VALIDATION OF PORE PRESSURE THEORY ON FIRE SPALLING OF CONCRETE

Abstract

Concrete is the most durable material among all the other construction material. It protects the embedded reinforcement from different kind of environmental degradation. Fire is one of the most severe environmental condition that challenges the property of concrete to protect its embedded materials. Fire spalling of concrete is not a new phenomenon but use of modern high strength concrete had reported more severe cases under fire. Spalling under the action of fire occurs due to participation of high pore pressure and thermal stresses. This thesis is focussed on creating a test setup to record the pressure variation inside the concrete member on exposure to elevated temperature. Two test series were performed during the entire duration of research work, one with comparatively smaller specimen without reinforcement and the other specimen was comparatively larger and had embedded reinforcement. The tests were performed to validate the pore pressure theory on fire spalling of concrete and also to test several parameters like curing condition, heating rate and grade of concrete. The second test series was performed to establish a relation between the spalling behaviour and presence of reinforcement. A new concept of “critical heating rate” was devised from the test results of specimen. As mentioned in various research papers that increasing the heating rate increase the risk of spalling, but the results and observation of tested specimen suggested that this relation is not linear, but complex. All the test results and observation to support this theory of “critical heating rate” is presented in detail in this thesis.