Reclaimed Asphalt Pavement Aggregates Research Articles

Validation of a sieve analysis procedure to quantify reclaimed asphalt pavement (RAP) binder availability

ABSTRACT Recycled binder availability (RBA) refers to the proportion of total recycled binder that is available to blend with virgin asphalt binder and is considered an inherent property of a given reclaimed asphalt pavement (RAP) stockpile. Recycled binder contribution (RBC) is the fraction of the recycled asphalt binder that is incorporated into the virgin binder within an asphalt mixture. Binder that is inside agglomerated RAP particles that do not separate during the mixing process is ‘unavailable’. This study validates a method to quantify RBA through comparative sieve analysis of RAP and recovered RAP aggregate, testing two hypotheses: (1) RAP agglomerations preexist and don’t fully break during production, and (2) RBA measurements estimate RBC. The method was applied to nine RAP sources from four states. The innovation was verified to accurately reflect RBC in asphalt mixtures through comparative tracer-based microscopy. Results showed RBA and RBC typically between 50-60%, indicating not all recycled binder blends with virgin binder. Further analysis of mixtures fabricated with different preheating and conditioning procedures suggested that RBC doesn’t vary significantly with laboratory production conditions. Thus, RBA measurements from sieve analysis show promise in estimating RBC in asphalt mixtures across production conditions, supporting the study’s hypotheses.

Circular Economy for Transport Infrastructure: An Overview of the Sustainable Use of Recycled Asphalt Shingles in Asphalt Mixtures

In North America and Europe, asphalt shingle waste created during the installation of roofing membranes and tear-off shingles retrieved at the end of the membrane’s life cycle are two major sources of municipal solid waste. Since almost 15–35% of recycled asphalt shingles (RAS) consist of an asphalt binder, the effective recycling of RAS into asphalt mixtures could also allow a reduction in the consumption of non-renewable resources such as asphalt binders. In this context, several studies investigating the use of RAS in asphalt mixtures can be found in the literature, although they exhibit widespread and sometimes conflicting information about the investigated materials, the mix preparation and testing methodologies and the experimental findings. Given this background, this review paper aims at summarizing the existing information and research gaps, providing a synthetic and rational picture of the current literature, where similar attempts cannot be found. In particular, different research studies show that the use of RAS in asphalt mixtures is an economical as well as an eco-friendly option. RAS with up to 20% by weight of binder or 5% by weight of aggregate/mixtures (eventually in combination with 15% reclaimed asphalt pavement aggregate) were found to be relatively suitable to improve the performance properties of asphalt mixtures, both in the laboratory and in the field. Adding RAS to asphalt mixtures could enhance their stiffness, strength and rutting resistance (i.e., high-temperature properties), while negatively affecting the mixtures’ fatigue and thermal cracking resistance. However, the addition of specific biomaterials (e.g., bio-binders, bio-oils) or additives to asphalt mixtures can mitigate such issues, resulting in lower brittleness and shear susceptibilities and thus improving the anti-cracking performance. On the other hand, the literature review revealed that several aspects still need to be studied in detail. As an example, RAS-modified porous asphalt mixtures (fatigue, rutting, moisture susceptibility and thermal cracking) need specific research, and there are no comprehensive research studies on the effects of the RAS mixing time, size and mixing temperature in asphalt mixtures. Moreover, the addition of waste cooking/engine oils (biomaterials) as asphalt binder rejuvenators in combination with RAS represents an attractive aspect to be studied in detail.

