Potential Use of Heavy Oil Fuel Ash for Smart and Sustainable Infrastructure

Amid the urgent global demand for sustainable, low-carbon construction materials, innovative strategies are essential for utilizing industrial by-products. Self-sensing materials enable structures to monitor their own conditions in real time, a capability driven by their electrical conductivity, where stress or damage induces measurable changes in resistivity. Heavy Oil Fuel Ash (HOFA), a largely underutilized residue of oil-fired power plants, poses significant environmental disposal challenges but also offers promising potential for reuse. This study investigates the feasibility of partially substituting Ordinary Portland Cement (OPC) with both untreated and water-treated HOFA. Mortar cubes (50 mm) and cylinders (75 × 150 mm) were prepared with 2, 4, and 6% replacement of OPC by HOFA. Compressive strength and electrical resistivity of HOFA-infused mortars were studied. Results showed that untreated HOFA incorporation provided moderate strength enhancement with decreasing resistivity (increasing conductivity). To further improve reactivity, HOFA was soaked in water for 4 h, dried, and reused. This treatment, by and large, improved compressive strength and increased conductivity. The findings demonstrate that HOFA, in both untreated and treated forms, has promising potential as a conductive filler for self-sensing without compromising strength. Its use not only diverts hazardous waste from landfills but also provides functionalization of cementitious composites. The study underscores the importance of optimizing treatment and dosage to balance strength and conductivity, paving the way for greener construction materials.