A lime-based coating for walls and its preparation method

Abstract

This invention relates to the field of building materials technology, and in particular to a lime-based coating for walls and its preparation method, comprising quicklime, graded quartz sand, a natural pre-gelled binder phase, natural plant fibers, and water. This invention forms a natural pre-gelled binder phase by mixing glutinous rice flour and white sugar in a limewater environment, and combines this with first and second quartz sand to form a graded quartz sand structure. This allows the natural pre-gelled binder phase to more uniformly coat the quicklime and graded quartz sand, thereby improving the dispersion uniformity, construction continuity, and adhesion stability of the slurry after application to the wall. Simultaneously, the graded quartz sand forms a skeleton filling structure, improving the density and surface hardness of the coating.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a lime-based coating for walls and its preparation method. Background Technology

[0002] Lime-based wall materials, as a traditional building decoration and protection material, have long been used in the base or finishing treatment of interior and exterior walls, ceilings, and columns. Lime itself possesses good natural alkalinity, certain mildew and moisture resistance, and good environmental friendliness. When combined with natural organic materials or inorganic aggregates, it can achieve both wall decoration and surface protection functions. With the increasing demand for green building materials and low-additive wall materials, the use of hydrated lime, natural organic binders, and natural aggregates to construct wall coating systems has become an important development direction in the field of lime-based coatings.

[0003] However, many existing natural lime-based wall coatings are made by directly mixing the components. The uniformity of the composite between the glutinous rice binder and the lime and aggregate particles is insufficient, which can easily lead to poor continuity of slurry construction and insufficient adhesion stability after application to the wall. In addition, pure lime slurry is prone to shrinkage during drying and natural carbonization. If the aggregate structure and crack-resistant structure design are insufficient, problems such as powdering, cracking, insufficient surface density, and poor long-term durability may occur.

[0004] Therefore, a lime-based coating for walls and its preparation method are proposed. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a lime-based coating for walls, comprising quicklime, graded quartz sand, a natural pre-gelled binder phase, natural plant fibers, and water; the graded quartz sand includes first quartz sand and second quartz sand with different particle sizes, the first quartz sand being used to form a supporting skeleton, and the second quartz sand being used to fill the gaps between the first quartz sands; the natural pre-gelled binder phase is formed by pre-gelling glutinous rice flour and white sugar in a lime water environment, and together with quicklime constitutes a binder matrix coating the graded quartz sand; the natural plant fibers are dispersed in the composite slurry formed by the binder matrix and the graded quartz sand, and are used to inhibit the drying shrinkage and cracking of the coating.

[0006] As a preferred embodiment of the present invention, the material comprises, by weight: 35 to 50 parts quicklime, 20 to 35 parts graded quartz sand, 8 to 18 parts glutinous rice flour, 3 to 10 parts white sugar, 0.5 to 5 parts natural plant fiber, and 20 to 40 parts water; the natural pregelatinized binder phase is formed by heating and gelatinizing glutinous rice flour, white sugar, and lime water, with a weight ratio of glutinous rice flour to white sugar of 1:0.3 to 1:1; the first quartz sand has a particle size of 0.15 mm to 0.60 mm, the second quartz sand has a particle size of 0.03 mm to 0.15 mm, and the weight ratio of the first quartz sand to the second quartz sand is 1:0.5 to 1:2; the natural plant fiber is one or more of cotton fiber, hemp fiber, bamboo fiber, and wood fiber, with a length of 1 mm to 8 mm, and the natural plant fiber is introduced into the composite slurry after being pre-impregnated and dispersed by lime water.

[0007] A method for preparing a lime-based coating for walls includes the following steps: S1, mixing quicklime with a portion of water and pre-slaking it to obtain a pre-slaking lime slurry; S2, pre-treating a first quartz sand and a second quartz sand by sieving to obtain graded quartz sand; S3, mixing glutinous rice flour, white sugar, and lime water and heating to gelatinize to obtain a natural pre-gelatinized binder phase; S4, pre-impregnating and dispersing natural plant fibers in lime water to obtain a pre-dispersed fiber slurry; S5, mixing the pre-slaking lime slurry with the graded quartz sand, then adding the natural pre-gelatinized binder phase and mixing, followed by adding the pre-dispersed fiber slurry and mixing to obtain an initial slurry; S6, allowing the initial slurry to stand and age, then stirring it again to obtain a lime-based coating for walls.

[0008] As a preferred embodiment of the present invention, the weight ratio of quicklime to water is 1:0.5 to 1:1.2, and the pre-slaking time is 2 hours to 12 hours.