Recycling of RAP (Reclaimed Asphalt Pavement) as aggregate for structural concrete: experimental study on physical and mechanical properties

The replacement of natural aggregate in concrete with artificial and/or recycled one has recently gained attention as meaningful strategy to reduce the environmental impact of structural concrete and promote circular economy principles. This study investigated the possibility to use Reclaimed Asphalt Pavement (RAP), in the “as received conditions”, as a partial or complete substitution of natural aggregate for structural concrete. RAP aggregate was firstly characterized in terms of grain size distribution, density, assessment of fines, chloride content, moisture content and water absorption. Subsequently, a total of twenty-four concrete mixes were designed, considering two cement types, two w/c ratios and several aggregate substitution percentages. For each mix, properties at the fresh and hardened state were investigated, such as workability, density and total open porosity, compressive strength, dynamic modulus of elasticity, and electrical resistivity. Results showed that RAP has a good potential to be used in reinforced concrete, provided that different water absorption and moisture content are considered in the mix design. RAP concrete was characterized by a lower density and increased total open porosity; however, an accurate tailoring of the concrete recipe could compensate the strength loss for several applications. Other properties, such as electrical resistivity and the relationship between dynamic modulus of elasticity and compressive strength did not result significantly altered by the presence of RAP.

Evaluation of the interface shear strength of concrete containing treated and untreated reclaimed asphalt pavement aggregates

Concrete production significantly contributes to carbon emissions and depletes natural resources, promoting increased interest in substituting traditional materials with recycled alternatives. This shift necessitates a thorough examination of recycled materials’ performance in concrete applications. This study aims to provide a better understanding of the shear transfer behavior of concrete containing reclaimed asphalt pavement (RAP) aggregates. To mitigate the potential negative impact of RAP aggregates, mechanical treatment was applied. The effects of RAP inclusion and mechanical treatment on the shear transfer strength of reinforced concrete were investigated. A total of twenty-four push-off specimens were tested to investigate the effects of aggregate replacement and the clamping reinforcement ratio on specimen behavior. Digital image correlation (DIC) was employed to monitor the strains and displacements, allowing for detailed tracking of the interface slip, crack width development, and reinforcement strain. The findings revealed that replacing natural aggregates with RAP aggregates resulted in lower compressive strengths and lower ultimate push-off strengths of the resulting concrete at equivalent effective water-to-cement (w/c) ratios. Specimens with higher reinforcement ratios retained residual strengths up to 77 % of the ultimate strength, even at relatively large slip and crack widths. The clamping reinforcement ratio was identified as the key factor influencing the ultimate and residual strengths for both types of concrete. The experimental results were compared to the strengths calculated by the ACI, PCI, AASHTO, and CSA design equations to evaluate their applicability when different aggregate types are used.

Embracing Sustainability in Rigid Pavement Construction: Unveiling Geopolymer Concrete’s Potential with Incorporated Reclaimed Asphalt Pavement Aggregates

Embracing Sustainability in Rigid Pavement Construction: Unveiling Geopolymer Concrete’s Potential with Incorporated Reclaimed Asphalt Pavement Aggregates

The influence of residual asphalt material in the mechanical behaviour of soil-RAP mixtures for use in paving

ABSTRACT The evaluation of Reclaimed Asphalt Pavement (RAP)’s suitability for pavement layers, optimises resource use, reduces environmental impact, and supports cost-effective practices. In this sense this study aimed to characterise soil-RAP mixtures to ensure they meet the quality standards required for pavement applications. The study examined two types of soil mixtures: one soil-RAP aggregates and the other soil-virgin aggregates (VAM) to understand the impact of residual asphalt binder on aggregate particles. Various mass contents (30%, 50%, 70%, and 90%) were tested alongside conventional soil-gravel mixtures with equivalent proportions and gradation of RAP and VAM. Additionally, the study investigated the effect of adding 2% cement on the performance of both recycled soil-RAP mixtures and conventional soil-gravel mixtures. The analysis includes granulometry, Atterberg Limits, MCT (Miniature, Compacted, Tropical) classification, soil chemical characterisation and microscopic images, compaction in Modified Proctor Energy, CBR, Resilient Modulus tests and stress–strain analysis. The results have revealed that the residual asphalt binder, surrounding RAP aggregates, has reduced the soil mixtures’ strength for different RAP contents. However, the study demonstrated that the addition of cement rendered the soil-RAP mixture feasible, enabling the application of the studied mixtures of RAP to constitute subbase and base layers.

