To assess the capacity of reinforced concrete (RC) structural members exposed to fire conditions, data on high-temperature mechanical properties of concrete is needed. While test standards specify detailed testing procedures for evaluating the mechanical properties of concrete at room temperature, there is a lack of guidance on test methods for measuring the mechanical properties of concrete at high temperatures. Currently, procedures to assess the mechanical properties of concrete at elevated temperatures between 20℃ and 750℃ are only provided by RILEM recommendations. However, these RILEM-specified high-temperature test methods were developed through property tests conducted on conventional concretes and thus, they might not be applicable for advanced concretes with higher strengths, such as high strength concrete (HSC) and ultra-high-performance concrete (UHPC). These high strength concretes have a dense microstructure which makes them vulnerable to explosive fire-induced spalling even at very low heating rates of 2℃/min recommended by RILEM. This study undertakes experiments on fiber-reinforced HSC and UHPC by subjecting them to different heating regimes including pre-oven-drying and adopting lower heating rates. Hydrothermal numerical modeling is also utilized to investigate the variation of pore pressure in different concrete types. The results of this study highlight the need for standardized methods to characterize high temperature response of spalling-susceptible concretes.