Effects of coral aggregate properties on the ultrasonic pulse velocity of concrete

For the non-destructive evaluation of concrete properties and internal damage monitoring, the ultrasonic pulse velocity (UPV) method has been widely employed; however, for coral concrete, crucial characterization parameters such as UPV are still unknown. Thus, this paper focuses on coral concrete UPV characteristics, especially with respect to porosity and compressive strength. The results show that the coral aggregate has diverse morphologies and complex internal struc-ture, which greatly affects the homogeneity of its UPV, which ranges from 2550-3850 m/s, and these are also the main reason for the UPV dispersion effect in coral concrete. Due to the lower UPV of coral coarse aggregate, the UPV of coral mortar was higher than that of coral concrete in the same condition. In addition, the three-dimensional of large-aggregate distribution in coral concrete had a remarkable effect on ultrasonic wave propagation path in coral concrete. It was also found that the coral concrete porosity, compressive strength and UPV are strongly correlated specifically the compressive strength and UPV are linearly positively correlated. The UPV of coral concrete in the dry state is approximately 3950-4450 m/s and its porosity is approximately 14.3 %-21.5 %, and the relationship between the two is more reliably characterized by an exponential function. Furthermore, the linear correlation between coral concrete strength and UPV can be effectively improved by reducing aggregate particle size, thus, the strength can be inferred by the UPV method within a certain range.