Lightweight construction material and panel comprising it

Abstract

A lightweight building material based on gypsum or plaster, characterized in that it comprises a curable matrix comprising, in an integrated manner: - 90-97.5% by mass of a mixture of water and a gypsum or plaster-based binder, and - 2.5-10% by mass of an alcoholic emulsion of an elastomer.

Description

Lightweight construction material and panel comprising it TECHNICAL SECTOR The present invention is related to the construction sector, materials technology, and industrial technology and production. Specifically, the present invention relates to a new lightweight construction material incorporating rubber waste. This lightweight construction material is particularly suitable for use in the manufacture of suspended ceiling panels in residential rooms, commercial premises, or any other space that may accommodate people, as well as for the production of panels or blocks for use as partition walls, linings, or interior partitions. BACKGROUND OF THE INVENTION Gypsum-based composite materials have been well-known and used in construction since antiquity. Their primary raw material is gypsum, a sedimentary rock formed by chemical precipitation with the composition CaSO₄·2H₂O, also known as gypsum dihydrate. Plaster of Paris is a specific type of powdered material, characterized by its whiteness and fine grind, with a particle size rarely exceeding 0.2 millimeters. These building materials set and harden upon contact with water through an exothermic reaction, which is beneficial in promoting the evaporation of any chemical agents that may have been introduced during the manufacturing process. Generally speaking, plasters without additives have a fast setting time of approximately 15 minutes, good adhesion to ceramic surfaces, and excellent hygrothermal regulation. For all these reasons, these materials have been widely used as interior wall coverings and as materials for manufacturing prefabricated interior panels and slabs. Additionally, in general terms they are characterized by having a minimum flexural strength of 1 MPa and a compressive strength of 2 MPa, with a variation in surface hardness inversely proportional to the water content of the mixture, as well as good thermoacoustic behavior and no reaction to the action of fire. However, increasingly stringent quality requirements and the growing industrialization of the construction sector have driven research into the development of new plaster products that improve the functionality of these materials and adapt to the evolving demands of the market. In this regard, the on-site application of plaster materials is becoming less frequent due to the difficulty in finding skilled labor, the need to reduce construction time, and the need to minimize the high volume of solid waste generated on construction sites. Therefore, these plaster-based materials are now primarily used to manufacture prefabricated elements that facilitate on-site assembly and offer good performance, such as partition walls, interior partitions, and suspended ceiling panels, among other applications. However, although these prefabricated plaster composites are now widely used in the building and civil engineering sectors, their integration into this market has been gradual and not without difficulties. Initially, these materials had to contend with a very traditional industrial sector that perceived these lightweight boards and panels as fragile, with low load-bearing capacity and inconsistent behavior at the joints. Many of these problems have been solved because construction systems made with these prefabricated elements are simpler to implement than traditional ones. Reinforcing fibers have been incorporated into the plaster matrix to improve its deformation capacity and resistance to breakage under bending stress. Furthermore, the use of lightweight aggregates has improved the thermal resistance of these composites and reduced their density, thus enhancing the energy efficiency of these construction solutions and lightening the final weight of the manufactured pieces. Therefore, although these additives can be beneficial, their use is contingent upon the final workability of the mixture, its texture and surface finish, variations in the physical and mechanical properties of the original compound, and the maximum amount permitted by the base compound during the manufacturing process. These additives, added in both solid and liquid states, have been previously studied by various researchers. The following are some relevant examples regarding the use of gypsum-based materials suitable for the production of construction materials, which can be used in the preparation of prefabricated elements and which are related to the material that is the subject of this invention: Application JP2002004536A describes the use of shredded fragments of discarded tire to join them with plaster to form a layered material, which is coated on its surface and forms plate-like objects. Application PT103824A refers to gypsum composite materials of varying quality that incorporate byproducts of industrial processes. These materials include cork granules as a lightweight agent and recycled tire textile fibers in percentages of up to 50% by volume, forming products applicable to construction, particularly for making partitions and interior wall coverings. Patent application CN113354377A presents a construction plaster that incorporates powdered rubber during its manufacturing process along with other components. This material offers the advantages of high tensile strength and a high water retention rate, making it a useful method for utilizing mirabilite gypsum. Application ES2732159A1 describes a gypsum material with powdered rubber from end-of-life tires and carbon fiber reinforcement. This results in a material with optimal flexural strength and good thermoacoustic performance. Finally, patent CN107162553A describes a prototype plaster for rendering and its preparation process. This material contains, among other ingredients, 40-42 