Objectives Development of optimal recipes of concrete mixtures using local natural raw materials in the form of gravel-sand mixtures from deposits of the Chechen Republic.Method The research methods adopted in the work are based on the theoretical principles and laws of designing and optimizing polydisperse multicomponent systems, the phase and structure formation of clinker minerals, the logic of mathematical calculations, the technological features of the structure formation of composite masses, the theoretical principles of controlling the rheological processes of mixes. All experimental data presented in the work were obtained according to the methods of current regulatory documents (GOST, recommendations, etc.).Result The paper presents the results of a study of the composition and properties of sand and gravel mixtures of deposits of the Chechen Republic and concretes based on them. In particular, the granulometric and chemical compositions and the physicomechanical properties of sand and gravel mixtures have been studied. An analysis of the scientific literature and experience in the use of sand and gravel in construction. The leading scientific schools of the country and abroad in the field of concrete science are presented. The rheological indices of concrete mixes were studied and the dynamics of the curing of concrete of different classes were obtained on the basis of unfortified sand and gravel mixtures in the presence of a chemical additive, the superplasticizer Polyplast SP-1.Conclusion It is proposed to use sand-gravel in its natural form in concrete for non-critical structures in its natural form without additional costs for enriching its composition. The feasibility of obtaining low-grade concrete with the use of sand and gravel mixtures without its enrichment and fractionation is established.

The anthropogenic load on the natural resource potential of the planet is growing rapidly. Therefore, special attention is paid to the development of less costly and low energy-consuming technologies for obtaining new building materials. Those materials do not require high-temperature and expensive technological processing, and this will allow the use of local secondary and substandard raw materials. The development of formulations for linker-free binders of alkaline activation based on fine powders of aluminosilicate nature will make it possible to obtain new effective building composites. The work reveals issues related to the theoretical foundations of the structure formation and strength of cement stone based on an alkaline activator. The research results, in our opinion, have a practical importance for the construction industry, since the proposed formulations of clinker-free cements can replace expensive and energy-intensive Portland cement, allowing creating strong and durable concrete and reinforced concrete structures. The results presented in this article were obtained in the framework of research on the implementation of scientific project No. 05. 607.21.0320. “Development of technology for new building composites based on linker-free binders of alkaline activation using substandard natural and secondary raw materials” supported by the Federal Target Program “Research and Development in Priority Areas of Development of the Scientific and Technological Complex of Russia for 2014-2020” The unique identifier for the agreement is RFMTFI60719X0320.

The paper deals with issues related to development of multicomponent binders (MCB) and high-quality concretes based on them. The production of such binders is based on the use of finely divided mineral additives of natural and technogenic origin. Particular attention is paid to the aggregate, the strength of coarse aggregate should be at least 20% higher than the strength of concrete, and the maximum particle size should not exceed 8-20 mm. At present, considerable experience was accumulated for production of multicomponent binders, and the results of studies conducted in this direction showed that the raw material potential of the Republic allowed obtaining high-quality class B30-40 concrete, and if we expanded the geography of the use of natural resources by regions of the North Caucasus, we could produce concretes with higher strength.

The paper studies the influence of composition and technological factors on rheological indicators of concrete mixes modified by various chemical additives. The rheological and water-reducing efficiency of super-and hyper-plasticizers in cement suspensions depending on their addition procedure was studied. The efficiency of a two-stage concrete mixing with the introduction of a plasticizer at the second stage with remaining 1/3 content of mixing water, which improves the efficiency of the additive by almost 20% in comparison with the traditional technology, was experimentally proved.