Effects of residual water on mechanical properties of cold mix based semi-flexible pavement composite towards a sustainable paving material

This study is an attempt to replace Hot Mix Asphalt (HMA) with Cold Mix Asphalt (CMA) to prepare Porous Asphalt (PA) skeleton for improving the sustainability of Semi-Flexible Pavement (SFP) composite material. Since CMA contains asphalt emulsion, the interaction between emulsion and cement-based grouting material is expected to affect the mechanical properties of the final SFP composite. Therefore, this study investigates the effects of water remaining in the PA mixture at the time of grouting on the mechanical properties of CMA based SFP composite (C-SFPM), using HMA based SFP composite (H-SFPM) as a reference. To prepare C-SFPM, emulsified PA specimens were grouted after different amounts of water (10%, 30%, 60% and 90% by weight, respectively) evaporated from the compacted specimen. The strength, stiffness, moisture damage resistance, ravelling resistance, interfacial bond strength, and microstructural change in C-SFPM and H-SFPM were evaluated at different curing periods. Different mechanical parameters were found to be significantly affected by the time of grouting. Specifically, the detrimental effect of water present in the emulsified PA was identified from ravelling based laboratory evaluation (Cantabro loss value as high as 97.9% was observed). The microstructural analysis also indicated that the formation of hydration product in C-SFPM would be significantly influenced by the amount of water present in the emulsified PA mixture at the time of grouting. Overall, this study indicates that water present in the emulsified mixture has a negative effect on the mechanical properties of C-SFPM.