In the article there was considered a possibility of off-grade materials utilization for making fine concrete with a multicomponent complex additive applied. Use of fine sands as raw material for fine concretes is actual for many regions in Russia because of deficiency of sands of necessary fineness modulus. There was considered the issue of utilization of fine sand and stale cement for reducing cost (loss), widening materials’ assortment for low-rise building, and energy- and resource-saving. To achieve the assigned purpose a multicomponent complex additive was applied. The research was carried out in full correspondence with the adopted design of the fractional factorial experiment. The acquired results were subject to a preliminary analysis and processing, and consequently dependences of strength properties upon varying factors were obtained. The obtained dependences made it possible to select optimal ingredients’ proportion of the complex modifying additive in order to increase strength properties of fine concrete based on off-grade materials. It was established that the use of optimal consumption of the complex additive components allows increase strength properties by 25-30% in comparison with the reference composition.

Keywords: fine concrete, fine sand, stale cement, complex additive, fractional factorial experiment, strength

There has been studied the influence of gypsum-cement-pozzolana binding agent composition on its key strength properties. The study was aimed on the definition of such consumption of gypsum-cement-pozzolana binding agent components, which could allow maximum ultimate compression strength with minimum consumption of Portland cement provided. As the components of gypsum-cement-pozzolana binding agent, there have been used plaster, Portland cement, and the most wide-spread in the region pozzolana additive. An experiment design was developed to fulfil the work. The research was held in correspondence with the design, and the acquired results made it possible to estimate and analyze descriptive statistics, and expose the influence of components on strength properties of gypsum-cement-pozzolana binding agent. In the course of the analysis it was specified that pozzolana additive consumption factor, and interaction of consumptions of plaster and Portland cement exert a positive influence on strength properties of gypsum-cement-pozzolana binding agent. There have been acquired mathematical models of the influence of gypsum-cement-pozzolana binding agent components consumption on ultimate compression and bending strength of gypsum-cement-pozzolana binding agent. The said model allow forecasting gypsum-cement-pozzolana binding agent composition to have a desired ultimate compression strength. An optimization was carried out and there was acquired a composition of gypsum-cement-pozzolana binding agent with maximum ultimate compression strength with minimum consumption of Portland cement provided.

Keywords: gypsum-cement-pozzolana binding agent, optimization of composition, ultimate strength, experiment design, descriptive statistics, superposed diagram, correlogram, ternar chart

A research of fibrous gypsum modified with a complex additive has been undertaken. The objective of the research was to identify influence and dosage of complex additive components upon fibrous gypsum water absorption. To fulfil the work there were used gypsum plaster and a modifying complex additive which consisted of the following components: polypropylene fibre, fine-dispersed inert aggregate, super-plasticizer and redispersing polymerous powder. To undertake the research designing an experiment took place and the central composition plan was implemented. The obtained research result made it possible to calculate and analyze descriptive statistics. Positive influence of the researched factors on water absorption decrease was revealed. It was established, that consumption of fine-dispersed inert aggregate and, super-plasticizer promote decrease of fibrous gypsum water absorption. Analysis and processing of the research data allowed obtain a mathematical model of influence of complex additive components consumption on fibrous gypsum water absorption and reveal a fibrous gypsum composition with the minimal water absorption. The obtained model allowed forecast a composition with the minimal water absorption.

Keywords: fibrous gypsum, water absorption, complex additive, modified, central composition plan, model, additive efficiency.

Modern trends of the concretes studies have been considered. Properties of the materials and additives used have been cited. There has been undertaken designing an experiment on a complex modifying additive application for a fine fibre-reinforced fine-sand cocrete. The results of the studies undertaken have been analyzed with regard to their statistical significance. On the bases of the reseach results there have been acquired regression equations for objective functions responses, namely ultimate strength on both compression and bending, and average density of fine fibre-reinforced concrete. There have been produced contour plots and those of response function surface - ultimate strength under compression for all combinations of the both factors. There have been determined the composition of the modifying additive, which ensures maximal strength properties for fine fibre-reinforced fine-sand concrete.

Keywords: fine concrete, complex additive, designing an experiment, strength, regression equation, plots of response function surface

The article discusses the prospects for the development of the combined technology of expanded fiber gypsum material. Based on the literature data, the optimal boundaries of the components were determined. To obtain the optimal composition, complete two-factor experiments were performed with changes in each factor at three levels. The results of the tests were obtained, on the basis of which regression equations were constructed, allowing to predict the characteristics of the resulting material, for the selection of the optimal composition.

Keywords: expanded gypsum, fibrogyps, fiber, strength, density

Some kinds of construction materials, notably rock is subjected to burning while producing construction materials. One of the materials is clay. The aim of the research is to ascertain if burning of clay rocks influences changes of specific and effective specific activity of natural radionuclides. The selected samples of clay were subjected to phasic burning. After each phase specific activities of natural radionuclides were establiched, and their effective specific activity was calculated. The undertaken research acquired data served a matter for further analysis and searching dependencies. The reserch results analysis having been made, it managed to establish, that there exists a correlation of different power degree berween burning temperature and specific activity. On the example of one of the clays researched there was drawn a polynomial regression pattern. When being aware of radiation characteristics and burning temperature of clay stock, the pattern will allow calculate radiation characteristics of the finished product. This will allow control (decrease) the radioactivity level of the finished product, i.e. ceramic materials and items.

Keywords: natural radioactivity, burning, clay rocks, radionuclide, correlation analysis, polynomial regression