HOMOGENEITY OF SELF-COMPACTING LIGHTWEIGHT CONCRETE MIXTURES ON HOLLOW MICRO-SPHERES

The actual direction in concrete science is considered to be the production of self-compacting (SCC) and structural light-weight (SLC) concretes. Combining the useful properties of these concretes makes it possible to obtain self-compacting structural lightweight concrete (LWSCC). The main problem of these concretes is the tendency to delaminate due to components of different densities (dense cement paste and lightweight aggregate). The research of domestic and foreign scientists has been devoted to this problem. The main focus of the study of the LWSCC bundle was on changing the structural parameters. The use of hollow microspheres as a lightweight aggregate is of interest. The actual tasks are to establish the features of the change the flow pattern of a concrete mixture of LWSCC with hollow microspheres under external influence and to establish the boundaries of variation of key prescription factors that lead to these changes. The most important issue is the uniformity of LWSCC, the identifica-tion of violations of which is fraught with methodological difficulties. LWSCC on hollow microspheres with a design average density of 1400 kg/m3 are the object of research. The rheological properties of concrete mixtures during oscillation are the subject of research. The viscosity was studied using a rotary viscometer. The experiments and the analysis of the results were performed using mathematical experimental planning. The uniformity of the LWSCC can be estimated from the rheological curve obtained by oscillation exposure. The kinetics of viscosity changes during oscillation is described by varying intensity, which indicates the transformation of the structure of the concrete mixture. This makes it possible to interpret sections of the rheological curve and establish the boundaries of structural transformations. It was found that the intensity of thixotropic liquefaction depends more on the concentration of plasticizer than on the W/C ratio. Increasing the flow rate in the concrete mixture reduces the initial viscosity, but makes the structure destabilized. Achieving high stability and low fluidity of LWSCC are in opposite ranges of variation of the studied factors, which requires the search for a compromise formulation solution based on achieving an optimal structure.