Experimental Investigation of Nano-Alumina Modified M30 Concrete for Enhanced Resistance to Acid and Sulphate Attack

Abstract

The long-term durability of concrete exposed to aggressive chemical environments is an important consideration for maintaining structural performance and service life. This study experimentally investigates the effect of nano-alumina on the acid and sulphate resistance of M30 concrete. Seven concrete mixtures, designated M0–M6, were prepared with nano-alumina contents of 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, and 3.0%, respectively. The durability performance was evaluated under sulfuric acid and sodium sulphate exposure using percentage weight loss and residual compressive strength as the principal indicators of deterioration. The results showed that nano-alumina incorporation generally improved the resistance of M30 concrete to chemical attack, with the most favourable performance obtained at moderate nano-alumina contents. Under acid exposure, M3 containing 1.5% nano-alumina recorded the lowest weight loss of 4.85%, compared with 8.25% for the control concrete, corresponding to an approximately 41.2% reduction. M3 also retained a residual compressive strength of 46.2 MPa after acid exposure, compared with 33.2 MPa for the control. Under sulphate exposure, the minimum weight loss of 2.45% was observed for M2 containing 1.0% nano-alumina, whereas M3 demonstrated the best residual-strength performance, retaining 47.2 MPa with only 2.9% strength loss compared with 7.0% for the control. The improved durability is attributed to matrix densification, pore refinement, and reduced permeability associated with nano-alumina incorporation. At higher nano-alumina contents, a slight reduction in performance was observed, which may be associated with nanoparticle agglomeration and localized weak regions. Overall, 1.5% nano-alumina was identified as the optimum dosage for achieving a balanced improvement in acid and sulphate resistance of M30 concrete.