphalt content, temperature, moisture content, dry density, and age of the RAP. ...
... Arulrajah et al. [16,17] reported the sensitivity of CB aggregates to moisture ratio in pavement base/subbase application. The successful use of RAP aggregates in low-traffic pavement application has been reported by several authors [18,19]. Studies on usage of recycled waste materials as a high value construction material in pavement applications have been performed by several authors and there are several cases of use of recycled materials in footpaths and pavement construction internationally [2,[5][6][7]. ...
... RAP can be used as a granular base or sub-base materials for the pavement structure [9,10]. Garg and Thompson (1996) conducted a study investigating the potential use of RAP as a base layer [9]. ...
Article
Full-text available
This research aims to determine the use of materials from reclaimed asphalt pavement layers directly with the addition of virgin aggregates without the addition of other additives (filler) intended for quality improvement based on the 2010 general specifications of the Indonesian National Standard. Utilization of these materials was used for base courses (class A), sub-base courses (class B), and courses without asphalt coverings (class S). The method used was the laboratory-experiment method and the analysis of the relationship was made using the regression equation. Based on the analysis, by combining the mixture with the virgin aggregates, it was revealed that the materials from reclaimed asphalt pavement layers can be used for the base courses by no more than 3 percent, for the sub-base courses by no more than 9 percent, and for the courses without asphalt coverings or shoulders by no more than 10 percent.
... As such, new disposal options must be continually sought to prevent the accumulation of RAP in stockpiles. The uses of RAP as granular materials for base and subbase applications have also been widely studied in recent decades (Maher et al. 1997, Papp et al. 1998, Cosentino et al. 2003, Attia 2010, Arulrajah et al. 2013, 2014, Hoy, Horpibulsuk, et al. 2016, Hoy, Horpibulsuk, Rachan, et al. 2016. Often, when solely used as an alternative aggregate, RAP does not meet the gradation and strength requirements for unbound base and subbase applications [e.g. ...
Article
In this research, marginal lateritic soil (LS) was used for improving the gradation properties of reclaimed asphalt pavement (RAP) prior to cement stabilisation for heavy and light-volume roads. The unconfined compressive strength (qu) of cement-stabilised RAP–marginal LS blends was found to increase with LS replacement due to the improvement of gradation properties and lower asphalt binder content. The soil–water/cement ratio (w/C) was successfully implemented for a particular RAP:LS ratio to integrate the effects of water and cement contents on strength development at the optimum water content and on the wet side of optimum. By incorporating a new parameter termed as the asphalt binder content (AS), a general strength relation equation was proposed for various water contents, cement contents and RAP:LS ratios. The general strength relation of cement-stabilised RAP-marginal LS blends is presented based on three critical material constants, which are A*, B* and k. The A* and B* constants mainly depends on curing time, while the k constant is essentially the same. The general strength relation was furthermore validated with measured strength data. The general strength relation is useful as a mix design tool for determining the optimal input of cement for various RAP:LS ratios to meet strength requirement for base and subbase applications. A mix design method with a minimum trial test is furthermore proposed in this paper.
... In recent years, efforts have been made to incorporate RAP into pavement base or subbase applications [1][2][3][4][27][28][29][30][31][32]. RAP stabilised with cement binders has been reported toperform satisfactorily in pavement base and subbase layers [2,3].The application of RAP and RCA in pavement base/subbase as an aggregate, however, has been limited due to the lack of reported laboratory testing and fieldtesting results [33].Most of the existing literature concludes that M R value increases with RAP content; however, the majority of the studies have only considered low RAP contents in the blends. ...
