Environmental Benefits of Fluorogypsum Reuse in the Production of Construction Materials

Abstract

Fluorohypsum is a solid, large-tonnage waste generated during the production of hydrofluoric acid. The volume of accumulated waste in the world is hundreds of millions of tons, which makes its utilization an increasingly urgent task. This article presents the results of research aimed at the use of fluorohypsum as a component of building materials. On the basis of the obtained data, the technological scheme of manufacturing products based on anhydrite binder is developed. It was established that the introduction of specialized additives into gypsum–anhydrite mixtures significantly increases the bond strength with the base (up to four times). The mixture of gypsum and anhydrite with a 75/25 arrangement provides tensile strength of up to 4.3 MPa and bending strength of 1.8 MPa, which exceeds similar indicators for traditional building materials. An economic analysis has shown a 20–25% reduction in the cost of composite production compared to the use of natural gypsum, which provides cost savings and makes these materials competitive.

1. Introduction

Modern scientific and technological progress throughout the world is directly linked to the global utilization of natural resources and the accumulation of man-made waste [1,2]. This is a reality that has to be reckoned with, and even the most necessary, technically advanced industrial complex, if its impact on nature extends beyond ecologically acceptable limits or becomes destructive, may be undesirable for society, if not today, then in the future [3,4].

Numerous scattered data on the properties of calcium sulfate wastes from hydrofluoric acid production, as well as the directions of their use, caused the need for staging experiments to clarify and systematize these properties for the most effective use of these wastes in the industry of construction materials.

The relevance of the work is that, along with the level of quality in determining the competitiveness of building materials, one of the most important factors is their low cost, which is achieved by energy- and resource-saving technological solutions. With the intensive development of the construction industry, there is an urgency for the production of high-quality and cost-competitive gypsum binders and products based on them [5,6,7]. They are characterized by lightness, ease of manufacture, good heat and sound insulation properties, biological resistance, fire resistance, chemical neutrality, as well as high architectural, decorative, and hygienic qualities.

Fluorohypsum is a solid anthropogenic waste generated during the production of hydrofluoric acid, the accumulation of which causes serious environmental problems [8,9]. More than 200 million tons of fluorohypsum are produced annually in the world, most of which is stored in landfills without further processing. The lack of effective disposal methods leads to the accumulation of these wastes, which occupy large areas and create unfavorable conditions for the environment. Fluorohypsum storage is associated with risks of soil and water pollution, as it contains vulnerable elements, including fluorine residues and heavy metals. For example, in the East Kazakhstan region, where hydrofluoric acid is produced, the annual accumulation of fluorogypsum waste reaches 30–35 thousand tons, and its cumulative volumes may exceed 100 thousand tons in the coming years [10], which aggravates the problem.

The use of fluorohypsum as a component of building materials seems to be a promising method of waste utilization, as it not only reduces the volume of waste but also reduces the need for traditional natural resources. The use of fluorohypsum in building materials can reduce disposal costs and minimize impacts.

The complexity of the problem of effective and rational use of production wastes is caused not only by the large volume of waste but also by the orientation of many sectors of the national economy for a long time toward the use of relatively clean mineral raw materials. At the same time, wastes from hydrofluoric fluoride production are a special type of secondary raw material for various branches of the economy [11]. Through their utilization, it is possible to form industrial complexes according to waste-free or low-waste technologies with minimum environmental pollution and maximum use of natural resources.

However, gypsum is not a suitable material for outdoor construction works due to its low resistance to water and insufficient mechanical strength [12,13,14]. To protect gypsum, it is necessary to prevent moisture penetration to avoid damage to the plaster coating. Gypsum obtained from various sources can be used as an additive raw material for the production of composite binders, which has been investigated by many scientists.

