Management of Chemical Processes in the Production of Thermal Insulation Materials to Improve Water Resistance and Environmental Safety

1. Introduction

Effective management of chemical processes has become one of the key factors determining the quality, durability, and environmental sustainability of modern construction materials [1]. In the production of thermal insulation materials, management decisions extend beyond conventional technological control and encompass the optimization of raw material selection, chemical composition, process parameters, resource efficiency, quality assurance, and environmental risk mitigation throughout the entire production cycle [2]. Contemporary manufacturing systems increasingly rely on integrated process management approaches that combine technological monitoring, environmental assessment, and decision-support strategies to ensure consistent product performance while minimizing energy consumption, waste generation, and emissions [1,2,3]. Consequently, the management of chemical processes has evolved into a strategic component of sustainable manufacturing, directly influencing both the operational efficiency of production systems and the long-term reliability of construction materials [2,4].

From a management perspective, improving the water resistance and environmental safety of thermal insulation materials requires comprehensive control of the physicochemical transformations occurring during material synthesis and curing [3,5]. Small deviations in the composition of raw materials, moisture content, reaction conditions, or processing parameters may significantly affect the formation of the pore structure, phase composition, and chemical stability of the final product, thereby influencing its durability under service conditions [4,6]. Therefore, effective management should incorporate continuous monitoring of critical technological variables together with systematic evaluation of material performance and environmental indicators [1,5,6,7]. Such an integrated management framework enables manufacturers not only to optimize production efficiency but also to support circular economy principles, reduce the environmental footprint of manufacturing processes, and improve the life-cycle performance of thermal insulation materials intended for sustainable construction [6,8].

Improving the energy efficiency of buildings has become one of the principal priorities of sustainable development and modern construction [1,3,4,8,9]. Thermal insulation materials play a decisive role in reducing heat losses, lowering energy consumption, and decreasing greenhouse gas emissions throughout the service life of buildings [10]. Consequently, the development of durable, environmentally safe, and resource-efficient insulation materials has attracted increasing attention from researchers and industry [3,10,11]. However, despite continuous improvements in the composition and manufacturing technologies of thermal insulation products, their long-term performance is often compromised by exposure to moisture [12]. Water penetration into porous structures may significantly deteriorate the thermal, mechanical, and structural properties of insulation materials, resulting in reduced service life and increased maintenance costs [12,13]. Therefore, evaluating the resistance of thermal insulation materials to water-induced degradation has become an important scientific and engineering challenge.

Recent studies devoted to the development of georeactor systems for the integrated processing of coal beneficiation waste aimed at recovering critical raw materials have demonstrated that these technologies generate considerable quantities of mineral by-products [1,3,7,14]. Depending on their mineralogical composition and physicochemical characteristics, these secondary resources can be effectively utilized in the production of construction materials, thereby supporting the principles of the circular economy and reducing the environmental burden associated with industrial waste disposal [3,7,15]. A substantial proportion of these by-products consists of aluminosilicate compounds, which possess favorable properties for the production of lightweight composite materials and inorganic insulation products [16].

The incorporation of aluminosilicate-containing industrial waste into thermal insulation materials offers several technological and environmental advantages [3]. Besides reducing the consumption of virgin raw materials, these mineral components improve the thermal insulation performance, reduce the density of composite systems, and contribute to more sustainable manufacturing processes [7,17]. Such an approach promotes the efficient utilization of technogenic resources while simultaneously decreasing landfill volumes and supporting the transition toward low-carbon construction technologies [1,3,18].

Current research on thermal insulation materials has mainly focused on thermal conductivity, compressive strength, density, porosity, and other engineering characteristics that determine their energy-saving performance [18,19]. Although these investigations provide valuable information regarding the functional properties of insulation materials, they frequently overlook the influence of prolonged moisture exposure on material durability [15,20]. Under real operating conditions, insulation systems are often subjected to repeated wetting–drying cycles, capillary water absorption, condensation, or prolonged contact with moisture, particularly in regions characterized by fluctuating humidity and temperature [3,16,21]. These processes gradually alter the internal pore structure, increase water absorption, reduce thermal resistance, and weaken the mechanical integrity of the material, ultimately shortening the operational lifetime of building envelopes [16,22].

Despite considerable progress in developing advanced thermal insulation materials, the long-term mechanisms governing water-induced degradation remain insufficiently understood [4,23]. Existing studies generally investigate water absorption as an isolated parameter without establishing its relationship with structural deterioration, dimensional stability, mechanical degradation, or potential changes in chemical composition [16,23,24]. Consequently, there is still a lack of comprehensive methodologies capable of simultaneously evaluating moisture resistance and the environmental performance of insulation materials under realistic service conditions.

