Self-cleaning and thermally insulating superhydrophobic geopolymer tile

Abstract

The invention relates to an environmentally friendly, mechanically durable geopolymer building material designed for use in the construction industry, characterized by water repellency and self-cleaning properties. Geopolymer materials provide a sustainable alternative to conventional cement-based products by reducing the carbon footprint and energy consumption in construction applications. The produced geopolymer tiles are intended for use in areas exposed to water, such as kitchens, bathrooms, balconies, terraces, and roofs. Through the self-cleaning mechanism, the material remains clean without being affected by environmental contaminants. This technology prevents the adhesion of water droplets to the surface, thereby avoiding moisture accumulation and enhancing resistance against corrosion, cracking, and surface wear. As the material does not absorb water, no thermal bridge forms within its structure, thus reducing heat transfer and contributing to effective thermal insulation and energy efficiency in buildings.

Description

[0001] SELF-CLEANING AND THERMALLY INSULATING SUPERHYDROPHOBIC GEOPOLYMER TILE

[0002] Technical Field

[0003] The present invention relates to a geopolymer-based construction material developed for use in the building and construction industry, which is environmentally friendly, exhibits high mechanical durability, and possesses water-repellent and self-cleaning properties.

[0004] Geopolymer materials represent a significant innovation in the construction sector by reducing the carbon footprint and energy consumption associated with conventional cement-based production. The geopolymer panels produced according to the invention are designed for use in areas exposed to water such as kitchens, bathrooms, balconies, terraces, and roofs. Through their self-cleaning capability, the materials remain clean without being affected by environmental contaminants.

[0005] This self-cleaning mechanism prevents water droplets from adhering to the surface, thereby avoiding the accumulation of water and moisture. As a result, the material demonstrates increased resistance against environmental factors such as corrosion, cracking, and surface wear. Since the material does not absorb water, no thermal bridge forms within its structure, effectively reducing heat transfer and contributing to improved thermal insulation. This feature provides significant energy savings in buildings where heat loss is considerable.

[0006] Furthermore, the production process of geopolymer materials requires no additional thermal input during curing or surface modification reactions, as these processes occur at room temperature. Consequently, the overall carbon footprint is reduced by up to 80% compared to conventional cement manufacturing, while also minimizing energy consumption.

[0007] These materials are considered an ideal alternative for construction companies, architects, and engineers seeking sustainable building solutions. Owing to their environmentally friendly production process and combined properties of thermal insulation, mechanical strength, water repellency, and self-cleaning capability, the invention offers an innovative and sustainable alternative for modem construction applications, particularly in projects emphasizing environmental sustainability and energy efficiency.

[0008] Background Art In the current state of construction materials:

[0009] Concrete is the second most consumed material in the world after water, with an annual consumption exceeding 10 billion tons, making it an indispensable component of modem life (Sun et al., 2018). Rapid urbanization, increasing migration from rural to urban areas, and the continuous demand for new infrastructure such as roads, buildings, bridges, dams, and railways have steadily increased the global demand for concrete.

[0010] The main component of concrete is cement, which is produced in large quantities to meet this demand. Traditionally, Portland cement has been the primary material used in the construction industry. When mixed with water, it hardens and gains binding properties. Concrete is obtained by mixing cement, water, aggregates (such as sand or gravel), and additives, and is widely used in building projects.

[0011] Advantages of Portland cement and concrete include:

[0012] High durability: Concrete exhibits high compressive strength and serves as a long -lasting building material.

[0013] Availability: The raw materials for cement and concrete are readily accessible worldwide. Versatility: It can be produced in various shapes and sizes.

[0014] However, cement production poses major disadvantages in terms of environmental sustainability. It requires large quantities of raw materials such as limestone and clay, leading to the rapid depletion of natural resources. For every ton of conventional Portland cement produced, approximately two tons of raw material are consumed and nearly one ton of greenhouse gases (CO2, NOX, SO2, etc.) are released into the atmosphere (Meyer, 2009; Sarker et al., 2013; Scrivener and Kirkpatrick, 2008).

[0015] Globally, cement production is responsible for approximately two billion tons of greenhouse gas emissions annually, accounting for about 7% of total global emissions (Amran et al., 2020; Arafa et al., 2017; Hamada et al., 2020). These emissions contribute significantly to global warming and climate change. The construction sector as a whole accounts for roughly one-third of total worldwide greenhouse gas emissions (Ruparathna et al., 2016).

[0016] Cement production consumes 12-13% of total global energy generation, while the construction sector overall consumes 40% of global energy and 25% of available water resources (Ruparathna et al., 2016). Global energy demand has increased by 1.8% annually over the past 40 years and is projected to reach 58% of total global energy consumption by 2050 (Nejat et al., 2015).

[0017] Given the limited availability and environmental impact of fossil fuels, the need for alternative renewable energy sources and energy-efficient solutions has become increasingly critical. Therefore, achieving energy savings in buildings through improved efficiency and the use of thermal insulation materials represents a key step toward global sustainability goals.

[0018] State of the art in thermal insulation materials:

[0019] Thermal insulation in buildings generally falls into two main categories: organic-based and inorganic-based insulation materials. Among organic insulation materials, the most common examples are extruded polystyrene (XPS) and expanded polystyrene (EPS). The most widely used inorganic insulation materials are rock wool and glass wool.