parts rubber powder, and its characteristics include good adhesion to surfaces, resistance to cracking, and faster application. While it is true that the material of this invention also facilitates the application process for the operator, it is a compound specifically designed for the production of prefabricated elements, and its manufacturing method and process are different, making them distinct. Consequently, there is a need in this technical field for new construction materials based on plaster or gypsum, specially designed for the manufacture of prefabricated, uniform and homogeneous boards and panels that have a lower density and good thermal performance, so that they can adapt to the growing needs of the construction sector. SUMMARY OF THE INVENTION A first object of this invention describes a lightweight building material based on plaster or gypsum. This material can be used for the manufacture of prefabricated interior building elements and has imminent application in the construction sector. In particular, the lightweight construction material based on gypsum or plaster comprises a curable matrix formed, in an integrated manner, by: • 90-97.5% by mass of a mixture of water and a gypsum or plaster-based binding material, and • 2.5-10% by mass of an alcohol-based emulsion of an elastomer. Unlike previous solutions, such as those mentioned in the background section, the present invention describes the use of an elastomer emulsion. The use of the emulsion allows for the creation of an integrated, curable matrix. The integration of the different components refers to the ability to obtain a more homogeneous paste during the kneading process, so that the paste can be distributed more uniformly onto a mold for curing, resulting in a product of superior quality compared to known products. The lightweight building material described above can be used to develop building elements. In a further object, the invention relates to a panel comprising the lightweight building material described herein. A panel according to the present invention is a flat building element, oriented in any direction in space. Thus, a panel can be oriented in a substantially vertical direction, acting, for example, as a wall lining or partition. Additionally, it can also be oriented in a substantially horizontal direction, acting, for example, as a suspended ceiling panel. The lightweight construction material, in its hardened state, presents a more homogeneous and uniform matrix with a decrease in density of approximately 15-40% compared to a known gypsum or plaster material. This innovative lightweight construction material can be manufactured through a process that includes the following stages: a) mix a gypsum-based binding material with water until a homogeneous liquid is obtained; b) add the elastomer emulsion to the homogeneous liquid, resulting in a liquid mixture; c) homogenize the liquid mixture to form a homogeneous paste; and d) cure the homogeneous paste until a lightweight construction material is obtained. The reduction in the density of the resulting material occurs during the curing of the homogeneous paste as a consequence of the synergistic effect between the mixture of gypsum-based binder and water, which generates the exothermic reaction, and the elastomer emulsion used. This synergistic effect gives the construction material greater porosity, resulting in a lighter product. Additionally, the construction material exhibits greater homogeneity and uniformity in its matrix, integrating the elastomer into the matrix of the binding material with good thermal behavior so that it can perfectly adapt to the growing needs of the construction sector. The following references are used in the figures: 1) prefabricated panel 2) Concealed rail in the wall lining for fastening 3) clamping profile 4) auxiliary anchoring structure to false ceiling 5) self-drilling screw 6) upper floor slab 7) Vertical enclosure or partition 8) lateral expansion joint E) Total thickness of the panel e) lateral thickness of the panel e1) first lateral sub-thickness e2) second lateral sub-thickness L) Panel length BRIEF DESCRIPTION OF THE DRAWINGS This document presents, for illustrative and non-limiting purposes, some possible applications of the new binding material developed in the present invention. For example, it shows the possible application of the developed material in the design of prefabricated suspended ceiling panels and its use in modular construction systems. A solution is presented showing a typical prefabricated panel whose dimensions can vary depending on the needs of the manufacturer or construction system. These diagrams are intended to complement the description of the invention in a concise manner. Figure 1 shows a perspective view of a designed lightweight plasterboard panel, with a straight edge finish for attachment by means of rails hidden in the lining. Figure 2 shows a perspective view of an engineered lightweight plasterboard panel, with a stepped edge finish for attachment by concealed side rails, including side edge detail. Figure 3 shows a cross-sectional view of a construction detail of a false ceiling panel with profiles anchored to the upper floor slab and meeting with a partition or vertical enclosure. Figure 4 shows a perspective view of a particular embodiment of a false ceiling panel comprising rails on which a top anchor is mounted. DETAILED DESCRIPTION OF THE INVENTION A first object of this invention describes a lightweight plaster or gypsum material. This material can be used for the manufacture of prefabricated interior construction elements and has imminent application in the construction sector. In particular, the lightweight construction material based on gypsum or plaster comprises a curable matrix formed, in an integrated manner, by 90-97.5% by mass of a mixture of water and a gypsum or plaster-based binder, and 2.5-10% by mass of an alcoholic-based emulsion of an elastomer. In one particular embodiment, the elastomer emulsion comprises, by mass, 5–10% elastomer fraction; 