Experimental study of the effect of high temperature on the passage speed of Ultrasonic Pulse Velocity (UPV) in alkaline slag concrete used in pavement

In this laboratory study, Ultrasonic Pulse Velocity (UPV) was investigated in high-temperature slag slag concrete used in pavement at high temperature at 90-day curing age, followed by scanning electron microscopy (SEM) imaging test in concrete. The overlap of the results was analyzed and investigated. In this regard, one mixing design was made of control concrete and three mixing designs were made of low-slag slag concrete containing 0, 4 and 8% nanosilica. Then, the optimal design obtained from the test results was selected from three designs of alkaline slag concrete and 1 and 2% of polyolefin fibers were added to it, and two other designs were made of alkaline slag concrete, new samples under room temperature and High temperatures were subjected to UPV, SEM and analysis. The results showed an 11% improvement (Scheme 3 compared to Scheme 2) in the passage of ultrasonic waves by adding nanosilica to alkaline slag concrete at room temperature, but the presence of polyolefin fibers reduced the UPV by 12% (Scheme 6 compared to Scheme 3). High heat application in concrete had harmful effects on the results of UPV and SEM test, so that the lowest and highest rate of decrease in ultrasonic wave velocity in concrete samples of 37 and 46%, respectively, belong to plan 1 (containing ordinary concrete) and plan 2. (Alkaline slag concrete without nanosilica) was obtained. Microstructural studies of SEM showed the coordination and overlap of the results obtained in this study.