This article is devoted to the study of the mechanical properties of fine-grained concrete used for flooring in industrial and civil buildings. Characterized by the well-known advantages (unlimited raw material base, manufacturability, high homogeneity), fine-grained concrete requires an increased consumption of cement to achieve the necessary mechanical characteristics - compressive strength, abrasion, impact resistance. An alternative to the known technological method is proposed an intensive separate technology (IST) for preparing fine-grained concrete mixtures using a high-speed mixer-activator in the presence of hydrophobized basalt fiber and a polycarboxylate superplasticizer Relaxol-Super PC. The use of IST leads to an increase in the strength of fine-grained concrete in compression by 1.9 times, impact resistance by a factor of 2, and a decrease in abrasion by 40... 50% in comparison with the control. The relevance of using the technology of monolithic floors for industrial and civil construction is due to a wide range of varieties of Portland cement, the grain composition of aggregates, as well as the simplicity of the technology for preparing a fine-grained concrete mixture.

Abstract. The materials of the proposed article are devoted to the study of mechanical properties of sand concrete with the addition of hydrophobized basalt fiber and polycarboxylate superplasticizer Relaxol-Super PC. Adding hydrophobic properties to the basalt fiber causes a decrease of water consumption of fine-grained concrete mixture, which leads to improved mechanical properties of concrete. The aim of the work was to increase the mechanical characteristics of sand concrete by introducing hydrophobized basalt fiber into its composition. The objective of the research is to study the effect of hydrophobized basalt fiber on the mechanical characteristics of sand concrete. The polycarboxylate superplasticizer Relaxol-Super PC (Budindustriya, Zaporozhye) was used to increase the mobility of the concrete mixture. Basalt fiber Bauson-basalt 12 mm long and 18 ± 2μm in diameter was used as a fibrous filler. Sand concrete mixture was prepared in a laboratory forced-action mixer. Dosing of Portland cement, quartz sand and basalt fiber was carried out by weight, water and water-reducing additive ‒ by volume, taking into account the density of the additive. The fiber was introduced into a dry cement-sand mixture. After mixing for 120 ... 150 seconds, water with a dosed amount of additive was introduced into the mixture. The hardening of samples concrete took place under normal conditions in a chamber with a temperature of 20 ± 20C and a relative humidity of at least 95%. The compressive strength of concrete was determined by testing the halves of the samples – beams 4×4×16 cm in size at 28 days of age. The abrasion of the investigated concrete was determined by testing cube specimens with an edge of 7.07 cm on an LKI-3 device in accordance with the procedure set forth in DSTU B.V.2.7-212: 2009 “Building materials. Concrete. Methods for determining abrasion “. The impact resistance of concrete was determined from the results of testing cubic specimens with an edge of 7.07 cm on a vertical dynamic laboratory test machine. Especially effective is manifested positive role hydrophobization basalt fiber in combination with the water-reducing additive Relaxol-Super PC. The introduction of hydrophobic fiber (2 kg/m3) and Relaxol – Super PC (1.2% by weight of cement) into the sand concrete mix provides an increase in the strength of sand concrete by 45 ... 48%, impact resistance by 45 ... 50%. The abrasion of concrete is reduced by 36 ... 48% compared to the control.