Article
Full-text available
In current road and pavement engineering practices, the lack of fresh natural aggregate (granular material) supplies with increasing processing costs have led to use various reclaimed/recycled materials from old structures as a source of construction materials. Reclaimed Asphalt Pavement (RAP), and Recycled Concrete Aggregate (RCA) have been used as aggregates for pavement construction for some time. This study is focused on the characterization of blended materials containing 50% and 75% of RAP with fresh granular materials and RCA to evaluate whether they are suitable for granular base/subbase layers of flexible pavements. A series of laboratory tests was performed to determine the resilient modulus (MR) and the constrained modulus (Mc) for both fresh granular materials and their blends. Statistically, the notable increase was found in the MR values of the blended samples containing 75% RAP material and 25% fresh granular, particularly at higher levels of bulk stresses. It was also found that the accumulative strains during cyclic loading generally increase with an increase in the percentage of RAP contents in the blended samples. Mc test results show an increasing trend with the increasing level of axial stress, however, Mc value decreases with increasing percentage of the RAP content. Never-the-less, the t-test showed that accumulative strains during Mc tests were found to increase significantly with an increase in the percentage of RAP contents.
... The sustainable usage of RAP leads to significant economical savings for the construction of new highway pavements (Hajj et al., 2010). RAP can be utilized as a construction material in road bases or subbases, asphalt cement binders, asphalt concrete aggregates, and as embankment or fill material (Arulrajah et al., 2013(Arulrajah et al., , 2014Attia, 2010;Cosentino et al., 2003;Maher et al., 1997;Papp et al., 1998). ...
Article
Pavement rehabilitation and reconstruction generate large quantities of reclaimed asphalt pavement (RAP). The improvement of the engineering properties of this RAP is required in order to enable it for use as environmentally friendly alternative construction material in road pavements. The durability of RAP when blended with crushed rock (CR) and stabilized with Portland cement was investigated in this paper. The CR replacement was found to improve the compactibility and durability of the stabilized RAP/CR material. For a particular RAP:CR ratio, the compaction curves of cement-stabilized RAP/CR blends were found to be essentially the same for all cement contents, but different for unstabilized blends; i.e., the maximum dry unit weight of cement-stabilized RAP/CR blends is higher than that of unstabilized RAP-CR blends. The wetting-drying (w-d) cycles led to a loss in weight of the cement-stabilized RCA/CR blends and to a subsequent reduction in strength. The w-d cycle strengths (qu(w-d) ) for a state of compaction (dry side, wet side or optimum water content) at any w-d cycle could be approximated from the corresponding initial soaked strength (prior to w-d tests) (qu0). The qu0 of cement-stabilized RAP/CR blends increased with an increasing CR replacement and an increasing cement content. Assuming that the CR replacement also results in an increasing cement content, w/[C(1 + kCR c)] was proposed as a critical parameter for developing qu0 and qu(w-d) predictive equations where w is the water content at the optimum water content, C is the cement content, k is the replacement efficiency, and CRc is the CR content. Based on the qu(w-d) predictive equation developed here, a design procedure for the laboratory mixing of cement-stabilized RAP/CR blends was proposed, which would be valuable for an accurate determination of the ingredients (RAP:CR ratio and cement content) required to attain the necessary strength at the design service life.
... RAP-asphalt mixes containing up to 35% RAP indicated that recycled mixes performed as good as the performance of conventional HMA in terms of moisture susceptibility and resilient modulus [13]. A study conducted in the State of New Jersey to evaluate the use of RAP in base and subbase applications indicated that the laboratory resilient modulus and field elastic modulus of the RAP has comparable strength with dense graded aggregate base and subbase material [14]. A recent study of different RAP-virgin aggregate blends ...
Chapter
Over the last decade, there has been a dramatic increase in the use of recycled materials/by-products as alternative ecomaterials in pavement construction on widely varying estimates. This increase is due to the scarcity and depletion of the natural resources and the need of large material quantities for the construction of pavement layers. Many kinds of recycled materials or by-products are exclusively employed in pavement construction such as reclaimed asphalt pavement (RAP), construction and demolition (C & D) waste, waste rocks, glass, steel slag, cement dust, rice husk and straw, wood sawdust, waste plastic bags, crumb rubber, waste engine and cooking oils, and others. Undoubtedly, the use of these recycled materials/by-products in pavement construction has many benefits on the short and long terms. Some of these benefits are minimizing the use of natural resources, saving millions of cubic meters in landfills, reducing carbon dioxide emissions, reducing energy consumption, and constructing sustainable pavements. However, some barriers to adopt such materials in pavement construction still exist worldwide. Such barriers are that lack of clients' confidence in such materials, lack of specifications and legalization, etc. This chapter highlights the current status of using recycled materials/byproducts in pavement construction worldwide, specifications, and the gained benefits in terms of economic savings, environmental impact, and sustainability. The chapter also outlines the existing barriers and limitations to the prevalence of recycled materials/by-products in pavement construction. Finally, it documents recent approaches and strategies to overcome some of these limitations for successful implementation of such materials in pavement construction.
