Development of laboratory performance of Indonesian rock asphalt (ASBUTON) in hot rolled asphalt mix

Rock asphalt exists in large quantities in Buton Island, Indonesia, and until late 1990s was used extensively in its natural state as a surfacing layer for existing road pavements. On the other hand, extensive maintenance of the Indonesian road network involves the use of very large quantities of bitumen-bound materials. Given the relatively high cost of refinery bitumen and the existence within the country of large resources of rock asphalt, the outcome of the research of natural rock asphalt becomes significant for those involved in implementing the highway maintenance programs. This paper describes some laboratory performances of Hot Rolled Asphalt (HRA) mixes type C and F, using an ASBUTON (Indonesian Rock Asphalt) as filler. The laboratory works, conducted at Highway Engineering Laboratory, Civil Engineering Department, Institute of Technology Bandung (ITB), are: Marshall Standard Test Marshall Immersion Test Wheel Tracking Test and Dynamic Resilient Modulus Test. The factors affecting Asbuton performances are discussed as procedures under consideration for improving the usage of these materials. In this research, Asbuton was used as a fine aggregate and filler in a Hot Rolled Asphalt (HRA) mixes type C and type F, according to the British Standard Specification : BS 594 part 1-1985. The results of Standard Marshall Test showed that the use of Asbuton filler will decrease the Optimum Bitumen Content and Marshall Stability, comparing to the use of "fly-ash" filler in HRA mixes. The results of Marshall Immersion test showed also the better performance of Asbuton filler (97.5% IRS), compared to "fly-ash" filler (82.5% IRS). The Wheel Tracking test gave also the same results as another test i.e. better performance of Asbuton filler (0.45 mm D-o), compared to "fly-ash" filler (1.38 mm D-o). Finally, the Resilient Modulus of HRA mix using Asbuton filler has higher value (3108 MPa) than HRA mix using "fly-ash" filler (2399 MPa), at the temperature of 25 degrees C). In General, almost all results showed that the use of Asbuton filler in HRA mix gives the better performance of mix, compared to the "standard" filler, such as "fly-ash" filler.