[0020] Each of these materials has distinct advantages and disadvantages. While EPS provides high thermal insulation performance and low density (15-30 kg / m3), it prevents building structures from “breathing,” exhibits low mechanical strength, and promotes the formation of moisture and mold within interior walls. Furthermore, as EPS is a combustible material (classified as B2 or B3 under DIN 4102), cladding entire buildings with it may pose serious fire hazards.

[0021] In contrast, fire-resistant insulating paints provide low combustibility but insufficient thermal insulation. Rock wool, on the other hand, provides high thermal insulation and noncombustibility (classified Al under DIN 4102). However, its high density (approximately 150 kg / m3) and elevated production cost represent major disadvantages. Moreover, the production of rock wool requires firing temperatures of 1400-1500 °C, resulting in additional energy consumption and CO2 emissions.

[0022] Although a 4 cm thick rock wool panel provides approximately 14% better thermal resistance compared with a 4 cm EPS panel, its application cost is 55% higher.

[0023] The purpose of the present invention is to produce a building material that achieves thermal insulation equivalent to that of a 4 cm rock wool panel while offering lower production cost, reduced CO2 emissions, and an environmentally friendly manufacturing process. According to the applicant’s research, there is currently no commercially available building material that combines both self-cleaning functionality and effective thermal insulation performance.

[0024] Prior Art and Competing Technologies

[0025] According to market research, no self-cleaning, thermally insulating, and superhydrophobic geopolymer-based building material has been commercially introduced either in Tiirkiye or worldwide. However, several companies and research institutes have been conducting studies on geopolymer technologies and have the potential to develop similar materials in the future.

[0026] Oyak Cement (Tiirkiye): The company has made progress in the production of low-carbon cements and offers environmentally friendly alternatives. It also employs calcined clays and other supplementary materials to reduce environmental impacts. These sustainable material development efforts generally align with the sustainability approach adopted in geopolymer technologies. Relevant patents filed by the company are listed in the corresponding section.

[0027] Kale Seramik (Tiirkiye): Kale Seramik is currently the only company in Tiirkiye producing geopolymer-based tiles using geopolymerization technology. The company manufactures humidity-controlled geopolymer tiles that maintain optimal moisture levels in indoor environments.

[0028] Wagners (Australia): A leading company specializing in the production of geopolymer concrete and materials, offering a broad range of commercial and industrial products.

[0029] Banah UK (United Kingdom): Banah focuses on geopolymer technologies and develops geopolymer materials for various structural and construction applications.

[0030] Zeobond (Australia): An innovative company providing low-carbon and environmentally friendly geopolymer concrete solutions.

[0031] Geopolymer Institute (France): A globally recognized institute engaged in research and development on geopolymer materials and applications, providing various material formulations and technical expertise.

[0032] U.S. Concrete (United States): A company developing geopolymer concrete solutions for various construction applications, focusing on durable and sustainable materials. Known Patents in the Field

[0033] Patent No. TR2021 / 005535 - “Method for Producing Geopolymer Concrete” This patent discloses the production of geopolymer concrete using waste slag. However, no surface modification or water-repellent property is described.

[0034] Patent No. TR2020 / 07215 - “High-Strength Geopolymer Composite Cellular Concrete” This invention relates to high-strength, low-density geopolymer composite cellular concrete compositions and methods. The produced concrete lacks hydrophobicity or thermal insulation features.

[0035] Patent No. TR2020 / 20058 - “Method for Producing Geopolymer Binder”

[0036] This invention concerns the production of geopolymer binders using slag derived from blast furnaces and basic oxygen furnaces during iron and steel manufacturing. The method allows the production of geopolymer binders with high compressive strength that require no thermal, water, or steam curing.

[0037] Patent No. TR2019 / 04809 - “Porous Geopolymer-Based Inorganic Insulation Material” This patent discloses an industrial production process for manufacturing geopolymer tiles. However, the produced tiles do not exhibit water repellency. The present invention introduces innovations by achieving superhydrophobicity simultaneously during the geopolymerization process, ensuring long-term water repellency throughout the entire tile structure rather than only on the surface.

[0038] Patent No. CN110183158A - “Preparation Method of Superhydrophobic Coating” This patent describes a surface modification process using a hydrophobic solution. In contrast, in the present invention, hydrophobicity is imparted during the bulk geopolymerization process, enabling the self-cleaning property to remain even after surface abrasion.

[0039] Patent No. CN105198296 A (B) - “Metakaolin-Based Geopolymer with Superhydrophobic Surface and Preparation Method Thereof’

[0040] This patent also relies on surface modification to achieve water repellency. The invention presented here differs in that hydrophobicity is integrated throughout the bulk structure simultaneously with geopolymerization, ensuring the preservation of self-cleaning functionality even after surface wear.

[0041] Patent No. CN114988734A (B) - “Preparation Method and Application of Silica Fume-Based Geopolymer Composite Hydrophobic Microspheres” According to the patent description, the hydrophobic effect is achieved through a physical surface modification, resulting in limited water repellency.

