Effect of water re-curing on the physico-mechanical and microstructural properties of self-compacting concrete reinforced with steel fibers after exposure to high temperatures

Abstract

The present work aims to investigate the influence of water re-curing- on the physico-mechanical properties and the microstructural of heat-damaged steel fiber-reinforced self-compacting concrete. The experimental approach involves subjecting self-compacting concrete specimens, with and without steel fiber reinforcement, to various high temperatures (400, 600, and 800 °C), with a heating rate of 5 °C/minute. After cooling to ambient temperature, these samples were subjected to water re-curing for 30 days. Non-destructive measurement techniques, such as those of the ultrasonic pulse velocity and dynamic modulus of elasticity, and destructive measurement techniques, such as those of the flexural strength and compressive strength, were performed to assess the level of thermal damage caused to specimens as well as the degree of recovery. Moreover, scanning electron microscope (SEM) analyses were also performed to examine the morphological changes that occurred in concrete and at the fiber/concrete interface. The results obtained showed that the water re-curing process has remarkable effects on the recovery of the microstructure of thermally damaged specimens and its physical and mechanical properties as well. The recovery rate was more important for temperatures above 400 °C. Furthermore, it was found that self-compacting concretes reinforced with steel fibers recurred after exposure to 400 °C and 600 °C exhibited better behavior than self-compacting concrete without fibers, particularly in terms of mechanical resistance.