In study [15], the influence of the type of mineral additives of pulverized fuel ash and blast furnace slag, the water/binder ratio, and the temperature on the properties and microstructures of fluorohypsum–Portland cement composite mortars was investigated. The mortars were cured under water at 20 and 40 °C for 90 days; all of them showed hydraulic behavior after gradually developing and maintaining their properties. The best compressive strength after 90 days (17.7 MPa) was for the binder with 5% blast furnace slag. P.E. Fraire-Luna and J.I. Escalante-Garcia [16] investigated the hydration and properties of composite cement pastes with 75% fluorohypsum; blast furnace slag and metakaolin were additional cementitious materials. The pastes were cured under water at 20 °C for 360 days. All pastes developed and maintained strength under water, except for the commercial gypsum pastes. The addition of metakaolin had a positive effect, with compressive strengths of 13.4, 13.8, and 14.6 MPa recorded after 360 days for systems with 0%, 5%, and 10% metakaolin, respectively. Fluorohypsum reacted rapidly in the first days, but it was still present after one year. Additives obtained from various sources can be used to produce composite binders, which has been investigated by many scientists [17,18].

Other authors [19] obtained gypsum–anhydrite–slag mixtures by mixing anhydrite with granulated blast furnace slag, Ca(OH)₂, and small amounts of Na₂SO₄-10H₂O and FeSO₄-7H₂O as activators. They proposed a mechanism for the conversion of anhydride to gypsum via transition double salts in the presence of activators. The activation of granulated slag with gypsum anhydride and Ca(OH)₂ to form ettringite and tobermorite was discussed. A relationship between the increase in strength and hydration products was reported.

The present study contributes to the field of industrial recycling, waste, and its use in building materials as an innovative solution for the utilization of fluorohypsum, a waste whose accumulation poses serious environmental risks. The novelty of this work lies in the development of a composite material based on fluorohypsum and anhydrite.

In connection with the above-mentioned growth of fluorohypsum waste accumulation on dumps, we conducted research on the possibility of its use for the preparation of dry construction mixtures. The purpose of our research is the utilization of fluorohydrite waste from the production of hydrofluoric acid at «UMP» JSC and the possibility of obtaining anhydrite-free anhydrite binder with a setting time of 30 min and a strength not less than 4 MPa.

2. Materials and Methods

2.1. Materials

The raw material used to produce an anhydrite binder is derived from gypsum-containing waste produced during hydrofluoric acid manufacturing. Anhydrite binder, also known as anhydrite cement, is formed by grinding naturally occurring or artificially prepared anhydrite (obtained through heating at 600–700 °C) together with activators. The main sources for the production of anhydrite binder are natural dihydrate gypsum and anhydrite, the quality standards of which are set out in the state standard GOST 4013-82-Gypsum and gypsoanhydrite stone for the production of binders [20].

Immediately after leaving the furnace, the waste appears as granulated gray material, with granule sizes ranging from 0.3 mm to 60–70 mm. Particle size was analyzed by dynamic light scattering on a Fritsch Analysette-22 instrument (“Fritsch”, Idar-Oberstein, Germany). The physicochemical characteristics of this waste and the feasibility of producing binder material from it have been previously studied, as described in [21]. The data obtained indicate that the properties of waste obtained at different times are similar, indicating a relatively homogeneous composition and constant production mode [22]. The chemical composition of the waste is shown in

Table 1. Chemical composition of the waste (wt.%).

Component	CaO	SO3	H2SO4	CaF2	Al2O3	Fe2O3	HF	SiO2	Cr2O3	TiO2	Na
Content (wt.%)	28–39	38–56	10–15	3	0.5	0.3	0.3	0.2	0.01	0.012	0.015

.

This stage is necessary to ensure the fineness of grinding to achieve a specific surface (S_sc) of the mixture of 8000 cm²/g in a ball mill to obtain optimal setting time. This process was carried out in a ball mill and a vibratory mill.

2.2. Methods

Due to the current lack of a special GOST for testing methods of dry building mixtures, in the study of the main technical indicators of the developed dry mortar mixtures on anhydrite binders, the following were used: GOST 5802-86 Construction mortars [23] (test methods: ISO 679) and GOST 23789-79 Gypsum binders [24] (test methods: ISO 679). Standard test methods were used to evaluate the following technical parameters: grain composition, moisture, bulk density, mobility, delamination of mortar mixture, water-holding capacity, water demand, and strength parameters.

