Influence of Matrix Quality and Environmental Conditions on Volume Change and Microcracking Behavior of Concrete

Concrete is a highly complex and heterogeneous engineering material. In its complex composite structure, it is not easy to understand its behavior either during hydration process or loading the material. Particularly the volume change during hydration results in initial defects and at the end these defects may influence its mechanical behavior under load. Individual properties of different phases like aggregate, matrix and the interfacial transition zone (ITZ) between the two, plays an important role on the microcracking behavior of the concrete. In this study, various techniques were used in determining the effect of hydration shrinkage crack on the microcracking behavior of the concrete including w/c ratio, silica fume and environmental conditions. Direct measurement by means of optical processing through Scanning Electron Microscope (SEM) is a way. On the other hand, the indirect measurements dealt with an overall study of the material by means of the tensile and the compressive strength measurements, the length and the volume change measurements and the prediction of the critical crack load from stress-strain diagrams. Conclusions were drawn from the direct and the indirect methods. The ultimate purposes of all the performed tests were used to measure the initial defects either in the ITZ or the matrix and their effect on the whole microcracking behavior of concrete. Keywords: SEM, ITZ, Cracks density, Compressive strength, Tensile strength, Volume change, Shrinkage.