[0042] Patent No. WO2016131925A1 - “Method for the Long-lasting Hydrophobization and / or Superhydrophobization of Concrete Surfaces”

[0043] This patent concerns a surface coating product designed to make conventional cement-based concrete superhydrophobic. However, surface coatings often lack long-term mechanical durability. The present invention differs in that it employs the geopolymerization technique, which produces significantly lower CO2 emissions than cement-based processes, and provides simultaneous bulk hydrophobicity rather than surface-only treatment.

[0044] Patent No. C A3002273 C - “Engineered Hybrid Cement-based Composition with Increased Wetting Resistance”

[0045] This patent discloses a film-coated cement-based composition to achieve hydrophobicity. The present invention, by contrast, contains no cement and does not rely on surface film coatings; instead, the entire geopolymer matrix is produced to be inherently superhydrophobic.

[0046] Patent No. KR102358366B1 - “Superhydrophobic Emulsion Composition and Superhydrophobic Cement Paste Added Thereto”

[0047] This patent involves a cement-based composition developed to produce superhydrophobic concrete. The present invention differs in that it employs geopolymerization, resulting in a superhydrophobic building material with substantially lower carbon emissions compared to cement-based formulations.

[0048] Summary Of The Invention

[0049] Technical Problem

[0050] The production of cement requires high energy consumption. Raw materials such as limestone and clay are calcined at approximately 1450°C, which demands a substantial amount of energy. This energy, derived mainly from the combustion of fossil fuels, results in significant emissions of CO2 and other greenhouse gases, negatively affecting the environmental sustainability of cement and concrete production.

[0051] Cement manufacturing releases large amounts of greenhouse gases (CO2, NOx, SO2, etc.), with approximately one ton of greenhouse gas emitted per ton of Portland cement produced. This contributes to global warming and climate change, and cement production alone accounts for around 7% of total global greenhouse gas emissions.

[0052] The raw materials required for cement production, such as limestone and clay, are obtained from natural sources. Their continuous extraction leads to resource depletion and environmental degradation. Approximately two tons of raw material are needed to produce one ton of Portland cement, which threatens the sustainable use of natural resources.

[0053] The cement manufacturing process also causes environmental pollution through dust and particulate emissions, water contamination, and damage to natural ecosystems. Waste generated from production facilities contributes to air, water, and soil pollution. Moreover, concrete structures can cause additional environmental impacts during their service life when exposed to chemicals and water.

[0054] Cement and concrete production require large amounts of energy and water. Cement production consumes approximately 12-13% of total global energy output, while the construction industry accounts for around 40% of total energy and 25% of global water consumption. This high demand threatens ecological balance and the sustainable use of natural resources.

[0055] Traditional concrete also exhibits limited chemical resistance. Its durability decreases in acidic or alkaline environments, leading to structural damage and environmental contamination. In addition, the permeability of concrete can cause pollution of water resources and underground water reserves.

[0056] Concrete structures require regular maintenance and repair to ensure long service life. Surfaces exposed to water undergo gradual wear, cracking, and structural damage, which reduce durability and create additional costs. The alkalinity of concrete can cause corrosion of embedded metals, shortening the service life and compromising the safety of structures.

[0057] Conventional concrete also provides poor thermal insulation, thus requiring additional insulation materials to improve energy efficiency in buildings. However, organic polymer- based insulation materials, while offering good thermal insulation, suffer from low mechanical strength, limited breathability, and flammability. In non-breathable buildings, condensation can cause mold and fungal growth, leading to health problems, particularly for children.

[0058] In contrast, inorganic materials such as glass wool and rock wool offer non-combustibility (Al class under DIN 4102) and breathability, but they have high density, are difficult to apply, and require firing at high temperatures (1400-1500°C), leading to additional CO2 emissions and high energy costs.

[0059] Considering these issues, there is an increasing need for environmentally friendly, energyefficient, and sustainable building materials. The disadvantages and environmental impact of traditional cement and concrete production highlight the necessity of developing innovative and sustainable alternatives such as geopolymer materials. Geopolymers provide lower energy consumption, reduced greenhouse gas emissions, high durability, and improved environmental sustainability, offering potential to replace both conventional cement-based materials and thermal insulation products.

[0060] Advantages of the Invention

[0061] Geopolymer materials offer numerous advantages over traditional Portland cement, both in terms of environmental sustainability and material performance.

[0062] Environmental Sustainability

[0063] Geopolymers exhibit a low carbon footprint. Unlike Portland cement, which emits large amounts of CO2 during production, geopolymers are synthesized at low temperatures and require significantly less energy, thereby substantially reducing CO2 emissions. This feature provides a major advantage in combating global warming and climate change.

[0064] Energy consumption is minimized, as geopolymer production does not require high- temperature calcination processes. Traditional cement production relies on energy-intensive calcination, which increases fossil fuel consumption. Geopolymers, produced at room temperature, offer substantial energy savings.

[0065] Geopolymers can be produced using industrial by-products and waste materials, such as metakaolin or other aluminosilicate sources, thus conserving natural resources and contributing to waste management.

