Concrete elements on off-grade aggregates for conductive network of reclamation systems

The article shows the results of the positive effect of format-alcohol plasticizer on the construction, technical and operational qualities of concrete that meets established regulatory requirements. A polynomial model of the 2nd order was obtained, the optimal dosage of the recommended plasticizer was determined, which makes it possible to increase the strength of concrete by 60-80% after heat treatment.

Introduction. Prefabricated elements for the network and structures of reclamation systems are manufactured at factories and landfills. After manufacturing, they are sent to the construction site, where they are installed and sealed. Prefabricated elements and structures, in comparison with monolithic ones, have a positive effect on the construction time (reduce them), help reduce labor costs and improve the quality of construction and installation work. In this regard, reclamation systems with a conductive network of prefabricated elements should be considered technically advanced and meeting reliability criteria.

Object. The object of the study is prefabricated elements of reclamation systems.

Materials and methods. To identify the effect of the physic-chemical effect of an aqueous solution of PFS on the strength and performance properties of concrete on aggregates with a high content of pulverized and clay particles, Novorossiysk Portland cement of the 500 brand was used, quartz crushed stone of the 5-40 mm fraction of the Potapovsky deposit with a content of pulverized and clay particles in the amount of 3.3-3.8%, and the waste of cam-non-fragmentation of quartzite fraction 0-5 mm (seeding) Potapovsky deposit with a size modulus of 2.50 with a content of pulverized and clay particles over 15%. Methods of experimental planning theory with the construction of a geometric image of the response function using linear algebra methods were used to solve prescription and technological problems. At the same time, the following ratios were observed: C+Height = 950 kg / m³, Height = 1270 kg / m³, where: C, Height, Sch – respectively, the cost of cement, sowing, crushed stone. Concrete mixtures on such aggregates have low mobility, which makes it difficult to mix them, as well as formability and compaction during vibration, which negatively affects the strength and performance of concrete. In this regard, to compensate for the negative impact of such aggregates on the quality of concrete and the reliability of prefabricated elements, it is proposed to use a plasticizing additive to the concrete mixture - a format-alcohol plasticizer, which is a by-product of the production of pentaerythritol, which is an aqueous solution of sodium formate, syrupforming substances and poly-alcohols – monopentaerythritol and polypentaerythritol. Concrete cubes with an edge of 100 mm were made from the prepared mixtures on a vibrating compaction table, which were then placed in a laboratory steaming chamber for accelerated strength gain. As for the frost resistance of concrete, the normalized characteristics were determined by the results of tests of concrete samples-cubes of 28-year-old age.

Results and conclusions. Studies have shown that the use of inexpensive non-conditioned fillers in the production of trays, pipes, plates and other prefabricated elements will ensure cost reduction in their manufacture without reducing the quality of products. To save cement and reduce the initial water content of mixtures, on aggregates with a high content of polluting particles, it is proposed to add a formate-alcohol plasticizer to the mixture. Its positive influence on the strength and operational properties of concrete meeting the established requirements has been established. By the method of experimental planning, a second-order polynomial model was obtained that adequately describes, at a 5% level of significance, the dependence of the strength of concrete on inexpensive nonconditional aggregates on cement consumption and the dosage of the PFS plasticizer: when cement is
dispersed from 250 to 550 kg/m³, the dosage of the plasticizer in the form of an aqueous solution in in an amount of 2.8-3.2% of the cement mass, it should be considered optimal; the addition of PFS plasticizer to the mixture increased the strength of concrete after heat treatment by 60-80%. Accelerated tests of concrete samples for sea resistance in a solution of sodium chloride confirmed the compliance of concrete on inexpensive local aggregates with an increased content of pulverized and clay particles with the mark 300.

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