The development of the technology of new binders and concrete involves the following stages: the selection and preparation of materials, designing the composition in accordance with requirements, preparation of the mixture and the formation of products, initial curing and setting, further hardening. All these stages are united in a single complex, in which each stage has its own special significance and simultaneously affects the efficiency of the entire technological complex.
Based on the literature analysis, we can state that to achieve greater efficiency of using the new generation of binding agents, it is necessary to use multicomponent complexes. This will allow to produce high-quality concrete of different purposes with the improved properties and different structures: coarse- or fine-grained, porous, fibrous. The basis of the new technology is the active management of technological redistribution through the use of chemical modifiers and active mineral components, optimization of compositions, mechanic-chemical activation and intensification of technological processes. The multicomponent composition of gypsum mixtures demands the study of their structurization via methods of mathematical modelling.
The article deals with the results of optimization of multicomponent composite binder based on gypsum-lime mixture. A mathematical model for stone strength was obtained in the form of a regression equation and the coefficients of this equation were analysed.
The analysis of mathematical dependencies and their graphical interpretation enabled us to determine the optimal amounts of amorphous silica and metakaolin in a binder, providing the highest stone strength at the age of 28 days.
The XRD showed that the basic crystalline phases of a composite stone at the age of 28 days are gypsum bihydrate, portlandite, calcite, ettringite and γ-Al2O3·2SiO2·2H2O (kaolinite).
The following construction characteristics of the stone were obtained: compressive strength – 9.50 MPa, average density – 1048 kg/m3, water resistance coefficient – 0.50, setting beginning – 19 min, setting end – 27 minutes, maximum temperature during hydration – 60 °C.
The optimal composition of the composite binder has been proposed: 54% G-5, 36% CaO, 5% amorphous silica, 5% metakaolin and 0.5% Na2B4O7·5H2O.
Composite stone is characterized by improved compressive strength (+35%) and water resistance (+20%) compared to a stone, the composition of which does not include amorphous silica and Na2B4O7·5H2O.
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