This issue becomes particularly important for highly porous and fibrous insulation materials, whose microstructure facilitates intensive water absorption and moisture migration [20,22,25]. Even relatively small amounts of absorbed water may initiate cumulative degradation processes, including pore collapse, loss of mechanical cohesion, reduction of thermal insulation efficiency, and irreversible structural damage [23,26]. Moreover, increasing attention has recently been devoted to the environmental safety of construction materials. Moisture may promote the leaching or migration of potentially hazardous chemical components into the surrounding environment, thereby creating additional environmental risks throughout the service life of buildings [23,27]. Therefore, evaluating only the engineering performance of insulation materials is no longer sufficient; environmental aspects should also be incorporated into comprehensive material assessment frameworks.

The scientific novelty of this research lies in integrating the assessment of water resistance with the evaluation of environmental safety to establish a comprehensive methodology for comparing thermal insulation materials. Unlike conventional approaches that primarily investigate isolated engineering properties, the proposed methodology considers the relationship between moisture-induced structural degradation and the potential environmental impact of the investigated materials. Such an integrated evaluation provides a more reliable basis for predicting long-term material performance under practical operating conditions.

Accordingly, the objective of this study is to investigate the influence of moisture exposure on the structural integrity and functional performance of thermal insulation materials through experimental assessment of their water resistance and simultaneous evaluation of their environmental safety. The obtained results are expected to support scientifically justified material selection for construction applications operating under humid conditions, improve the durability of building envelopes, reduce maintenance costs, and contribute to the development of environmentally sustainable construction materials consistent with the principles of the circular economy.

2. Management of Chemical Processes: Materials and Experimental Methodology for Assessing Water Resistance and Environmental Safety of Thermal Insulation Materials

The management of chemical processes during the production of thermal insulation materials was based on the systematic control of raw material composition, technological parameters, and physicochemical transformations governing the formation of the material structure [3,7,16,23,28]. Particular attention was paid to the selection of aluminosilicate-containing components, optimization of the chemical composition, regulation of mixing and curing conditions, and monitoring of key process variables affecting pore formation, water resistance, and environmental safety [3,4,28,29]. Such an integrated process management approach ensured stable manufacturing conditions, minimized process variability, and improved the reproducibility and quality of the produced insulation materials.

The experimental methodology for assessing water resistance was based on simulating the prolonged action of an aqueous environment on representative material specimens, followed by a comprehensive evaluation of changes in their physical and mechanical properties [4,24,30]. The investigation included measurements of mass variation, structural integrity, and mechanical strength after immersion in water for a specified exposure period [20,24]. In addition, visual and analytical examination methods were employed to identify structural deterioration, delamination, crack formation, and loss of material integrity resulting from moisture exposure [16,31]. The obtained results were further integrated with the assessment of environmental safety by evaluating the potential release and migration of chemical constituents under moisture conditions. This combined methodology established a direct relationship between the management of chemical production processes, the resulting microstructural characteristics of the materials, their resistance to water-induced degradation, and their environmental performance throughout the expected service life.

Water absorption, expressed as the relative increase in the mass of a specimen after exposure to water, is considered one of the principal indicators characterizing the resistance of thermal insulation materials to water-induced degradation. This parameter reflects the ability of the material to resist moisture penetration into its porous structure and, consequently, serves as an indirect measure of its long-term durability under humid operating conditions. The determination of water absorption was performed in accordance with internationally recognized and national testing standards and recommendations [8,16,30,32]. The parameter describes the percentage increase in specimen mass after immersion in water for a specified exposure period t and is calculated as follows:

$$W\left(t\right)={\displaystyle \frac{m\left(t\right)-m_0}{m_0}}\cdot 100\%$$

(1)

where m₀ is the initial mass of the specimen (g), m(t) is the specimen mass after water exposure for time t (g), and W(t) is the water absorption expressed as a percentage. Higher values of W(t) indicate greater moisture uptake, suggesting increased susceptibility of the material to deterioration of its thermal insulation performance, dimensional stability, and structural integrity.

To quantify the influence of moisture on the mechanical performance of the investigated materials, a strength loss index was introduced. This indicator characterizes the degradation of the material by comparing its mechanical strength before and after exposure to the aqueous environment [4,8,16,30,33]. The index provides an objective assessment of the deterioration of load-bearing capacity resulting from moisture penetration and is determined according to:

$$K_s\left(t\right)={\displaystyle \frac{{\sigma }_0-\sigma \left(t\right)}{{\sigma }_0}}\cdot 100\%$$

(2)

Alternatively, the residual strength ratio may be expressed as:

$$R_s\left(t\right)={\displaystyle \frac{\sigma \left(t\right)}{{\sigma }_0}}$$

(3)

where σ₀ denotes the initial compressive or tensile strength (MPa), while σ(t) represents the corresponding strength after water exposure for time t (MPa). Whereas the strength loss index reflects the degree of mechanical degradation, the residual strength ratio directly indicates the proportion of the original mechanical properties retained after moisture conditioning.

