DEVELOPMENT OF THE COMPOSITION OF ARCHITECTURAL SELF-COMPACTING CONCRETE WITH ENHANCED PERFORMANCE PROPERTIES

The construction of monolithic vertical structures from vibrating concrete mixtures is often accompanied by the formation of concrete surface defects in the form of irregularities, pores and cavities, which increases their permeability and worsens their properties. The analysis of works in the field of improving the operational properties of concrete has shown the effectiveness of complex chemical additives, which can significantly increase water and frost resistance. In this paper, the possibility of obtaining architectural self-compacting concrete with in-creased performance properties and reduced surface porosity is considered, achieved through the combined use of Portland cement binder, ground blast furnace granular slag, polycarboxylate superplasticizer, antifoaming admixture based on glycolic ether and an air-entraining additive based on an amphoteric surfactant. Based on the method of mathematical experimental planning, the optimal composition of self-compacting concrete was developed and multifactorial quadratic dependences of workability, viscosity, average density of concrete, entrained air content, compressive strength of concrete, surface porosity on the content of air-entraining additives and antifoaming admixture were obtained. It was found that the joint introduction of a polycarboxylate superplasticizer, an air-entraining additive based on an amphoteric surfactant and a antifoaming admixture based on glycolic ether leads to a decrease in surface porosity by 8.2-10.7 times and a pore size, the distances between them by 1.2 times, the total pore area by 8.3-11.8 times, ensuring a predominant pore content with a diameter of 12-22 microns in an amount of 65%. It was also shown that the developed concrete mixtures have high water resistance W20, frost resistance F_1 500, determined by the third accelerated method, with peeling of the surface from 5 to 7% and a depth of 0.1 mm, loss of strength from 4.6 to 5.6% compared with the control composition.