2.5–7.5% peracetic acid (CH3CO3H); and 85–95% ethanol (C2H6O). Ethanol (C2H6O) is a highly volatile, colorless, aliphatic organic chemical compound with a very pungent, ethereal odor and is also flammable. Peracetic acid, for its part, is a colorless organic compound with the formula CHCOH and a characteristic pungent odor. The synergistic effect of these two compounds allows the production of a suitable elastomer emulsion according to the present invention. In particular, a mass percentage composition of the elastomer emulsion may consist of 6% elastomer fraction, 5% peracetic acid, and 89% ethanol. To prepare this emulsion, the mixture should be kept under agitation for a preferred period of 24 hours and then stored in airtight containers. However, once prepared, the emulsion should ideally be used within 48 hours. The preferred use period of 24 hours and the maximum use period of 48 hours should be understood as a reference to the unit of measurement used, where the common reference unit is the day. Therefore, the agitation period can be understood as approximately 20–30 hours. In another particular embodiment, the elastomer particles have a mean diameter such that they remain suspended in the elastomer emulsion. In a more particular embodiment, the mean particle diameter is less than 0.8 mm. Using a larger diameter would cause the particles to precipitate, hindering or even preventing the ethanol / acid mixture from producing the desired compound. Therefore, using a larger diameter would require a longer stirring time compared to an emulsion where the elastomer particles remain in suspension. In another, more specific embodiment, the elastomer used is rubber, and more preferably recycled rubber from end-of-life tires. The recycled rubber from end-of-life tires corresponds to a powder fraction with an average diameter of less than 0.8 mm. It is a dark-colored polymeric material with an angular morphology and a moisture content of less than 0.75% by mass. It should be noted that this type of recycled raw material may contain impurities as a result of the recovery process. However, the content of textile impurities should not exceed 0.50% of the total mass, and the content of steel impurities should not exceed 0.10% by mass. It is important to note that an increase in the rubber emulsion content exceeding 10% could negatively affect the physical and mechanical properties of the designed lightweight construction material, as well as cause difficulties in the setting of the mixture. However, a quantity of less than 2.5% of the total rubber emulsion would not be detrimental to the binder / water mixture, although it does not guarantee that the desired effects will be achieved when combining all the additives. The lightweight plaster of the invention may comprise a recommended quantity of 1 kg of plaster for the execution of the mixtures and application of the percentages indicated above, in order to be able to make the paste with sufficient ease and facilitate the mixing of the components. In a particular embodiment, the gypsum-based binder is an E-35 type plaster or similar, consisting primarily of calcium sulfate hemihydrate and which may contain setting regulators. This type of binder is characterized by a flexural strength greater than 1 MPa and a compressive strength greater than 2 MPa. It is a base material frequently used in the manufacture of prefabricated partition panels and suspended ceiling tiles, as well as for the creation of moldings, wall coverings, and other in-situ applications for building interiors. In one particular embodiment, the binding material further comprises reinforcing fibers. These reinforcing fibers may comprise between 0.1 and 5% of the mass of the building material. These fibers may be of artificial or synthetic origin, such as glass, polypropylene, or nylon fibers, as well as fibers of vegetable origin, such as hemp or coconut. The addition of these fibers improves the final flexural strength of the composites, thus enabling the design of thinner, larger-surface-area prefabricated elements and reducing the risk of brittle fracture. For the use of these fibers, regardless of their artificial or natural origin, premixing with the binder, for example, dry plaster powder, is recommended. Additionally, the amount of water, understood as mixing water, to be added is between 60% and 70% by weight of the plaster content. Mixing water is defined as the amount of water necessary to combine with a gypsum-based binder to obtain a workable mixture that will subsequently harden into a solid piece. That is, in a particular formulation of the lightweight construction material, the water-to-binder ratio by mass is between 0.6 and 0.7. This lightweight construction material has several technical characteristics that distinguish it from other materials currently available on the market. It is characterized by an apparent density, in its hardened state, ranging from 1,200 to 700 kg / m³, preferably between 1,100 and 800 kg / m³, and most preferably between 1,080 and 860 kg / m³. Furthermore, it has a Shore C surface hardness of between 4 and 75 Shore C units, according to ASTM D2240 and ISO 868 standards. This construction material also has a flexural strength of between 1.0 and 2.8 MPa and a compressive strength of between 2.0 and 3.9 MPa, according to UNE-EN 13279-2. Additionally, it has a reduced thermal conductivity coefficient between 0.15 - 0.21 W / m·K, according to the stored hot plate method according to the UNE-EN 12664 standard.These values ​​correspond to measurements taken from 7 days onwards and with samples cured prior to testing at 40 ± 2 ºC and 50 ± 5% relative humidity for 24 hours. The previously described construction material can be used for the development of building elements. Thus, in a further object, the invention relates to a panel (1) that is prefabricated comprising the lightweight construction material described herein. A panel (1) according to the present invention is a flat building element, oriented in any direction in space. Thus, a panel can be oriented