CARBON-COATED-GLASS-FIBER-REINFORCED CEMENT COMPOSITES .1. FIBER PUSHOUT AND INTERFACIAL PROPERTIES

Interfacial mechanical properties of carbon-coated-S-glass-fiber-reinf orced cement were characterized by a fiber pushout technique. The push out experiments were conducted on model composites, where the S-gIass monofilaments with and without carbon coating were unidirectionally em bedded in ordinary portland cement. Interfacial properties, including bonding strength, frictional stress, residual stress, and fracture ene rgy, were extracted from the previously developed progressive debondin g model, The composite with a carbon interface exhibited a weaker inte rfacial bonding strength and frictional stress than did the composite without a carbon interface, The interfacial fracture energy of the com posite with a carbon interface was 7.9 J/m(2), as compared to 47.6 J/m (2) for the composite without a carbon interface. The composite with t he carbon interface exhibited a smaller residual clamping stress (Is M Pa), in comparison to that for the composite without a carbon interfac e (69 MPa). Scanning electron microscopy observations indicated that t he filament without a carbon coating was significantly attacked by the alkaline environment and was strongly bonded onto the matrix, whereas the filament with a carbon coating remained intact under the same cur ing conditions. These studies suggest that carbon coating provides the glass fiber with significantly improved corrosion resistance to alkal i in the cement environment.