Design and evaluation of stone matrix asphalt using stiffer grade crumb rubber modified bitumen

Stone Matrix Asphalt (SMA) is primarily used as a surfacing layer material since it is found to perform well under heavy traffic conditions and at the same time is more cost-effective when compared to the conventional dense graded mixes. An attempt has been made in this study to incorporate a stiffer grade crumb rubber modified bitumen (CRMB) for design of SMA. Extensive laboratory studies on mixes prepared with different modified binders and normal binders (with fibers) were conducted. The results obtained indicate that SMA designed using CRMB-70 and CRMB-80 performs well under heavy traffic conditions and at the same time without significant drain-down. Further, CRMB-80 is found to be suitable at high temperatures since it yields a very low accumulated strain and is thus recommended for designing rut resistant durable mixes. In addition, CRMB-80 yields the least rut depth of 4.5 mm even after 20,000 load repetitions.