Recuring Studies on Concretes Subjected to Elevated Temperatures and Suddenly Cooled by Water Quenching

Abstract

Concrete is found to undergo degradation when subjected to elevated temperatures during an accidental event, such as fire and lose substantial amount of its original strength. The loss of strength in concrete is mainly attributed to the decomposition of Calcium Silicate Hydrate (C-S-H) and release of chemically bound water, which begins when the exposure temperature exceeds 500°C. When such a concrete is supplied with water and allowed to recure, it is found to recover substantial amount of its lost strength. This work is carried out to investigate the effect of recuring on strength recovery of un-blended and blended concrete specimen (100 mm cubes) subjected to elevated temperatures from 400°C to 700°C, in steps of 100°C, for a retention period of two hours at the designated temperatures. The concrete cubes immediately after exposure were subjected to thermal shock by quenching them in water, and then temperature of thermally shocked concrete is allowed to cool to room temperature. The cooled specimen were then recured in water for 1, 3, 7, 14, 21, 28, 56 days and tested for compressive strength recovery. These studies were carried out for Portland Cement (PC) based concrete and Portland & Granulated Blast Furnace Slag (70% PC + 30% GGBS) based concrete (blended concrete), and some interesting results are presented and discussed in this paper.

Performance and microstructural investigations of processed lateritic fine aggregates in blended cement mortars exposed to elevated temperatures

“…The loss of strength is minimal up to 300 8C. However, this loss in strength can be recovered to a certain extent through rehydration (Prashant et al, 2015;Yaragal and Babu, 2011;Yaragal et al, 2015). Nevertheless, with an increase in exposure temperature from 350-550 8C, calcium hydroxide in the matrix decomposes into calcium oxide and water.…”

“…However, this loss in strength can be recovered to a certain extent through rehydration (Prashant et al. , 2015; Yaragal and Babu, 2011; Yaragal et al. , 2015).…”

Evaluation of mechanical properties and post-fire cured strength recovery of recycled aggregate concrete

“…The rehydrated products are comparatively lesser in size and volume to that of original hydrated products by plugging the voids and honeycombs and thereby regaining the lost strength (Poon et al. 2001; Yaragal et al. , 2015).…”

“…This method involves the curing of exposed concrete specimens to sustained elevated temperatures over a period of time wherein, a substantial amount of original strength of concrete can be recovered. The rehydrated products are comparatively lesser in size and volume to that of original hydrated products by plugging the voids and honeycombs and thereby regaining the lost strength (Poon et al 2001;Yaragal et al, 2015).…”