Influence of Palm Oil Fuel Ash on Sulfate Resistance of Mortar and Concrete

Abstract

Pozzolanic materials, either natural or artificial, have long demonstrated their effectiveness in producing high-performance concrete. Artificial pozzolans, such as fly ash and rice husk ash have gained acceptance as supplementary cementing materials in many parts of the world. Perhaps the latest addition to the pozzolanic ash family is palm oil fuel ash, a waste material obtained on burning of palm oil husk and shell in the palm oil milling industry. This paper presents laboratory test results on the performance of palm oil fuel ash (POFA) in mortar and concrete containing the ash as a partial replacement of normal portland cement against sulfate attack. Mortar bars having dimensions of 25 x 25 x 250 mm, and 100 mm concrete cube specimens were cast with a fixed water-cementitious material ratio of 0.5 where normal portland cement was replaced by 30% POFA by mass. After 28 days of moist curing, the specimens were put into 10% sodium sulfate solution with alternate wetting and drying cycles. During the test period of over one year, the mortar bar specimens were periodically subjected to expansion measurements while the concrete cube specimens were tested for change in mass. Finally, examination of the deteriorated materials through X-ray diffraction analysis was carried out to elucidate the mechanism of deterioration. It has been observed that the specimens with POFA, in general, exhibited significantly higher resistance to the sulfate attack than those prepared with normal portland cement alone.