Since water-induced degradation affects not only the mechanical properties but also the internal structure of thermal insulation materials, an integrated structural degradation index was proposed to comprehensively evaluate the overall deterioration process. This parameter combines the effects of moisture absorption, mechanical degradation, and visually observable structural damage into a single assessment criterion [8,16,30,34]. Visual observations included the appearance of cracks, delamination, swelling, loss of cohesion, pore collapse, and other structural defects caused by prolonged interaction with water. The structural degradation index is defined as:

$$D\left(t\right)=\alpha W\left(t\right)+\beta K_s\left(t\right)+\gamma I_v\left(t\right)$$

(4)

where Iᵥ(t) is the visual damage score determined using a predefined rating scale (0–1 or 0–5), while α, β, and γ are weighting coefficients established either by expert evaluation or by normalization procedures. The integrated degradation index D(t) enables simultaneous consideration of physical, mechanical, and morphological changes occurring during water exposure, thereby providing a more comprehensive characterization of the degradation mechanisms than individual indicators alone.

To evaluate the overall resistance of thermal insulation materials to water-induced deterioration, an integrated water resistance index was introduced. This parameter represents the inverse measure of the cumulative structural and physicomechanical degradation and serves as a comprehensive indicator of the material’s durability under humid service conditions [16,30,35]. The integrated water resistance index is expressed as:

$$R_w\left(t\right)={\displaystyle \frac{1}{1+D\left(t\right)}}$$

(5)

For practical engineering applications, a simplified expression may also be employed:

$$R_w\left(t\right)=a\cdot R_s\left(t\right)+b\cdot \left(1-W\left(t\right)\right)$$

(6)

where a and b are weighting coefficients reflecting the relative contribution of residual mechanical strength and water absorption to the overall water resistance of the material.

Values of the integrated water resistance index R_w(t) approaching unity indicate excellent resistance to moisture penetration, preservation of structural integrity, and maintenance of the functional properties of the investigated thermal insulation material. Conversely, values approaching zero correspond to severe structural deterioration accompanied by substantial moisture absorption and pronounced mechanical degradation. Therefore, an increase in water absorption W(t) and strength loss Kₛ(t) is directly associated with a reduction in R_w(t), indicating progressive deterioration of the material under prolonged exposure to water. The proposed system of performance indicators provides a comprehensive framework for evaluating the combined effects of moisture on the physical, mechanical, and structural behavior of thermal insulation materials and establishes a quantitative basis for comparing their long-term durability and environmental performance.

The economic efficiency of the developed thermal insulation composites was evaluated based on the material composition, consumption of individual components, and the experimentally determined performance characteristics. The assessment was aimed at identifying the formulation providing the most favorable combination of material cost and functional performance. Such a cost-effectiveness approach is relevant for thermal insulation materials, for which economic feasibility should be considered together with the achieved thermal and functional properties [36,37,38]. In particular, previous studies have demonstrated the applicability of economic assessment for comparing insulation materials with different compositions and performance characteristics [36,37]. Since the investigated compositions differ in cement content, water-to-cement ratio, aluminum powder content, and the presence of polymer-modifying additives, these parameters were considered as the main cost-forming factors.

For the preliminary economic assessment, the material cost was calculated as the sum of the costs of the individual components used in each formulation. A component-based approach to the economic assessment of insulation materials has also been applied in previous research, where the costs of individual raw materials were used to determine the overall cost of the developed insulation mortar [36]. The cost of one batch was determined according to:

$$C_b={{\displaystyle \sum }}_{i=1}^n{m}_i{P}_i,$$

(7)

where c_b is the material cost of one laboratory batch, m_i is the mass of the i-th component, and P_i is its unit price. The water consumption was calculated from the corresponding water-to-cement ratio. For compositions containing polymer modifiers, an indicative allowance for the polymer component was included according to the level of modification. The calculated batch costs were subsequently normalized to the mass of the prepared material:

$$C_m={\displaystyle \frac{C_b}{M_b}},$$

(8)

where C_m is the estimated material cost per kilogram and M_b is the total mass of the corresponding formulation.

This preliminary cost assessment provides a basis for comparing the economic attractiveness of the investigated formulations while avoiding the assumption that the lowest material cost necessarily corresponds to the best-performing insulation solution. Previous research has emphasized the importance of considering the cost-effectiveness of thermal insulation materials in conjunction with their thermal performance and applicability [37,39]. More comprehensive assessments may additionally incorporate energy savings, environmental impacts, and economic payback over the service life of the insulation material [38,40].

A total of ten thermal insulation specimens with different mix compositions were manufactured to investigate their resistance to water-induced degradation. All specimens were subjected to identical water immersion tests, followed by visual and structural assessment to evaluate changes in their physical condition. Representative specimens (Nos. 4 and 7) are shown in Figure 1, demonstrating the typical appearance of the materials before testing and after prolonged exposure to water. The visual observations provide qualitative evidence of the influence of moisture on the structural integrity and surface morphology of the investigated thermal insulation materials and complement the quantitative results obtained from the water resistance measurements.

