Evaluating the effects of using reclaimed asphalt pavement and recycled concrete aggregate on the behavior of hot mix asphalts

Abstract

In this research, the performance of hot mix asphalts mixes (HMA) with RAP and RCA was evaluated, in terms of their Marshall stability, flow, and volumetric properties, to verify their applicability as a replacement for the natural aggregate in the flexible pavement surface layers of HMA mixtures. The experimental work was divided into two phases; the first phase investigated the crushed limestone, white hard-rock, and basalt aggregate materials with a nominal maximum aggregate size of 19 mm. The second phase studied the replacement of crushed limestone, by weight, with the RAP and RCA at different asphalt cement contents. The coarse and fine aggregate of the recycled materials were used at four percentages of 25%, 50%, 75%, and 100%, respectively. The experimental test results showed that replacing limestone with recycled aggregate materials affected the mechanical characteristics, mainly the volumetric properties of the HMA. Using RCA in the hot asphalt mixes violated the upper limit of 5% for the air voids property and increased the optimum asphalt content (OAC) up to 5.96% for mixes prepared with 50% RCA. The results also revealed that adding RAP aggregate to the limestone in the HMA improved their Marshall stability, and the highest value of 29.32 kN was recorded for the asphalt mixes prepared with 75% RAP at 3% asphalt content. The combination of RAP and RCA aggregates indicated that as the RCA proportion in the mix increased, lower load capacity was observed and higher OAC compared to the other asphalt mixes.

Keywords

• Sustainability
• RAP
• RCA
• Asphalt
• Marshall
• Stability