Ultralight cement-fiber composite sheet and its production process

Abstract

This claim is related to the lightweight concrete mix design, structure and production process of a type of reinforced cement board that is typically used to cover the exterior walls of exterior walls or interior walls exposed to moisture (such as bathroom, kitchen and utility walls), in all types of residential, commercial and public buildings. Although it is possible to use it for the interior walls of exterior walls or all interior walls and even to cover false ceilings. This sheet is used as a cover in the so-called drywall system and also in the cold-rolled lightweight metal structure (LSF), so all the requirements related to the construction and installation of these systems must be observed and finally this sheet (board) is connected to those structures (master and runner) by screws. The usual dimensions of this board can vary, but its usual dimensions are 240 x 120 cm, which can be produced in thicknesses of 1.5 to 5 cm, but the preferred thickness is 2.5 cm. The core of these lightweight concrete pieces contains slow-burning polystyrene grains, the dry density of which is between 600 and 800 kg / m3; the walls (both sides) of which are made of alkali-resistant fiberglass mesh and are in the form of a composite. The production process of these pieces is one-stage, meaning that the core and reinforcement with mesh are all concreted in one stage, so the connection between the mesh and the core concrete is well done, and no additional adhesives or cement paste are used. Conventional methods use a Hatschek machine or methods that use a roller to spread and finish the concrete, but this method uses special molds that produce pieces with a suitable finished surface where the mesh is located on the two outer faces of the board. This type of cover sheet has greater durability and resistance than other common types due to its greater thickness and is completely nailable. Also, due to the use of very light concrete in its core, it has low density, low thermal conductivity, and finally, appropriate toughness, which makes it easy to transport and install. At the same time, it has very good resistance to impact and off-plane loads. Its mixing design is such that, while providing sufficient mechanical resistance, it has a minimum amount of water absorption.

