STRENGTH AND DEFORMATION PROPERTIES OF STRUCTURAL-THERMAL INSULATION LIGHTWEIGHT CONCRETES

Abstract

The purpose of this study is the experimental determination and generalization of the strength and deformability characteristics of structural– thermal insulating lightweight concretes based on porous aggregates using multicomponent binders, in order to obtain design parameters required for the structural design of concrete and reinforced concrete elements, as well as to substantiate the feasibility of their application in construction and in the restoration of damaged facilities. Methodology. The research was carried out using a combined computational- experimental approach to the design of lightweight concrete mixtures, which included the selection of the type of porous aggregates, determination of the content of multicomponent binders, and optimization of particle size distribution and water content of the concrete mix. Tests of cubic and prismatic specimens were performed to determine strength, modulus of elasticity, and deformability characteristics in accordance with current standards. Experimental data were processed using methods of mathematical statistics and regression analysis with a confidence level of 95%. Results. The influence of the type of fine aggregate, the type of porous coarse aggregate, and the composition of multicomponent binders on the strength and deformability properties of expanded clay concrete, expanded clay perlite concrete, and keramzite concrete within the strength range of 5–30 MPa was established. Regression relationships were obtained for cube and prism strength, modulus of elasticity, limits of microcrack initiation, as well as shrinkage and creep deformations. It was shown that the use of lime and fly ash in binder compositions reduces Portland cement consumption without deterioration of deformability and crack resistance characteristics. It was also found that the modulus of elasticity of lightweight concretes with quartz sand exceeds that of concretes with porous sands by an average of 10–20%. Scientific novelty. For lightweight concretes based on local porous aggregates, generalized regression models were developed that describe the dependence of strength and deformability characteristics, as well as microcrack initiation limits, on mixture composition factors. Quantitative relationships between tensile strength and the critical stress intensity factor were established, enabling the assessment of crack resistance of lightweight concretes in structural calculations. Practical relevance. The obtained results can be used in the design of lightweight concrete mixtures and in determining the design properties of concrete and reinforced concrete structures for residential and public buildings. The proposed compositions improve the technical and economic efficiency of construction by reducing cement consumption and ensuring the rational use of local materials and industrial by-products.