Dynamic mechanical properties of fiber-reinforced lightweight aggregate concrete exposed to high temperature

This study investigates the dynamic mechanical behavior of PVA fiber-reinforced concrete with varying lightweight aggregate (cloud concrete stone, CCS) replacement ratios (0 %, 50 %, and 100 % by weight) pre- and post-exposure to high temperatures. Mechanical response and damage mechanisms of PVA fiber-reinforced specimens (CCSC-PVA) under static and dynamic compressive loading are analyzed across various temperature levels (200, 400, 600 and 800 °C) with a 10 °C/min heating rate. A series of quasi-static and split Hopkinson pressure bar tests are used to investigate the influence of temperature level and strain rate on the dynamic compression behavior of CCSC-PVA. The quasi-static tests primarily include compressive strength, mass loss and damage, while the dynamic tests focus on damage morphology, stress-strain curves, dynamic increase factor, and dynamic impact toughness. The high-speed digital image correlation (DIC) technology is used to quantitatively analyze the full-field strain distribution and cracking characteristics of dynamic impact damaged CCSC-PVA after high temperature. The results revealed that high temperature has a considerable strain-rate hardening impact, with the stress-strain curve initially rising and declining. Dynamic compressive strength, dynamic increase factor (DIF), and dynamic impact toughness all increase with strain rate but decrease with temperature. High temperature damage causes the local strain regions on the specimen surface to gradually expand, and further DIC strain cloud mapping illustrates a three-stage crack evolution process. The findings of this study can provide crucial insights into the dynamic mechanical properties of PVA fiber-reinforced lightweight aggregate concrete after exposure to high temperature.