Description

Description of the invention Title of the invention Ultralight fiber cement composite liner and its production process Technical background of the relevant invention This claim concerns the structure and production process of a type of reinforced cement cladding (board, sheet) that is used to cover the exterior walls of various residential, office, and public buildings or walls that are exposed to moisture. Technical problem and stating the objectives of the invention One of the materials that has been used for years as wall and ceiling coverings in buildings is fiber cement board, which is produced in both smooth and corrugated forms. Given that asbestos fibers were used in their production, its production has been banned in foreign countries for more than 30 years, and in our country, its production has been stopped in the last decade. An alternative method for its production is to use short or long fibers made of cellulose or polymer. Given that the best method for producing this type of fiber cement sheets is the Hatschek machine or flow-on method, changes should be made in the mixing plan in addition to changes in the production process. Some factories in Iran have attempted to reform their production lines and for a while produced products with alternative fibers, but with the increasing cost of the fibers used and the sanctions, a number of them have practically closed down, or even some that are still active have very high production costs and it is difficult to compete with other products. Another product that has been available for nearly two decades and was also imported into Iran for a while is a type of cement sheet reinforced with fiber mesh, the core of which is usually made of ordinary concrete or lightweight concrete containing mineral or synthetic lightweight aggregates and its thickness is 12.5 mm. The supply of this product in Iran has been stopped for various reasons. The problem with this type of cement board is its relative brittleness, which causes it to crumble during transportation and sometimes during installation. The production method of this type of sheet is also continuous and is often done by the flow-on method or other modified methods, but it is not possible to produce it by the Hatschek method. In these methods, the lower and upper fiber meshes are placed on the sheet faces before and after pouring the cement mortar, respectively. The main problem with this type of cement board in our country is the sound that is created due to the low thickness after installation due to impact (drum-like sound and hollow wall), which creates a feeling of insecurity. Also, the inability of these types of sheets to be nailed, which causes problems in installing some non-structural extensions. In addition, they cannot be a good thermal insulator on their own (because in most cases, insulation is not placed inside the space between two boards, and in addition, previous generation cement boards are a kind of thermal bridge), and overall, they have not been very well received in Iran. In addition to these issues, most domestically produced fiber cement sheets do not meet the requirements of cement sheets suitable for external load-bearing walls due to their water absorption and low flexural strength when wet. Accordingly, in the present claim, the three main problems of this type of sheet have been resolved according to the cultural and administrative conditions of the country; a) The thickness of the claimed sheet is 25 mm (although it is possible to produce thicknesses of 20 to 50 mm and even more), this increases the bending strength and impact resistance and does not suffer any damage or breakage during transportation and installation. This thickness, along with the lightweight concrete structure used, allows for nailing and screwing, and to a large extent improves the thermal performance of the constructed walls and reduces the effect of thermal bridges. b) The use of lightweight concrete containing polystyrene and special polymers, while achieving a very low density, has provided a compressive strength of at least 3.5 MPa, which reduces the weight of the sheet, ease of transportation and installation, appropriate thermal performance, and ultimately good toughness, which, unlike foreign samples, is not brittle and does not crumble easily. c) The production method in this invention is very simple and low-cost, while the final product has a good quality and finished surface. A description of the state of the prior art and the history of developments related to the claimed invention. As explained in the previous paragraph, cement sheets can be divided into three general categories in terms of structure and production method: the first two categories are similar in structure (containing cement paste and short or long fibers) but their production method is different. One is made by the Hatschek method and the other by the flow-on method (of course, there are other methods, but they are not economical and industrial). The third category is different from the first two categories in terms of structure and components, but is usually produced by the flow-on method. Some of the similar international patents are as follows, but as stated in this description and claim, none of the registered cases correspond to the present invention (according to the set of claim clauses), and this invention is innovative: AU 2010201485B2: Fiber cement board with modified fiber. US20100234491A1: Method and material for manufacturing fiber cement board. CN107428026A: method and apparatus for manufacturing fiber cement board. US8273174B2: Method of making a fiber cement board with improved properties and the product. US8273174B2: Method of making a fiber cement board with improved properties and the product. US 4428775 A: Reinforced Cement Sheet Product Containing No Asbestos for Fabricating on Hatschek Machine. US 5393214 A: Apparatus for Manufacturing a Fiber Reinforced Inorganic Hardened Body. US 20040043682 A1: Composite Board. US 20040229978 A1: Polymer-modified Fiber-cement Composition. Below are a number of domestic patents, but none of them match the presented invention in terms of structure, application, or even materials: Registration number 66576: Prefabricated EPS lightweight concrete composite panel with perlite method reinforced with polypropylene fibers. Registration number 72684: Nick Panel technology for industrial production and construction of lightweight, quick-to-build exterior walls with a facade for exterior building cladding. Registration number 47557: Manufacturing of lightweight concrete panels - ceiling and wall beams. Registration number 81418: Non-load-bearing, ultra-lightweight concrete monolithic wall. Registration number 31504: Cement and polystyrene composite panels. Registration number 64002: Construction of a completely prefabricated ultra-lightweight concrete wall panel. Providing a solution to an existing technical problem along with an accurate, sufficient, and integrated description of the invention This claim includes two techniques in the field of mix design and structure as well as production method. The first technique is the mix design that uses a type of ultra-light and resistant concrete and the second technique is the combination of this lightweight concrete with alkali-resistant glass fiber mesh placed on both sides. This combination reduces the density and ultimately reduces the weight of the cover, increases the bending strength and impact resistance and ultimately creates toughness. The use of a special mixture design, polymeric materials, superplasticizer additives and silica fume results in a dense, non-separating structure with minimal cement paste, which, together with the mesh, creates a reinforced cement board that is nailable and screwable, has low water absorption, high bending strength and compressive strength, and ultimately has very good ductility and toughness. Also, due to its durability against environmental factors, this cover sheet is a very suitable option for use in drywall systems (set includes stud and runner) as well as wall coverings and even ceilings and floors in the LSF light steel structure system. The structure of this cover sheet is as shown in Figure 1, which can be produced in different dimensions, but the preferred dimensions are 240 x 120 cm. Its thickness is between 20 and 50 mm, with a preferred thickness of 25 mm. The ingredients include: 1- Types of Portland cement or mixed cement or white cement; 2-Silica fume; 3-Peralumina cement (if needed); 4-Superplasticizer additives; 5-Set control additives (accelerant or retarder); 6-Polymer additives to create adhesion and also prevent separation; 7-Expanded and slow-burning polystyrene granules with different densities and granulations; 8- Silica or carbonate filler (fine sand); 9- Mineral or synthetic lightweight aggregates (as appropriate); 10- Alkali-resistant glass fiber mesh; 11-Water. Using the standing seam molding production method allows for pouring concrete and placing the fiber mesh on the outer faces of the sheet in one step, which, while creating proper correlation with the concrete core, is a very economical and convenient production method for industrial production. This production method also allows for the production of sheets with a thickness of 20 mm and above, which has the advantage of increasing the thickness in addition to being economical compared to existing methods. In the production method, a special lightweight concrete mixer with a minimum capacity of one cubic meter and a special lightweight concrete transfer pump are used, with the help of which the concrete is transferred from the mixer to the molds. Using this pump makes it easy to fill the mold quickly and to the desired thickness. The molds are in a standing form (filling arm) according to Figure 2, which contains 15 to 70 molds in a set (chassis). After filling and compacting the concrete in the mold and initial setting, the molds are transferred to a special room and are removed from the mold a maximum of one day later. The covers are cured for 3 days and then packaged and stored. Table 1- Technical specifications of ultra-lightweight cement-fiber composite liner Dimensions Length, mm Width, mm Thickness, mm 2400-300 900-1200 20-50 Compressive strength 28 days, MPa 0.4±0.5 Flexural strength 28 days, MPa ≥0.7 Dry density, kg / m3 660±40 Thermal conductivity, W / mK 0.135 Fire classification Non-combustible Explanation of shapes, maps and diagrams Figure 1 shows the overall structure of the pusher, which consists of a lightweight concrete core and is reinforced with glass fiber mesh on both sides. An image of the fabricated sample is also included for better presentation and to ensure the possibility of producing a prototype. Figure 2 shows the mold used, which plays a major role in the production method and process. Figure 2 shows the flowchart of the production method. A clear and precise statement of the advantages of the claimed invention over prior inventions. This claim includes the mixing design and structure of a type of ultra-lightweight fiber-cement composite push-sheet (board, sheet) and its production process. The core of this push-sheet is made of ultra-lightweight concrete containing polystyrene grains, which is reinforced with glass fiber mesh on both sides (according to Figure 1). The use of lightweight polystyrene concrete with this density and compressive strength has not been used in the manufacture of push-sheets. In other cases, this type of concrete has been used to manufacture panels reinforced with or without rebar, with a minimum thickness of 50 mm, while in this claim, instead of panels, push-sheets with a maximum thickness of 50 mm have been used (there are many differences between the performance of panels and push-sheets, and in technical definition they are completely two different elements). The lightweight concrete used is characterized by a very low density of about 650 kg / m3 and a high compressive strength compared to the density (3.5 to 5 MPa). Reinforcing these sheets with glass fiber mesh increases the flexural strength, impact resistance and toughness of the sheets. Based on the performance of this cement-fiber composite, it is very suitable as a covering for walls exposed to moisture or places where impact resistance is required. The method of producing these liners is not used for cement sheets, and the methods of producing cement sheets are Hatschek, Flow on, or lying down molding, or other methods, which are completely different from the presented method, which is standing molding and side filling and using a special pump combined with placing a fiber mesh. The method of placing the mesh in the mold wall and simultaneously concreting the core and combining it with the cement paste, which causes cohesion with the concrete of the sheet core, is a characteristic of the production method, both in terms of performance and implementation. Description of at least one implementation method for implementing the invention Explicit mention of the industrial application of the invention This product is used for use in drywall systems (set including stud and runner) as well as wall coverings and even ceilings and floors in the LSF light steel structure system.

