Effects of freeze-thaw damage on fracture properties and microstructure of hybrid fibers reinforced cementitious composites containing calcium carbonate whisker

The effects of freeze-thaw (F-T) damage on fracture properties and microstructure of steel-PVA hybrid fibers reinforced cementitious composites containing calcium carbonate whisker (CW-SPFRCC) were investigated in this paper. Three-point bending tests were carried out to study the fracture properties of CW-SPFRCC after different F-T cycles based on Double K fracture criterion. Compared with SPFRCC, the relative fracture parameters in CW-SPFRCC dropped less within 0 to 50F-T cycles, while rapid deterioration was observed in 50 to 100F-T cycles, indicating that the presence of CW could effectively delay F-T damage in SPFRCC. Moreover, fracture parameters were estimated to quickly predict the fracture behavior of CW-SPFRCC subject to F-T cycles. The microstructures of CW-SPFRCC was analyzed using scanning electron microscope (SEM), vacuum epoxy impregnation (VEI), mercury intrusion porosimetry (MIP) and optical microscope observation (OM), respectively. SEM results showed that PVA fiber and CW maintained intact morphologies subject to F-T cycles, but the surface of steel fibers was severely corroded by F-T actions. The results of VEI and MIP demonstrated that better frost resistance of SPFRCC was related to the improved pore structure because of the presence of CW. Furthermore, F-T damage was more likely to occur on the interfacial transition zone (ITZ) of steel fibers or aggregates. Finally, a parabolic model of F-T damage was developed to predict the service life on-site of CW-SPFRCC. (c) 2021 Elsevier Ltd. All rights reserved.