[0066] Performance Properties

[0067] Geopolymer materials exhibit high durability and long service life due to their strong chemical resistance to acids, salts, and other aggressive agents. This makes them suitable for harsh environments such as marine structures, sewage systems, and chemical processing facilities. Geopolymer tiles possess low water absorption and superhydrophobic characteristics, providing excellent moisture control and waterproofing performance. These properties make them ideal for applications in humid environments and water-exposed structures.

[0068] Geopolymers demonstrate high compressive and flexural strength, making them suitable for load-bearing structural applications. Compared with conventional concrete, they are more durable and exhibit longer lifespan under mechanical and environmental stress.

[0069] Brief Description of the Drawings

[0070] Figure 1 shows the FTIR spectrum of the geopolymer containing FAS.

[0071] Figure 2 shows the FTIR spectrum of the geopolymer containing OTES.

[0072] Figure 3 shows the surface contact angle image of the geopolymer tile containing FAS.

[0073] Figure 4 shows the surface contact angle image of the geopolymer tile containing OTES.

[0074] Figure 5 shows the effect of abrasion test cycles on the surface hydrophobicity.

[0075] Figure 6 shows the changes in surface water contact angle of the tile after the water droplet impact test.

[0076] Figure 7 shows the EDX spectrum of the geopolymer containing FAS.

[0077] Figure 8 shows the SEM image of the geopolymer containing FAS.

[0078] Figure 9 shows the TGA curve of the geopolymer material.

[0079] Figure 10 shows schematic representations of the tiles produced according to the invention in different geometries.

[0080] Detailed Description of the Invention

[0081] The problems of high energy consumption and carbon emissions associated with conventional cement and concrete production are addressed through geopolymer technology. The ability to produce geopolymers at low temperature using environmentally friendly materials provides both energy savings and a reduction of environmental impact. Furthermore, the resistance of geopolymer tiles to water and moisture ensures long service life and structural sustainability. These characteristics demonstrate that geopolymers are a superior alternative to traditional materials. The production process can be summarized as follows. First, an alkaline solution consisting of sodium silicate, sodium hydroxide, and water is prepared at room temperature. This alkaline solution is thoroughly mixed with metakaolin, which serves as the aluminosilicate source, until a homogeneous mixture is obtained. The mixture is sieved and weighed before being placed into stainless-steel molds prepared for hydraulic pressing. The mixture is shaped under a hydraulic press into tiles with dimensions of 5.5x 11 cm, 5x6 cm, or 10x 10 cm. The production steps are described in detail below.

[0082] Pretreatment of Metakaolin

[0083] • Before the geopolymerization process, metakaolin is dried in an oven at 100°C for 2 hours to remove residual moisture.

[0084] • After drying, the metakaolin is allowed to cool to room temperature naturally before use in the reaction.

[0085] Optimization of Geopolymer Composition

[0086] The composition ratios used in this invention were optimized based on previously published work (Akarken and Cengiz, 2023, QI Journal) and were integrated into the present product design.

[0087] Preparation of the Alkaline Solution

[0088] The alkaline solution required for geopolymerization consists of sodium hydroxide (NaOH), sodium silicate (Na2SiOs, commonly known as water glass), and deionized water. The process strategy involves establishing a sol-gel reaction utilizing the exothermic heat (approximately 45-48°C) released during the reaction between NaOH, sodium silicate, and water, together with the basic medium provided by NaOH and the water present in the solution. When the reaction temperature reaches its maximum point, fluoroalkylsilane (FAS) or octyl triethoxysilane (OTES) is added dropwise to the mixture, thereby initiating the sol-gel process.

[0089] The reaction steps are as follows:

[0090] • NaOH, sodium silicate, and water are placed into a reaction flask and mixed using a magnetic stirrer at 500 rpm.

[0091] • For the production of tiles, 97.5 g of metakaolin is mixed with 3.41 g NaOH, 33.47 g sodium silicate, 4.9 g water, and 2.09 g silane (FAS or OTES). • During mixing, the temperature is continuously monitored with a digital thermometer.

[0092] • When the temperature reaches its maximum value (45-48°C), FAS or OTES is added dropwise over a period of two minutes.

[0093] • The solution is kept under stirring until it cools to room temperature, and the entire process takes approximately two hours.

[0094] • At the end of this period, a hydrophobic alkaline solution is obtained.

[0095] Production of Geopolymer Tiles

[0096] The production steps are carried out in the following sequence:

[0097] • The metakaolin powder, previously dried to remove moisture, is weighed and sieved to prevent agglomeration.

[0098] • The hydrophobic solution cooled to room temperature and the metakaolin are mixed in a granulator or mechanical mixer at a ratio of 30 wt% hydrophobic solution to 70 wt% metakaolin until a homogeneous mixture is obtained.

[0099] • The moist metakaolin powder is sieved again to avoid clumping.

[0100] • The entire batch of moist powder is divided into three portions of approximately 47 g each, corresponding to one tile per portion.

[0101] • Each 47 g batch of hydrophobic metakaolin mixture is placed into the mold of a hydraulic press.

[0102] • The powder is evenly distributed in the mold using a spatula to ensure uniform thickness.

[0103] • The mixture is pressed under a pressure of 400 kg / cm2for one minute.

[0104] • After pressing, the tiles are removed from the mold.

[0105] • To prevent cracking, the tiles are wrapped with stretch film.