Claims

Claim What is claimed: Claim 1) Presentation of a plan to manufacture a type of lightweight cement-fiber composite push sheet (board) with a core containing lightweight concrete with the following mixing design and components, which is reinforced with alkali-resistant glass fiber mesh on both sides: Portland cement or blended cement or white cement (35 to 70 weight percent), silica fume (2 to 10 weight percent), peraluminum cement (if needed) (0 to 20 weight percent), superplasticizer additives (0 to 1 weight percent), set control additives (accelerating or retarding) (0 to 0.5 weight percent), polymer additives (based on PVA polymer) to create adhesion and also prevent separation (0 to 0.5 weight percent), expanded and slow-burning polystyrene granules with different densities and granulations (0.005 to 0.5 weight percent), filler (sand) Fine) silica or carbonate (0 to 2% by weight), mineral or synthetic lightweight aggregates (as appropriate) (0 to 5% by weight), alkali-resistant glass fiber mesh (two square meters per square meter of cover sheet), water (10 to 30% by weight). Claim 2) According to claim 1, each cover sheet has a length of 1200 to 3000 mm, a width of 900 to 1200 mm, a thickness of 20 to 50 mm, a dry density of 660 ± 40 kg / m3, and a compressive strength of 0.4 ± 0.5 MPa. Claim 3) The method of producing this fiber-cement composite liner is by using a set of molds that are placed side by side and filled vertically, that is, from a dimension of 20 to 50 millimeters, with lightweight concrete (claimed in claim 1). Claim 4) According to claim 3, in this production method, first a mesh layer is placed on both sides of the mold and then lightweight concrete prepared by a mixer is poured into the mold using a pump, so it is completely different from the conventional Hatschek or Flow on methods.

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