Mathematical Modeling the Process of Concreting the Monolithic Structures Made of the Fine-Grained Mixes

Introduction. Implementation of the innovative technologies and materials into construction industry is constrained due to a number of reasons related to the insufficiently well studied production processes of the highly efficient innovative materials and their high cost. Therefore, studying the production process of the monolithic concrete structures, which is bearing the features of concreting the structures made of the self-compacting mixes and is targeting the prime cost reduction by using the construction waste, is relevant. The research aims at experimental and statistical modeling the dependence of the rheological properties of the fine-grained self-compacting concrete mixes and physical and mechanical properties of concretes on two recipe factors — consumption of superplastifying additive and grain-size composition of an aggregate containing the construction waste.

Materials and Methods. To prepare the fine-grained self-compacting concrete mixes, the Portland cement CEM 0 52,5N, natural quartz sand, crushed concrete sand mixed of three fractions 0.63–5.0 mm and a chemical additive — an ester-based polycarboxylate superplasticizer Polyplast PK, were used. The technological properties of the fine-grained self-compacting mixes (workability, viscosity, fluidity) were determined using the standard methods. The shear yield stress for the mixes was determined by means of an instrument consisting of a cylinder with a mouth and a glass base with marked circumferences. Modeling the rheological and physical-mechanical properties of the fine-grained self-compacting concretes was carried out based on the two-factor simplex sum mathematical planning visualised in a hexagon figure inscribed in a circle, which is one of the most appropriate methods of solving the technological problems in the construction materials science.

Results. The experimental-statistical models of the rheological properties of the fine-grained self-compacting mixes and strength properties of concrete were obtained, providing the adequate description of the experiment data.

Discussion and Conclusion. The mathematical planning used in the experiment made it possible to comprehensively assess the influence of two most significant recipe factors on the process of concreting the monolithic reinforced concrete structures made of fine-grained self-compacting mixes using the aggregate from the construction waste. It was determined that the optimal content of the crushed concrete grains in natural sand was 30–35 %, and proportion of the superplasticizer Polyplast PK was 1.2–1.25 % to the weight of binder.

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