[0106] • The wrapped tiles are placed in an oven preheated to 80°C and dried for two hours.

[0107] • After drying, the tiles are allowed to cool naturally to room temperature, completing the production process.

[0108] Mechanical Strength Tests of the Geopolymer Material • The flexural strength of the geopolymer blocks and tiles was measured using a Gabrielli S.R.L CR5 strength testing device.

[0109] • The compressive strength was determined using an Ele International testing machine.

[0110] • The measured strength values are given in Table 1.

[0111] Table 1. Compressive and flexural strength values of FAS- and OTES-modified geopolymer materials

[0112] Structural Characterization of the Geopolymer Materials

[0113] In the FT-IR spectrum shown in Figure 1 for FAS-modified geopolymer tiles, the H-O-H bending vibration is observed at 1641 cm and Si-0 stretching bands appear at 1034 In addition, Si-O-Al vibrations are detected at 546 cm1and 538 and Si-O-Si stretching vibrations at 452 cm1(Abbas et al., 2024). In geopolymer FT-IR spectra, bands around 1643 cm1correspond to O-H stretching vibrations and deformation of hydroxyl groups (Alouani et al., 2019).

[0114] • The similarity of the FT-IR spectra of FAS- and OTES-modified geopolymers indicates the presence of siloxane bonds and hydroxyl groups in each tile. The presence of these bonds supports the formation of the targeted structures in the produced materials (Figures 1 and 2).

[0115] Surface Characterization of the Geopolymer Tiles

[0116] Water contact angle analysis:

[0117] • The first surface test is the water contact angle measurement (Figures 3 and 4). Measurements were performed using a Dataphysics OCA15EC contact angle instrument.

[0118] • The objective is to observe the interaction of water droplets with the tile surfaces and to determine the angle at which the droplet rests on the surface.

[0119] • On hydrophobic surfaces, the contact angle is expected to be as high as possible. If the angle is 90° or greater, the surface is considered hydrophobic; droplets can roll off the surface but still exhibit some adhesion. • If the angle is 150° or greater, the surface is considered superhydrophobic; droplets make minimal contact with the surface and become nearly spherical, enabling easy roll-off.

[0120] Figure 3 shows the water contact angle image of the FAS-modified geopolymer tile, and Figure 4 shows that of the OTES-modified tile. The droplets make very limited contact with the surface and exhibit contact angles of 158° and above. Accordingly, both surfaces can be classified as superhydrophobic.

[0121] Contamination test:

[0122] The second surface analysis is the contamination (self-cleaning) test, which is required to assess the self-cleaning capability. Coal dust was sprinkled onto inclined tiles. Water droplets were then applied to the surfaces, and the extent to which the deposited dust was removed by the droplets was evaluated.

[0123] Appearance of different liquid droplets on the hydrophobic geopolymer surface:

[0124] • To assess the response of the modified geopolymer tiles to various liquids, droplets of coffee, water dyed blue with food coloring, red wine, milk, and tea were deposited onto the material and photographed.

[0125] • Both materials repelled coffee, water, wine, milk, and tea droplets.

[0126] • These observations indicate that the FAS- and OTES-modified geopolymer structures exhibit superhydrophobic character and a water-repellent surface.

[0127] Surface Durability Tests of the Geopolymer Tiles

[0128] To evaluate the durability of superhydrophobicity in service conditions, abrasion, water droplet impact, and water immersion tests were conducted, simulating representative application environments. a. Abrasion test

[0129] A tile was placed on coarse sandpaper (grit 80) and loaded with a 100 g weight. The test comprised three steps per cycle: (1) the tile was pushed along the sandpaper over a 25 cm distance using a ruler; (2) the tile was rotated 90° counterclockwise to stand perpendicular to the initial orientation; (3) the tile was again pushed along the sandpaper. Each set of three steps was defined as one cycle. The water contact angle was measured after each cycle. As shown in Figure 5, despite exposure to coarse sandpaper, the tile remained superhydrophobic at the end of the test. Because hydrophobicity in these tiles is not provided by a surface coating but is integrated throughout the bulk structure, the hydrophobic property is retained even upon surface wear. b. Water droplet impact test

[0130] Another method to analyze mechanical stability was the droplet impact test. Water droplets were released from a height of 45 cm onto a tile inclined at 45°. Droplets of 50 pL impacted the surface at an approximate velocity of 2.8 m / s at a rate of about 120 drops per minute for 9 hours. The surface water contact angle was measured and recorded every hour. In total, approximately 64,800 droplets corresponding to about 3240 mL of water were applied.

[0131] The results are presented in Figure 6. At the end of the 9-hour test, the contact angle decreased from 160° to 154°, and the surface retained its superhydrophobicity, indicating stable performance despite repeated droplet impacts. c. Water immersion test

[0132] In this analysis, a geopolymer tile was immersed in water for 1, 3, 7, 14, and 21 days in a beaker. Prior to immersion, the tiles were dried at 60°C for 12 hours to remove moisture, and their dry masses were recorded. After immersion, the tiles were again dried at 60°C for 12 hours and reweighed to evaluate possible dissolution and water uptake.

