The study is devoted to the generalization of the existing world experience on the impact of recycled polyethylene terephthalate (PET) products when they are added to concrete on its characteristics. Analysis of the available data shows the effectiveness of the use of PET fiber in a concrete matrix in order to recycle plastic waste, facilitate concrete structures, save cement consumption and improve the strength characteristics of concrete. But the researchers did not come to a consensus on the effective consumption of fiber during reinforcement, the influence of the shape of the fibers used on the properties of fiber concrete, as well as the areas of application of this material.

Keywords: concrete, concrete matrix, fiber, dispersed reinforcement, polyethylene terephthalate, tensile strength, compressive strength

This article contains the results of a study of the strength characteristics of building mortars of various compositions based on magnesia binder (magnesia oxychloride cement). The results obtained: the final compressive strength (28-day) within the studied compositions is from 12 to 45 MPa, the kinetics (rate) of strength growth on the first day of hardening is from 22 to 38%, on the third day of hardening – 33-68%, on the seventh day – from 50-88%, and about 120% from the design (28-day) with further hardening.

Keywords: magnesia oxychloride cement, magnesia binder, magnesia mortar, magnesia concrete, caustic magnesite, magnesium chloride, compressive strength, strength set kinetics

The article collects and structures information about the effect of chemical additives on the properties of concrete and concrete mix. The relevance of topic is due to the fragmentation of the background information and the lack of data on the study of new additives. The presentation of information in the form of a morphological table simplifies the selection of additives and reduces the risk of errors in the selection of concrete composition. Mineral additives were not considered in this article.

Keywords: construction materials, concrete, concrete mix, chemical additives, concrete properties, concrete composition, modified concrete

This article contains the results of a study of the strength characteristics of concrete with the addition of various amounts and shapes of recycled polyethylene terephthalate (PET) fibers. In general, the use of fiber in concrete from waste PET materials (obtained by mechanical grinding), rather than heat-treated, can increase the tensile strength. The compressive strength is reduced. Industrial flex is not recommended to be used as a fiber (additive) in concrete, as this leads to a decrease in strength characteristics. Increased tensile strength is provided through the use of specially prepared PET fiber. The conducted research proved the possibility of using PET fiber in concrete from waste PET materials (obtained by mechanical grinding) PET fiber is recommended for use in concrete structures to increase tensile strength.

Keywords: concrete, concrete matrix, fiber, dispersed reinforcement, polyethylene terephthalate, tensile strength, compressive strength