The presence of dust, asphalt film and agglomerated particles is considered to be the primary reason for reducing the properties of Reclaimed Asphalt Pavement (RAP)-inclusive concrete. A surface treatment method Abrasion and Attrition (AB&AT) was employed for removing these contaminants. Gaps were identified from the available literatures and efforts have been made to bridge them in order to increase the usage of RAP aggregates in concrete pavements. Six mixes were prepared by partly replacing the Natural Aggregates (NA) with RAP aggregates in different proportions. It was learnt that processing Dirty RAP (DRAP) aggregates by the AB&AT method could remove contaminants considerably as a result of which stronger bonding is exhibited at the interface of the aggregate and hydrated mortar matrix. Incorporation of beneficiated RAP aggregates in concrete improved the workability considerably but it was found to have reduced hardened concrete properties. However, the results were found to lie within the permissible limits for producing concrete mix having 40 MPa compressive strength.

Poor affinity of asphalt toward mortar paste has been testified as the primary reason for reducing the reclaimed asphalt pavement (RAP)–inclusive concrete properties, although the effect of dust present in RAP aggregates due to extraction of RAP using demolition techniques has not been investigated so far. The present paper discusses the effect of different extraction methods on the mechanical properties of fine RAP aggregates. Also, the effect of incorporation of fine RAP aggregates on fresh, mechanical, and durability properties of concrete has been investigated. It was found that as the substitution level of fine natural aggregates (NA) by fine RAP (0, 25, 50, 75, and 100%) increases, the properties of concrete tend to decrease gradually. From the present laboratory investigation, it is learnt that 50% fine RAP (extraction made using demolition technique) can be used for construction of major highways, whereas 100% fine RAP may be suggested for less important roads and in lower layers of pavement.

In the present study, the adverse effect of dust on the properties of concrete containing 75% fine reclaimed asphalt pavement (RAP) (75F) (obtained using an uncontrolled milling technique) is minimized by using higher doses of superplasticizers (SP) in combination with silica fume (SF), flyash (FA), and bagasse ash (BG). It was found that the 75F mix requires at least double the amount of SP to achieve the recommended slump value. Moreover, improvement in the fresh state was found to enhance the hardened properties of the 75F mix significantly. Inclusion of the considered mineral admixtures was found to further enhance the compressive strength, splitting tensile strength, and abrasion resistance; however, inclusion of BG and FA resulted in comparable flexural strength. The determination of water absorption and permeable voids was found to be affected by the asphalt film, suggesting this testing should be conducted at a temperature lower than 50°C. Based on the results of the economic analysis, the addition of extra doses of SP should be considered as the best and most economical way of minimizing the effect of dust present in fine RAP aggregates, whereas inclusions of BG and FA could further make the concrete cheaper and more durable.

Efforts have been made in the recent past to enhance the strength properties of reclaimed asphalt pavement (RAP) concrete via inclusions of supplementary cementitious materials (SCMs), but only some of the durability problems could be rectified. In this study, an attempt is made to improve the performance of a roller compacted concrete pavement (RCCP) matrix containing 50% combined RAP fraction (R50 mix) by adopting a nontraditional methodology, i.e., including SCMs in additions of portland cement. The studied SCMs were silica fume (SF), fly ash (FA), and bagasse ash (BA). The results indicated that inclusions of all the SCMs (except BA) would not affect the fresh properties of R50 mix to a great extent but could degrade the quality of RCCP considerably. Microstructural analysis confirmed that asphalt cohesion failure is mainly associated with RAP mixes, with or without SCMs, and therefore, attempts to enhance the performance of RAP concrete would not be possible without removing the asphalt film. Interestingly, the considered mixes demonstrated higher flexural strength than the permissible ACI 325.10R-95 (ACI 2001) limit of 3.67 MPa for pavement application. Also, the SF and BA mixes exhibited better durability properties, in fact, better than the reference conventional mix, in terms of abrasion resistance and resistance to aggressive sulfate and chloride ions, indicating their suitability, especially in regions of aggressive ions and high-speed moving vehicles.

In the present study, the potential of supplementary cementitious materials such as silica fume (SF), fly ash (FA), and sugarcane bagasse ash (SCBG) for enhancing the durability properties of pavement quality concrete (PQC) mixes containing 75 % fine reclaimed asphalt pavement (75RAP) is assessed. Different physical and durability properties such as water absorption, total permeable voids, initial rate, secondary rate and coefficient of water absorption, and performance in sulfate and chloride-rich environments were evaluated. It was found that the ASTM recommended temperature of 110 ± 5°C for evaluating water absorption and permeable voids should be changed to 48 ± 2°C to prevent the melting of asphalt present in RAP. Similarly, the duration for completely drying the specimens shall be at least eight days. It was observed that incorporation of fine RAP could compromise with the durability of the PQC mixes significantly. Inclusions of all the considered admixtures (except SF) were found to have an insignificant effect on the modulus of rupture, however, significant enhancement in the durability properties of 75RAP mix was observed (except SCBG). The blending of 15 % FA with 10 % SF was found to enhance the durability performance of 75RAP mix better than the mix containing natural aggregates.