Microstructure and compressive strength of self-compacting concrete incorporating palm oil fuel ash exposed to elevated temperatures

Abstract

Palm oil fuel ash (POFA) has been extensively used to substitute cement in the production of self-compacting concrete (SCC) to lessen its production cost, health hazard, energy consumption problems and environmental pollution caused during the production of cement. Nevertheless, the impact of elevated temperatures on self-compacting concrete produced with POFA (POFA-SCC) has not been studied extensively. When designing the fire resistance of concrete at elevated temperatures, its compressive strength is of primary interest. This research endeavor is carried out to study the impact of elevated temperatures on the microstructure and compressive strength of SCC produced from POFA with 15% replacement level by weight of cement. The 28 days compressive strength of SCC samples was determined using concrete cubes. Subsequently, the SCC samples were subjected to elevated temperatures which varying from 200 to 1000 °C at an intermission of 200 °C utilizing an automatic regulated electric furnace for duration of 120 min after reaching the requisite temperatures. After heating, mass losses and compressive strength were evaluated. The microstructures of SCC were also examined by scanning electron microscope and X-ray diffraction analysis. Results revealed that there was an incessant loss in mass of the cubes with upsurge in temperature. There was an upsurge in the values of compressive strength at 400 °C whereas it fluctuated sharply at the range of 400–600 °C, 600–800 °C and 800–1000 °C for the two mixes. The results of the microstructures showed the transformation of calcium silicate hydrate (C-S-H) into distinctive phases. The outcome of this research will be applicable in high fire resistance structures and also help to minimize the waste from palm oil factory.