Carbon fiber reinforced cement composites improved by using chemical agents

By using short pitch-based carbon fibers (0.5% by weight of cement, 0.28 vol.% of cement mortar, or 4.5 Kg fibers/m³ cement mortar), together with a water reducing agent and an accelerating admixture, the compressive, tensile and flexural strengths of the carbon fiber reinforced cement mortar were found to increase by about 18-31%, 113-164% and 89-112%, respectively, compared to the corresponding plain cement values. The ductility was also much improved. In addition, the electrical resistivity decreased to 0.1% of the plain cement value. The optimum fiber length was 3.0 - 5.1 mm. By arranging unidirectional continuous carbon fibers (0.25% by weight of cement or 0.13 vol.% of cement mortar) near one side of a cement specimen, together with the use of a water reducing agent and an accelerating admixture, the flexural strength of the specimen increased by 170% compared to the plain cement value.