AGE EFFECT ON THE CHARACTERISTICS OF FIBRE CEMENT INTERFACIAL PROPERTIES/

The experimental findings of an investigation on the age development o f interfacial properties of polyethylene fibers in a cementitious matr ix are reported. It was found that the interfacial bond strength matur es much faster, in less than 7 days, in comparison with bulk property development, which typically takes 14-28 days. A parallel ESEM study o f the microstructure development in the interfacial transition zone su pported the fact that the rapid early age saturation of the interfacia l adhesive bond strength is associated with the growth of a CH rim aro und the fibre periphery. The formation of the CH layer appears to be c ompleted much earlier than the hydration process of the bulk material. The slip-dependent friction after initial debonding was found to deve lop with age up to 28 days, gradually converting from a slip-weakening to a slip-hardening behaviour. These findings should be useful in int erpreting early age fibre-reinforced cementitious composite properties .