Production of rubberized concrete utilizing reclaimed asphalt pavement aggregates and recycled tire steel fibers

The integration of waste tire elements into concrete, specifically granular rubber and discrete steel fibers, signifies a substantial advance in the pursuit of sustainable alternatives for rigid concrete pavements. This incorporation not only improves the ductility of rigid concrete pavements, but also augments their energy absorption capabilities. Similarly, replacing natural aggregates in concrete with reclaimed asphalt pavement (RAP) aggregates makes a large contribution to the reduction of negative environmental impacts, while conserving natural resources from depletion. This investigation explores the potential application of recycled rubber particles from waste tires (WTRR) and RAP aggregates as partial substitutes for natural fine aggregates, and evaluates their impact on the performance of rigid concrete pavements. Eight mixes were cast, each with two variables: (i) fine aggregate type (fine rubber (FRu) aggregates, fine asphalt (FAs) aggregates, and combinations of both types of aggregate) replacing 50 % of the natural fine aggregate; and (ii) waste tire recycled steel fibers (WTRSF) content (0 and 40 kg/m3). The axial compressive stress–strain, flexural load–deflection, and direct shear strength behaviors, together with the dry unit weight and volume of permeable voids for all concrete mixes were investigated and compared. The results show that, although the flexural and shear strengths decrease with the inclusion of FRu and/or FAs, the use of WTRSF noticeably mitigates the losses in strength that arise from the use of WTRR and/or RAP aggregates alone. The inclusion of WTRSF enhances the strain capacity of the concrete and allows the development of adequate post-peak energy absorption capacity in flexural and shear loading. Additionally, the dry unit weight of the proposed composites decreased by as much as 8 %, and their volume of permeable voids lies within the limits of high-durability concrete mixes (9–12 %). Hence, the proposed sustainable concrete composites are promising composites for rigid concrete pavement construction.

Aggregate uniformity of recycled asphalt mixtures with RAP from refined decomposition process: Comparison with routine crushing method

In consideration of skyrocketing price in pavement materials and ever-increasing attention to environment preservation, the utilization of reclaimed asphalt pavement (RAP) into asphalt mixtures has gained more and more favor. However, the uniformity of virgin and RAP aggregate in recycled asphalt mixtures (RAM) has not yet been studied due to the difficulty in informational extraction of multi-structures. To address this, white dolomite was used as virgin aggregate to be distinguished from RAP aggregate based on their color difference. The shear gyratory compactor specimens of RAM were prepared and saw-cut, and then meso-structures including virgin aggregate, RAP aggregate and asphalt mortar were extracted using digital image processing (DIP) technology. The DIP processes mainly involved retention of blue channel for image graying, newly proposed double-threshold OTSU method for image segmentation and image morphology processing. The aggregate uniformity index (AUI) was proposed based on the coefficient of variation of aggregate area ratio. The influences of RAP that were pre-processed by refined decomposition (RD) and routine crushing (RC) and its content on the aggregate uniformity were evaluated. The results demonstrate the efficacy of the improved DIP approach, as evidenced by the maximum mean absolute error between laboratory-measured and image-estimated gradation that is lower than 7.8 %. The addition of RAP into asphalt mixtures is adverse to the aggregate uniformity. The higher the RAP content, the inferior the aggregate uniformity of RAM, which attributes to the agglomeration of RAP materials. RAP agglomeration leads to the heterogeneity of RAP aggregate and thus dominates the heterogeneity of the whole aggregate. Therefore, the aggregate uniformity of RAM produced by RD-RAP is superior to that produced by RC-RAP. The superior degree is 9 %.

