INVESTIGATION OF THE CRACK RESISTANCE OF CEMENT STONE AND ROCKS

It is well known, that the most important structural elements of the cement composite is a cement stone (matrix), filler grain (disperse phase) and their bond. Based on the two-component micro-, meso- and macro-structural model, technical properties of concrete are determined by the strength, deformability, the volume of cement stone and of fillers. They also depend on the genesis of geometric and petrographic characteristics of fillers, their bond with cement stone, the nature and the number of macro- and micro-defects of the structural elements and zones of the bond. In accordance with the approach of fracture mechanics of composites, the real strength of the material is related to the fracture energy, modulus of elasticity and the size of the defect of the structure which gives rise to the beginning of the destruction. At this, it was theoretically foreseen and experimentally proved, that the disperse phase influences three above mentioned factors which strength depends on [1]. It should be noted, that the crack resistance is the most important parameter of strength. It characterizes the ability of a material structure to resist the beginning of the movement and development of cracks at mechanical and other force impacts and is the most important parameter of the limit state of the structure. In this regard, the evaluation of parameters of the mechanics of rocks, used as fillers (dispersed phase) and the cement stone (matrix phase) for concrete, influencing factor of the actual strength of the cement composite, is not only of theoretical interest, but also of great practical importance, since the issues in regards to the problem of choosing fillers are very poorly addressed in the professional literature, especially re the new generation of concretes.