Abstract
This study aims at investigating the reutilization of heavy oil fuel ash (HOFA) as a cement replacement material in low grade concrete applications.Preliminary investigation and material characterisation of HOFA using scanning electron microscopy and X-ray energy-dispersive analysis, X-ray diffraction analysis, BET gas adsorption method and loss-on-ignition was performed. Various percentage replacements of Portland cement with HOFA were investigated by mortar testing and assessment of two low grade concretes to be used as a flowable backfilling material and concrete masonry units.The ash contained a high amount of unburned carbon, had a high specific surface area, low density and was X-ray amorphous. Incorporation in a cement-based mixture led to an extended setting time, increased water demand and high levels of Portlandite were observed. A suitable flowable fill concrete was achieved when limiting the cement replacement to 30%. Strength reductions were avoided with the concrete masonry units, and units of adequate strength were produced with replacement levels of 20%.Inclusion of HOFA in a concrete effected the hydration reaction of Portland cement. A 30% and at least 20% cement replacement for flowable fill concrete and hollow masonry units respectively is recommended.
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