The results of a study of crack resistance obtained during the development of fine-aggregate concrete for architectural elements are presented. The crack resistance study of 27 different proportions of compositions was carried out in accordance with DSTU B V.2.7-227: 2009 using experimental statistical modeling methods. Due to the fact that the method of initiating the initial crack in the samples changes the distribution of the technological fields of strain, the tests were carried out on two series of samples. The data obtained show that the crack sealing method changes the deformative-stressed state of the composite. So, crack resistance for one concrete composition can vary, from the conditions of the experiments, from 3 to 40 %. Based on the obtained values of the characteristics of the material, in particular, for the coefficient of technological impact on crack resistance, which describe the fields of these criteria in the coordinates of the factors of concrete composition, models were built. The results of the model are presented on 5 factor diagrams of the form “cubes squared”. An analysis of the constructed diagrams showed that the initial conditions for the organization of the structure of concrete determine its ability to resist the development of various types of cracks. During the introduction of finely dispersed fibers at an optimal dosage of fine sand grains (50 % in a sand mixture) and a slight replacement of cement with zeolite (from 2 to 3.4 %), it is possible to reduce the technological damage to the decorative composite, thereby improving crack resistance.
The results of the study of prescription factors influence on shrinkage deformations of multi-component material of architectural products are presented. Studies of the influence of composition factors on the value of composite samples shrinkage were carried out according to a symmetrical 5-factor design with 27 experiments. Depending on the nature of action on fine-grained concrete, variable raw materials are combined into two groups of factorscement-sand system modifications, parameters of dispersion reinforcement. Based on the results of the conducted trials of the full-scale experiment, kinetic curves and correlation dependencies were built. The results of researchers on introduction of active fine pozzolana instead of part of binder are confirmedzeolite promotes growth of free shrinkage of concrete, especially during early hardening period up to 7 days with low level of its plasticization. At the same time the degree of carbonation of concrete compositions with a high dosage of pozzolana and superplasticizer is absent. The shrinkage measurement results show that hybrid fibers with high dispersion are stochastically distributed in the cement system, they form a three-dimensional framework, can affect the distribution of volumetric changes. As a resultit will allow to preserve decorative and operational characteristics of architectural products in time. The amount of shrinkage deformations depends on the capillary pressure when the sample is dry, which is defined by the nature of porosity. In turn, the nature of porosity is responsible for the water absorption of the material. Therefore, in operation, optimization of decorative concrete compositions can be carried out for volume (or weight) water absorption and capillary water absorption. In order to estimate the durability of architectural elements, besides characteristics of strength and water absorption, it is necessary to take into account the carbonization stability of decorative concrete and the value of shrinkage deformations. It is planned, with the help of methods of computer materials science, to assess the influence of prescription factors on the dynamic elastic modulus of decorative concrete.
The article presents the results of studies of the influence of alkali-resistant glass fibers of different lengths on the functional properties of decorative concrete. It is based on the data of an experiment carried out according to the optimal unsaturated plan, which includes 27 different compositions of the material. The combinations of the decorative compositions had equal mobility of the mixture, with the minimum and maximum water-cement ratio of 0.36 and 0.55, respectively. Based on the results of the experiment, the primary experimental-statistical models describing the effect of composition factors on the properties of the material made it possible to reveal that an increase in the level of plasticization of the compositions allows to increase the utilization factor of the strength of glass fibers. The efficiency of hybrid reinforcement of decorative composites with glass monofilaments has been confirmed through the implementation of a number of computational experiments (CE). The analysis of the CE results showed that the introduction of hybrid highly dispersed fibers into the initial composition of polystructural decorative concrete, with their different quantitative combinations, makes it possible to improve a number of its functional characteristics and thereby ensure the preservation of the artistic and aesthetic expressiveness of products.
The article considers issues relating to the decorative concrete stability to frost impact. The study of the influence of prescription factors on the frost resistance value of composite compositions, manufactured of high-mobility mixtures, was carried out according to a symmetrical 5-factor plan with 27 experiments. Depending on the nature of the effect on the decorative composite, the variable raw materials are grouped into two groups of factors - modifications of cement-sand system, parameters of dispersed reinforcement. Kinetic curves, correlation, experimental-statistical model were constructed based on the results of the field experiments. The results of the research demonstrated – the use of zeolite instead of part of cement, glass fibres and fillers of optimal granulometric composition in combination with a plasticiser contributes to reducing integral porosity and provides the preservation of composite strength, and accordingly, resistance to climate impacts, saving the decorative properties during the operation of the decorative composite.
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