X-ray diffraction analysis of powders and composite polymers was performed on an Xpert PRO PANalytical diffractometer (Philips Corporation, Amsterdam, The Netherlands). During our study, a voltage of 40 keV and a current of 30 mA were applied to the anode copper tube, radiation was Cu-Kα (λ = 1.541 Å), the imaging step was 0.02°, and the counting time was 0.5 s/step [25]. Phase analysis on the basis of the obtained diffractogram lines was carried out using HighScore Plus 5.2.0 software complexes.

In addition to standard test methods, Vick’s apparatus was used to evaluate the beginning and end of setting time. The use of Vick’s apparatus makes it possible to determine more accurately the beginning of dough thickening when testing mortars, which contributes to the correct assessment of the duration of workability of plaster mortars, especially when using the mechanized method of their application.

The determination of shrinkage deformations according to GOST 25544 has the disadvantage of a lack of opportunity to assess the deformation of the sample at the initial stage of mortar hardening, because the manufacture of samples—beams and sticking control points—takes more than a day [26]. To eliminate this disadvantage and to obtain more accurate data on the deformation processes of anhydrite mortars during hardening, a special technique was developed.

At the initial stage of testing, a metal perforated plate 0.5–0.6 mm thick was placed in a rubber mold with an internal cavity with dimensions of 100 cm in length, 5 cm in width, and 2 cm in depth. After preparation of the solution of the specified mobility, the entire inner cavity of the rubber mold was filled with it.

After two days, the mold was removed and the sample was placed on a horizontal plane for further curing at normal temperature and humidity for 28 days. When the slab specimen was stored for 3, 7, 14, 21, and 28 days, the deflection of the slab was measured along the middle of its length with a caliper to the nearest 0.1 mm.

The magnitude of shrinkage deformations during the curing of the plate specimen is proposed to be determined by a bending calculation of strip specimens reinforced from one surface.

When processing the measurement results, the following assumptions are taken as a basis for the calculation: the shrinkage deformations of the mortar are the same along the entire length of the specimen, so the curvature is also the same along the entire length of the plate specimen; there are no shrinkage deformations on the reinforced surface of the specimen, i.e., they are equal to zero. Since it is assumed that the curvature of the specimen is the same along its entire length, the specimen is bent along a circle with radius R equal to the distance from the center of curvature to the unreinforced surface of the specimen (Figure 1).

Geometrically, the unreinforced surface is a segment of a circle with a radius of curvature R, and the parameters of this segment can be determined by the following formula:

$$R={\displaystyle \frac{{\alpha }^2+f^2}{2f}}$$

(1)

where α is a half chord equal to 500 mm and f is the deflection boom in mm.

The values of f and α are determined during the experiment. Then, by using these experimental values and Formula (1), we determine R by calculation for each measurement step and calculate the curvature, equal to 1/R.

It is known from the course of resistance of materials that in the pure bending zone, where the curvature of the curved axis of the beam is the same along its entire length, the curvature can be determined from the relative strains in the compressed and tensile zones of the beam (Figure 1).

$${\displaystyle \frac{1}{R}}={\displaystyle \frac{{\mathsf{\epsilon }}_{c.}-{\mathsf{\epsilon }}_t}{h}}$$

(2)

In our case, with respect to a curved plate specimen, this would be as follows: ${\mathsf{\epsilon }}_{\mathrm{c}}$ = ${\mathsf{\epsilon }}_t$, and ${\mathsf{\epsilon }}_t$ = 0.

Hence, the magnitude of shrinkage strain was calculated from the following equality:

$${\displaystyle \frac{1}{R}}={\displaystyle \frac{{\mathsf{\epsilon }}_s}{h}}$$

(3)

where ${\mathsf{\epsilon }}_s$ is the shrinkage deformation value, in mm/m; and h is the plate thickness, in mm.