[0133] Following immersion for 1, 3, 7, 14, and 21 days, only a 0.012% change in mass was observed. Given the small magnitude, this difference is attributed to incomplete drying or moisture reabsorption under ambient conditions after drying. These results indicate negligible interaction with water even during prolonged exposure. Consistent contact angle values further support long-term retention of surface properties in water-exposed environments.

[0134] EDX and SEM Analyses of the Geopolymer Tiles

[0135] • Considering the composition of metakaolin, its richness in silica and aluminum makes it an ideal raw material for geopolymerization.

[0136] • Examination of the EDX spectra of FAS-modified geopolymer tiles (Figure 7) shows that the material is rich in silica and aluminum.

[0137] • These results support successful incorporation of metakaolin into the geopolymer structure.

[0138] • In the EDX spectrum of the FAS-modified tile (Figure 7), the presence of approximately 2.1% F is attributed to the FAS, indicating its successful incorporation into the geopolymer network.

[0139] • Figure 8 presents the SEM image of the FAS-modified geopolymer tile. As reported by Jaya et al. (2018), metakaolin exhibits a heterogeneous morphology consisting of irregular, plateletlike particles forming a dense matrix.

[0140] • Alouani et al. (2019) similarly reported that metakaolin consists of irregularly shaped particles.

[0141] • In Figure 8, unreacted metakaolin regions are indicated by arrows. The low presence of unreacted metakaolin in the tiles is consistent with the observed hydrophobicity.

[0142] • Local porosity and heterogeneities in geopolymer matrices are considered to arise from the heterogeneous morphology of metakaolin and its correspondingly non-uniform reaction.

[0143] Thermal Performance Tests of the Geopolymer Material

[0144] Thermogravimetric analysis

[0145] • Thermogravimetric analysis (TGA) was performed using a PerkinElmer TGA 8000 at the Central Research Laboratory of OMU.

[0146] • TGA curves were obtained by holding the geopolymer powder sample at 30°C for 2 minutes, then heating from 30°C to 1000°C at 10°C / min, followed by an isothermal hold of 3 minutes at 1000°C (Figure 9).

[0147] • The first major mass loss occurred at 114.9°C, attributed to the gradual release of free water from pores within the geopolymer (Kong, 2010).

[0148] • After the event at 114.9°C, practically no further mass loss was observed; thus, once free pore water was removed, the geopolymer structure remained stable up to 1000°C.

[0149] • At 1000°C, the total mass loss was approximately 9%, arising almost entirely from the water loss at 114.9°C. No additional mass loss was recorded at higher temperatures, indicating high- temperature stability of the structure.

[0150] High-temperature exposure in a muffle furnace

[0151] • An additional method to assess thermal behavior was prolonged exposure at elevated temperatures in a muffle furnace. For this test, geopolymer specimens were produced in 4 * 4 x 4 cm dimensions. The specimens were heated to target temperatures and their properties examined after exposure.

[0152] • The method follows the procedure detailed in the prior work “Fabrication and characterization of metakaolin-based fiber reinforced fire resistant geopolymer” (Akarken and Cengiz, 2023). • A Magma Therm MT1107-B2 muffle furnace was used. The temperature increased at 5°C / min to 200°C, 400°C, and 800°C.

[0153] • Upon reaching each target temperature, specimens were held for 1 hour. Subsequently, the furnace was allowed to cool, and changes in the specimens were examined.

[0154] • Considering the combined heating and cooling periods, the specimens were exposed to elevated temperatures for approximately 8-10 hours in total. In contrast to TGA (short exposure of small powders under controlled flow), this bulk-specimen protocol assesses long-duration thermal stability under more severe conditions, making the results directly relevant to practical service.

[0155] • Table 2 reports compressive strength values (MPa) after high-temperature exposure. As expected, strength decreased with increasing temperature.

[0156] • Prior to testing, the geopolymer exhibited a compressive strength of 108.7 MPa.

[0157] • For the specimen exposed to 200°C, the compressive strength was 75.6 MPa after the heating cycle.

[0158] • According to the American Concrete Institute (Concrete Terminology, 2013), concretes with compressive strength >55 MPa are considered high-performance; therefore, the material exposed to 200°C and subjected to an hour-long hold, followed by furnace cooling, still meets the high-performance range.

[0159] Table 2. Compressive strength of the geopolymer specimen before and after high-temperature exposure (MPa)

[0160] Flame Test

[0161] • Another method used to evaluate the thermal insulation performance of the geopolymer tiles is the flame jet test.

[0162] • The test was conducted in accordance with ISO 2685:1998 (Sarazin et al., 2021).

[0163] • In this method, one surface of the geopolymer tile was exposed to a direct flame while the temperatures of both the flame-exposed (hot) surface and the opposite (cold) surface were measured simultaneously. • The cold-side temperature data were recorded in real time on a computer via thermocouples.

[0164] • The hot-side temperature was measured using both thermocouples and a laser thermometer.

[0165] • When the hot side reached approximately 1000°C under the flame, the maximum temperature recorded on the cold side was 180°C, demonstrating significant thermal resistance of the tile.

[0166] Industrial Applicability

[0167] The invention is suitable for industrial applications and has a wide range of potential uses. The closest comparable industrial product is the “Cura Tile” produced by Kale Seramik, indicating that the manufacturing process of the present invention poses no difficulties for industrial implementation.

