Mix design procedure for crumb rubber modified hot mix asphalt concrete
To improve the performance of hot-mix asphalt concrete at high temperatures, crumb-rubber is typically used. Although hot-mix asphalt concrete (HMAC) consisting of crumb-rubber has been successfully placed and have performed well over the years, the laboratory design and preparation of specimens are sometimes problematic. The current Texas Department of Transportation (TxDOT) mix crumb rubber HMAC design procedure is cumbersome and requires preparing a large number of laboratory specimens to carry out an appropriate mix design. The purpose of this research project was to identify the problems with and provide solutions to the current procedure. To evaluate the performance of HMAC consisting of crumb rubber, TxDOT specifies Static Creep Test and Hamburg Wheel Tracking Device (HWTD) test. To perform Static Creep test, the specimens are prepared using Texas Gyratory Compactor (TGC) while HWTD specimens are prepared using Superpave Gyratory Compactor (SGC). Since the specimen size and compaction efforts are different for the two devices, it is quite possible that the specimens prepared with two devices may exhibit different performances. Therefore, another objective of this study was to identify the influence of compaction device on performance of HMAC consisting of crumb rubber. To modify current mix design procedure and to identify influence of compactive effort on performance, the material of known performance was gathered and evaluated. The results indicate that the modified procedure can be used to prepare specimens using SGC or TGC and the two performance tests exhibited similar trends.
Swami, Vaibhav, "Mix design procedure for crumb rubber modified hot mix asphalt concrete" (2005). ETD Collection for University of Texas, El Paso. AAI1430213.