Abstract:

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.

Key words: road engineering, porous asphalt mixture, gradation optimization, virtual test, coarseness