... The utilization of RAP can reduce construction costs and prevent environmental pollution [6]. However, often low strength and stiffness are in the way of an enormous quantity of RAP to be taken by the construction industry [3,[7][8][9][10][11]. Researchers tried to mix RAP with other virgin or recycled materials to use it in pavement base and subbase, however, the strengths of these blends most often do not meet minimum strength or durability requirements [4,8]. ...
Article
Full-text available
Mechanistic and microstructural characteristics of roller-compacted concrete (RCC) produced from recycled asphalt pavement (RAP) and geopolymer cement binder (GPC) were evaluated and compared with mixtures produced from ordinary Portland cement (OPC). It was found that RCC using geopolymer binder exhibited higher unconfined compressive strength, modulus of elasticity, and flexural strength as compared to the mixture containing ordinary Portland cement. It was also discovered that the mechanical properties of the developed concrete depend on mixture constituents: sodium hydroxide molarity, the ratio of sodium silicate to sodium hydroxide, curing temperature, and gradation of RAP. The experimental results showed that RCC using geopolymer binder exhibited compressive strength, modulus of elasticity, and flexural strength in the range of 8.4–21.1 MPa, 18.3–35.0 GPa, and 2.9–4.1 MPa, respectively. On the other hand, RCC using 12% OPC presented similar mechanical strengths of 13.2 MPa, 32.8 GPa, and 3.32 MPa, respectively. Regression analysis was also performed to establish the relationship between mechanical characteristics and various mixture constituents. Morphological and microstructural analysis proved the formation of geo-polymeric compounds. Based on the mechanistic characteristics, the developed roller-compacted RAP-Geopolymer concrete could be used as a strong pavement base in composite pavement system or wearing course of low volume roads.
... The utilization of RAP can reduce construction costs and prevent environmental pollution [9]. However, often low strength and stiffness are in the way of an enormous quantity of RAP to be taken by the construction industry [4,[10][11][12][13][14]. Researchers tried to mix RAP with other virgin or recycled materials to use it in pavement base and subbase; however, the strengths of these blends most often do not meet minimum strength or durability requirements [5,11]. ...
Conference Paper
This article studied the feasibility of low calcium fly ash-based geopolymer concrete (GPC) containing Recycled Asphalt Pavement (RAP) as a road construction material. The effect of RAP on the mechanistic characteristics of GPC was evaluated with the variation of mixture constituents including the molar concentration of NaOH, Na2SiO3 to NaOH ratio, and alkali to fly ash ratio as well as curing temperature. Compression, flexural, splitting tensile, and semi-circular beam tests were conducted to investigate the compressive and tensile characteristics of RAP-GPC mixtures. The microstructure and morphology investigations were performed using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR).
... Well-graded good quality aggregates along with asphalt coating can be obtained if the RAP is processed and screened properly [1]. Studies in the past have recommended the use of RAP for subgrade, GSB and base layer application [2][3][4][5][6]. The effect of RAP can be studied by separating the binder and aggregates and investigating the properties and their influence separately [7]. ...
Chapter
In modern days, life without the transportation industry is unimaginable. The roadways play a vital role in improving the economy of the country. As the roadways require necessary strengthening, rehabilitation or reconstruction depending on the severity of the damage caused to the structure during its service life, enormous quantity of RAP will be generated. It is essential to recycle and reuse the RAP generated in the pavement construction as it can help in preserving a large quantity of conventional construction materials. In this study, the strength characteristics of the bituminous mix with recycled binder or aggregates are compared with that of the conventional bituminous mix through laboratory investigation. The test result indicated that the recycled binder or aggregates can be effectively used in the bituminous mix satisfying the MoRT&H requirements up to a certain percentage. The recycled aggregates of up to 20% give maximum stability and ITS in comparison with conventional mix providing an eco-friendly, economical solution for the construction of pavements.
