Concrete structures are often subjected to a variety of loading conditions. Under ultimate load design , concrete structures can resist these loads without evident deformation. However , under service , tension cracks will develop and depending on their location , they may impair load carrying capacity.

It is generally believed that microcrack development is preceeded by formation of a relatively long microcracked region. A large number of studies have indicated that due to formation of this process zone (microcracked zone) , Linear Elastic Fracture Mechanics (LEFM) principles are not applicable to concrete. However , a number of nonlinear models can be developed if the length of this zone can be determined. Determination of process zone length is a difficult experimental problem , mainly due to difficulties involved in accurate detection of microcracks during loading in a typical experiment. Furthermore , as some recent studies indicate , surface microcracks progress further than their internal counterparts. Determination of internal deformations and microcracks are even more challenging than the mere surface flaw detection mentioned earlier. Survey of technical literature indicate , inexistence of an accurate internal deformation measuring technique for concrete.

In the present study , a new technique is developed for measurement of internal deformation in cementitious composites. main emphasis is given to the development of the technique , and measurement of deformations in the process zone. Results from experiments on compact tension , and three point bend specimen are presented.