vertically, acting, for example, as a partition. Additionally, it can also be oriented horizontally, acting, for example, as a ceiling tile. Figure 1 shows a perspective view of a lightweight plasterboard panel (1) with a straight edge finish for mounting using concealed rails (2) in the wall lining. Figure 2 shows a perspective view of a lightweight plasterboard panel with a stepped edge finish for mounting using concealed side rails, including a side edge detail. In these particular embodiments, the panel (1) can be defined by a length (L) and a total thickness (E). Depending on the curing process used to obtain the construction material, different configurations of the panel (1) can be developed. Thus, Figure 1 shows an embodiment with a straight side, of thickness (e), while Figure 2 refers to an embodiment with a split side, where a first lateral sub-thickness (e1) and a second lateral sub-thickness (e2) are defined. Figure 3 shows a cross-sectional view of a construction detail for securing a suspended ceiling panel (1) with profiles anchored to the upper slab and meeting a partition or vertical enclosure. Figure 4 shows a perspective view of a particular embodiment of a suspended ceiling panel (1) comprising rails (2) on which an upper anchor is mounted. In particular, the upper anchoring system comprises a fastening profile (3), which can be attached to the concealed rail (2) of the panel (1). The fastening profile may include or be attached to an auxiliary structure (4) for anchoring to the suspended ceiling. The auxiliary structure (4) can be attached to a floor slab of the upper floor (6) by means of, for example, a self-drilling screw (5). The arrangement of this panel (1) is carried out leaving a lateral expansion joint (8) with respect to the vertical enclosure or partition (7). As a result of using this lightweight construction material, the hardened product has a more homogeneous and uniform matrix with a density reduction of approximately 15-40%. In other words, a panel (1) like the one described above shows a significant reduction compared to a gypsum or plasterboard panel obtained using traditional methods. The process of developing this innovative building material comprises the following stages: a) mix a gypsum-based binding material with water until a homogeneous liquid is obtained; b) add the elastomer emulsion to the homogeneous liquid, resulting in a liquid mixture; c) homogenize the liquid mixture to form a homogeneous paste; and d) cure the homogeneous paste until a lightweight construction material is obtained. In a particular embodiment of this process, the elastomer emulsion is obtained by magnetic stirring of the elastomer for a period of not less than 24 hours in an airtight container. Additionally, it is advisable to let the homogeneous liquid settle before adding the elastomer emulsion. This allows for initial hydration of the binding material, optimizing the formation of the characteristic crystalline structure of the plaster used. The mixing of the binding material and water can be carried out for 15 to 45 seconds using a figure-eight motion. The mixture should then rest for at least 30 seconds and no more than 60 seconds. Finally, the liquid mixture should be homogenized for 30 to 60 seconds using figure-eight motions until a smooth paste is obtained. Depending on the desired construction material matrix, the manufacturing process can begin with an additional stage, prior to stage a) of mixing, where reinforcing fibers are added to the water or the rest of the binding material in a range of 1-5% by mass relative to the total weight of the binding material. In a preferred embodiment, it is advisable to carry out the mixing at ambient temperatures between 15-25 °C. Excessive heat can cause excessive evaporation of the mixing water, resulting in poor hydration of the binding material. Conversely, very low temperatures slow down the setting process and can negatively affect the curing of the material. The curing process for the production of a lightweight construction material as described in the present invention can be carried out in multiple embodiments depending on the final destination of the construction material. To carry out the curing, the homogeneous paste is placed in a mold, then left to rest until its setting process is complete and finally unmolded. The homogeneous paste should be added to the mold gradually. Additionally, the mold walls in contact with the construction material can be coated with a release agent to facilitate removal during demolding. In a particular embodiment, the setting process, which includes the curing stage of the material, takes place over a period of between 20 and 120 minutes. If no setting accelerators are added, the homogeneous paste must remain in the mold for a period of no less than 60 minutes. It should be noted that, during this setting process, the exothermic reaction promotes the hardening of the mixture and the evaporation of the alcoholic solvent from the elastomer. Thus, in a particular embodiment, the plaster in contact with water will promote the hardening of the mixture and the evaporation of the remaining ethanol- and peracetic acid-based solvent, resulting in a homogeneous integration of the NFU rubber residue into the plaster matrix. Finally, the construction material obtained after the process should be removed from the formwork, resulting in the desired prefabricated panel. This process must be carried out with particular care if reinforcing fibers have not been added to the matrix of the lightweight construction material of the invention. Optionally, the curing process may include a subsequent oven drying stage. In one particular embodiment, the oven drying comprises a 24-hour heat treatment at a temperature of 4–50 °C of a construction material that is at least 6 days old. In one particular embodiment, the method may comprise a final step of adhering reinforcing paper to at least one face. Specifically, this reinforcing paper may be adhered to the face perpendicular to the panels (1) subjected