Composition Design Of SMA-8 For Thin Overlay And Experimental Study On Crafts And Pavement Performance

SMA mixture pavement has been appears a long time and it has been used more than ten years in our country. SMA often used in New road construction in our country and the nominal maximum particle size is generally greater than 13.2mm. In some projects,SMA about the maximum diameter of 9.5mm has a successful application, but the maximum particle size generally are 13.2mm. When used in the construction of thinner overcoat, Its diameter is too big, so it is necessary to study the finer particle size. There is no 8mm profile setting in the particle size of the specification, but directly from 4.75mm to 9.5mm. This paper analyzes the different grading design factors, And proposed SMA-8 concept. SMA-8 9.5mm pass rate is 100% and using a special 8mm aperture sieve to verify 8mm aggregate pass rate of more than 90%. SMA-8 mixes nominal maximum particle size is smaller than the SMA-10, which can reduces the pavement thickness, so its more suitable as a thin overlay for preventive maintenance engineering. The grading of SMA-8 is thicker than SMA-5, so it can ensure the skid resistance of the pavement better.This study first designs SMA-8 gradation range by analyzing the Impaction of 2.36～ 4.75mm aggregate content range to aggregate physical properties、the matching about nominal maximum aggregate size and pavement thickness and referring to other more successful overlays grading. Marshall test was conducted for different grading design. SMA-8 volume characteristics were analyzed from the three aspects of the asphalt content、rwo tranches of coarse aggregates mixture ratio and key sieve pass rate. Compaction effects were analyzed combining with two different warm mix agent. The results showed that, the greatest impact on the volume indicators is the key sieve passed rate, followed by the asphalt content,the smallest is two tranches of coarse aggregates content ratio.Then the road performance were studied,and the elevated temperature properties、low temperature performance and water stability were analysised about the SMA-8 with different warm mix agent congtent.Finally, Small straights accelerated loading tests were carried for analyzing the long-term performance of different overlay about SMA-8, etc. The results show that SMA-8 has a good Long-term performance.