EXTRA FINE-GRAINED CONCRETE FROM WASTE OF MINING CONCENTRATION PLANT FOR CONSTRUCTION PRODUCTS

Abstract

The theoretical substantiation of the production of especially fine-grained concrete (EFC) from the waste of the Poltava Mining Concentration Plant as a fine-grained aggregate has been performed. Its structure is substantiated taking into account the contacts between the angular aggregate grains, the possibility of increasing strength by introducing mineral fillers and microfillers with particles 5 times smaller than the aggregate grains and cement particles, respectively, is proved. The determination of the composition of EFC from the waste of the Poltava MCP was substantiated by determining and ensuring the optimal value of the coefficient of displacement of aggregate grains by cement paste m opt = 1.89 with the inclusion of dusty fractions of the aggregate. The optimal composition of EFC Aggregate : Cement : Water = (3–3.15):1:0.5 with mandatory use of superplasticizer additive to ensure W/C = 0.5 was determined and experimentally confirmed. The dependences of compressive and tensile strength of EFC on: type and content of superplasticizer additives were experimentally investigated; ratio of aggregate content to cement content; microsilica content; pressing pressure. It was established that the maximum strength of EFC is achieved in the case of the use of superplasticizers: polycarboxylate 1.5 % or sulfonaphthalinformaldehyde 1 % by weight of cement. It was also established that with the same A:C = 3:1 and W/C = 0.5, the strength of EFC on the waste of Poltava MCP exceeds the strength of fine-grained concrete on natural, especially fine-grained sand: in compression - by 2 times, in tension - by 1.9 times and reaches 35 MPa at the age of 28 days. The addition of microsilica in the amount of up to 15 % of the mass of cement allows to further increase the compressive strength by 44 %, and the tensile strength by 20 %. It is proposed to form EFC products by layer-by-layer pressing with a layer thickness of 5 mm. It was experimentally established that the maximum strength is achieved at a pressing pressure of 12 MPa.