Transport properties of fire-exposed concrete

Abstract

Concrete has a good reputation for fire resistance because it has low thermal conductivity and is non-combustible. However, concrete loses strength when exposed to elevated temperatures as a result of damage to the pore structure and chemical degradation of the calcium silicate hydrate. Reports on strength loss due to fire exposure are ubiquitous in the literature. However, there have been limited reports on the changes in the pore structure, which greatly affects the durability of the concrete. In cases where the strength is sufficient for the structural element to remain in service, other considerations, such as the durability of the structural element comes into play. The ingress of aggressive agents is typically through means, such as water, which leads to sorptivity being a particular important transport property of the degraded concrete. The sorptivity of the concrete will depend on the age of the sample at the time of damage, the cement content, w/c of the original mix design, as well as the length of time the damaged concrete has been re-exposed to water. These properties are reported along with mechanical properties to better demonstrate the complexity in the relationship between transport properties and strength. Furthermore, sorptivity can become crucial to predicting long term durability as well as identifying potential repair mechanisms. Copyright © 2009 Japan Concrete Institute.