Fire events remain a severe hazard despite significant progress in the construction industry. The high-temperature resistance of concrete structures highly depends on the properties of their ingredients. The present study provides an analytical review of the available experimental studies investigating the influence of high temperatures on the residual mechanical characteristics of concrete, namely compressive and tensile strength, as well as the modulus of elasticity. This paper primarily focuses on the influences of supplementary cementing materials, including silica fume (SF), fly ash (FA), and ground granulated blast furnace slag (GGBFS), as well as different aggregate types. The literature findings show that the mechanical characteristics of concrete are degraded dramatically due to heat-caused changes in concrete. In addition, the mechanical properties of concrete are highly influenced by the types of aggregate and the amount of supplementary cementing materials at both high temperatures and room temperature. The inclusion of FA and GGBFS improves the high-temperature resistance of concrete. However, high contents of FA and GGBFS result in adverse effects on the properties of concrete. This review will provide a basis for future studies and enhance the knowledge of the behaviour of reinforced concrete structures subjected to high temperatures.

The polymer matrices currently used for the fabrication of fiber reinforced polymer (FRP) reinforcing bars soften near their glass transition temperature $T_g$ , resulting in a reduction of mechanical strength. This paper discusses the effect of high temperatures on the bond behavior of three types of glass FRP (GFRP) reinforcing bars using standard pullout tests. The bars were 16 mm in nominal diameter with different surface treatments, including sand-coated and ribbed surfaces. The tests were conducted under steady-state and transient temperature protocols for a temperature range of 25°C–360°C at the concrete-to-bar interface. In addition, the effect of embedment length was investigated for a limited number of specimens. The bond failure modes were assessed in detail for different bars. The results for temperatures below 80°C are relevant for elevated service temperatures, and higher temperatures have important implications for performance in fire. At temperatures such as those that would be experienced in a fire (i.e., above 200°C), bond strength dramatically deteriorated, and the retained strength was below 17%. The glass transition temperature of the matrix material was found to be critical for the bond performance of GFRP bars in fire scenarios. The results in this paper are needed to develop rational design guidelines for embedment and anchorage of GFRP bars to obtain the required fire endurance (e.g., 2–3 h) that has been demonstrated through separate full-scale fire tests.

One-way glass fibre reinforced polymer (GFRP) reinforced concrete slabs at elevated temperatures are investigated through numerical modeling. Serviceability and strength requirements of ACI-440.1R are considered for the design of the slabs. Diagrams to determine fire endurance of slabs by employing “strength domain” failure criterion are presented. Comparisons between the existing “temperature domain” method with the more representative “strength domain” method show that the “temperature domain” method is conservative. Additionally, a method to increase the fire endurance of slabs by placing FRP reinforcement in two layers is investigated numerically. The amount of fire endurance gained by placing FRP in two layers increases as the thickness of slab increases.