Analysis of the fracture surface morphology of concreternby the method of vertical sections

The examinations carried out have confirmed a relationship existing between the character of fracture surfaces and the composition and structure of (basalt and gravel) concretes. For both concretes investigated, a very good correlation was obtained between the profile line development factor, RL, and the fracture surface development factor, RS. With the increase in the RL parameter, the fracture surface development factor RS also increased. Agreement between the proposed relationship of RS = f(RL) and the proposal given by Coster and Chermant (1983) was obtained. Stereological examinations carried out along with fractographic examinations made it possible to obtain a statistical model for the determination of RL (or RS) based on the volume of air voids in concrete, Vair , the specific surface of air pores, the specific surface of coarse aggregate, SVagg., and the volume of mortar, Vm. An effect of coarse aggregate type on the obtained values of the profile line development factor, RL , as well as on the relationship RS = f(RL) was observed. The increment in the fracture surface development factor RS with increasing RL parameter was larger in basalt concretes than in gravel concretes, which was a consequence of the level of complexity of fractures formed, resulting chiefly from the shape of coarse aggregate grains.