Abstract
Direct tension tests of carbon fiber reinforced cement composites were carried out to examine the influence of fiber addition upon initial cracking strength, ultimate tensile strength, modulus of elasticity, elogation and crack spacing. In this study, low modulus carbon fiber made from oil pitch was used. The range of the volume fraction of carbon fiber was 0.5% to 5%. According to the test results, a significiant improvement in tensile strength and elongation was observed at 3 to 5% fiber addition of low modulus carbon fibers. The tensile strength was 80 to 140kg/cm^2 and the ultimate tensile strain was about 11000×10^<-6> at the fiber volume. However, the efficiency factor of carbon fiber was about 25 to 60%. The experimental values obtained were compared with the theoretical values. We modified the theoretical formulae taking into account the fiber efficiency factor. The calculated values using the modified formulae and the experimental values showed a good agreement.
