With growing global emphasis on sustainable construction practices, this study explored the use of Class F fly ash as a partial replacement for Ordinary Portland Cement (OPC) in concrete, particularly for water-retaining structures. The
research investigated the compressive strength and durability performance of fly ash concrete, with and without the inclusion of a crystalline waterproofing admixture (Sika WT-220 PMY). A concrete mix design targeting 35 MPa
compressive strength was first developed using the British Method prepared by Building Research Development, with a ratio of 1:0.45:1.18:2.51 (cement : water : fine aggregate : coarse aggregate). Class F fly ash sourced from Sultan
Abdul Aziz Power Plant was substituted at 5 %, 10 %, 15 %, and 20 % by weight of cement in the design mix. Compression test results showed decreasing trend with increasing fly ash replacement, with 5 % being the optimal replacement which achieved the highest compressive strength of 35.86 MPa among all substitution levels. The Sika WT-220 PMY was incorporated into the concrete mix with 5 % fly ash replacement. A total of 4 different concrete mixes were prepared, which were control mix, control mix with Sika, 5 % FA mix and 5 % FA + Sika mix. Durability was assessed through initial surface absorption test (ISAT), sorptivity test, and water absorption test. All three tests showed similar results in which the incorporation of fly ash and Sika WT-220 PMY demonstrated better durability performance than plain OPC control mix.
Concrete mix with 5 % Fly ash and Sika WT-220 PMY outperformed the other mix. Compared to the control mix, the optimized 5 % fly ash and Sika WT-220 PMY mix demonstrated a 26.09 % reduction in Initial Surface Absorption Test (ISAT) values, a 13.86 % decrease in the sorptivity coefficient, and a 24.56 % reduction in overall water absorption. These findings confirm the beneficial effects of fly ash and crystalline waterproofing admixtures in improving the
durability performance and sustainability of concrete.
Key Words: Fly Ash Concrete, Waterproofing, Compressive Strength, Durability Performance, Sustainable Construction
Subject Area: TA401-492 (Materials of engineering and construction