Can Reclaimed Asphalt Pavement Aggregates be Effectively Utilized in Designing Paving-Grade Geopolymer Concrete? An Experimental Study with Strength Prediction Using Machine Learning Algorithms

Can Reclaimed Asphalt Pavement Aggregates be Effectively Utilized in Designing Paving-Grade Geopolymer Concrete? An Experimental Study with Strength Prediction Using Machine Learning Algorithms

The Effect of Refined Separation on the Properties of Reclaimed Asphalt Pavement Materials

Refined separation not only controls the variability of reclaimed asphalt pavement (RAP), but also improves the mixing ratio of RAP and the quality of recycled asphalt mixtures. This study examines RAP treated with various refined separation frequency parameters, analyzes the variation rules and the variability of RAP aggregate gradation, asphalt content, asphalt properties, and aggregate properties, and calculates the maximum mixing percentage of coarse RAP material by using the gradation variability control method and the asphalt content variability control method. The results show that the variability of gradation and asphalt content of coarsely separated RAP is considerable, and a refined separation process significantly reduces the variability of gradation and asphalt content of RAP; the agglomeration of RAP decreases with an increase in the refined separation frequency; and the RAP agglomeration of three kinds of RAPs (E1, E2, and E3) under a refined separation frequency of 55 Hz reduces by 6.40%, 4.30%, and 4.30%, respectively, as compared with that of coarsely separated RAPs. The asphalt content of the refined separation RAP gradually decreases with an increase in frequency, and the asphalt content of E1 and E2 (55 Hz) was only 0.95% and 1.10%, respectively. The maximum percentage of RAP in recycled asphalt mixtures was calculated using the gradation variability control method and the asphalt content variability control method, respectively. The maximum proportions of RAP were 45% and 33% for A1 (0 Hz), respectively, and the maximum proportions of RAP for E1 (55 Hz) were all 100%. The results of the two methods show that the process of refined separation can increase the maximum proportion of blended RAP materials. They also demonstrate that the refined separation process can increase the maximum blending ratio of coarse RAP materials, thereby improving the quality of the RAP, increasing the proportion of RAP blending, and ensuring the quality of the recycled asphalt mixture. In conclusion, the refined separation process holds promise for maximizing the potential value of RAP and optimizing its recycling, environmental, and economic benefits.

RECYCLING OF ASPHALT PAVEMENT AGGREGATES AND WASTE PLASTIC BOTTLES IN ADDITION TO HOT-MIX ASPHALT PRODUCTION: ADEQUATE RECYCLING RATE

This study focused on the recycling of asphalt pavement aggregates and waste plastic bottles (WPB) in addition to hot-mix asphalt (HMA) production. To achieve this objective, non-probable sampling methods were used to gather samples from the study locations. Crushed stone aggregate (CSA), bitumen, mineral filler, reclaimed asphalt pavement aggregate (RAPA), and WPB were the ingredients employed based on the requirements in the standard specification for asphalt concrete production. Initially, the Marshall Stability Test was then carried out using CSA with 6% and bitumen levels of 4.0, 4.5, 5.0, 5.5, and 6% by weight of the total mix to ascertain what the bitumen content should be with RAPA with replacement rates of 10, 20, and 30% and that of WPB with 2, 6, 8, 10, 12, and 14%. In the Marshall Stability Test, which consisted of three trials of 195 samples and 60 mix designs, 45 were for the control mix and 150 for the replacement proportion. In the Marshall Stability Test, the ideal value for CSA was 5.1%; for RAPA, 5.1%; and for WPB, 7.7, 5.5, 5.4, 5.0, 5.5, and 5.4% optimum bituminous content (OBC). 20% RAPA and 10% WPB by weight of OBC in the stability-modified asphalt mix satisfies Ethiopian Road Authority (ERA) and American Society for Testing and Material (ASTM) specifications for all qualities tested. Finally, for improved asphalt mix performance, a combined 70% CSA, 20% RAPA, and 10% WPB should be used in asphalt mixes at 5.0% OBC. These experimental Marshal Stability Test findings satisfy the necessary specifications of ERA and ASTM for all tests used in HMA production. Thus, this proportion is strongly advised.

