Microcracking in Concrete under Compression: its Gradient Mechanisms and Reflection in Macro

problem alyzed in terms of lateral strong gradient mechanisms dient strains and cause micro ratio between the concrete's elastic moduli. High strength matrix and aggregate close, behaves as a from randomly oriented crystals. is shown ulation of laterally tensioned Poisson's ratio o{ a single gradient strains between is s acting as "pistons". models ~-~H~L~i~~ microcracks, their stochasticity and why, _·.__, .-1.LJlJ'L.L<;l_L macrocracks, they are stable, accordance experiments. The Poisson mechanisms are ing any brittle material such as concrete, rock, ceramics - need initial microcracking to and realize degeneration. The models of gradient mechanisms are based on measurable parameters. suffice to exhaust 445 capacity of increasing compression without recourse to shear stresses. On the macrolevel nonlinear behavior of a concrete under com- pression is described by the central function: O' = eEG, where the Gaussian - G expresses the stochastic character of the heterogen's sur- vival and comprises two parameters: the limiting strain of elasticity (atrophy threshold) ea, and the scattering factor - d. The gradient models were linked with the above macroparameters and it was shown that the strength of a brittle solid under compression is a function of its resistance to microrupture and of the gradient factor. Definitions heterogeneous solid will be referred to as a heterogen. is a heterogen which consists of a continuous matrix (aggregate) that 'float' in the matrix without contact. Concrete is an artificial matrogen with the granulome- try given and ~L44'~L~~ very close control. Another kind of heterogen and a case of is a crystalon, which is built of randomly oriented Heterogen heterogeneous solid. SSc - the curve stress-strain relationship. e - longitudinal e2 - lateral strain induced by load; E, E* - transverse · and their gradients, resp.