... The use of RAP can solve storage problems and environmental pollution while at the same time it can reduce construction costs (EPA, 2019;Davorin, 2008& Ryszard, 2016. However due to the low strength and durability properties of RAP, its usage as a construction material is limited to landfill, low strength base or subbase and replacement of few percentages of natural aggregates in hot mix asphalt (HMA) and conventional Portland cement concrete (Copeland, 2011;Chesner, 2019;Hansen, 2014;Hoyos, 2011;Arulrajah, 2013;Hajj, 2010;Maher, 1997;Ramzi, 1999;Huang, 2006& Huang, 2005. Although Ordinary Portland Cement (OPC) is being used as a popular binder for a long time, its increasing production generates an enormous amount of CO 2 in the atmosphere, which is also raising environmental concerns (Malhotra, 2010;Naik, 2015& Salloum, 2007. ...
... Previous research has been conducted that has made attempts to incorporate RAP into the base course of flexible pavements by combining RAP with virgin aggregate (VA) (2)(3)(4)(5)(6)(7)(8). Previous literature indicates that the use of 100% RAP is not suitable for base course because of its high strain accumulation potential, temperature susceptibility, and creep. ...
Article
Full-text available
The purpose of this research was to investigate the effect of changes in grain size distribution to the permanent deformation of two different fine processed reclaimed asphalt pavement (RAP) blended with base course virgin aggregate (VA). Grain size distribution of the RAP-VA blends were created following two different approaches. The first approach was based on mixing RAP and VA to have one grain size distribution regardless of how much RAP was added to VA (herein referred as engineered mixture design). The second approach was based on mixing RAP and VA with as-is gradation from the plants to proportions determined by weight and not controlling the outcome of the specific grain size of the mixture. This approach resulted in various grain size distributions (herein referred as as-is mixture design). The engineered mixture design was useful to quantify the effect of adding RAP to the blends but was not a realistic approach to create blends that may be achieved in the field. The as-is mixture design not only could be achieved in the field as demonstrated in this study but also resulted in better performance in terms of permanent deformation. This manuscript describes the comparison of these two approaches and a methodology to optimize the gradation and develop thresholds for RAP-VA blends that may result in similar or better performance than 100% as-is VA that is used to construct base course in pavement systems.
... RAP-asphalt mixes containing up to 35% RAP indicated that recycled mixes performed as good as the performance of conventional HMA in terms of moisture susceptibility and resilient modulus [13]. A study conducted in the State of New Jersey to evaluate the use of RAP in base and subbase applications indicated that the laboratory resilient modulus and field elastic modulus of the RAP has comparable strength with dense graded aggregate base and subbase material [14]. A recent study of different RAP-virgin aggregate blends ...
