Abstract :
Microstructural changes that occur over time around fibers in the cement matrix, leading to an enhanced bond and stiffening of the interfacial transition zone, may result in a reduction in the mechanical properties of the composite. Micromechanical modeling of processes of this kind suggest that such aging trends may occur in microfiber reinforcement but not in macrofiber reinforcement. Degradation in mechanical properties of the composite will show up only when a "pessimum" combination of parameters exist, particularly brittle microfibers in a very dense matrix. Therefore, in the development of new cementitious composites, interfacial effects of this kind should be considered, because aging due to such mechanisms can be demonstrated to occur in practice. Thus, it is not sufficient to assess the durability of cementitious composites by considering only the chemical stability of the fiber in the alkaline cementitious matrix.