Utilization of wollastonite, jarosite, and their blends for the sustainable development of concrete paver block mixes containing reclaimed asphalt pavement aggregates.

While several research studies considered the utilization of reclaimed asphalt pavement (RAP) aggregates for asphalt and concrete pavements, very few attempted its possible utilization for precast concrete applications like concrete paver blocks (CPBs). Moreover, few attempts made in the recent past to improve the strength properties of RAP inclusive concrete mixes by incorporating certain supplementary cementitious materials (SCMs) have reported an insignificant or marginal effect. The present study attempts to comprehensively investigate the utilization potential of some locally and abundantly available materials having suitable physicochemical properties to improve the performance of a zero-slump CPB mix containing 50% RAP aggregates. The studied filler materials, namely, wollastonite (naturally occurring calcium metasilicate mineral) and jarosite (hazardous zinc industry waste), were used to replace 5-15% and 10-20% by volume of Portland cement in the 50% RAP CPB mix. Apart from their individual effects, the efficacy of wollastonite-jarosite blends was also investigated. Considering the lack of indoor storage facilities and economic aspects of CPBs, the influence of water spray curing regime on the performance of the RAP CPB mixes was studied and compared to that of continuous water curing regime. Inclusion of the considered fillers was found to statistically and significantly enhance the flexural strength, tensile splitting strength, and abrasion resistance of the 50% RAP CPB mix; however, the compressive strength (in most cases), permeable voids, water absorption, and water permeability properties showed an insignificant improvement. Results of thermogravimetric analysis confirmed the occurrence of pozzolanic reactivity, and microstructure analysis revealed improvements in packing of concrete matrix and ITZ with filler inclusion qualitatively substantiating the improvements in strength and durability characteristics. The toxicity characteristics of heavy metals that may leach from the hazardous jarosite-based RAP CPB mixes were found to be within permissible limits. Based on the performance requirements specified by IS, IRC, and ASTM standards, all the RAP CPB mixes with filler inclusions fulfilled the acceptance criteria for heavy traffic applications, and water spray curing can enact as an alternate method for curing these mixes. However, to avail maximum performance benefits, it is recommended to use 5% wollastonite, 15% jarosite, and a combination of 10% wollastonite and 10% jarosite as a Portland cement substitute to produce sustainable eco-friendly RAP CPB mixes.

Quantifying the agglomeration effect of reclaimed asphalt pavement on performance of recycled hot mix asphalt

The utilization of reclaimed asphalt pavement (RAP) is becoming widespread in asphalt pavement industry. However, the agglomeration of RAP might exist during asphalt mixture production, which can affect the performance of asphalt mixtures. This study aimed to develop an innovative RAP agglomeration quantification method and investigate the agglomeration effect on performance of recycled hot mix asphalt (RHMA). The inherent agglomeration rate (IAR) and relative agglomeration rate (RAR) were defined and quantified by using the gradation curves. The RAP agglomeration was further determined under different mixing conditions including aggregate size, mixing time, temperature, etc. The influence of RAP agglomeration on hot mix asphalt mixture (HMA) was characterized through wheel rutting, low-temperature cracking, and moisture resistance testing. Results showed that RAP agglomeration do exist during asphalt mixture production, especially for high RAP content. The gradation curves from screening test proved to be an effective approach for RAP agglomeration quantification. The agglomeration rates of No.1, No.2, and No.3 RAP aggregates could be reduced by 5.7, 6.5 and 39.8 % under appropriate mixing conditions. But the fine RAP aggregates were easily re-agglomerated to form the coarse RAP aggregates. The ratio of 150 % between virgin coarse aggregate and RAP aggregate could avoid re-agglomeration issue for No.2 and No.3 RAP aggregates. Based on the rutting, low-temperature cracking, and moisture resistance tests, the impact of agglomeration phenomenon on the performance of plant RHMA with containing 100 % RAP was more than that with containing 50 % RAP.