Chapter
Over the last decade, there has been a dramatic increase in the use of recycled materials/by-products as alternative ecomaterials in pavement construction on widely varying estimates. This increase is due to the scarcity and depletion of the natural resources and the need of large material quantities for the construction of pavement layers. Many kinds of recycled materials or by-products are exclusively employed in pavement construction such as reclaimed asphalt pavement (RAP), construction and demolition (C&D) waste, waste rocks, glass, steel slag cement dust, rice husk and straw, wood sawdust, waste plastic bags, crumb rubber, waste engine and cooking oils, and others. Undoubtedly, the use of these recycled materials/by-products in pavement construction has many benefits on the short and long terms. Some of these benefits are minimizing the use of natural resources, saving millions of cubic meters in landfills, reducing carbon dioxide emissions, reducing energy consumption, and constructing sustainable pavements. However, some barriers to adopt such materials in pavement construction still exist worldwide. Such barriers are that lack of clients’ confidence in such materials, lack of specifications and legalization, etc. This chapter highlights the current status of using recycled materials/byproducts in pavement construction worldwide, specifications, and the gained benefits in terms of economic savings, environmental impact, and sustainability. The chapter also outlines the existing barriers and limitations to the prevalence of recycled materials/by-products in pavement construction. Finally, it documents recent approaches and strategies to overcome some of these limitations for successful implementation of such materials in pavement construction
Conference Paper
Research on reclaimed asphalt pavement (RAP) material has been on its high all over the world since last three decades. Sustainability, cost effectiveness and eco-friendliness of RAP make it a potential secondary alternative in pavement applications. Often, to meet the strength and stiffness requirements, RAP is blended with virgin aggregates (VA) at various proportions. The resilient modulus (Mr) of base material plays a major role in deciding the pavement thickness. A considerable amount of variability in the Mr values of RAP is observed from laboratory and field studies all over the world. In view of the increased usage of RAP, there is a definite need to understand the statistical variability associated with the Mr of RAP. In this paper, the variability associated with Mr is quantified statistically. Based on the compilation of Mr values from several published studies, the average values of mean, standard deviation, coefficient of variation (COV), and the best fit probability density functions for Mr are computed. The appropriate distributions for RAP and VA mixes are discussed. The outcome of the study will be useful to quantify the performance of the flexible pavements using reliability based design optimization (RBDO) framework which is based on the probability theory.
Article
The resilient modulus (MR) of unbound aggregates has been widely accepted as the principal mechanical property required in the mechanistic-empirical design/analysis of pavement structures. Resilient moduli measured through repeated triaxial load testis highly desirable to characterise granular materials. However, because of the complexities encountered with the test, other laboratory tests would be desirable if a reliable correlation could be established. Reclaimed asphalt pavement (RAP) and recycled concrete aggregate (RCA) have potential to be used as base and subbase material in substantial percentage to achieve economy and to minimise the undesirable environmental effects linked with the use of virgin aggregates. This paper presents a correlation developed between MR value and constrained modulus (MC) on the basis of experimental results obtained for 32 reconstituted granular samples containing virgin aggregates, RCA and RAP materials. Proposed model considers the effect of stress state through the experimentally determined MC, value while model parameters are correlated to the percentage of RAP materials in the reconstituted blends. Statistical analysis of the suggested correlation on the basis of t-test demonstrate encouraging results in terms of its strength and significance.
Article
The use of reclaimed asphalt pavement (RAP) aggregate materials in road construction reduces natural resource depletion and promotes the recycling of RAP materials for other applications. However, product variability and low resilient moduli characteristics often limit RAP applications in road bases. Stabilization of RAP materials with cement was hence attempted in a research study to evaluate the effectiveness of cement treatments in enhancing resilient characteristics of RAP aggregates. The present paper describes the results from a series of resilient modulus tests that were conducted in a laboratory environment using a repeated load triaxial test setup. The effects of three different cement dosages and various confining and deviatoric stress levels on the resilient modulus (M(R)) response of treated RAP materials were studied. M(R) values of untreated and cement-treated RAP aggregates ranged from 180 to 340 MPa and 200 to 515 MPa, respectively, which reveal the enhancements with cement treatment. Regression modeling analyses of M(R) test results, by using two- and three-parameter models, are also presented. The analyses show that both models are reasonably capable of capturing the effects of stress levels on treated RAP resilient properties. Test results were also analyzed to determine structural coefficients for pavement design purposes, which ranged from 0.16 to 0.22, suggesting a greater structural support of cement-treated RAP layers when compared with untreated aggregates. DOI: 10.1061/(ASCE)MT.1943-5533.0000268. (C) 2011 American Society of Civil Engineers.
Article
The purpose of this study is to determine which utilisation of recycled asphalt pavement (RAP) in various roadway applications is the most cost efficient. Using a method developed by the National Asphalt Pavement Association, a system was devised to assess the costs and benefits of using RAP in hot plant mix. A similar process was developed to evaluate the value of using RAP in gravel roads and bases. The system normalises all of the costs and benefits into savings per tonne of RAP as a means of equal comparison. Factors such as savings from dust loss, layer coefficients, haul and decreased need of virgin aggregates were taken into account. Finally, a case study was conducted using these three different applications. Such analysis can be used by other agencies interested in identifying the most cost-effective methods for using RAP in roadway construction.
