Dust pollution of the air during the reloading of construction waste into a container

. The dismantling of building structures, especially inside the existing buildings, is accompanied by an intensive release of dust into the surrounding air and the surrounding areas, which negatively affects the environment, workers and residents of neighboring houses. The article studies the properties of the released dust when dismantling waste is dumped into a special container, the intensity of dust settling and the spread of dust particles. Recommendations are presented to reduce dusting and the negative impact of waste during the dismantling of building structures on the environment.


Introduction
Capital repairs of buildings and structures, dismantling of building structures are accompanied by the formation of a large amount of waste.Waste is collected in open containers by dropping them through window openings.
When dropped into a container from a height, finer dust particles are formed, which spread to nearby areas.In addition, building renovations are often carried out inside existing buildings.including residential, which negatively affects the quality of the air environment and the sanitary and hygienic environment for both workers and the population.
Wastes from the dismantling of building structures mainly consist of broken concrete, fragments of bricks, finishing materials, and plaster.

Methods
For the practical implementation of the study of the spread of dust particles during reloading of construction waste, a comprehensive analysis was used, including an analysis of the properties of dust of various building materials, determination of the dispersed composition of dust, as well as the intensity of dust settling on nearby territories.
The object of study in this paper is a two-story building made of ceramic bricks with reinforced concrete floors.
The study of the dispersed composition of dusts that enter the air as a result of the dismantling of building structures was carried out by microscopy.
For the study, dusts of cement, reinforced concrete structures, lime coating and ceramic bricks were taken.On the basis of the data obtained, integral curves of the distribution of dust particles by diameters were constructed.
Determination of the power of dust release from stationary sources was used the technique of Professor E.I. Boguslavsky and professor V.N.Azarov by assessing the intensity of dust emission.
The total value of dust emissions from the sourceМ в g/h, is determined by: M1 -is the mass of dust carried away by atmospheric air, g; M2 -is the mass of dust deposited on the surface, g.
Considering the dependence of the M1 value on meteorological conditions, the studies were carried out in calm weather.
The main idea of this method is to determine the amount of dust deposited on a special flat bowl per unit of time when dumping construction waste.The bowls are laid out on horizontal surfaces, from 2 to 6 meters from the container (dusting source) around the circumference through an angle / 4, then the settling dust is collected and the bowl is weighed: G -the mass of dust deposited on the bowl, kg;; F-the area of the bowl, m 2 ; -the time during which the measurements were taken, h The final value of dust emission of the sector is determined by the formula: Gmax -the maximum value of dust settling determined from the distribution curve , g/(m 2 h) α --a coefficient depending on the characteristics of the dust, determined experimentally, 1/m. -degree measure of the central angle of the considered sector, deg; xk -distance from the container (source), m.The measurements were carried out with two options for the location of the container on the construction site:  a single source of dust emission (container), surrounded by a building wall on one side (Fig. 1);  a single source of dust emission (container), surrounded on three sides by a building (Fig.

Results and discussion
According to the results of the analysis of the physicochemical properties of dust entering the air during the dismantling of building structures, there is a similarity in the physicochemical properties of the dust of the materials from which the dismantled structures were made.Thus, the properties of the dust generated during the reloading of ceramic brick masonry waste coincide with the properties of the dust released during the production of the ceramic brick itself.According to the integral curves of the distribution of the masses of dust particles by diameters (Fig. 3) constructed as a result of studying the dispersed composition of dust, it can be seen that the dust of ceramic bricks and the dust of cement stone of structures made of reinforced concrete are significantly larger than lime dust (median diameters, respectively, d50 = 50 mkm, 50 = 48 mkm и d50 = 16 mkm).This fact allows us to solve the problem of separating dust waste depending on the type of material of the dismantled structures.Due to the different sizes of dust particles for each type of dust, the trajectory of particle movement in separation or dust trapping devices will also differ, which will be a criterion for selecting the most effective cleaning devices.In cases where lime materials predominate and, as a result, the release of predominantly fine dust during the formation of waste, we can talk about the complexity of organizing the process of capturing and cleaning emissions, given.
Measurements of the intensity (Table 1) of dust settling showed that the average density of dust settling ranges from 0.21 kg/(m2h) to 0.597 kg/(m2h), which indicates significant dusting and, as a result, air pollution around the container.
An assessment of the dust emission power during the reloading of construction waste into containers, performed on the basis of the data obtained, made it possible to establish that the maximum dust emission is observed when the container is located in a cramped position on three sides, which is due to the removal of part of the dust pollution by atmospheric air.

Conclusions
Based on the studies carried out and the results obtained, it can be concluded that it is necessary to develop and implement measures and devices for the localization and purification of dust emissions.
Taking into account the features of the investigated source of dust, namely the possibility of moving it to different positions in relation to the sides of the building, used for shelter, localization and purification of emissions, the device must be modifiable and easily change structurally and principally under operating conditions

Fig. 1 .Fig. 2 .
Fig. 1.Layout of trap bowls at a single source of dust emission (container) surrounded by a building wall on one side

Fig. 3 .
Fig. 3. Integral distribution curves of dust particles by diameters released during dismantling during major repairs of the building: 1-lime finish; 2-cement stone connecting joints; 3-ceramic brick; 4cement stone reinforced concrete structures.

Table 1 .
Results of the assessment of the dust emission rate