Improving the Properties of RAP-RCCP Mixes by Incorporating Supplementary Cementitious Materials as Part Addition of Portland Cement

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.