Feasibility Study on Use of Washed-Reclaimed Asphalt as a Partial Replacement of Natural Aggregate in Dry-Lean Concrete as Base Course for Rigid Pavement

Abstract

Dry-lean concrete (DLC) lies below the wearing course of the rigid pavement section to overcome the major reasons for its failure, such as improper base support, seepage of underground water, and frost action. DLC is generally manufactured with a huge aggregate-to-cement ratio, which lies below the wearing course of the rigid pavement section. In this study, reclaimed asphalt pavement (RAP), a waste material, derived from the milling process of flexible pavement wearing course, has been used as a partial replacement of natural coarse aggregates in DLC made from portland pozzolana cement (PPC). Initially, the feasibility of using washed reclaimed asphalt pavement (WRAP) and comparing the results with dirty reclaimed asphalt pavement (DRAP) as a partial replacement of natural coarse aggregate has been investigated. It was found that WRAP gave better results as compared to DRAP for satisfying DLC conditions. The reason is demonstrated using SEM images showing variation in formation of CSH gel due to the presence of dust particles. Further, strength and durability properties (acidic environment, water absorption, and alkalinity) were determined to check its durability of WRAP-incorporated concrete (WRAPC). The percentage of WRAP and DRAP was varied from 0%–50% by weight of natural aggregate. Also, nondestructive tests like ultrasonic pulse velocity (UPV) and rebound hammer test were performed to determine the quality and dynamic young’s modulus of WRAPC. It was found that the optimal curing period and optimum WRAP addition were 21 days and 20% respectively. An equation has been developed to determine the optimum moisture content (OMC) for varying percentage of moisture and RAP content. The equation was validated with the results of researchers and a variation of only 3.3% was found. It was observed that 20% WRAP incorporated in DLC gives optimal results in terms of strength and durability.