to the bending stress they must withstand. The reduction in density occurs during the curing of the homogeneous paste, as a result of the synergistic effect between the mixture of gypsum-based binder and water, which generates the exothermic reaction, and the elastomer emulsion used. Additionally, the construction material exhibits good thermal performance, making it perfectly suited to the growing needs of the construction sector. Furthermore, the manufacturing process of the invention is carried out in accordance with standard UNE-EN 13279-2:2014. Example 1 As an example, the quantities for three embodiments of the construction material that have been tested for the realization of this invention are shown (Table 1): Table 1. Mass proportions for the preparation of the compounds During the kneading process, the recommendations of the EN 13279-2 standard were followed. Obviously, there are differences from the standard when adding the prepared rubber emulsion once the water / plaster mixture in liquid state had been homogenized. A gentle mechanical mixing method was used with machinery. This type of mixing achieves better results and allows for automation of the process. In contrast, more vigorous mechanical mixing at high speed can affect the setting of the material, generating what is known as dead plaster, which would render it unusable. Furthermore, if reinforcing fibers, whether synthetic or natural, are added, they should be incorporated at a concentration of 1-5% by weight of the binder, either dispersed in the dry plaster powder or in the mixing water. The pouring into the mold was carried out gradually and progressively. Although optional, the interior walls of the molds were coated with oil to facilitate subsequent demolding. Alternatively, grease could have been used for this purpose. Additionally, any trapped air in the liquid mixture was removed. Finally, the leveling and surface smoothing of the flat surfaces of the precast elements was carefully performed, avoiding surface damage that could affect the final appearance of the composite. Once the material was kneaded and hardened, after seven days, as recommended by EN 13279-2, its mechanical properties were tested. In this particular case, the test specimens were dried for one day (24 hours) in a drying oven at a temperature of 45 ± 5 °C. This drying process allowed the evaporation of any remaining ethanol and peracetic acid within the compound, as well as any excess kneading water, homogenizing the sample prior to testing. Several tests were carried out to characterize the material of the invention (Table 2). Table 2. Average of the results of the properties of the compounds prepared. In general, the plaster material became lighter as the rubber emulsion content increased, and its thermal conductivity decreased. On the other hand, the mechanical properties were negatively affected, with a progressive decrease in flexural strength, compressive strength, and surface hardness. Thus, with the aim of improving the mechanical behavior of the developed lightweight gypsum compounds and enhancing their use in prefabricated boards and panels, a particular embodiment may include one or more reinforcing paper sheets on the faces perpendicular to the bending stress. These industrialized panels allow for a wide variety of shapes and geometries, thanks to the fact that the compound, initially prepared in a liquid state, hardens, adopting the shape of its container. Once hardened, these prefabricated elements can be machined, drilled, painted, and treated with various surface finishes. Finally, in situations where the material described in the invention must be manufactured on-site, protective masks should always be worn to avoid inhaling the gases produced by the rubber emulsion. Likewise, adequate ventilation and ambient temperatures between 10 and 30 °C are recommended to avoid disrupting the curing process of the manufactured compounds. As previously mentioned, lightweight construction materials can serve as a base for manufacturing prefabricated panels for modular construction, both vertical and horizontal, especially for interior spaces. In other words, these prefabricated panels, thanks to their numerous design possibilities and versatility, can be used for everything from suspended ceilings and false ceilings to interior wall linings, partitions, and partition walls. Due to its reduced density compared to traditional plaster, this material is particularly useful for manufacturing lightweight suspended ceiling panels. These suspended ceilings can be continuous and either demountable or fixed, with rectangular dimensions of 1000 × 600 mm² or square dimensions of 600 × 600 mm² recommended. These dimensions are considered suitable for facilitating installation and preventing potential flexural failures caused by excessive deflection in the center of the suspended panel. Additionally, it is worth noting that rectangular panels should be reinforced with synthetic fibers (e.g., fiberglass, basalt, polypropylene, or nylon) or natural fibers (e.g., abaca, straw, wood, hemp, coconut, or palm) embedded in the plaster compound matrix. Furthermore, counter-molds can be used on the reverse side of the panels during the curing process of the developed material, in order to reduce the thickness of the central area of ​​the precast element. Likewise, metal fittings (preferably aluminum) can be incorporated into the back and sides of these panels during the curing process, to facilitate their subsequent assembly and installation. For prefabricated panels used for vertical partitions, walls, or interior linings, it is advisable to use two panels on each side likely to be in contact with a walkable area to stiffen the structure. Finally, it should be noted that prefabricated panels made with this new gypsum material, which incorporates rubber waste, can be reinforced with sheets of Kraft paper or similar material adhered to their surface. This paper can be applied during the material's curing process or after the prefabricated panel has hardened.