Figure 1 presents the visual condition of the investigated thermal insulation specimens before and after immersion in water. Prior to testing (Figure 1a), the specimens exhibited a uniform surface texture and regular geometry without visible defects. The side view after exposure (Figure 1b) indicates that the specimens generally retained their geometric integrity, although slight changes at the edges can be observed. The top view after immersion (Figure 1c) demonstrates minor variations in surface color and texture, suggesting the influence of moisture on the material structure. More pronounced degradation is visible in Figure 1d, where one of the specimens exhibits localized surface damage associated with moisture-induced deterioration. These observations confirm that prolonged exposure to water affects the physical condition of thermal insulation materials, while the degree of degradation depends on their composition and structural characteristics.

The selection and characterization of the investigated thermal insulation materials were performed within the framework of chemical process management aimed at improving water resistance and environmental safety. The evaluation was based on a comprehensive analysis of the materials’ microstructure, physicomechanical properties, chemical stability, and expected performance under moisture exposure. This approach enabled the identification of the key material characteristics governing water-induced degradation and provided the basis for developing an integrated methodology for assessing both durability and environmental performance.

The investigated materials comprised porous and fibrous thermal insulation products widely used in modern building construction due to their high thermal efficiency and low density. These materials were selected because their highly developed pore structure makes them particularly susceptible to moisture penetration, structural degradation, and deterioration of thermal insulation performance during long-term operation. Representative specimens were chosen considering their microstructural characteristics, density, manufacturing technology, and anticipated service conditions to ensure the reliability and reproducibility of the experimental results.

The environmental safety assessment was incorporated into the overall management strategy for chemical production processes and focused on evaluating the potential environmental impact of the materials investigated throughout their service life. Attention was devoted to the possible release and migration of chemical constituents following prolonged moisture exposure and progressive material degradation. The assessment considered the interaction between the material and the aqueous environment, enabling the identification of potential environmental risks associated with the leaching of hazardous substances. The obtained results were interpreted in accordance with relevant international standards and environmental regulations, providing an objective basis for determining the environmental acceptability of the investigated thermal insulation materials. Consequently, the proposed management-oriented methodology establishes a direct relationship between production process control, material quality, long-term water resistance, and environmental safety, thereby supporting scientifically justified decision-making in the development of sustainable thermal insulation materials.

3. Results and Discussion of Chemical Process Management and Water Resistance Assessment

As discussed in the previous sections, the resistance of thermal insulation materials to water-induced degradation represents one of the most important performance indicators governing their long-term reliability and service life. From the perspective of chemical process management, water resistance is not merely a material property but rather the outcome of controlled technological operations, including the selection of raw materials, optimization of chemical composition, regulation of mixing and curing conditions, and stabilization of pore formation during manufacturing. Effective management of these chemical processes directly determines the ability of the final product to preserve its structural integrity, mechanical strength, and thermal insulation performance under prolonged exposure to moisture. Consequently, improving water resistance should be considered an integral objective of production process management rather than solely a post-production quality characteristic.

In addition to ensuring moisture resistance, the management of chemical processes must simultaneously provide the required thermal insulation performance of the manufactured materials. The thermal conductivity of insulation products is strongly influenced by their microstructure, pore distribution, density, and phase composition, all of which are formed during the production process and may subsequently change as a result of moisture penetration. Therefore, comprehensive experimental investigations were carried out to evaluate the thermal conductivity of the developed insulation materials while considering both their initial structural characteristics and the progressive degradation caused by water exposure. This integrated approach made it possible to establish the relationship between process-controlled manufacturing parameters, moisture-induced structural transformations, and changes in heat-transfer properties, thereby providing a scientific basis for optimizing chemical process management to simultaneously improve water resistance, thermal efficiency, and environmental safety throughout the service life of the investigated materials.

3.1. Experimental Investigation of the Water Resistance of Thermal Insulation Materials

The water susceptibility of the investigated material compositions was determined experimentally by evaluating their mass change after exposure to water. Prior to testing, each specimen was weighed to determine its initial dry mass, after which the samples were immersed in water for a predetermined period under controlled experimental conditions. Following exposure, the specimens were removed from the water, gently drained to eliminate excess surface moisture, and weighed again. The difference between the initial and final masses was used to quantify the degree of water uptake. The mass increase, expressed as a percentage of the initial dry mass, was adopted as a quantitative indicator of the water susceptibility of the material. This parameter provides a direct measure of the extent to which moisture penetration and water absorption affect the physical stability of the developed thermal insulation compositions.

The experimental tests were performed according to a unified procedure developed based on previously established stability criteria [3,4]. To ensure the reliability, reproducibility, and comparability of the obtained results, all specimens were tested under identical experimental conditions. In particular, the temperature of the aqueous medium, the ratio between the specimen mass and the volume of water, and the duration of water exposure were kept constant for all investigated compositions. The samples were prepared and tested using the same procedure, thereby minimizing the influence of uncontrolled experimental factors. Such standardization made it possible to attribute the observed differences in water susceptibility primarily to variations in the composition and proportions of the constituent components rather than to differences in testing conditions. The obtained mass-change values were subsequently used for comparative assessment of the water resistance of the developed materials.

