High-Strength Concrete Enhancement Using Fine Metakaolin and Palm Oil Fuel Ash: A Comprehensive Study

Abstract The increased use of high-strength concrete in construction leads to significant carbon dioxide (CO 2 ) emissions due to extensive cement manufacturing. To mitigate this, additives like fine metakaolin and palm oil fuel ash can enhance concrete performance and reduce the carbon footprint. In Stage 1, cement was partially replaced with 10%, 20%, and 30% FMK to find the optimal amount for further testing in Stage 2. The best-performing FMK mix was then combined with varying percentages of POFA (5%, 10%, and 15%) as cement replacement. Tests for slump, water absorption, compressive strength, flexural strength, and SEM analysis were conducted on concrete samples containing FMK and POFA. Initially, the FMK and POFA improved the concrete workability, but it declined with 20% to 30% FMK in Stage 1 and 20% FMK with 10% to 15% of POFA in Stage 2. The small particle sizes of FMK and POFA acted as fillers, reducing water absorption. The 20M5P mix demonstrated the highest compressive and flexural strengths and the lowest water absorption compared to the control sample and other mixes. Scanning electron microscopy analysis confirmed that FMK and POFA promoted a pozzolanic reaction involving alumina oxide, silica oxide, and calcium oxide with calcium hydroxide from cement, enhancing the hardening process of the concrete.