Fire-induced spalling of ultra-high performance concrete: A systematic critical review

Ultra-high performance concrete (UHPC) is a novel concrete class characterized by a compressive strength of more than 150 MPa. One of the most significant drawbacks of employing UHPC is that is very low permeability owing to its great compactness of dense structure increases the risk of fire-induced spalling. It is challenging for fire safety and structural engineers to predict and analyze this issue due to the lack of widely accepted and reliable models for concrete spalling. Therefore, understanding the fire-spalling characteristics of UHPC exposed to high temperature or fire is vital for ensuring the safety of a UHPC-based structural fire design. To date, the fire-induced spalling behaviour of UHPC has not been thoroughly investigated. To address this informational gap, this article aims to assess various aspects of UHPC by focusing on fire-induced spalling and its influencing factors, spalling mechanism, microstructure characterization, prevention measures, and mitigation strategies. Moreover, this critical review summarizes and evaluates the results of thermal spalling tests and fire-induced spalling modeling undertaken on UHPC in developing a manual regulation protocol. This paper aims to provide insights into improving the existing design guidelines for the fire-spalling-resistant design of UHPC members, this facilitating wide-scale adoption of robust and sustainable UHPC. Given the merits of the study topic, the review strategies and initiatives can then be leveraged to give insight into areas that will be highly beneficial for future experiments and research of UHPC applications by research centers and construction industries globally.