Analysis of skeleton contact stability of graded aggregates system and its effect on slip creep properties of asphalt mixture

Abstract

Geometric characteristics are the essential properties of aggregates, which form the gradation skeleton through contact effect among aggregates and further affect the deformation characteristics of asphalt mixture. In this investigation, the skeleton contact stability of graded aggregate system was evaluated and the slip creep properties of asphalt mixture were analyzed from the geometric characteristics of aggregates. First, the skeleton stability index (SSI) was constructed with the geometric characteristics of aggregates based on the idea of variable weight, and the effectiveness of SSI in representing the skeleton contact stability was verified by the maximum slip force (Fm). Secondly, the interface slip creep test of asphalt mixtures were performed, a quantitative model with three-stage of creep deformation was put forward to calculate the deformation in each stage, and the migration creep rate (SM), steady-state creep rate (SS) and creep life (FT) were proposed to characterize the slip creep properties of asphalt mixture. Finally, the effect of skeleton contact stability of graded aggregate system on the slip creep properties of asphalt mixture was analyzed. The results indicate that SSI has a good correlation with Fm, which can effectively characterize the skeleton contact stability of graded aggregate system, and a larger SSImeans a bigger skeleton contact stability. According to the deformation mechanism, the deformation behavior of asphalt mixture was divided into instantaneous elasticity, migration creep, steady-state creep and creep failure stage. Among them, SMdetermines the deformation level of asphalt mixture, SSreflects the deformation potential of asphalt mixture, and FT embodies the creep length of asphalt mixture. In migration creep stage, the slippage of aggregate induces asphalt mortar to flow; while in steady-state creep stage, the flow of asphalt mortar drives the aggregate to slip. The aggregate slippage and asphalt mortar flow promote and superimpose each other, resulting in the deformation of asphalt mixture.