Using ultrasonic pulse velocity to evaluate residual compressive strength of post-fire-curing concrete

摘要

In this paper, the ultrasonic pulse velocity (UPV) is used to quantitatively evaluate the residual compressive strength of post-fire-curing concrete subjected to elevated temperatures. A series of tests were performed to examine the relationship between the residual UPV and strength of post-fire-curing concrete. Cylindrical specimens were made of concrete with various mixture proportions, and heated in an electric furnace to temperatures ranging from 400 to 1000 °C with an exposure time of 2 hours. After exposing to elevated temperatures, the concrete specimens were cooled down in the ambient air or water tank and then cured in water for different curing durations. These specimens were tested at the 7th, 30th, 90th and 180th days after heating. For each test, the pulse velocity and compressive strength were measured. Experimental results show that the residual compressive strength of concrete decreases as the exposure temperature increases. In addition, prolonging the water-curing duration and extending the test days will help restore concrete strength significantly. Finally, a general relationship between the residual strength and UPV ratios can be established to estimate the residual strength ratio of post-fire-curing concrete with a measured residual UPV ratio.