Article
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The use of recycled materials for construction is beneficial to both the environment and the economy. Recycled asphalt pavement (RAP) is one of the most commonly used recycled materials. Different state departments of transportation allow the use of RAP in base materials using various RAP percentages. Unlike conventional crushed aggregate, RAP exhibits a high resilient modulus, but also low resistance to permanent deformation, which contradicts the relationship between the modulus and permanent deformation in the permanent deformation model for unbound materials found in the mechanistic-empirical pavement design guide (MEPDG). In this study, repeated triaxial tests are conducted on samples containing different percentages of RAP and crushed aggregate. Permanent deformation prediction models for granular base course materials, introduced in 1989 by Tseng and Lytton, are modified by adding the RAP percentage as a parameter for base course materials containing RAP. The results indicate that the proposed model accounts for the effects of RAP reasonably well. Further studies are needed to validate the new rutting model by including different virgin aggregates and RAP mixtures under various testing conditions.
Article
Reclaimed asphalt pavement (RAP) is reprocessed hot-mix asphalt pavement material that contains asphalt and aggregates. A viable solution for disposing of large quantities of RAP is to incorporate it into base and subbase applications for highway construction. This paper compares the expansive properties of RAP materials, especially the ones including recycled steel slag aggregates, with those of the virgin aggregates to evaluate their potential use as pavement base materials. Seventeen RAP materials and virgin aggregates collected in Illinois were tested for their expansive characteristics in the laboratory, following the ASTM D4792 test method. The specimens in California bearing ratio test molds were submerged into a high-alkali cement-water solution and kept soaked at 70 degrees C to accelerate hydration reactions. Some steel slag aggregates showed considerably high expansion potential, up to 6.2% swell, when compared with other virgin aggregates, such as siliceous gravel and crushed dolomite, which had minor or almost no expansion. The RAP materials, which often had lower densities, exhibited more of an initial settlement or contraction before any expansion with time. Two RAP materials-surface RAP, with 92% steel slag aggregates, and steel slag RAP-gave the maximum expansion amounts of 1.69% and 1.46%, respectively. Although the RAP materials had much lower tendencies to expand than did the virgin steel slag aggregates, the use of RAP materials containing high percentages of steel slag aggregates may have to be avoided in the pavement substructure layers, depending on the level of expansion.
Article
Full-text available
The resilient modulus (Mr) of granular materials is one of the basic mechanical property required for the mechanistic-empirical design of flexible pavement structures. Reclaimed asphalt pavement (RAP) has a potential to be used under controlled conditions in different layers of the pavement structure in considerable percentages with the fresh granular materials. Inherently, it is a challenge to perform repeated load triaxial tests as routine tests for the determination of Mr values due to rather complicated, time con- consuming and expensive procedure involved. Hence, as a substitute, empirical constitutive models are also adopted for the estimation of Mr values under a range of loading conditions. This research paper presents an evaluation of five different constitutive models commonly used for the estimation of Mr values incorporating 27 number of experimental data sets obtained during this research work. Statistical analysis of data shows that the models presented by Uzan (1985, 1992) and Witczak and Uzan (1988) are desirably efficient to predict the Mr values while the model presented by Johnson et al. 1986 has the least certainty. On the basis of experimental results, a new constitutive model is also proposed which exclusively takes into account the value of bulk stress and the percentage of RAP contents used in the blended samples tested under a range of loading conditions as specified in AASHTO T 307. The new model may generate the coefficient of determination (R2) in the range of 0.81–0.95. Furthermore, t-test demonstrates that the value of t-statistic is many folds the corresponding value of the t-critical, suggesting a strong correlation between the measured and the estimated Mr values in addition to a fair distribution of the data points along the unity line. Experimental investigations also indicate that the presence of the RAPmaterials in the blended samples make them more pressure sensitive when compared with the samples containing virgin materials only. Data shows that in blended samples containing 50% and 75% of RAP contents by mass, the residual strain may increase of the tune of 500% and 2500% when compared with the corresponding value for the virgin material for the specified cyclic loading conditions. This response of the blended samples certainly identifies some undesirable consequences with the use of RAP materials at higher percentages in the pavement structures.
