The role of aggregate and cement paste in the deterioration of the transitional interface zone of pervious concrete during freeze-thaw cycles

Improving the performance of the cement matrix is an effective method to enhance the freeze-thaw (F-T) damage resistance of pervious concrete. However, the interfacial transition zone (ITZ) is the weakest component. The purpose of this paper is to evaluate the effect of ITZ on the deterioration of pervious concrete under F-T circumstances. The evolution of the compressive strength of samples under water and salt F-T conditions was obtained by uniaxial compression tests. Additionally, the development of the ultrasonic velocities and the relative dynamic modulus of elasticity were examined. Changes in the microstructure and the pore structure were also continuously monitored. The results demonstrate that as the number of F-T cycles rises, compressive strength and dynamic elastic modulus diminish, and the deterioration of samples in 3% NaCl solution is more severe than that in water. Within 100 F-T cycles, cement paste samples with the identical w/c as pervious concrete showed no discernible strength deterioration, and detrimental porosity did not alter considerably. Scanning electron microscopy (SEM) results showed that the performance difference between aggregate and ITZ and the expansion stress lead to debonding at the interface of aggregate and cement, which is the primary culprit for the worsening of pervious concrete under F-T conditions. This work serves as a reference for the deterioration mechanism and durability enhancement of pervious concrete under F-T circumstances.