Strain Hardening Behavior of Engineered Cementitious/Geopolymer Composites Under Sulfuric Acid Erosion

This study presents a comparative durability assessment of Engineered Geopolymer Composites (EGCs) against a Engineered Cementitious Composite (ECC) under prolonged sulfuric acid (H₂SO₄) attack. This work addresses a critical gap by systematically comparing the strain-hardening performance and degradation mechanisms of lightweight fiber-reinforced composites under aggressive chemical exposure. Four lightweight mixtures—three EGCs with varying slag/fly ash contents (S-EGC: 100% slag; FAS-EGC: 50% slag; FA-EGC: 100% fly ash) and one lightweight ECC control—were fabricated using expanded glass granule (EGG) aggregates and immersed in a 5% H₂SO₄ solution for up to 120 days. Before exposure, the incorporation of slag significantly enhanced pre-exposure mechanical properties; S-EGC showed the highest ultimate strength, while the FAS-EGC mixture provided the best balance of strength and ductility, achieving a tensile strain capacity of 3.21%. The lightweight EGCs demonstrated superior acid resistance compared to the lightweight ECC. After 120 days of exposure, the S-EGC composite retained the highest residual compressive strength (81.59%), while the ECC retained significantly less. Significantly, all exposed EGC and ECC specimens maintained their multiple cracking and deflection-hardening behavior, retaining approximately 50% of their total deflection capacity after four months. Microstructural analysis confirmed that the superior resistance of S-EGC is attributed to its stable, cross-linked alumino-silicate polymer structure. These findings confirm that lightweight slag-based EGCs are a highly durable and ductile sustainable alternative for structural applications in aggressive environmental settings, such as wastewater treatment infrastructure and chemical plants.