Numerical Study of Thermal and Strength Properties of Multilayer Concrete Blocks with Variable Density

This article presents the results of a numerical study of the construction and technical characteristics of multilayer concrete wall blocks. The study focuses on the development of wall building elements that integrate structural strength, thermal insulation, and protective–decorative functions by creating a stable multilayer concrete structure consisting of concretes with different compositions, variatropic architecture, and discretely graded density. The development of durable multilayer concrete technologies is hindered by several major challenges, including the absence of a scientifically validated methodology for designing multilayer concrete structures, which complicates the determination of the optimal geometric parameters of the elements, as well as the difficulty of forming individual layers with the required thickness. The objective of the study was to analyze the thermal and strength properties of numerical models of a multilayer wall block consisting of two to five concrete layers of variable densities. ELCUT-7 (thermal properties) and SolidWorks Simulation 2022 SP4.0 (strength properties) software packages were used to create and study the numerical models. The initial data for creating the numerical models were the results of experimental studies of concrete of various compositions and structures with a density of 500–2200 kg/m3. Several variants of block models with two to five layers were studied. The variants differed in the thickness and composition of the concrete layers, as well as the position of the layers in the block structure. A comparative analysis of the calculated values of thermal transfer resistance for blocks with a different number of layers and variable concrete density was performed. The appropriateness of concrete blocks containing three or more layers was proven. Increasing the number of layers in blocks creates a variatropic structure for multilayer concrete, eliminating sharp variations in the density of adjacent layers while maintaining the thermal efficiency of the wall enclosure. Increasing the number of layers in concrete blocks expands the possibilities for combining layer compositions and thicknesses. In multilayer concrete blocks, it is possible to reduce the thickness of the highly porous layer by thickening the less porous adjacent layers without compromising thermal performance. Blocks with four and five layers of concrete of variable densities are comparable in strength and structural efficiency to blocks with fewer layers. For the same thermal resistance, the thickness of the five-layer block is 38–48% less than that of a conventional single-layer concrete element. Furthermore, the structural efficiency coefficient of the four- and five-layer blocks is 1.08–1.12 times higher than that of a three-layer block with equivalent load-bearing capacity. The results of these numerical studies serve as the basis for designing manufacturing processes for wall blocks with variatropic structures.