Application and validation of fly ash based geopolymer mortar as grouting material in porous asphalt concrete

To verify the feasibility of using fly ash based geopolymer (FAG) mortar in the porous asphalt concrete, the FAG was designed as the grouting material to fabricate the semi-flexible asphalt mixture. The fluidity of the fresh FAG mortar and the mechanical properties of cured FAG were firstly investigated to characterize its workability. The fulfilling status of FAG grouting asphalt concrete (FAGAC) was validated by both the theoretical calculation method and 3D-CT scanning method. In addition, the interfacial energy parameters between the FAG and the asphalt matrix was investigated. Then, the road performance was extensively studied using the dynamic uniaxial compression test, semi-circular bending test, moisture resistance test and fatigue test. The results showed that the water–solid (W/S) ratio of FAG mortar significantly affected the technical performance of FAG mortar and FAGAC. The mechanical strength of cured FAG mortar, high-temperature stability and moisture resistance of FAGAC decreased with the increase of W/S ratio. Meanwhile, the low-temperature crack resistance, anti-fatigue performance and the interface energy between FAG and asphalt matrix firstly increased with the increase of W/S value, then decreased as the W/S ratio exceeded 0.45. The optimum parameters for FAGAC were reckoned as 24% residual air voids of asphalt matrix, 0.45 W/S ratio of FAG which filling 90% volume of matrix voids. Finally, the ranking priority for the factors affecting the FAGAC performance was specified, including the compression strength of cured FAG mortar, the interface energy between FAG and asphalt matrix, as well as the residual air voids of FAGAC.