Water susceptibility was determined by ten experimental compositions formulated through systematic variation of the principal formulation components. The experimental results obtained for all ten compositions, together with the calculations performed using the mathematical framework presented in Section 2 of this paper, are summarized in Table 1. The selected experimental design provides a basis for identifying relationships between the formulation parameters and the resulting resistance to water saturation. In addition to enabling a direct comparison of the investigated compositions, the obtained dataset was used to assess the applicability of the proposed mathematical model for describing the degradation behavior of thermal insulation materials under moisture exposure. The combination of experimental measurements and mathematical analysis makes it possible to identify the compositions providing improved water resistance and to establish the contribution of individual formulation parameters to the overall stability of the material.

To visualize the influence of the main formulation parameters on the water susceptibility of the thermal insulation material, a three-dimensional response surface is presented in Figure 2. The surface was constructed based on the results of ten experimental tests and characterizes the variation in water susceptibility, W(t), as a function of the water-to-cement ratio (W/C) and aluminosilicate powder content. The obtained values of W(t) range from 2.1% to 6.8%. The color scale provides an additional representation of the intensity of the water susceptibility response, with blue and cyan regions corresponding to lower W(t) values, whereas yellow, orange, and red regions indicate progressively higher values. The experimental points plotted on the response surface demonstrate good consistency with the general trend of the modeled dependence and provide a visual representation of the effect of the investigated formulation parameters.

Analysis of the response surface demonstrates a pronounced and systematic increase in water susceptibility with increasing both the water-to-cement ratio and the aluminosilicate powder content. The lowest value of W(t), equal to 2.1%, was obtained for the composition characterized by a W/C ratio of 0.55 and an aluminosilicate powder content of 0.14 g (Test No. 1). As the W/C ratio and aluminosilicate powder content increase, the response surface gradually shifts from the blue–green region toward the yellow–red region, indicating an increase in the material’s susceptibility to water penetration. The highest experimentally determined value, 6.8%, was observed for Test No. 10 at a W/C ratio of 0.65 and an aluminosilicate powder content of 1.07 g. Thus, within the experimental range investigated, simultaneous increases in both parameters are associated with a deterioration in the water resistance of the developed thermal insulation compositions.

The observed dependence can be attributed to the combined influence of the mixture’s water content and the gas-forming action of aluminosilicate powder during material formation. An increase in the W/C ratio can contribute to the formation of a more developed pore structure after hardening, potentially facilitating water penetration into the material. At the same time, increasing the aluminosilicate powder content intensifies the formation of gas-generated pores, which may increase the open porosity and, consequently, the ability of the material to absorb water. The progressive increase in W(t) from 2.1% to 6.8% therefore indicates that the combined variation of these parameters has a substantial effect on the moisture sensitivity of the thermal insulation compositions. These results confirm the importance of controlling both the W/C ratio and aluminosilicate powder content when optimizing the formulation for improved water resistance and providing an experimental basis for further analysis using the proposed mathematical model.

To quantitatively describe the relationship between the formulation parameters and the water susceptibility of the developed thermal insulation material, a second-order response surface regression model was considered. The proposed model accounts for both the individual effects of the water-to-cement ratio and aluminosilicate powder content, as well as their nonlinear and interaction effects:

$$W\left(t\right)=a+b_1\left(W/C\right)+b_{2}A+b_3{\left(W/C\right)}^2+b_4{A}^2+b_5\left(W/C\right)A,$$

(9)

where $W\left(t\right)$is the water susceptibility of the material (%), W/C is the water-to-cement ratio, A is the aluminosilicate powder content (g), and $a,b_1,b_2,b_3,b_4,$and $b_5$ are empirical regression coefficients. The linear terms describe the primary contribution of each formulation parameter, whereas the quadratic terms account for possible nonlinear changes in the response. The interaction term (W/C). $A$characterizes the combined effect of the two parameters and makes it possible to determine whether their simultaneous variation produces a response different from the sum of their individual effects. Such a model is therefore more suitable for describing the response surface shown in Figure 2 than a purely linear relationship.

The use of a mathematical response surface model is necessary because the experimental results demonstrate a systematic dependence of water susceptibility on both the water-to-cement ratio and aluminum powder content. The model provides a quantitative basis for evaluating the contribution of individual formulation parameters and their interaction, as well as for identifying composition ranges associated with improved water resistance.

Interpretation of the obtained response surface indicates a systematic increase in water susceptibility with increasing water-to-cement ratio and aluminum powder content. As shown in Figure 2, the lowest water susceptibility, 2.1%, was obtained at a W/C ratio of 0.55 and an aluminum powder content of 0.14 g, whereas the maximum value of 6.8% was recorded at a W/C ratio of 0.65 and an aluminum powder content of 1.07 g. The response surface therefore demonstrates that both formulation parameters contribute to the moisture sensitivity of the material. Within the investigated experimental range, the effect becomes particularly pronounced when both parameters are simultaneously increased, indicating a combined influence on the pore structure and water penetration capacity of the composite.

