As a kind of monocrystal reinforcing material, CaCO3 whisker has good characteristics of high strength, high module and high thermal stability. This research aims to optimize the microscopic structure of fiber cement mortar by adding CaCO3 whiskers and improve the macroscopic mechanical properties. The results showed that CaCO3 whiskers increased the flexural and compressive strength of cement mortar at 3d age by 29.5% and 19.8% at maximum respectively, which fell to 7.2% and 13.0% at 28d age; when CaCO3 whiskers content was 10% and polypropylene fibers content was 0.05%, compared with the pure cement mortar, the flexural and compressive strength were increased by 32.4% and 29.4% at 3d age and 7.6% and 4.6% at 28d age respectively; when the fiber length was 9mm, the composite effect of whiskers and fibers was more ideal; through the SEM analysis, the reinforcing mechanisms of CaCO3 whiskers and polypropylene fibers in cement mortar were discussed.

CaCO3 whiskers were incorporated into the cement mortar in this study and the effects of whiskers on the impact resistance of mortar were investigated. The results showed that CaCO3 whiskers could improve the impact resistance of cement mortar before initial cracking. When the whisker content was 10%, the reinforcing effect was optimal. But after initial cracking, the capacity of matrix to resist further impact load was not improved significantly. By observing the failure modes of specimens, it was shown that the crack branches of whisker-reinforced cement mortar were increased, which indicated the brittleness of matrix was decreased and the toughness was improved to some extent. In addition, the reinforcing mechanisms of CaCO3 whiskers in the cement mortar were also discussed

Low tensile strength and high brittleness are the inherent defects of cement-based composites. So improving the toughness effectively is an urgent need for developing high-performance cement materials. The aim of this study is to study the toughening effect by mixing CaCO3whiskers and polypropylene fibers in cement mortar. The results showed that CaCO3whiskers could increase the split tensile strength of cement mortar of 28d age by 26.2% at maximum with the whisker content of 10wt.%; when CaCO3whiskers content was 10wt.% and polypropylene fibers content was 0.20vol.%, the split tensile strength of cement mortar was increased by 21.1% at 28d age; when the fiber length was 19mm, the composite toughening effect of whiskers and fibers was more effective. The toughening mechanisms of CaCO3whiskers and polypropylene fibers in cement mortar were also discussed.

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