Substituting the value of R from Formula (1), we determine the relative value of shrinkage during the curing and drying of the sample during the experiment.

$${\mathsf{\epsilon }}_y={\displaystyle \frac{2hf}{{\alpha }^2{f}^2}}$$

(4)

The linear shrinkage value in mm/m is determined after multiplying by 103 (length of the plate sample in mm).

3. Results and Discussion

3.1. Selection of Plaster Mortar Composition

Based on the X-ray diffraction (XRD) results shown in Figure 2, the differences in crystallinity between the initial and activated fluoranhydrite powders are evident.

Initial powder (Figure 2a): The XRD pattern of the unactivated fluoranhydrite shows broad and low-intensity peaks, which suggests a relatively low degree of crystallinity. This broadening indicates a less ordered crystal structure, with the possible presence of amorphous phases. The lower peak intensity reflects the retention of the original crystalline structure with minimal lattice defects or phase changes.

After mechanical activation (Figure 2b): In contrast, the XRD pattern of the mechanically activated fluoranhydrite displays sharper and more intense peaks. The increase in peak intensity signifies a higher degree of crystalline ordering, indicating that mechanical activation has enhanced the crystallinity of the material. The mechanical activation process likely introduces lattice defects, which promotes the formation of distinct crystalline phases. The reduction in the amorphous phase content, evidenced by the clearer and more intense peaks, suggests that the material structure becomes more ordered and crystalline as a result of activation.

Achieving a specific surface area (S_sc) of 8000 cm²/g is critical for obtaining the optimal setting time. The fineness achieved through grinding in a ball mill and vibratory mill ensures that the material has a high surface area, which can enhance reactivity and phase formation during activation.

In summary, mechanical activation not only enhances crystallinity but also introduces beneficial structural changes, making the fluoranhydrite more reactive and structurally ordered. This process is essential for optimizing the material’s physical and chemical properties for subsequent applications.

The composition of the plaster solution was selected based on the main technical properties of gypsum plaster mixes of the Rotband type. The technological and technical properties of plaster mortars similar in composition based on anhydrite binder, obtained by joint grinding of anhydrite flour with the addition of 5% Portland cement PC 400 PO and 1% K₂SO₄, were studied.

Additionally, to study the possibility of regulating the terms of the beginning and end of setting of the prepared plaster mortars and the workability of the applied mortars, the properties of the plaster mixtures with a content of building gypsum and anhydrite (G/A) at ratios ranging from 25/75% to 75/25% and the same initial mobility of the mortar mixture (Pk 12 (9–10 cm)) were investigated.

It is established that the water–solid ratio for gypsum plaster mortars is 0.52%, for anhydrite mortars it is 0.39%, and for plaster mortars based on gypsum–anhydrite binder, it is within 0.45–0.47%. Data on the setting time of such mortars are given in

Table 2. Setting times of mortar mixtures.

Type of Binder	Beginning of Setting (Hours)	End of Setting (Hours)	Processing Time (Hours)
Gypsum G5	1.0–1.5	1.5–2	up to 2
G/A = 75/25%	1.5–2.0	2.0–2.5	17–20
G/A = 50/50%	2.0–2.5	2.5–3.0	18–20
G/A = 25/75%	2.5–3.0	3.0–4.0	19–21
anhydrite binder	2.0–2.5	3.5–4.0	up to 8

.

The choice of gypsum and anhydrite ratios (75/25, 50/50, and 25/75) is based on our results from previous studies [20,21], which have shown that combining these components in certain proportions achieves the best mechanical properties. These ratios were chosen to investigate the balance between rapid setting and strength preservation trade-offs. In particular, a higher proportion of gypsum provides rapid setting and improved strength in the initial stages, while the addition of anhydrite favors an increase in density.

If for gypsum mortars the beginning of setting was within 1.5 h, for anhydrite mortars it was 2–2.5 h, and the end of setting increased up to 4 h. Of particular interest is the determination of the duration of the workability of plaster mortars with different gypsum–anhydrite ratios after application to the wall surface. The duration of the workability of the applied mortars was estimated by the time of preservation of the initial strength, at which it is possible to carry out the operation of smoothing and sanding the surface with additional moistening of the surface.

