To improve the interfacial bonding properties of polypropylene fiber-cement matrix, a new type of nano-silica modified polypropylene fibers was prepared by direct blend-spinning. As a comparison, Another polypropylene fiber was modified by surface chemical deposition of the silica particles by sol-gel method. The distribution of nano-particles on the fiber surface was observed with scanning electron microscope (SEM). This paper focuses on the effects on crack-resistance properties of fiber reinforced mortar(FRM) and present the mechanism of improving fiber-matrix interfacial properties, especially. The results demonstrate that the modified fiber with well-distributed of nano-silica has excellent mechanical properties, and crack resistance. The interfacial property of fiber-matrix is improved because of silica’s hydration activity. As the use of two kinds of modified fiber, the cementitious materials crack area is significantly decreased. In conclusion, the modified fiber by chemical deposition method which has slightly better overall performance.

Effect of plastic stage curing on long-term properties of high performance concrete (HPC) was studied, thereafter, the mechanism is also analyzed. Results showed that compared to compressive strength, the permeability of surface concrete (especially for silica fume concrete) was more sensitive to plastic stage curing, and deteriorations due to insufficient plastic stage curing cant be eliminated by later longer time of wet curing. Furthermore, the deterioration of pore structure and formation of microcracks were main reasons for insufficient plastic stage curing that affected properties of concrete.