Experimental Study on Mix Design Methods of Hot-laid Bituminous Mixtures −Effects of very Fine Particle Size Filler and Mixing Temperature on the Results of Marshall Test−

摘要

When paving with bituminous mixtures in fields，they should be kept in the maximum temperature ranges， in which bitumen is not excessively degraded. 　　The purposes of heating bituminous materials are to improve the adhesive property of bitumen to aggregates and thereby to enhance the workability of the bituminous mixtures， because the lower viscosity of bituminous materials makes it wet well and adhere to the surfaces of the aggregate particles in a shorter time. In ASTM， the adequate viscosities are said to be obtained by the specified mixing and compaction times of 85+_-10sec and 140+_-15sec respectively. These are the working temperatures of the mixtures estimated from bitumen itself. An adequate working temperature， however，as it varies with many working conditions， cannot be determined simply by the viscosity of the working bitumen ； for example， the adequate working temperature varies with the kinds, quality and amounts of bitumen and finer as well as with the particle sizes of other aggregates. 　　Consequently，it became necessary to examine and determine the adequate mixing temperature of the bituminous mixture at which bitumen is not hardened unreasonably. Using the undersizes of filler 37μm and 74μm sieves and changing F/A from 0 to 2.0，this study first carried out a series of Saybolt Furol viscosity tests and found out that the adequate mixing temperatures were 144℃ and 180℃, followed by Marshall tests to clarify the effects of bitumen in the mixtures