Compressive strength and piezoresistivity of smart cement paste modified with waste steel slag

This study intends to examine ordinary Portland cement (OPC) with a constant water-to-cement ratio (w/c) of 0.38 and different concentrations of steel slag (SS) from 0 to 30% weight of dry cement behaves in terms of compressive strength, electrical resistivity, and piezoresistivity. Since iron is the main constituent of steel slag, adding steel slag may improve electrical resistivity, which is the main requirement for structural health monitoring of cementitious material. Therefore, using the two-probe (2P) and four-probe (4P) approaches, the resistivity of cement paste was compared and measured from early curing to 28 days. The ideal value of steel slag was chosen for the electrical resistivity and piezoresistivity of cement paste at various curing times based on the compressive strength (CS) findings of smart cement paste modified with various steel slag contents. Since the wire probe is not considered in four-probe, the findings show that 4P is more accurate than 2P for detecting electrical resistivity. According to the findings of the pie-zoresistivity test, adding 15% of steel slag to cement improves piezoresistivity by 71% compared to cement alone and decreases compressive strength by 16.9% compared to cement without steel slag. At the same time, they were increasing compressive strength and piezoresistivity by 15.85 and 64%, respectively, while substituting 5% of the steel slag with cement weight. The electrical resistivity of cement paste was predicted using a Vipulanandan p-q model during 28 days of curing, as well as the change in electrical resistivity as a function of compressive strength at 3, 7, and 28 days. The Vipulanandan p-q model accurately predicted both the characteristics of elec-trical resistivity and piezoresistivity.