Assessment for Fire Damage in Concrete Structures with Electrical Resistance Measurement

When devising plans for repairing and reinforcing concrete structures after a fire, one must evaluate the effects of heat on concrete. When a fire occurs in a concrete structure, the moisture contained within it evaporates owing to high temperatures. The authors investigated methods to assess the effect of heat by correlating the drying process during a fire with the heating temperature. In this study, a method for evaluating the drying degree of concrete after fire exposure was examined by measuring the electrical resistance, which is closely related to the moisture content of concrete. Initially, a method was investigated to measure the electrical resistance in the depth direction from the surface of fire-damaged concrete. Subsequently, the electrical resistance of the specimens heated to simulate fire conditions was measured, and the relationships among the electrical resistance, moisture content, and heating temperature were compared. Measuring the electrical resistance of the surface of concrete damaged by fire and then comparing it to the resistance of unheated concrete allows one to identify the area that had been heated to 150 degrees C or more and became almost completely dry.