Strength and crack resistance of cement composites under multilevel reinforcement

The working hypothesis is confirmed that the required fracture toughness of structural concrete can be provided by multi-level reinforcement: at the level of the crystalline joint of cement stone – carbon nanotubes, and at the level of fine-grained concrete – various macro-sized fiber fibers (steel, polymer). Reinforcement of a crystalline splice with carbon nanotubes leads to an increase in tensile strength by 20 %, an increase in Young’s modulus. With dispersed reinforcement of concrete modified with nanoparticles at the level of fine-grained concrete, the tensile strength increases by 109 %, the critical stress intensity coefficient (crack resistance index) increases by 280 % at normal separation, and by 48 % at transverse shear.