Mechanical performance of TRUHPC composites under freeze-thaw cycles

This study aims to analyze the durability of textile-reinforced ultra-high-performance concrete (TRUHPC) composites under freeze-thaw cycles (FTCs). To clarify the frost resistance mechanism, mechanical property tests of the UHPC matrix, pullout tests of carbon fiber-reinforced polymer (CFRP) grid-UHPC matrix interfaces, and axial tensile tests of the TRUHPC plates were conducted. In addition, changes in microstructure were also evaluated quantitatively through thermogravimetric and mercury intrusion porosimetry tests, and qualitatively through scanning electron microscopy test. The results showed that after subjected to 100 FTCs, the rehydration products primarily accumulated at the interfacial transition zone (ITZ) between the steel fibers-matrix, rather than at the CFRP grid-matrix interface, resulting in a denser microstructure. Consequently, the flexural strength of the matrix was significantly increased by approximately 52.9 %, which enhanced the tensile properties of the TRUHPC composite. However, as the number of FTCs increased, the flexural strength of matrix, the pullout strength of CFRP grid-UHPC interface, and tensile strength of TRUHPC composite reduced obviously due to greater frost damage and higher stress concentration at the steel fibers-matrix and CFRP grid-matrix interfaces. Even so, the compressive strength of the hybrid fiber UHPC matrix almost constant even after 700 FTCs.