It was found that gypsum mortars have the lowest period of workability according to this indicator. Pure anhydrite plaster mortars occupy an intermediate position, and for gypsum–anhydrite mortars—with a ratio of gypsum–anhydrite 75/25%—the duration of workability increases to 20 h. This allows using gypsum–anhydrite mortars both for manual and mechanized application.

The developed compositions of anhydrite and gypsum–anhydrite binders for plaster mortars on the basis of dry mixtures prolonged the terms of their workability in comparison with gypsum plaster mortars. The modifying additives used in these compositions—Rutacel 25,000 in the amount of 0.15–0.2%, Esamid NA, Esapon 1214, and Esapon 1850 in the amount of 0.02–0.03% by weight of the dry mixture—have an effect on the process of hydration of the developed binders and their basic technical properties, similar to that noted in traditional gypsum mortars.

3.2. Mechanical Properties of Plaster Mortars

Figure 3 is a graph showing the compressive test results of different specimens of gypsum and anhydrite mixtures and pure gypsum and anhydrite. The gypsum-dominated mixtures (G/A 75/25 and G/A 50/50) show high compressive strength (4.3 MPa and 3.8 MPa, respectively), indicating the significant influence of gypsum on the strength of the mixture. According to the studies of other scientists, intermediate compounds between sulfate and anhydrite are not formed, and the accelerating effect of additives is due to other reasons. Activating effect of gypsum additives is that the particles of additives serve as crystallization centers that contribute to the rapid removal of the supersaturated solution of double hydrate formed during the hydration of anhydrite from the state of equilibrium with the release of CaSO₄-2H₂O in the precipitate, as a result of which supersaturation is reduced and conditions are created for the dissolution of new portions of anhydrite.

In Figure 4, it is possible to see the results of the flexural tests of specimens of composite mortars with different percentages of gypsum and anhydrite, from which it can be seen that G/A 75/25 shows a high flexural strength of 1.8 MPa and G/A 50/50 shows 1.7 MPa. This indicates the importance of selecting the mix composition to achieve optimum mechanical properties.

Interior finishing of walls and ceilings with plastering mortars from dry mixes can be made on the surfaces of various wall materials. Therefore, the study of the bond strength of hardened gypsum, anhydrite, and gypsum–anhydrite mortars has been given special attention. The effect of cellulose ethers (Rutacel 60RT-25000) and starch esters (Esamid NA) on the bond strength of gypsum and gypsum–anhydrite mortars with the substrate was determined, and the results are summarized in

Table 3. Improvement in compressive strength with additives.

Binder Composition	Tensile Bond Strength (MPa)
	Mortar with Additive 0.25% Plast Retard _______________ Mortar with Additive 0.05% Tartaric Acid		Mortar with Additive 0.1% Rutacel + 0.25% Plast Retard + 0.02% Esamid NA _______________ Mortar with Additive Rutacel 0.1 + 0.05% Tartaric Acid + 0.02% Esamid NA		Mortar with Additive 0.1% Rutacel + 0.25% Plast Retard + 0.02% Esamid NA + 0.5% Neolith _______________ Mortar with Additive 0.1% Rutacel + 0.05% Tartaric Acid + 0.02% Esamid NA+ 0.5% Neolith
	Aging 7 Days	Excerpt 28 Days	Aging 7 Days	Excerpt 28 Days	Aging 7 Days	Excerpt 28 Days
Gypsum G5	0.15 0.1	0.14 0.14	0.47 0.47	0.5 0.51	0.9 0.9	0.91 0.91
G/A = 75/25	0.10 0.16	0.11 0.1	0.46 0.46	0.51 0.52	0.82 0.8	0.83 0.83
G/A = 50/50	0.12 0.12	0.13 0.13	0.46 0.45	0.49 0.48	0.85 0.8	0.8 0.79
G/A = 25/75	0.05 0.05	0.06 0.06	0.41 0.42	0.37 0.47	0.65 0.6	0.63 0.63

.

