Spalling of concrete in fire – an overview and local relevance

Abstract

Concrete has traditionally been considered as a material with favourable fire resistance. The development of modern concretes with low permeability has, however, resulted in the increased occurrence of spalling when exposed to fire. Recent fire damage in South Africa during the riots in July 2021 resulted in such damage. This paper presents an overview of explosive spalling of concrete in fire, recent local observations, and developments in the field. It is shown that various (often interrelated) factors influence the susceptibility of concrete to spall in fire, and that much research is still needed to fully understand the phenomenon and, specifically, how to accurately predict its occurrence. Recent observations in South Africa support conclusions in the literature that, as an accidental loading case or as life-safety performance criteria, overall structural integrity is rarely compromised. However, as the use of higher concrete grades increases, the relevance of this risk should be considered by practising engineers.