PROSPECTS FOR FURTHER APPLICATION OF BRICKS SELECTED FROM BUILDINGS AND STRUCTURES DAMAGED AS A RESULT OF MILITARY ACTIONS

Introduction. Currently, the construction industry is a topical issue in the use of secondary waste generated in the process of human life [1] or obtained as a result of crushing construction products and structures damaged as a result of military operations, natural disasters and demolition of existing buildings and structures [2]. Such a direction of activity is recycling, that is, one of the options for processing waste. One of the ways to implement this topic is to obtain concrete compositions by using secondary aggregates obtained as a result of crushing construction products and structures damaged as a result of military operations, natural disasters or demolition of existing buildings and structures. Analysis of the current state of development and research of concretes showed that aggregates for reuse can be obtained based on crushing construction products and structures made of concrete, reinforced concrete, brick, glass, etc., which were damaged as a result of military operations, natural disasters or demolition of existing buildings and structures. In addition, the use of secondary aggregate is an important condition for preserving the environment and reducing the burden on natural resources. Analysis of publications has shown that structural concrete can be obtained on secondary aggregates, crushed from the material of structures damaged as a result of military operations, natural disasters or demolition of existing buildings and structures. The use of secondary concrete aggregate for obtaining structural concrete is known [3; 4] where the authors claim that if high-quality and well-sorted recycled aggregate is used, concrete with the required strength can be obtained. However, it is noted that the bottleneck in the use of secondary aggregates is the heterogeneity of the aggregate structure, which is two-component and consists of dense primary aggregate and porous residual cement mortar. With such a structure of the secondary aggregate, the primary aggregate and residual cement mortar can also work separately, especially under the influence of periodic moistening, low and high temperatures. In the literature there is information about the use of cullet with a bulk density of 700 kg/m3 as an aggregate for the production of concrete [5]. However, the widespread use of cullet is restrained by the economic component, namely, that the secondary processing of cullet is more effective for the production of new glass-based products. It is known to use secondary aggregate crushed from clay ordinary and silicate bricks in concrete compositions [6; 7]. In this case, such aggregates should be considered single-component, since the masonry elements from which the specified brick is selected contain a minimum amount of mortar from the joints and most of this mortar disappears from the aggregate during the grinding process. Aggregates made of crushed brick have increased surface porosity and crack resistance [7], which significantly affects the suction of moisture from the cement dough. However, this effect increases the adhesion between the cement paste and the aggregate, and therefore the destruction of concrete based on crushed brick aggregate occurs, unlike concrete on aggregate obtained as a result of crushing concrete, not by the aggregate-cement contact. The purpose of the work is to determine the possibility of using in concrete compositions the aggregate obtained as a result of crushing ordinary clay bricks damaged as a result of the destruction of buildings and structures during military operations. Conclusions. The possibility of using in concrete compositions the aggregate obtained as a result of crushing ordinary clay bricks damaged as a result of the destruction of a building during military operations was considered. As a result of the study of the brick in laboratory conditions, it was established that it corresponds to the M100 brand in strength and has an average density of 1 740 kg/m2. Such a brick is waterproof, as it has a softening coefficient of 0.84, and its water absorption is 16.38 %. The secondary aggregate, which is obtained by crushing ordinary clay bricks, has a bulk density of 935 kg/m3 and can be divided into two parts by fractional composition: large – fractions of 5–25 mm in the amount of 65.8 % and fine – fractions of 0.16–5 mm in the amount of 16.0 %. Based on the obtained characteristics of ordinary clay bricks and secondary aggregate crushed from this brick, structural concrete compositions will be developed for use in the construction of buildings and structures.