It follows from the data in Table 2 that when water-retaining additive Rutacel is added to the solution, as well as the addition of thickener Esamid NA based on starch ester, the bond strength increases by 4 times compared to the solutions without the addition of these chemical additives, which indicates their effectiveness.

The strength of adhesion to the substrate of hardened anhydrite compositions with the introduction of the above additives at 28 days of exposure is 0.5–0.6 MPa, which exceeds the strength of adhesion of compositions with a percentage ratio of G/A 50–25/50–75% by 20–25%.

When redispersible polymer powder (RPP) is added to gypsum–anhydrite compositions in the amount of 0.5% of the dry mixture weight, the strength of adhesion of the mortar with the base improves by 1.5–2 times; at the same time, RPP addition does not increase the adhesion ability of anhydrite mortars.

The technical parameters of plaster mixtures and mortars based on them are presented in

Table 4. Technical indicators of plaster mixtures and mortars based on them.

Name of Technical Indicators	Value of Indicators
	Plaster Mix (Manual)		Plastering Machine Mix
	Gypsum	Anhydrite	Gypsoanhydrite
Bulk density of dry mix, kg/L	0.76	0.95	0.81
Water–solid ratio, V/T	0.5–0.55	0.41–0.42	0.42–0.43
Moisture content of the mixture, %, (not more)	0.5	0.4	0.4
Water-holding capacity of the solution, %	98.5	98.8	99.5
Setting time, h   - commencement   - end	1.0–1.5 1.5–2.0	2.0–2.5 3.5–4.0	1.5–2.0 2.0–2.5
Processability, h	2	up to 8	up to 20
Compressive strength, MPa	4.5–4.9	3.5–3.9	4.0–4.3
Bending strength, MPa	1.5–2.0	1.5–1.9	1.5–1.8
Bond strength with the base, MPa	0.4–0.5	0.5–0.6	0.4–0.5

.

As a result of the conducted research, the compositions of anhydrite and gypsum–anhydrite mortar mixtures for plastering works indoors, which can be used both for manual and machine application, have been developed.

Compared to conventional binders:

-

the chemical stability of anhydrite binder is higher than that of gypsum but lower than that of cement. Due to the possibility of modification, anhydrite binder can be adapted to different conditions of application.

-

in terms of mechanical properties, anhydrite binder is superior to gypsum materials, which makes it more suitable for use in mortars. However, in terms of strength, it is inferior to Portland cement.

Anhydrite binder wins on economic and environmental parameters due to the following:

-

Utilization of waste (fluorohypsum) as raw material.

-

Reduced waste disposal costs and energy consumption compared to cement.

-

Lower CO₂ emissions compared to Portland cement during production.

3.3. Technological Scheme of Dry Mix Production

Figure 5 outlines the technology of the production of dry anhydrite mixtures. The technological scheme of production is developed, and the selection of the main equipment for the production of plaster mixtures is made.

3.4. Technical and Economic Indicators of Anhydrite Binder Production

The use of man-made fluorogypsum instead of natural gypsum or other traditional materials allows one to reduce raw material costs. Waste fluorogypsum is often obtained in the process of industrial production and can be used practically free of charge or at minimal cost. This is especially relevant in regions where natural gypsum reserves are limited and it is necessary to transport it from other areas, which increases the cost of the final product.

According to the results of the pilot batch production, the technical and economic efficiency of production and application of the developed dry plaster and floor mixtures was calculated. The technical and economic indicators of production of plaster and floor mixtures on anhydrite binders compared with cement binder are presented in

Table 5. Technical and economic indicators of production of plaster and floor mixtures on anhydrite binders compared with cement binder.

