Comparative Study of Surface Coatings for Enhancing the Durability of Concrete

Abstract

The durability of reinforced concrete structures in tropical and humid climates is frequently compromised by the rapid ingress of moisture and aggressive ions, leading to premature corrosion and structural deterioration. This paper presents a comprehensive comparative study evaluating the effectiveness of three distinct surface coating systems, Polyurethane (PU), Acrylic (AC), and Silicon-based (SI), in enhancing concrete durability. The research investigates coating performance across three concrete grades (M15, M25, and M35) to understand the relationship between substrate quality and the necessity of surface protection. Water absorption tests were conducted in accordance with BS 1881-122:1983, with measurements recorded at precise intervals up to 168 hours (7 days). Results demonstrate that PU coatings provided the most robust and grade-consistent protection, reducing 24-hour water absorption by approximately 53% for M15, 59% for M25, and 59% for M35 relative to uncoated controls. Acrylic coatings performed comparably to PU on M15 concrete but showed progressively wider performance gaps on denser grades. Silicon-based treatments were found to be largely ineffective under prolonged hydrostatic immersion, particularly on M25 and M35 concrete. The study confirms an inverse relationship between coating benefit and concrete grade for penetrating-type treatments, and provides grade-specific recommendations for the Sri Lankan construction context.