The observed dependence can be explained by the structural changes occurring during material formation and hardening. An increase in the water-to-cement ratio generally promotes the development of a more porous structure after hardening, with a corresponding increase in the volume and connectivity of pores through which water can penetrate. At the same time, increasing the aluminum powder content intensifies the gas-forming process and contributes to the formation of additional pores. If these pores become interconnected, the resulting increase in open porosity facilitates water penetration and leads to higher values of W(t). Thus, the experimentally observed increase in water susceptibility is associated with the combined effect of the initial water content and gas-forming agent on the final pore structure of the thermal insulation composite.

Across the ten investigated compositions, the water susceptibility varied from 2.1% to 6.8% by mass, depending on the formulation parameters, including the cement-to-filler ratio, water-to-cement ratio, aluminum powder content, and the presence of polymer-modifying additives. The compositions characterized by lower W(t) values, particularly within the range of approximately 2.1–3.0%, correspond to formulations with a more favorable balance between the binder and microsphere components and with polymer additives present. The latter can contribute to improved cohesion of the matrix, modification of the pore-wall structure, and reduction of capillary water penetration. In contrast, the compositions with W(t) values of approximately 5.5–6.8% are associated with higher aluminum powder contents and increased W/C ratios, which promote a more developed pore structure and, consequently, greater water uptake.

The obtained results demonstrate that water susceptibility should be considered as an important criterion when optimizing porous thermal insulation composites. Although the formation of a highly porous structure is beneficial for reducing density and thermal conductivity, excessive development of open and interconnected pores may adversely affect moisture resistance and long-term stability. Therefore, the formulation should be selected by balancing the requirements for low density, low thermal conductivity, mechanical performance, and resistance to moisture penetration. The combined analysis of the experimental data and the response surface provide a quantitative basis for identifying formulation ranges that ensure a more favorable balance between thermal insulation performance and water resistance.

The results also confirm that the performance of the developed thermal insulation material is determined not by the content of an individual component alone, but by the combined interaction of the formulation parameters and the resulting material structure. In particular, the aluminum silicate microspheres contribute to the formation of a lightweight porous structure and can reduce thermal conductivity, while excessive porosity may result in lower mechanical strength and increased moisture sensitivity. Polymer and chemical modifiers can improve matrix homogeneity and reduce the accessibility of capillary pathways for water penetration. Consequently, the optimal composition should be determined by considering the interrelated effects of the binder content, microsphere concentration, W/C ratio, gas-forming agent, and modifying additives.

The experimental findings make it possible to formulate a composition–structure–property relationship for the investigated thermal insulation composites. Within the study formulation range, control of the W/C ratio and aluminum powder content is particularly important because these parameters directly affect the development of the pore structure and, consequently, the water susceptibility of the material. The obtained results provide a basis for further optimization of the compositions with respect to their density, thermal conductivity, mechanical strength, and moisture resistance. In particular, the experimentally identified formulations with a density of up to 550 kg/m³ and a thermal conductivity below 0.12 W/(m·K) demonstrate the potential for practical application in building envelope structures, provided that their mechanical and durability characteristics satisfy the corresponding operational requirements.

Overall, the study establishes a quantitative relationship between the formulation parameters, pore structure, and water susceptibility of the developed thermal insulation composites. The obtained results demonstrate that controlling the W/C ratio, aluminum powder content, and modifying additives is essential for achieving an appropriate balance between low density, thermal insulation efficiency, mechanical performance, and moisture resistance. The proposed response surface approach provides a useful basis for predicting the behavior of the material and selecting formulation ranges with improved operational stability.

3.2. Assessment of the Environmental Safety of the Developed Thermal Insulation Materials.

Based on the experimental results demonstrating a variation in the water susceptibility of the investigated thermal insulation compositions from 2.1% to 6.8% by mass, a set of formulation and technological measures can be considered to improve their environmental performance and long-term stability. The first and most important approach is the optimization of the material composition at the design stage with the aim of developing a sufficiently closed and stable pore structure. Such optimization can limit water penetration, reduce moisture-induced degradation, and potentially decrease the migration of fine particles or soluble components from the material during prolonged exposure to moisture. Attention should be given to controlling the water-to-cement ratio and the content of the gas-forming agent, as these parameters strongly influence the development and connectivity of the pore structure and, consequently, the material’s susceptibility to water penetration.

