POSSIBILITIES OF USING GYPSUM WASTE IN THE PRODUCTION OF BUILDING MATERIALS

ВОЗМОЖНОСТИ ИСПОЛЬЗОВАНИЯ ГИПСОВЫХ ОТХОДОВ В ПОВТОРНОМ ПРОИЗВОДСТВЕ СТРОИТЕЛЬНЫХ ИЗДЕЛИЙ

Жигалев Павел Максимович

студент, Национальный Исследовательский Московский Государственный Строительный Университет,

РФ, г. Москва

Юдина Ирина Ивановна

научный руководитель, старший преподаватель, Национальный Исследовательский Московский Государственный Строительный Университет,

РФ, г. Москва

АННОТАЦИЯ

В данной статье рассматриваются возможности использования гипсовых отходов в повторном производстве строительных материалов. Целью исследования является изучение двух видов гипсового вяжущего материала с детальным сопоставлением их свойств, определением преимуществ и недостатков каждого из них, проводится анализ возможности использования гипсовых отходов в строительной индустрии.

ABSTRACT

 This article examines the possibilities of using gypsum waste in the repeated production of construction materials. The aim of the study is to investigate two types of gypsum binding materials through a detailed comparison of their properties, identifying the advantages and disadvantages of each, and analyzing the potential for using gypsum waste in the construction industry.

Ключевые слова: гипсовые отходы; вторичный гипс; переработка строительных отходов; гипсовые вяжущие; устойчивое строительство; ресурсосбережение; строительные материалы.

Keywords: gypsum waste; recycled gypsum; construction waste recycling; gypsum binders; sustainable construction; resource efficiency; building materials.

In the modern conditions of development of the construction industry, issues of rational use of natural resources and reduction of negative environmental impact are becoming particularly relevant. Construction is traditionally one of the most resource-intensive sectors of the economy, consuming significant volumes of mineral raw materials and subsequently generating large amounts of waste. In the structure of construction waste, a significant share is occupied by gypsum-containing materials, such as plasterboards, partition blocks, plaster compositions, and decorative products.

The active growth of the construction sector, various processes of reconstruction and demolition of buildings, lead to an increase in the amount of gypsum waste. In most cases, such waste is disposed of by landfilling at solid municipal waste sites, which is accompanied by a number of negative consequences for the environment. These consequences include an increased load on landfills, deterioration of ecosystem conditions, as well as irrational use of mineral resources.

Among construction materials, gypsum occupies a special place due to its specific physicochemical properties. One of the most important features of gypsum is its ability to undergo reversible processes of dehydration and hydration. The main component of gypsum materials is calcium sulfate in the form of dihydrate (CaSO₄•2H₂O). When heated, the dihydrate transforms into the hemihydrate form (CaSO₄•0.5H₂O), and upon subsequent interaction with water, it again forms the crystalline structure of the dihydrate. It is this feature, consisting in the ability of gypsum to become suitable again for reuse after processing, that makes it possible to consider gypsum waste not simply as construction debris, but as potential secondary raw material.

Today, when increasing attention is paid to sustainable development and resource conservation, the reuse of construction waste becomes particularly important. The use of gypsum waste in the production of construction materials makes it possible to simultaneously solve environmental and economic problems: to reduce the volume of waste disposal, to decrease the consumption of natural raw materials and to increase the resource efficiency of production.

Within the framework of this study, two types of gypsum binders were considered: primary construction gypsum obtained from natural raw materials and secondary gypsum formed as a result of processing gypsum waste. The main objective is not only to describe these materials, but also to provide a detailed comparison of their properties with the identification of the advantages and disadvantages of each of them, as well as to explain the reasons for these differences.

The comparison of the properties of primary and secondary gypsum, as well as the analysis of the reasons for their differences, make it possible to determine the conditions under which the recycled material can be used most effectively and without significant deterioration of the performance characteristics of construction products.

Primary gypsum is obtained from natural gypsum stone, which undergoes a full technological processing cycle: crushing, grinding, and thermal treatment under strictly controlled conditions. As a result, a material with a stable chemical composition and a stable particle structure are obtained. One of the key advantages of primary gypsum is its high uniformity. This is due to the fact that the raw material undergoes industrial preparation and purification and the calcination process is carried out under specified temperature conditions, ensuring the formation of such a structure.

The stability of the structure directly determines how predictable the properties of the material will be. Primary gypsum is characterized by constant water demand, stable setting times, and consistent strength indicators in repeated tests. This is explained by the fact that the particles have similar shapes and sizes and they do not contain foreign inclusions capable of affecting the hydration process described above. In addition, the absence of impurities ensures the uniform formation of the crystalline structure during hardening, which positively affects the strength of the products.

However, the use of primary gypsum is associated with a number of significant disadvantages. Firstly, it requires the extraction of natural raw materials, which leads to the depletion of deposits and disruption of natural landscapes. Secondly, significant energy consumption is required at the stages of crushing, grinding, and calcination, which increases the cost of the material and is accompanied by emissions into the environment. Thus, the high technological stability of primary gypsum is achieved at the expense of significant natural and energy resources.

Secondary gypsum is formed from waste of gypsum-containing materials generated at various stages of the life cycle of construction products. Its main advantage is the possibility of reusing already existing material without the need to extract new raw materials. This is directly related to the fact that the chemical basis of gypsum (calcium sulfate) is preserved even after the hardening process. Repeated thermal treatment makes it possible to partially restore the binding properties of the material, which makes it suitable for further use.

The environmental advantages of secondary gypsum are due to the reduction of waste volumes, as well as to the decrease in the need for natural gypsum extraction. The economic benefit is manifested in the reduction of costs for raw materials and waste disposal. Thus, the advantages of secondary gypsum are directly related to its origin as a recycled material and its further efficient application.

