Some Characteristics of Foamed Bitumen Mixes

Abstract

A study was conducted at the School of Engineering of Griffith University on characterization of a range of foamed bitumen stabilized mixes in the laboratory. Marshall and servo-controlled gyratory compactors were used in specimen preparation. A closed-loop, servo-controlled dynamic loading system was utilized to determine the resilient modulus. It was found that the Marshall compaction method produced higher resilient modulus values compared with the gyratory compaction method. Moreover, Marshall compaction showed an optimum bitumen content associated with the maximum density. The gyratory compactor produced specimens that were less dependent on bitumen content but had higher density values. The temperature used to cure the specimens was also examined. An accelerated curing temperature of 60°C was found to be too high, resulting in an over-estimation of the resilient modulus compared with specimens cured at an ambient temperature. Furthermore, the resilience test results also showed that the resilient modulus was significantly affected by the applied strain; with higher strain, a lower modulus resulted. Because of its relatively low bitumen content and use of lime additive, the resilient modulus of foamed bitumen mixes is affected by temperature variation less than that of typical hot-mix asphalt concrete mixes.