The effect of various fire‐exposed surface dimensions on the spalling of concrete specimens

Abstract

SUMMARYConcrete spalling due to fire exposure is often defined as the sudden detachment of fragments from a concrete surface. It can be quantified by various parameters of which weight loss and spalling depth are the most common ones. The risk of spalling is influenced by many factors such as concrete composition, heating rate and applied testing methods. A reduced scale testing method should be developed to analyse the spalling behaviour and to understand its effectiveness in more detail. As a subsection of this development, this study aimed to analyse the effect of different-sized, circular heated areas in semi full-scale fire tests. Therefore, vermiculite slabs with varying cut-outs in their centre were placed between a specimen made of a spalling-sensitive concrete and the combustion chamber. The combustion chamber was heated following a standard fire curve. Our experimental results show that the thermal expansion inside of equal-sized specimens is strongly dependent on the size of the heated area. In addition, this area also affects thermal stresses. They decrease as a result of lower temperature gradients for tests with smaller unheated boundary areas. Apart from this, the analysis of fragments shows no correlation between their relative volume distribution and the heated area.

Synergies between Heat- and Stress-Induced Spalling Theory Applied to Rock and Concrete in Tunnel Applications

“…Lateral and longitudinal reinforcement in concrete structures reduces spalling severity and preserves structural integrity. Higher heating rates and larger heated surface areas increase the risk of spalling due to extreme thermal gradients and thermal stresses [10,31,[52][53][54], while some studies have reported conflicting results [44].…”

Development and application of a simulation approach for fire and structure interaction of concrete members subject to spalling

“…A practical approach to determine the critical spalling temperature could rely on a simulation of a small‐scale fire test of a concrete sample. However, development of such an approach would not be trivial because the likelihood of spalling has been shown to be a function of the area exposed to the fire Moreover, Dwaikat and Kodur made several simplifying assumptions that affect the accuracy of the pore pressure predictions.…”