基于抗车辙稳定性的多孔沥青混合料级配优化

Gradation Optimization of Porous Asphalt Mixtures Based on Rutting Resistance

为了对多孔沥青混合料进行级配比选和优化,基于离散单元方法建立粗集料骨架结构的力学模型,对空隙率相近但级配不同的PAC-13骨架结构进行虚拟试验,并通过粗集料的CBR,混合料的车辙、剪切、飞散、劈裂等室内试验进行验证.试验结果表明:空隙率相近但级配不同的多孔沥青混合料骨架结构的力学性能、高温稳定性、抗飞散性能差异显著;对于PAC-13,将9.5～16mm和4.75～9.5mm的颗粒含量之比定义为粗值,粗值大有利于混合料的高温性能,粗值小有利于混合料抵抗飞散;推荐PAC-13的最佳粗值区间为0.8～1.1,并根据这一指标优化了多孔沥青混合料的级配范围,将9.5mm筛孔通过率由60%～80%调整为56%～68%;优化后粗集料骨架结构的力学性能和混合料的抗车辙稳定性显著提高.

In order to make a gradation selection and optimization of porous asphalt mixtures,first,a mechanical model to describe the skeleton structure of coarse aggregates was established based on the discrete element method.Then,some virtual tests of PAC-13 mixtures with similar air voids rather than different gradations were carried out.The simulation results were finally verified through the tests for CBR,the rutting resistance,the shear,the raveling and the split of coarse aggregates in laboratory.Test results indicate that there exist considerable differences in mechanical properties,high-temperature stability and anti-raveling performance among the PAC-13 mixtures with similar air voids rather than different gradations,that the PAC-13 mixtures with larger coarseness,namely the mixtures with higher content ratio of 9.5~16 mm particles to 4.75~9.5 mm particles,are of better high-temperature performance,while those with smaller coarseness are of better anti-raveling performance,and that the optimal coarseness ranges from 0.8 to 1.1.After the gradation optimization of porous asphalt mixtures according to the optimal coarseness,the content of mineral aggregates passing 9.5 mm sieve decreases from regularly-used 60%~80% to 56%~68%,and the mechanical properties of the coarse aggregate skeleton and the rutting resistance of the mixture both greatly improve.