Potential Use of Reclaimed Asphalt Pavement Aggregate and Waste Plastic Bottles for Sustainable Asphalt Pavement Production

The main objective of this study was to evaluate the potential use of reclaimed asphalt pavement aggregate (RAPA) and waste plastic bottles (WPBs) for sustainable asphalt pavements production in hot weather conditions. To enhance the adhesion between neat bitumen, RAPA, and WPBs-coated aggregates, a rougher surface texture is created for aggregate particles in the modified asphalt mix. This improvement enhances asphalt mix engineering properties, rutting resistance, and stability. However, bituminous mixtures containing 20% RAPA exhibit tendencies toward strip resistance, this mixture is weak in terms of strength and incapable of supporting loads when utilizing the RAPA. Therefore, due to the moisture susceptibility of the RAPA, it is advised to employ several types of aggregates in future studies to determine the optimal aggregate that can resist stripping and, at the same time, handle heavy loads. Finally, for better asphalt mix performance, it is recommended to use a combination of 70% crushed stone aggregate, 20% RAPA, and 10% WPBs in asphalt mix with a 5.0% optimum modifier content. The experimental results for tensile strength ratio, proportional rut depth, and mean rut depth meet the required specifications of the Ethiopian Road Authority for all properties tested. Therefore, this combination is strongly advised for use in hot mix asphalt production.

Chemical and Microstructural Changes in Reclaimed Asphalt Pavement Aggregates by Pyrolysis

Chemical and Microstructural Changes in Reclaimed Asphalt Pavement Aggregates by Pyrolysis

Influence of Reclaimed Asphalt Pavement Aggregates on Strength and Durability Properties of Concrete Mixes in Rigid Pavements

The use of Reclaimed Asphalt Pavement (RAP) aggregates in rigid pavements instead of conventional aggregates in Himalayan regions solves the problem associated with shrinking natural resources and dumping of wastes. This study studied the effect of partial replacement of conventional coarse aggregates by RAP in Dry Lean Concrete (DLC) mixes suitable for rigid pavements. A total of 114 specimens (cubical and cylindrical) were cast and tested for mechanical and durability properties as per ASTM and IS code guidelines, partially replaced with CRAP by 25%, 50%, and 75% by weight. The simultaneous effect of fly ash addition by partial replacement of cement by it was also studied. The study concludes that 25% partial replacement by CRAP with 10% fly ash as partial replacement of cement led to the achievement of the strength benchmark as mandated by IRC SP 44 (2014). It was also observed that durability properties such as resistance to acid attack, sulphate attack and carbonation also improved in DLC mixes, including CRAP and fly ash, when compared to control mixes.

Influence of key parameters on the performance of RAP-inclusive geopolymer concrete pavements: An approach integrating sensitivity analysis

The current study investigates the integration of Reclaimed Asphalt pavement (RAP) aggregates into geopolymer concrete, thereby providing a promising avenue for reinforcing sustainability in rigid pavement systems. Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBS) based geopolymer mixes were designed to accentuate the performance with regards to varying molarity of NaOH (10 M-16 M), aggregate replacement levels (0%−100%) and curing periods. The experimental findings revealed a significant decrease in 28 days of compressive and flexural strength within 14 M-100% RAP mixes (57.6% and 39.7%, respectively). Nevertheless, GPC mixes incorporating 50% coarse RAP successfully met the prescribed strength criteria, making them suitable for Pavement Quality Concrete (PQC) applications. Additionally, the assessment of porosity and Water Absorption (WA) revealed a noticeable decrease with an increase in molarity as well as RAP fractions in the mix. Long-term performance was further assessed through resistance to surface abrasion, showing a maximum abrasive depth of 0.302 mm for 10 M-100%RAP mixes, thus affirming the durability of the RAP-GPC system. Rapid Chloride Penetration Test (RCPT) additionally demonstrated that the presence of adhered asphalt in RAP aggregates reduces porosity and enhances resistance to chloride ingress. Subsequently, the microstructural analysis and the study of solid-state NMR aided in comprehending the matrix behaviour, potentially linked to the performance of the mixes. The experimentally obtained compressive strength results were further statistically analysed through the Sensitivity Analysis (SA) approach, thereby providing a comprehensive understanding of the interplay between various strength-affecting parameters.