[0168] The production process of the geopolymer tiles, with its innovative and environmentally friendly features, offers great potential for the industrial sector. The process begins with the preparation of an alkaline solution, followed by thorough mixing with metakaolin to obtain slightly moist metakaolin powder. The moist powder is then placed into molds under a hydraulic press, pressed, and shaped into tiles. After pressing, the tiles are placed in an oven and dried for two hours, after which they are ready for use. The entire production process is carried out at room temperature.

[0169] The essential equipment required for the production of geopolymer tiles includes one mechanical mixer or granulator and one hydraulic press. Therefore, production can be easily implemented in any existing ceramic factory, construction material facility, or newly established plant.

[0170] Since the entire process is conducted at room temperature, it consumes significantly less energy and emits less carbon dioxide compared to traditional cement-based production methods. Conventional cement manufacturing requires high-temperature calcination, which consumes substantial energy and releases large amounts of CO2. In contrast, the production of geopolymer materials provides an environmentally friendly alternative with low energy requirements and minimal carbon emissions.

[0171] Additionally, the prototype geopolymer tiles developed in this invention possess high mechanical strength, chemical resistance, and superhydrophobic properties, making them highly attractive for use in the construction industry as well as in various other industrial applications. REFERENCES

[0172] Akarken, G., Cengiz, U., 2023. Fabrication and characterization of metakaolin-based fiber reinforced fire resistant geopolymer. Appl. Clay Sci. 232, 106786.

[0173] Amran, Y.H.M., Alyousef, R., Alabduljabbar, H., El-Zeadani, M., 2020. Clean production and properties of geopolymer concrete; A review. J. Clean Prod. 251, 119679.

[0174] Arafa, M., Tayeh, B.A., Alqedra, M., Shihada, S., Hanoona, H., 2017. Investigating the effect of sulfate attack on compressive strength of recycled aggregate concrete. Journal of Engineering Research and Technology 4.

[0175] Alouani, M., Alehyen, S., & El Achouri, M. (2019). Preparation, characterization, and application of metakaolin-based geopolymer for removal of methylene blue from aqueous solution. Journal of Chemistry, 2019.

[0176] Hamada, H., Tayeh, B., Yahaya, F., Muthusamy, K., Al-Attar, A., 2020. Effects of nano-palm oil fuel ash and nano-eggshell powder on concrete. Constr. Build. Mater. 261, 119790.

[0177] Kong D.L.Y., Sanjayan J.G. 2010. Effect of Elevated Temperatures on Geopolymer paste, Mortar and Concrete. Cement and Concrete Research 40(2): 334-339.

[0178] Meyer, C., 2009. The greening of the concrete industry. Cement and Concrete Composites 31, 601-605.

[0179] Nejat, P., Jomehzadeh, F., Taheri, M.M., Gohari, M., Abd. Majid, M.Z., 2015. A global review of energy consumption, CO2 emissions and policy in the residential sector (with an overview of the top ten CO2 emitting countries). Renewable and Sustainable Energy Reviews 43, 843- 862.

[0180] Ruparathna, R., Hewage, K., Sadiq, R., 2016. Improving the energy efficiency of the existing building stock: A critical review of commercial and institutional buildings. Renewable and Sustainable Energy Reviews 53, 1032-1045.

[0181] Sarazin, J., Davy, C. A., Bourbigot, S., Tricot, G., Hosdez, J., Lambertin, D., & Fontaine, G. (2021). Flame resistance of geopolymer foam coatings for the fire protection of steel. Composites Part B: Engineering, 222, 109045. Sarker, P.K., Haque, R., Ramgolam, K.V., 2013. Fracture behaviour of heat cured fly ash based geopolymer concrete. Mater. Des. 44, 580-586.

[0182] Scrivener, K.L., Kirkpatrick, R.J., 2008. Innovation in use and research on cementitious material. Cem. Concr. Res. 38, 128-136.

[0183] Sun, Z., Lin, X., Vollpracht, A., 2018. Pervious concrete made of alkali activated slag and geopolymers. Constr. Build. Mater. 189, 797-803.

[0184] American Concrete Institute, Concrete Terminology, 2013. https: / / www.concrete.org / topicsinconcrete / topicdetail / High%20Performance%20Concrete7se arch=High%20Performance%20Concrete

Claims

CLAIMS1. A pressed geopolymer-based tile comprising a body and at least one outer surface, wherein both the body and said at least one outer surface comprise at least one silane.

