Rutting and surface-initiated cracking mechanisms of semi-flexible pavements with cement asphalt emulsion pastes

The semi-flexible pavement (SFP) has been used as a promising wearing course in heavy traffic roads. It is crucial to investigate the main failure mechanisms caused by different influencing factors on SFPs at medium and high temperatures. In this research, utilising a three-dimensional (3D) finite-element model (FEM), the performance of SFP and conventional pavement under realistic tire-pavement contact stresses was compared by computing the critical responses associated with rutting and top-down cracking (TDC). Besides, experimental studies were conducted on typical asphalt concrete (AC16) and four types of SFP mixtures grouted with cement paste and cement asphalt emulsion pastes (CAEPs) to evaluate their rutting resistance and fatigue cracking potential at medium and high temperatures. The numerical analysis results indicated that SFP mixtures with lower asphalt emulsion (AE) content enhanced rutting resistance significantly while TDC potential was reduced at higher percentages of AE. Compared to dual-tire assembly, the wide-base tire led to less TDC damage and asphalt layer (primary) rutting, but more subgrade (secondary) rutting once carrying the same load. Moreover, based on the findings of laboratory evaluation, SFP with CAEP presented the best performance in terms of fatigue life and permanent deformation when AE to cement by weight (AE/C) was no more than 0.4.