The high temperature rutting and low temperature cracking of asphalt pavement due to severe temperature susceptibility of asphalt cement have led to the research of polymer modified asphalt (PMA) ― an alternative way of asphalt mixture binder. The improved high temperature deformation resistance of PMA has been generally accepted but, within the cost effective polymer concentration, a few applications demonstrated negative results as regard to low temperature cracking resistance when compared with neat asphalt. Few microscopic mechanical analyses have been addressed to solve this problem. In this paper, PMA is treated as a two-phase composite material with the oily fraction of base asphalt swelled polymer particles dispersed in an asphalt matrix. A two-layer built-in model was thus developed to evaluate the effects of elastic modulus, coefficient of thermal expansion, volume fraction, particle size, and PMA film thickness on temperature and boundary force induced interface stresses. By comparison with one single inclusion model and modified Eshelby model, it is found that this two-layer built-in model is suitable for the evaluation of PMA. The calculation results show that there are five factors which can be beneficial to enhancing low temperature cracking resistance of PMA: (1) thickening PMA film in PMA mixture design; (2) increasing polymer content within the cost effective range; (3) reducing polymer particle size; (4) selecting soft and asphalt compatible polymer; and (5) incorporating polymers with the coefficient of thermal expansion smaller than that of asphalt.
展开▼