A second important approach involves the use of functional modifiers and protective additives to improve the stability of the composite microstructure and reduce its interaction with the aqueous environment. The incorporation of polymeric components at optimized concentrations can contribute to improved matrix cohesion, reduced accessibility of capillary pathways, and lower water penetration. In addition, surface hydrophobic treatments may be considered for applications where the material is exposed to periodic or elevated moisture levels. Such treatments can form a protective barrier at the material surface, thereby slowing water ingress and reducing the probability of moisture-induced structural degradation. The selection and concentration of modifying components should, however, be optimized together with the basic formulation parameters to avoid adverse effects on density, thermal conductivity, mechanical strength, and the overall environmental performance of the composite.

A third aspect concerns the management of the material throughout its service life, particularly under operating conditions characterized by elevated or cyclic humidity. Considering the experimentally established relationship between formulation parameters and water susceptibility, compositions with simultaneously high water-to-cement ratios and increased aluminum powder contents should be used with caution in areas subjected to direct or periodic moisture exposure. Appropriate design solutions, including protection against direct water ingress and adequate moisture management within building envelope systems, can contribute to maintaining the structural integrity and functional properties of the insulation layer. In addition, periodic technical inspection of insulated building elements may be recommended for applications with significant moisture exposure. Such monitoring can help identify early signs of deterioration and provide a basis for timely maintenance or replacement of the insulation material.

A fourth component of the proposed approach is the incorporation of water susceptibility into the environmental and performance assessment of thermal insulation composites. The established composition–structure–property relationships provide a basis for considering water susceptibility as an additional indicator of material stability alongside density, thermal conductivity, and mechanical strength. However, the experimentally determined range of 2.1–6.8% should not itself be interpreted as a universal environmental safety threshold, since such limits require additional validation through long-term durability tests, leaching assessments, and application-specific regulatory requirements. Therefore, further research should focus on establishing quantitative relationships between water susceptibility, structural degradation, and the potential release of material constituents under realistic environmental conditions. Such an approach would enable a more comprehensive assessment of the environmental performance of the developed composites throughout their service life and at the end-of-life stage.

The results indicate that environmental safety of porous thermal insulation composites should be addressed through an integrated approach combining formulation optimization, pore-structure control, moisture protection, and life-cycle monitoring. The experimentally established dependence of water susceptibility on the W/C ratio and aluminum powder content provides a practical basis for selecting compositions with improved moisture resistance. At the same time, assessment of environmental safety should extend beyond water susceptibility and include long-term durability and potential leaching behavior. This approach is particularly relevant for composites incorporating secondary raw materials, as it combines resource efficiency with the need to ensure stable and environmentally responsible performance throughout the material life cycle.

3.3. Economic and Environmental Assessment

To assess the economic feasibility of the developed thermal insulation compositions, a preliminary material-cost analysis was performed for all ten experimental formulations. The assessment was based on the consumption of the individual components and their respective unit costs. Since the investigated formulations differ in cement content, water-to-cement ratio, aluminum powder content, and the presence of polymer modifiers, these parameters were considered the principal cost-forming factors using the equations 7, 8.

In accordance with the scaling principle applied to the water-to-cement ratio, the amount of water was adjusted proportionally to the cement content for each formulation. The resulting material cost was subsequently expressed per kilogram of mixture. For an additional volumetric comparison, a reference density of 550 kg/m³ was adopted, corresponding to the upper density value established for the developed thermal insulation composites. The resulting estimated economic indicators are summarized in Table 2. For conversion from Ukrainian hryvnia to euro, the reference exchange rate of 51.27 UAH/EUR was used [41].

The calculations indicate that the estimated material cost normalized to the mixture mass ranges from approximately €0.120 to €0.161/kg across the ten investigated formulations. The lowest specific material cost was obtained for Composition No. 1, at approximately €0.120/kg, whereas the highest value was obtained for Composition No. 10, at approximately €0.161/kg. When expressed on a volumetric basis using the reference density of 550 kg/m³, the estimated material cost ranges from approximately €66.04 to €88.43/m³.

An important observation is that the composition with the lowest estimated material cost is not simply the composition with the lowest cement content. Although reducing the cement content decreases the contribution of the binder to the total cost, this effect can be offset by the increasing content of relatively expensive functional components, particularly aluminum powder. This explains the progressive increase in the specific material cost observed for compositions with higher aluminum powder contents. Therefore, economic optimization cannot be reduced to minimizing the amount of an individual component and should instead consider the complete formulation.

The economic assessment also demonstrates a favorable relationship between material cost and water susceptibility. Composition No. 1, which has the lowest estimated specific cost of approximately €0.120/kg, also exhibits the lowest experimentally determined water susceptibility, equal to 2.1%. In contrast, Compositions No. 9 and No. 10 exhibit considerably higher water susceptibility values of 6.2% and 6.8%, respectively, together with higher estimated specific material costs of approximately €0.144/kg and €0.161/kg. This coincidence indicates that Composition No. 1 represents a particularly promising formulation for further optimization because it combines relatively low material cost with improved resistance to moisture.

