Elastic modulus evolution and fracture behaviour of pervious concrete incorporating fly ash and alccofine

Pervious concrete provides effective stormwater infiltration but often exhibits low stiffness due to its interconnected pore structure. This study investigated the influence of fly ash (FA) and Alccofine (AF) as supplementary cementitious materials on the hydraulic, mechanical, elastic, and microstructural behaviour of pervious concrete. FA was incorporated at 15–25%, while AF was used at 4–12% replacement of cement. The results showed a strong correlation between porosity and permeability (R² = 0.87), highlighting the influence of pore structure on hydraulic performance. Alccofine reduced porosity and permeability, with a minimum permeability of 0.28 cm/s obtained for the ternary blend containing 25% FA and 12% AF. The static elastic modulus increased from approximately 8 GPa in FA-rich mixes to 13.25 GPa in AF-rich mixes. The dynamic modulus values were 23–37% higher than the corresponding static values. A strong correlation (R² = 0.97) between static and dynamic modulus indicated the potential applicability of ultrasonic pulse velocity for stiffness estimation. Microstructural observations revealed a denser Ca–Si–Al-rich matrix in AF-modified mixes. The ternary blend containing 25% FA and 12% AF reduced cement content by 37% while maintaining adequate permeability and improved elastic performance, demonstrating its potential for pervious pavement applications.