Research On The Quality Control Technology Of Large Stone Asphalt Mixture

The Large Stone Asphalt Mixes (LSAM) was the mixes of aggregates which hadnominal maximum particle size of25to63mm. LSAM was used for base cause asembedded squeeze skeleton-gap structure, so it was also known as the Large Stone PorousAsphalt Mixes (porosity13%above). The majority of expressway in China was constructedas semi-rigid base asphalt pavement structure which usually got disease of ruts, cracks andpit slots etc. Compared with ordinary asphalt pavement, the large stone asphalt stabilizedmacadam flexible base pavement showed high stiffness, high strength and significantlyresistance to fatigue that can effectively avoid the cracks. The mainly research on LSAM inChina was focused on gradation optimization design, the results could hardly constitute thequality control system.The asphalt mixture was considered as a three spatial dispersion network structure inmortar theory. In the structure of asphalt mixture, coarse aggregates, fine aggregates andfillers appeared as dispersed phase in asphalt mixture, mortar and mastic. the presence ofthe. The asphalt mastic was the basement in this three dispersion level. Its composition andperformance could directly affect the road performance of asphalt mixture. Related researchshowed that the properties of mastic and mortar were the decisive factor on lowtemperature crack resistance, water stability of mixture. Because of the larger particle sizeof the coarse aggregates, filling of fine aggregates was also very important. It directlyaffected asphalt adsorption, as well as the porosity of mixture which determined theperformance of large particle size aggregate skeleton and permeability.A series of tests were put forward to research the mineral fillers and fine aggregatesincluded performance test on aggregates, SHRP test on asphalt mastic, sand equivalent,methylene blue test on fine aggregates, water stability performance test and trabecular lowtemperature test to carry out the research on quality control technology of LSAM from theperspective of fillers and fine aggregates. The study found that different lithologies andfineness usually led to different performance indicators. There was high correlationbetween hydrophilic coefficient and high temperature properties of the asphalt mastic, aswell as the methylene blue value and low temperature performance. Both of them could beimportant quality control indicators. The addition of hydrated lime and silica fume couldcause the glue viscosity substantially increased, but also appeared adverse effect in the lowtemperature crack resistance. Impurities, such as carbon dust and clay filler wouldsignificantly reduce the temperature properties of the mortar. Compared with the sandequivalent method, the methylene blue value was more sensitive to distinguish impuritiesfrom mineral fillers. Research on LSAM road Performance was carried out on the basis ofthe best shear behavior of aggregate gradation. The research showed that LSAM had goodwater stability and the stability degree enhanced with increasing of the filler-bitumen ratio.Hydrated lime, as an anti-stripping agent, could improve the stability degree higher. Fineaggregate gradation had other influence. When2.36mm passing ration range from80%to 85%, the water stability performance of mixture was best. The filler would affect the lowtemperature crack resistance of the mixture. Hydrated lime made the cold brittleness of themixes higher, as well lower the strain. The binding ability to asphalt of dolomite filler wasweaker than that of limestone filler, came out the stress decreased, the strain increased. Thefiller should be selected according to practical environment of the local engineering.