Strength Activity Index and Microstructural Characteristics of Treated Palm Oil Fuel Ash

Abstract — The strength activity index of mortar and microstructural characteristics of pastes containing treated palm oil fuel ash (POFA) have been investigated. POFA obtained from a palm oil mill was treated via sieving, grinding and heating at temperature of 450°C for 90 minutes in order to improve the pozzolanic reactivity of the POFA. The pozzolanic reactivity of the treated POFA was evaluated by conducting strength development tests according to ASTM C311. The hydration products of hardened pastes were analyzed by means of thermogravimetric analysis (TGA), x-ray diffraction (XRD), and scanning electron microscopy (SEM) in order to quantify the influence of the treated POFA which was used at different POFA/cement ratio ranging from 0 to 0.8. After 28 days, the strength activity index of the treated POFA with ordinary Portland cement exhibited very good performance and was higher than 100%. At 90 days, the strength activity index increased to 101.72 %. Using TGA, XRD, and SEM, a significant reduction in Ca(OH)2 content was observed with increasing amount of treated POFA. The development of C-S-H gel was higher when POFA/cement ratio was raised up to 0.3. Index Terms- Palm oil fuel ash; Strength activity index; Hydration products. 1