Mathematical Modeling of Technological Processes of Concreting Monolithic Structures From Fine-Grained Mixtures

Abstract

Introduction. The introduction of innovative technologies and materials in the construction industry is constrained by a number of reasons associated with insufficient knowledge of technological processes and the increased cost of highly efficient innovative materials. Therefore, studies in the field of monolithic concrete technology, reflecting the features of concreting structures from self-compacting mixtures and aimed at reducing their cost due to the use of construction waste, are relevant. The purpose of this work is experimental and statistical modeling of rheological characteristics of finegrained self-compacting concrete mixtures and physical and mechanical properties of concretes depending on the influence of two recipe factors — consumption of superplastifying additive and particle size distribution of aggregate including construction wastes.Materials and Methods. For the preparation of fine-grained self-compacting concrete mixtures, portlandcement  CEM 0 52,5N, natural quartz sand and crushed concrete sand of a mixture of three fractions of 0.63–5.0 mm and a chemical additive - a superplasticizer based on polycarboxylate esters Polyplast PK were used. Process characteristics of fine-grained self-compacting mixtures (workability, viscosity, fluidity) were determined by standard methods. The shear limits of the mixtures were set by means of an instrument comprising a cylinder with a nozzle and a glass base with circumferential marking. Modeling of rheological and physical-mechanical properties of fine-grained self-compacting concretes was carried out using a two-factor simplex-summed plan on a hexagon inscribed in a circle, which is one of the most convenient for solving technological problems of construction materials science.Results. Experimental-statistical models of rheological characteristics of fine-grained self-compacting mixtures and strength properties of concrete were obtained, adequately describing experimental data.Discussion and Conclusion. The use of mathematical planning methods of the experiment made it possible to comprehensively assess the influence of the two most significant recipe factors on the technological processes of concreting monolithic reinforced concrete structures from fine-grained self-compacting mixtures using aggregate from construction waste. It was established that optimal content of grains from crushed concrete in natural sand is 30–35 %, and dosage of superplasticizer Polyplast PK is 1.2–1.25 % of binder weight.