MATHEMATICAL MODELING QUALITY INDICATORS OF MIXING MIXTURES

Abstract

In the article are developed mathematical models of dependence of indicators of properties of mixes for masonry on their multicomponent structure. There is optimized parameters of the component composition make it possible to obtain mixtures for masonry and mortars based on them with low thermal conductivity and high strength. The use of conventional traditional sand-cement mixtures for masonry for masonry of aerated concrete blocks does not achieve the required thermal characteristics of the structure. Classic mixtures for masonry do not belong to the class of thermal insulation due to high thermal conductivity. The thermal conductivity of aerated concrete blocks is 0.055–0.340 W/m·K, and the thermal conductivity of mixtures for masonry may be higher by an order of magnitude. However, solutions based on these mixtures for masonry have a relatively high compression ratio (0.4–1.0 MPa). No less important factor is that the thickness of the seam of solutions based on traditional mixtures for masonry is not less than 10 mm. The use of compositions due to the increased dispersion of the components allows to reduce the thickness of the adhesive seam to 2–5 mm, the area of cold bridges and the total thermal conductivity – by 15%. Special requirements for water retention are set for heat-insulating mixtures for masonry of aerated concrete blocks, the porosity of which reaches 70–85%. The high porosity of the material of the elements and a significant rate of absorption of moisture of the base requires the stabilization of this indicator at the level of 97–98% due to the introduction of appropriate water-retaining modifiers. When laying aerated concrete blocks with thermal insulation properties, it is advisable to use such mixtures, the thermal conductivity of which in solution is not higher than the same value of the blocks themselves. As a binder in mixtures for masonry, taking into account the peculiarities of the thin-layer technology, is usually used fast-setting Portland cement. It was decided to develop a mixture for masonry of aerated concrete blocks, which will contain the following components: portlandcement, modified fly ash microspheres and the additive Tylose 30000 YP2. Unmodified fly ash microspheres with a content of from 5 wt. % to 50 wt. %, followed by a study of thermal conductivity, adhesion strength to the substrate and compressive strength. With increasing content of fly ash microspheres in the composition of thermal insulation mixtures for masonry, the thermal conductivity of the latter decreases.