Chapter
Concrete is a widely used construction material all over the world. However, the raw material resources used for making concrete are degrading day by day. This gives scope for researchers to experiment with new materials for replacement which will help to conserve natural resources and further limit environmental concern caused due to the extraction of materials and emission of carbon dioxide during the process of manufacturing. Moreover, a lot of modern-day constructions require the use of high-grade concrete, leading to the development of High Performance Concrete (HPC). Partial replacement of cement in HPC with fly ash, GGBS, metakaolin and silica fume presents an environmentally friendly way of dealing with increased construction demands. Although studies have been carried out on partial replacement of cement with mineral admixtures in HPC, the performance of the combination of mineral admixtures in HPC has received little to no attention. This paper deals with the study of compressive strength, tensile strength and durability of M40 grade concrete partial replacement of cement with combinations of different mineral admixtures. Three combinations of mineral admixtures namely a combination of fly ash and silica fume, fly ash and metakaolin, and fly ash and GGBS were used for the replacement of 15% of cement by weight. A comparison of strength and durability of different combinations are presented and discussed.
Article
Full-text available
Reclaimed asphalt pavement (RAP) and blends of RAP with virgin aggregate (VA) were characterized in this study to be utilized as base course aggregate. Multi-stage and single repeated load triaxial (RLT) tests were conducted in the laboratory to characterize the materials. The results from these tests were used to develop a mechanistic design approach that is suited not only for virgin but also for recycled materials that are prone to excessive plastic deformations under repeated loads. The design approach presented in this study allows the users to select different pavement structure configurations in terms of base course and HMA thicknesses, where the selected configuration can withstand the repeated loads without undergoing significant permanent strains. Such design approach was achieved with the laboratory tests that were conducted with variety of stress ratios (σ1/σ3) that represented different pavement layer configurations and beyond. Principles of shakedown theory were utilized to define the boundaries of plastic shakedown, creep shakedown, and incremental collapse. This study demonstrated that the use of failure and plastic shakedown boundaries were crucial to the proposed mechanistic design approach.
Article
Road rehabilitation and reconstruction generate large supplies of reclaimed asphalt pavement (RAP) aggregate, and recycling into asphalt paving mixtures is the predominant application. Cement kiln dust (CKD), also known as cement bypass dust, is a by-product material generated during production of portland cement. In Oman, where recycling of pavement materials is not practiced, a first attempt was made at combining two by-product materials for use in road construction. Conservation of natural resources and preservation of the environment are two benefits that could be gained by reusing waste materials. The potential use in road bases of CKD-stabilized RAP and RAP with virgin aggregate mixtures was investigated. Physical, compaction, and unconfined compressive strength tests were conducted on RAP and virgin aggregate blends of 100% to 0%, 90% to 10%, 80% to 20%, and 0% to 100%. Samples were prepared using CKD at 0%, 3%, 5%, 7%, 10%, 15%, and 20% and were cured for 3, 7, and 28 days in plastic bags at room temperature. Results indicate that the maximum dry density and unconfined compressive strength of RAP generally increase with addition of virgin aggregate and CKD. The moisture content-dry density curves for CKD-stabilized RAP aggregate mixtures did not show a distinctive peak similar to that of the 100% virgin aggregate blend. Longer curing periods will produce higher strength values. CKD content of 15% seems to be the optimum for achieving maximum strength.
Article
The utility of noncontacting proximity sensors for the measurement of small strains in resilient modulus tests is evaluated. The proximity sensor measurements of resilient modulus were compared with those obtained from linear variable differential transformers. The important issue of granular soil sample preparation and its effect on the magnitude of resilient modulus was evaluated. Two methods were proposed to facilitate sample preparation and to provide good contact between the soil and the loading platen. The effect of conditioning sequence on sample integrity was also investigated for the two proposed methods of compaction. In addition to the experimental program, a number of constitutive models, used for prediction of resilient modulus of granular soils, were examined; and model predictions were compared with the test data.