Analysis of the fracture surface morphology of concrete by 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, SVₐᵢᵣ 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.