2. The tile according to Claim 1, characterized in that said at least one silane is selected from hydrolyzable silanes including methyl trimethoxysilane, ethyl triethoxysilane, propyl trimethoxysilane, propyl triethoxysilane, butyl trimethoxysilane, butyl triethoxysilane, pentyl trimethoxysilane, pentyl triethoxysilane, hexyl trimethoxysilane, hexyl triethoxysilane, heptyl trimethoxysilane, heptyl triethoxysilane, octyl trimethoxysilane, octyl triethoxysilane, nonyl trimethoxysilane, nonylt riethoxysilane, decyl trimethoxysilane, decyl triethoxysilane, undecyl trimethoxysilane, undecyl triethoxysilane, dodecyl trimethoxysilane, dodecyl triethoxysilane, tridecyl trimethoxysilane, tridecyl triethoxysilane, tetradecyl trimethoxysilane, tetradecyl triethoxysilane, pentadecyl trimethoxysilane, pentadecyl triethoxysilane, hexadecyl trimethoxysilane, hexadecyl triethoxysilane, heptadecyl trimethoxysilane, heptadecyl triethoxysilane, octadecyl trimethoxysilane, octadecyl triethoxysilane, nonadecyl trimethoxysilane, nonadecyl triethoxysilane, tetramethoxysilane, tetraethoxysilane, phenyl trimethoxysilane, phenyl triethoxysilane, 1H,1H,2H,2H- perfluorooctyl trimethoxysilane, 1H,1H,2H,2H- perfluorooctyl triethoxysilane, 1H,1H,2H,2H- perfluorononyl trimethoxysilane, 1H,1H,2H,2H- perfluorononyl triethoxysilane, 1H,1H,2H,2H- perfluorodecyl triethoxysilane, 1H,1H,2H,2H- perfluorodecyl trimethoxysilane, vinyltris (2- methoxyethoxy) silane, tris ( trimethylsiloxy) silane, isobutyl ( trimethoxy) silane, trimethoxy (3,3,3-trifluoropropyl) silane, trimethoxy (2-phenylethyl) silane, trimethoxy (3- (methylamino) propyl) silane, trimethoxy (7-octen-l-yl) silane, methyltris (2- methoxyethoxy) silane, and ethoxytris (2 -methoxyphenyl) silane.

3. A production method for obtaining a geopolymer-based tile comprising a body and at least one outer surface, characterized in that the method comprises:- incorporating at least one silane into the structure by applying a sol-gel process in an alkaline solution;- adding at least one clay and / or clay mineral to obtain a mixture; and- pressing the mixture.

4. The method according to Claim 3, characterized in that the alkaline solution is mixed with said at least one silane, followed by the addition of said at least one clay and / or clay mineral to the obtained mixture.

5. The method according to any one of Claims 3 or 4, characterized in that said at least one silane is selected from the group consisting of methyl trimethoxysilane, ethyl triethoxysilane, propyl trimethoxysilane, propyl triethoxysilane, butyl trimethoxysilane, butyl triethoxysilane, pentyl trimethoxysilane, pentyl triethoxysilane, hexyl trimethoxysilane, hexyl triethoxysilane, heptyl trimethoxysilane, heptyl triethoxysilane, octyl trimethoxysilane, octyl triethoxysilane, nonyl trimethoxysilane, nonyl triethoxysilane, decyl trimethoxysilane, decyl triethoxysilane, undecyl trimethoxysilane, undecyl triethoxysilane, dodecyl trimethoxysilane, dodecyl triethoxysilane, tridecyl trimethoxysilane, tridecyl triethoxysilane, tetradecyl trimethoxysilane, tetradecyl triethoxysilane, pentadecyl trimethoxysilane, pentadecyl triethoxysilane, hexadecyl trimethoxysilane, hexadecyl triethoxysilane, heptadecyl trimethoxysilane, heptadecyl triethoxysilane, octadecyl trimethoxysilane, octadecyl triethoxysilane, nonadecyl trimethoxysilane, nonadecyl triethoxysilane, tetramethoxysilane, tetraethoxysilane, phenyl trimethoxysilane, phenyl triethoxysilane, 1H,1H,2H,2H- perfluorooctyl trimethoxysilane, 1H,1H,2H,2H- perfluorooctyl tri ethoxy silane, 1H,1H,2H,2H- perfluorononyl trimethoxysilane, 1H,1H,2H,2H- perfluorononyl triethoxysilane, 1H,1H,2H,2H- perfluorodecyl triethoxysilane, 1H,1H,2H,2H- perfluorodecyl trimethoxysilane, vinyltris(2- methoxyethoxy) silane, tris( trimethylsiloxy) silane, isobutyl ( trimethoxy) silane, trimethoxy (3,3,3-trifluoropropyl) silane, trimethoxy (2-phenylethyl) silane, trimethoxy (3- (methylamino)propyl) silane, trimethoxy (7-octen-l-yl) silane, methyltris (2- methoxyethoxy) silane, and ethoxytris (2 -methoxyphenyl) silane.

6. The method according to any one of Claims 3 to 5, characterized in that said at least one clay and / or clay mineral is selected from bentonite, kaolin, metakaolin, sepiolite, kaolinite, halloysite nanotubes, altered granodiorite, montmorillonite, illite, vermiculite, smectite, beidellite, mica, saponite, rectorite, chlorite, attapulgite, SiCh, their derivatives, modified forms, or combinations thereof, all of which contain Al and Si atoms.

7. The method according to any one of Claims 3 to 6, characterized in that said at least one silane is used in an amount ranging from 1.45% to 4.45% by weight relative to the total weight of the composition.

8. The method according to any one of Claims 3 to 7, characterized in that said at least one clay mineral is used in an amount ranging from 65% to 70% by weight relative to the total weight of the composition.

9. The method according to any one of Claims 3 to 8, characterized in that the prepared composition comprises 2-3% by weight of SiCWAbCh and 0.12-0.25% by weight of Na2O / SiO2.

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