Advanced cement-based composites

Plain, unreinforced cementitious composites, in general, and concrete, in particular, are characterized by low tensile strengths, and low tensile strain capacities; that is, they are brittle. Much importance has been given in the recent years to overcoming the brittleness of cement matrix and also the improvement of its durability. The tensile strain capacity of cement-based materials can be dramatically improved by the addition of fibers. A small amount of coarse fibers have been successfully used in bulk concrete construction to overcome brittleness of concrete. In conventional fiber reinforced concrete fibers do not alter significantly the properties of the matrix. The response of such composites is characterized by strain softening, in a manner similar to unreinforced concrete. Considerable advances in processing technologies, improvement in materials and in our understanding of micromechanics of cement-based composites have led to a new class of advanced composites. Such composites exhibit not only substantially increased tensile strength but strain hardening rather than softening. To develop cost-effective advanced cement composites, an accurate micromechanical understanding of how fibers reinforce quasi-brittle matrices is necessary. This paper summarizes our evolving understanding among processing, micromechanics and properties.