To investigate the high-temperature performance evolution of aerogel modified polypropylene fiber mortar and recycled aggregate concrete (APMRAC) structures under fire exposure with increasing service years. A correlation between laboratory-accelerated carbonation time and actual service duration is established in this study based on the carbonation depth equivalence principle. Silica-enhanced mortar was employed to fabricate integrally cast APMRAC specimens. The effects of varying carbonation durations on the high-temperature performance of aerogel modified polypropylene fiber (APM), recycled aggregate concrete (RAC), and APMRAC were analyzed, with underlying mechanisms elucidated through SEM, EDS, and TG. The results indicate that 17 days of accelerated carbonation in the laboratory correspond to 50 years of natural exposure, yielding a carbonation depth of 17.9 mm. Carbonation markedly reduces the alkalinity of the matrix, thereby weakening the thermal stability of both APM and RAC components. The compressive strengths of APM and RAC under 900 °C exposure drop to 5.2 and 25.6 MPa, respectively. Under identical conditions, the interfacial temperature of APMRAC rises to 367 °C, remaining below the code-specified limit of 380 °C. Microscopic analysis reveals that carbonated APM forms more stable crystalline CaCO 3 at early stages, enhancing its thermal stability up to 700 °C.
Wang et al. (Wed,) studied this question.