Name	Cost of Mortar Mix Based on Anhydrite and Gypsum–Anhydrite Binder, USD.		Cost of Cement Binder-Based Mortar Mix, USD.		Savings in Manufacturing Cost of Anhydrite and Gypsum–Anhydrite Binder-Based Mixtures Over Cement-Based Mixtures, USD.
	USD 1	1 m3	USD 1	1 m3	USD 1	1 m3
Plaster mixes	17.08	25.68	23.33	28.89	6.25	3.21
Flooring mixes	20.14	30.27	2.71	34.20	5.54	3.92

.

The technical and economic indicators (TEIs) of plastering surfaces with gypsum mortar mixture Knauf MP 75 and the gypsum–anhydrite mixture developed by mechanized and manual methods, respectively, are given in

Table 6. TEIs of plastering surfaces with gypsum mortar mixture MP 75 and developed gypsum–anhydrite mixture.

N. n/n	Name Indicators	Unit Dimension	Mechanized Plastering of Surfaces		Plastering Surfaces by Hand
			Walls	Ceilings	Walls	Ceilings
1	Duration of work	hr.	9.5	11.8	22.3	26.8
2	Labor intensity per 100 m2	man-hr.	51.24 51.26	63.76 63.78	65.9 66	79.46 79.47
3	Machine capacity	mach.-hr.	6.01	7.02	0.2	0.23
4	Maximum number of workers.	man.	6	6	3	3
5	Output per 1 man-hr	m2	1.95	1.57	1.52	1.26

* Note: above the line—labor intensity when plastering with gypsum mortar; below the line—with gypsum–anhydrite mortar.

.

The economic effect of the production of flooring mixture based on anhydrite binder and plastering mixture based on gypsoanhydrite binder, in comparison with the use of cement–sand mortar as screed and plaster, is as follows: for plastering mortars, USD 5.54 per ton and 3.92 USD/m³; for the production of flooring mortars, USD 6.25 per ton and 3.21 USD/m³.

The economic effect of plastering a finishing surface with the developed compositions is expressed in a reduction in terms of work duration by 2 times, a 20% reduction in labor intensity for 100 m² of surface, and a 25% increase in output per person when comparing machine production of plastering works with manual methods.

The obtained data indicate that the developed compositions of dry modified mixtures with the use of anhydrite binders not only allow one to reduce the cost of mortar mixtures but also contribute to reducing the duration of work and increasing labor productivity.

Natural gypsum and cement require processing costs, whereas fluorogypsum is a simple product available at a significantly lower price. Replacing natural gypsum with fluorogypsum can reduce raw material costs by approximately 30%, leading to direct savings.

4. Conclusions

The research conducted, which is the use of fluorohypsum as a binder component for building materials, has progressive economic and mechanical advantages. The characteristics of technogenic wastes generated during hydrofluoric acid production were studied, demonstrating their potential suitability for use in producing anhydrite binders and various building materials based on these binders.

The existing practices for producing construction materials from anhydrite binders were analyzed based on the technical literature and industry sources.

Mixtures of gypsum and anhydrite in ratios of 75/25 and 50/50 exhibit high compressive strength values (4.3 MPa and 3.8 MPa, respectively) and flexural strength values (1.8 MPa and 1.7 MPa). This highlights the crucial role of gypsum in enhancing the mechanical properties of the final products and underscores the importance of carefully selecting the composition to achieve optimal performance.

The developed compositions not only reduce the cost of producing building mixtures but also halve the time required for work completion, decrease labor intensity for finishing 100 m² of surface area by 20%, and increase labor productivity by 25% when using machine application compared to manual methods.

These findings emphasize the high economic efficiency of the new materials and their potential for widespread use in the construction industry. The use of such formulations helps lower production costs, accelerate construction workflows, and increase labor productivity, making them highly suitable for mass adoption in finishing and construction processes.

5. Future Research Area

Future research may focus on measuring the impact of external factors (such as humidity, temperature, and mechanical effects) to assess the effectiveness of these materials for outdoor use in various climatic conditions. Another promising direction is exploring ways to improve the water resistance of fluorogypsum composites, which would expand their range of applications. Implementing these technologies in mass production requires such optimization testing.