OZONE TREATMENT OF CARBON-FIBER FOR REINFORCING CEMENT

Ozone treatment of isotropic-pitch-based carbon fiber was found to inc rease the surface oxygen concentration and change surface oxygen from C-O to C=O, thereby causing the contact angle between fiber and water to be decreased to zero. Thus, the bond strength between fiber and cem ent paste was increased and the tensile strength, modulus and ductilit y of carbon fiber reinforced cement paste were increased. Moreover, th e degree of dispersion of fibers in mortar was increased and the effec tiveness of the fibers for reducing the drying shrinkage was improved. As a consequence, the strain sensing ability of carbon fiber reinforc ed mortar was improved in terms of increased gage factor and better re peatability. The ozone treatment did not affect the morphology, tensil e strength or volume electrical resistivity of the fiber itself. (C) 1 998 Elsevier Science Ltd. All rights reserved.