Claims

1. A lightweight building material based on gypsum or plaster, characterized in that it comprises a curable matrix comprising, in an integrated manner: - 90-97.5% by mass of a mixture of water and a gypsum or plaster-based binder, and - 2.5-10% by mass of an alcoholic emulsion of an elastomer.

2. The lightweight building material according to claim 1, wherein the mass percentage matrix of the elastomer emulsion comprises: 5-10% elastomer fraction; 2.5-7.5% peracetic acid (CH3CO3H); and 85-95% ethanol (C2H6O).

3. The lightweight building material according to claim 2, wherein the elastomer particles comprise a mean diameter of less than 0.8 mm.

4. The lightweight construction material according to claim 3, wherein the elastomer is rubber.

5. The lightweight construction material according to claim 4, wherein the rubber is recycled rubber from end-of-life tires. 6.The lightweight construction material according to any one of claims 1 to 5, wherein the binding material further comprises reinforcing fibers.

7. The lightweight construction material according to claim 6, wherein the percentage of reinforcing fibers is in the range of 1–5% with respect to the total weight of the binding material.

8. The lightweight construction material according to any one of claims 1 to 7, wherein the water / binder mass ratio is between 0.6 and 0.

7.

9. A panel characterized in that it comprises a lightweight construction material according to any one of claims 1 to 8.