In this experimental investigation, the high-yield strength-deformed-steel (HYSD) and glass-fibre-reinforced-polymer (GFRP) rebars were employed to assess the bond behaviour at RT, 1000ºC, 2000ºC and 3000ºC. Natural river sand has been completely replaced with manufactured sand (MS) in the production of concrete, wherein it was observed that, the residual compressive strength decreases as the temperature increases. Based on ultrasonic pulse velocity (UPV) test results, the quality of concrete can be categorised from “Excellent to Good”. The bond strength of HYSD bar specimens reveals higher values compared to specimens with GFRP bars at RT, 1000ºC, 2000ºC and 3000ºC. The specimens with HYSD bars show lower slippage when compared to specimens with GFRP bars at elevated temperatures and the pullout failures have been noticed for the specimens at elevated temperatures. Based on experimental investigation, the mathematical equations have been suggested for predicting the bond stress at high temperatures.
The mix design has been conducted in line with IS 10262:2019 following material characterization. The samples were cast in the prescribed mix ratios and cured for 28 days. After curing, the samples were then dried for 48 h to remove any moisture and prevent cubes from spalling during heating. The samples were placed in an electrical furnace of 10000ºC capacity and heated to the desired temperatures for 2 h. The specimens were cooled to room temperature (RT) in the furnace, and non-destructive testing such as UPV and rebound hammer tests were performed to evaluate the quality of the post-heated specimens. The compression and pullout tests were performed to evaluate the post-heat mechanical behaviour. The analysis and interpretation of results were performed to examine the behaviour of specimens exposed to sustained elevated temperatures, and conclusions were drawn at the end of the research.
The specimens with HYSD bars reveal greater bond strength than specimens with GFRP bars at each interval of temperatures. The maximum slippage was observed for the specimens with GFRP bars at 3000ºC. This indicates increase in slip with rise in temperatures.
The bond strength of HYSD bar samples is higher than that of GFRP bars at RT, 1000ºC, 2000ºC and 3000ºC. At higher temperatures, specimens with HYSD bars exhibit lesser slippage than specimens with GFRP bars, and pullout failures were observed. Based on experimental data, mathematical formulae for estimating bond stress at high temperatures have been proposed.