However, secondary gypsum has a number of disadvantages that limit its use. The main one is the heterogeneity of its composition. Unlike primary gypsum, secondary raw material may contain various impurities, including paper fibers, residues of adhesive compositions, cement particles, and other foreign substances. This is due to the fact that the initial waste is formed from different sources and it does not always undergo ideal purification.

Another important disadvantage is the change in the structure of particles. Since the material has already undergone the hardening process, its crystalline structure is partially disrupted. During repeated calcination, the structure is not fully restored in its original form, which leads to the formation of particles with a more complex shape and increased specific surface area. This, in turn, explains the increase in the water demand of secondary gypsum (more water is required to wet such a structure).

The change in structure also affects the hardening process itself. The presence of microdefects and impurities may disrupt the uniformity of crystallization, which leads to a decrease in the strength of the material. In addition, impurities may act either as catalysts (accelerators) or inhibitors (retarders) of setting, which reduces the stability of technological characteristics. For example, the presence of fine particles may act as crystallization centers and accelerate setting, whereas inert inclusions may slow down this process.

The comparison of primary and secondary gypsum shows that at the level of chemical composition the differences between the materials are minimal. In both cases, the main component of their composition is calcium sulfate, which preserves the fundamental possibility of reusing gypsum waste as a binder. This is a key factor determining the prospects for recycling this type of waste.

However, when moving to the analysis of structure and technological properties, the differences become more pronounced. Secondary gypsum after processing is characterized by greater structural heterogeneity. The particles of the material have a more complex shape and increased specific surface area, which is associated with a repeated hardening cycle and subsequent calcination. As a result, the nature of interaction of particles with water is changing.

One of the most noticeable differences is the increase in the water demand of secondary gypsum. On average, the water demand may increase by 5–15 percent compared to primary gypsum. In practice, this leads to the need to adjust the composition of construction mixtures, since an increase in water content may affect the final strength characteristics.

The setting time of secondary gypsum generally remains close to the indicators of the primary material; however, their stability decreases. Depending on the degree of purification of the initial raw material and the presence of impurities, deviations are possible both towards acceleration and towards retardation of the hardening process.

The most significant differences are manifested in strength characteristics. When using secondary gypsum as part of a binder material, there is a tendency for a decrease in the strength of products. At the same time, the degree of strength reduction directly depends on the proportion of secondary gypsum. When introducing up to 10–15 percent of recycled material, the strength characteristics remain practically at the level of primary gypsum. When increasing the content to 20–30 percent, a decrease in strength by an average of 10–15 percent is observed and it remains acceptable for a number of construction products. At higher proportions, the use of secondary gypsum becomes limited without the use of additional modifying additives.

Taking into account the identified features, it is possible to determine the most rational areas of application of secondary gypsum. First of all, this includes the production of non-load-bearing construction products, such as partition slabs, gypsum blocks, and finishing elements. In these cases, strength requirements are not critical, which makes it possible to compensate for possible deviations in material properties. At the same time, environmental and economic efficiency, under conditions of increasing requirements for environmental safety, acts as an additional advantage of using secondary gypsum.

In conclusion, it should be noted that gypsum waste can be considered not only as a by-product of construction activity, but also as a real reserve of secondary raw materials for the reproduction of construction products. The possibility of their reuse is determined by the preservation of the chemical basis of gypsum and its ability, after appropriate processing, to again exhibit binding properties.

In the course of the study, it was established that the use of secondary gypsum is most promising in cases where the decisive role is played not by the maximum strength of the material, but by the combination of technological, environmental, and economic efficiency. Despite the fact that recycled gypsum is inferior to primary gypsum in terms of structural stability and a number of performance indicators, its properties, when the necessary conditions are met, remain sufficient for the production of non-load-bearing construction products and finishing materials.

Consequently, the expediency of using secondary gypsum is determined not by its complete identity to natural raw materials, but by the possibility of rationally compensating for existing limitations through waste sorting, their purification, control of processing modes, and adjustment of mixture compositions. This approach makes it possible to reduce the volume of construction waste disposal, to decrease the consumption of natural resources and at the same time to expand the raw material base of the construction industry.

The recycling of gypsum waste represents a promising direction for the development of modern construction, corresponding to the objectives of resource conservation and environmental safety. Further improvement of processing technologies and stabilization of the properties of secondary gypsum will make it possible to increase the efficiency of its use and to expand the areas of practical application.

References:

1. Alfimova, N. I. Overview analysis of methods for obtaining binders from gypsum-containing industrial waste / N. I. Alfimova, E. A. Shcherban, A. V. Tverdokhlebov [et al.] // Vestnik BGTU im. V. G. Shukhova. — 2019. — No. 8. — P. 8–19.
2. Baruzdin, A. A. Prospects of recycling in construction for the creation of innovative composite materials / A. A. Baruzdin, N. V. Klyuev, A. S. Fedyuk [et al.] // Vestnik TGTU. — 2021. — Vol. 27, No. 3. — P. 411–427.
3. Korovyakov, V. F. Gypsum binders and their application in construction / V. F. Korovyakov // Russian Chemical Journal. — 2003. — Vol. 47, No. 4. — P. 18–25.
4. Pudovkin, A. N. Application of gypsum production waste in wall construction materials / A. N. Pudovkin, A. A. Yudin, E. I. Ganeeva [et al.] // Vestnik Evraziiskoi Nauki. — 2021. — Vol. 13, No. 1.
5. Shchukina, E. G. Study of properties of gypsum waste and production of gypsum materials based on it / E. G. Shchukina, N. V. Arkhincheeva // Vestnik VSGUTU. — 2013. — No. 3(42). — P. 48–53.