Acid resistance of lightweight potassium-activated GGBS concrete with LECA and pumice: Strength and durability explained through microstructure

Abstract

Concrete exposed to aggressive environments, including industrial and wastewater systems, require durable and sustainable alternatives to conventional cement-based materials. Alkali-activated concrete (AC) produced from industrial by-products offers significant potential

however, the combined effects of lightweight aggregates and potassium-based activation on long-term performance remain underexplored. This study investigates mechanical and durability performance of potassium-activated ground granulated blast furnace slag (GGBS) concrete incorporating lightweight aggregates. Natural coarse aggregate (NCA) was replaced with lightweight expanded clay aggregate (LECA) and pumice at replacement levels of 0, 10, 20, 30, 40, 50, and 100% to produce concretes with varying densities. Mechanical performance was evaluated to identify optimum replacement levels. Based on strength performance, the optimum mixtures were identified as 10% LECA (AC-L10) and 20% pumice (AC-P20). Durability was assessed through acid attack tests using 5% H2SO4, HCl, and HNO3 solutions for exposure periods up to 90 days, during which mass loss and residual mechanical strengths were measured. Microstructural evolution and degradation mechanisms were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM) coupled with Energy Dispersive X-Ray Spectroscopy (EDX). The results show that the optimized lightweight mixtures exhibited higher compressive strength and significantly improved acid resistance than the control mix. Enhanced performance was attributed to internal curing by lightweight aggregates, refinement of the interfacial transition zone, and formation of a relatively stable potassium aluminosilicate gel with reduced calcium availability. XRD, FTIR, and FESEM-EDX analyses corroborated these findings, demonstrating limited acid ingress, suppressed gypsum formation, and reduced decalcification. © 2026 Elsevier Ltd