Freeze–thaw durability and service-life prediction of PBO and carbon UHP-FRCM systems

Abstract

Commercial fiber–reinforced cementitious matrix (FRCM) systems suffer from early matrix cracking, permeability, and fabric–matrix debonding. Novel ultra–high–performance (UHP) cementitious matrices were developed and incorporated into polyparaphenylene benzobisoxazole (PBO) and carbon (C) fabrics to produce UHP–FRCM composites. The UHP matrices included either steel fibers, ultra–high–molecular–weight polyethylene (UHMW–PE) fibers, or hybrid combinations of both types. An experimental program was conducted to evaluate the durability and tensile performance of the new composite under freeze–thaw (F–T) exposure compared to commercial systems. Standalone matrices were subjected to 300 F–T cycles, while FRCM coupons were tested in direct tension after exposure to 0, 100, and 300 F–T cycles. Commercial matrices exhibited severe degradation, with mass loss of 16–22% and relative dynamic modulus of elasticity (RDME) decreasing to ∼ 60% after 300 cycles, whereas UHP matrices experienced limited mass loss of 1.6–3.0% while maintaining 85% of their RDME. At the composite level, commercial FRCM coupons exhibited significant tensile degradation, with cracking and ultimate stresses reduced to 23–34% and 52–63% of their original values, respectively. In contrast, UHP–FRCM coupons retained 75–95% and 83–90% of their original values, respectively. Test results revealed severe cracks localization in commercial FRCM systems (crack widths of 1600–2000 µm), while UHP–FRCM systems maintained distributed cracking with reduced widths (80–450 µm). A Weibull–based damage model predicted up to a twofold increase in service life for UHP–FRCM systems compared to the commercial ones. The results support the application of UHP–FRCM systems in infrastructure requiring high durability and extended service life under harsh environmental conditions.