Performance of cement mortar mixes containing fine reclaimed asphalt pavement aggregates and zinc waste

Cement mortar mixes were prepared to test the suitability of fine reclaimed asphalt pavement (FRAP) aggregates as a replacement for natural fine aggregates (NFA). With different amounts of NFA (25%, 50%, 75% and 100% by weight) replaced with FRAP aggregates, the mechanical qualities of the mortar mix deteriorated. To counteract this, jarosite – a waste from the zinc industry – was used as a partial replacement for cement (replacements of 5%, 10% and 15%). The jarosite improved the microstructural, mechanical and shrinkage properties. For example, compared with the control mix (100% NFA), the mix containing 25% FRAP aggregates showed a 5.5% reduction in hardened density and a 14% reduction in compressive strength. With the addition of 10% jarosite, there was an increase of 4.85% in hardened density and 7% in compressive strength with respect to the mix containing 25% FRAP aggregates. It is thus suggested that 10% jarosite is used when FRAP aggregates are used to make cement mortar mixes. A cost analysis was also performed. The findings of this work are expected to inspire rational mix design recommendations for mortar mixes including FRAP aggregates, as well as bringing environmental and economic benefits by reducing carbon dioxide footprints.

Variations in strength and stiffness of cement-stabilized reclaimed asphalt pavement and marginal lateritic soil blends in tropical climate

This article investigated the effects of temperature on the variations in strength and stiffness of cement-stabilized reclaimed asphalt pavement (RAP) and marginal lateritic soil (MLS) as a sustainable bound base course of flexible pavement. A site investigation to assess the temperature profile of highway pavement in the northeast of Thailand was conducted to find the temperature variation of pavement structure in tropical country. Laboratory tests including unconfined compressive strength (UCS), modulus of elasticity (E50), and indirect tensile strength (ITS) tests were conducted on cement-stabilized RAP and MLS blends at varying mix proportions and temperatures. It is evident that the temperature significantly affects the strength and stiffness of specimens containing RAP due to the presence of bitumen covering the RAP aggregate. The additional MLS and cement can reduce the viscoelasticity of RAP aggregate. The strength reduction due to the temperature is characteristic of the RAP mixtures with MLS and cement. The normalized relationships of UCS and temperature and the empirical correlations between E50 and ITS versus UCS were presented. This set of relationships is a valuable tool for the mix design of cement-stabilized RAP and MLS blends as a bound base course in tropical countries.

Influence of Reclaimed Asphalt Pavement Aggregates on Strength and Durability Properties of Concrete Mixes in Rigid Pavements

The use of Reclaimed Asphalt Pavement (RAP) aggregates in rigid pavements instead of conventional aggregates in Himalayan regions solves the problem associated with shrinking natural resources and dumping of wastes. This study studied the effect of partial replacement of conventional coarse aggregates by RAP in Dry Lean Concrete (DLC) mixes suitable for rigid pavements. A total of 114 specimens (cubical and cylindrical) were cast and tested for mechanical and durability properties as per ASTM and IS code guidelines, partially replaced with CRAP by 25%, 50%, and 75% by weight. The simultaneous effect of fly ash addition by partial replacement of cement by it was also studied. The study concludes that 25% partial replacement by CRAP with 10% fly ash as partial replacement of cement led to the achievement of the strength benchmark as mandated by IRC SP 44 (2014). It was also observed that durability properties such as resistance to acid attack, sulphate attack and carbonation also improved in DLC mixes, including CRAP and fly ash, when compared to control mixes.