STRUCTURAL DIVERSITY AND PROPERTIES OF CONCRETES AT LONG-TIME HARDENING

Abstract

The potential possibility of increasing the level of mechanical properties of composites on mineral binders remains during the long period. The initial structures hereditarily determine the change of the properties of the finished material in time. It can be assumed that an increase in the structural diversity of concretes should lead to such the organization of a structure that will guarantee the preservation or increase of the level of quality indicators at long terms of hardening (up to 720 days). The conducted researches showed that concrete of long hardening with the structure organized at selective adhesion of a cement matrix to the surface of dense or porous aggregates differed are more resistant to external influences. That is, those concretes, organization of structure which happened under the conditions of diversity of interphase interactions at the level of a macrostructure. This was ensured by the use of aggregates with various condition of a surface. The directed change of a ratios of adhesive-cohesive bonding forces at the surfaces of partition between a cement part and the surface of an aggregates provided structures, which caused increase the compressive strength of concrete by 18% and  the module of elasticity by 24% at reducing the water by 29-36% and the open capillary pore volume by 44%. The structure of concrete organized at selective adhesion was the densest in comparison with of concrete of other structures. At the same time, the damage of material by technological cracks and inner surfaces of partition has grown more for concrete, the structure of which was provided by a variety of conditions of interactions between the cement matrix and aggregates. Favourable change of the parameters of these elements, along with the processes of hydration of relict binder grains, causes an improvement in time of indicators of the mechanical and deformative properties of concrete. Thus, structural diversity determines the potential changes of the concrete structure at long-hardening that must be taken into account at designing compositions and technology of the concrete, intended for difficult operating conditions.