Influence of Recycled Asphalt Concrete Pavement Gradation on CBR of Mixed Materials

Abstract

Due to its inherently low compactibility, Reclaimed Asphalt Pavement (RAP) cannot be directly used as a landfill material for road structures without improving its engineering properties. One simple and economical method to enhance RAP is by adding RAP with soil to improve the gradation without the addition of cementitious materials. However, the gradation of RAP, which is a by-product of
the removal process of old asphalt concrete pavements, varies depending on the penetration speed during the milling process. Therefore, it is important that construction planning considers not only the economic benefits, but also the impact of RAP gradation on the bearing capacity of the mixed materials. In this research, the different gradations of RAP were mixed with lateritic soil and crushed rock at various weight ratio. The mixed materials were compacted and tested using California Bearing Ratio (CBR) to investigate the influence of RAP gradation on bearing capacity. Based on the test results, the CBR value increased with the amount of both types of soil added. However, the maximum CBR value of the mixed material was not governed by the gradation of RAP, but controlled by the CBR of the mixed soil, which is equal to the CBR of mixed soil at the maxing ratio of optimal mix proportion point and will constant after beyond this point. Coarse-grained RAP not only offers greater cost benefits compared to fine-grained RAP, but also provides better bearing capacity at the same mixing ratio.