Synergistic effects of clinoptilolite and supplementary cementitious materials on chloride resistance in concrete

Abstract

Chloride ingress is a critical challenge for concrete durability, particularly in structures exposed to marine environments and deicing salts, as it accelerates steel reinforcement corrosion. This study investigates the synergistic effects of clinoptilolite, a natural zeolite, and supplementary cementitious materials (SCMs) such as fly ash and ground granulated blast-furnace slag (GGBS) on enhancing chloride resistance in concrete. The primary objective was to evaluate the combined impact of these materials on chloride penetration and chloride-binding capacity, aiming to develop durable and cost-effective concrete formulations. Concrete specimens were prepared with varying percentages of clinoptilolite (5%, 10%, and 15% by weight of cement) and SCMs (20% fly ash and 30% GGBS). Chloride penetration resistance was assessed using rapid chloride permeability tests (RCPT), while chloride-binding capacity was evaluated through leaching tests and chemical titration of pore solutions. Microstructural analyses using SEM and XRD were conducted to observe changes in the pore structure and chloride-binding phases. The results demonstrated that the incorporation of clinoptilolite and SCMs significantly reduced chloride penetration and enhanced chloride-binding capacity. The mix with 15% clinoptilolite and 30% GGBS exhibited the highest resistance to chloride ingress, with a 45% reduction in chloride penetration compared to the control. Statistical analysis using ANOVA confirmed the significance of these findings (p