When the material cost is expressed per cubic meter, Composition No. 1 has an estimated cost of approximately €66.04/m³, compared with €88.43/m³ for Composition No. 10. The difference is approximately €22.39/m³, corresponding to a reduction of approximately 25.3% relative to Composition No. 10. This difference demonstrates that optimization of the formulation can have a measurable economic effect, particularly when the material is considered at the scale of building construction.

From an engineering perspective, however, the economic efficiency of the developed composite should not be evaluated solely on the basis of its material cost per kilogram or cubic meter. The developed compositions are characterized by a combination of low density and reduced thermal conductivity. In particular, the experimentally obtained thermal conductivity below 0.12 W/(m·K) and density of up to 550 kg/m³ indicate their potential for use in building envelope structures. The relatively low density can reduce the dead load imposed on structural elements, while the low thermal conductivity can contribute to reducing heat transfer through the building envelope. Consequently, the economic effect may extend beyond the direct cost of the insulation material and include potential savings associated with structural requirements and energy consumption during building operation.

The water susceptibility results provide additional economic consideration. The investigated compositions demonstrated water susceptibility in the range of 2.1–6.8%, with the lowest value obtained for Composition No. 1. Improved resistance to moisture may contribute to maintaining the functional characteristics of porous thermal insulation materials during service and potentially reducing the frequency of maintenance or replacement. However, this potential life-cycle economic effect requires verification through long-term durability and field-scale investigations and should not be interpreted solely from the water susceptibility results.

An additional economic advantage of the proposed approach is associated with the potential use of secondary or waste-derived raw materials in the production of thermal insulation composites. Their incorporation can reduce the demand for virgin raw materials while simultaneously increasing the value of industrial by-products. From the perspective of the circular economy, this provides a combined resource-efficiency and environmental benefit. Nevertheless, the actual economic advantage of secondary raw materials should be assessed using local availability, transportation costs, processing requirements, and quality-control costs.

Overall, the preliminary economic assessment identifies Composition No. 1 as the most promising formulation among the ten investigated compositions. It combines the lowest estimated specific material cost (approximately €0.120/kg), the lowest estimated cost at the reference density (€66.04/m³), and the lowest experimentally determined water susceptibility (2.1%). The results demonstrate that optimization of the formulation can simultaneously improve economic and functional performance. The proposed cost-assessment methodology provides a basis for further techno-economic and life-cycle evaluation of the developed thermal insulation composites, particularly when secondary raw materials are incorporated into their composition.

4. Conclusions

This study established the effect of the main formulation parameters on the water susceptibility and performance of the developed thermal insulation composites. Experimental results obtained for ten formulations demonstrated that water susceptibility varied from 2.1% to 6.8% by mass. The response surface analysis confirmed a systematic increase in water susceptibility with increasing water-to-cement ratio and aluminum powder content. The lowest value of 2.1% was obtained for Composition No. 1 at a W/C ratio of 0.55 and an aluminum powder content of 0.14 g, whereas the maximum value of 6.8% was recorded for Composition No. 10. These results confirm that controlling the W/C ratio and gas-forming agent content is critical for regulating pore structure and moisture resistance.

The obtained composition–structure–property relationships demonstrated that the performance of the thermal insulation composites is determined by the combined effect of the binder, aluminum silicate microspheres, aluminum powder, water content, and polymer modifiers rather than by an individual component. The formation of a controlled porous structure provides the required combination of low density and thermal insulation performance, while excessive development of open porosity increases water susceptibility and may adversely affect mechanical stability. Within the investigated range, the developed materials achieved a density of up to 550 kg/m³ and a thermal conductivity below 0.12 W/(m·K), indicating their potential for application in building envelope structures. Polymer modification additionally contributed to improved structural cohesion and reduced moisture sensitivity.

The preliminary economic assessment demonstrated that formulation optimization can provide a favorable combination of functional and economic performance. The estimated material cost for the investigated compositions ranged from approximately €0.120 to €0.161/kg, corresponding to €66.04–88.43/m³ at a reference density of 550 kg/m³. Composition No. 1 was identified as the most economically favorable formulation, with an estimated material cost of approximately €0.120/kg (€66.04/m³). Importantly, this composition also exhibited the lowest water susceptibility of 2.1%, indicating that the lowest estimated material cost coincided with the most favorable moisture-resistance result among the investigated formulations. The use of secondary or waste-derived raw materials provides an additional potential economic and environmental advantage by reducing the consumption of virgin resources and supporting circular-economy principles.

Overall, the results demonstrate that the developed approach enables the targeted optimization of thermal insulation composites by simultaneously considering water resistance, thermal insulation performance, material density, formulation cost, and environmental sustainability. The identified optimal composition provides a promising basis for further technological development and scale-up. However, the economic assessment presented in this study represents a preliminary material-cost analysis and should be complemented by full-scale production costs, long-term durability testing, leaching assessment, and life-cycle analysis. Further research should therefore focus on validating the identified formulation under realistic temperature and humidity conditions and establishing its long-term environmental and techno-economic performance in building applications.