[0009] As a preferred embodiment of the present invention, the weight ratio of glutinous rice flour, white sugar and water is 1:0.3 to 1:1:2 to 1:4, the heating temperature is 60 degrees Celsius to 95 degrees Celsius, and the heating and stirring time is 15 minutes to 40 minutes.

[0010] As a preferred embodiment of the present invention, the particle size of the first quartz sand is 0.15 mm to 0.60 mm, the particle size of the second quartz sand is 0.03 mm to 0.15 mm, and the weight ratio of the first quartz sand to the second quartz sand is 1:0.5 to 1:2; the pre-impregnation time of the natural plant fiber is 10 minutes to 60 minutes.

[0011] As a preferred technical solution of the present invention, the pre-hydrated lime slurry and graded quartz sand are first mixed, then the natural pre-gelled binder phase is slowly added for a second mixing, and finally the pre-dispersed fiber slurry is added for final mixing; the standing aging time is 2 to 24 hours, and the stirring time is 3 to 10 minutes.

[0012] Compared with the prior art, the beneficial effects that this invention can achieve are: This invention forms a natural pre-gelatinized binder phase by mixing glutinous rice flour and white sugar in a limewater environment, and combines it with first and second quartz sand to form a graded quartz sand structure. This allows the natural pre-gelatinized binder phase to more evenly coat the quicklime and graded quartz sand, thereby improving the dispersion uniformity, construction continuity, and adhesion stability of the slurry after application to the wall. At the same time, the graded quartz sand is used to form a skeleton filling structure, which improves the density and surface hardness of the coating.

[0013] This invention incorporates natural plant fibers and combines them with a preparation method involving pre-slaked lime and initial slurry aging and re-stirring. This allows the natural plant fibers to form a relatively uniform crack-resistant bridging structure in the lime-based composite slurry, reducing the probability of cracks and powdering in the coating during drying shrinkage and natural carbonization. As a result, without relying on chemically synthesized additives, this invention improves the crack resistance, mildew and moisture resistance, and long-term durability of the lime-based wall coating. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the component composition of the present invention; Figure 2 This is a schematic diagram of the layered application of the present invention after construction; Figure 3 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0015] To make the technical means, creative features, objectives, and effects of this invention easier to understand, the invention is further described below with reference to specific embodiments. However, the following embodiments are merely preferred embodiments of this invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are all within the protection scope of this invention.

[0016] Example 1: As Figure 1-2 As shown, a lime-based wall coating comprises, by weight: 35 to 50 parts quicklime, 20 to 35 parts quartz sand, 8 to 18 parts glutinous rice flour, 3 to 10 parts white sugar, 0.5 to 5 parts natural plant fiber, and 20 to 40 parts water. By forming a natural pre-gelatinized binder phase with glutinous rice flour and white sugar in a limewater environment, and combining it with graded quartz sand to form a skeleton filling structure, and then combining it with natural plant fiber to form a crack-resistant bridging network, the lime-based coating can achieve a balance of workability, adhesion stability, crack resistance, and durability without introducing chemically synthesized additives.

[0017] Furthermore, the slaked lime is selected from calcium hydroxide powder or lime paste obtained by slaking, preferably slaked lime with uniform fineness and no obvious unslaked particles; using slaked lime as the inorganic binder can, on the one hand, gradually form a stable hardened layer through natural carbonization after coating, and on the other hand, utilize the natural alkalinity of lime material itself to improve the anti-mildew and moisture resistance of the wall surface.

[0018] Furthermore, the quartz sand includes first quartz sand and second quartz sand, wherein the particle size of the first quartz sand is larger than that of the second quartz sand. The first quartz sand is used to form a supporting skeleton, and the second quartz sand is used to fill the gaps between the first quartz sand particles. Preferably, the particle size of the first quartz sand is 0.15 mm to 0.60 mm, and the particle size of the second quartz sand is 0.03 mm to 0.15 mm. The weight ratio of the first quartz sand to the second quartz sand is 1:0.5 to 1:2. By setting quartz sand with different particle size grades, the overall shrinkage of the lime slurry during the drying and film-forming process can be reduced, and the internal density and surface hardness of the coating can be improved.

[0019] Furthermore, glutinous rice flour and white sugar together constitute a natural organic toughening component. Glutinous rice flour is used to form a binding paste under heating and stirring conditions, while white sugar is used to improve the dispersibility, lubricity, and extensibility of the glutinous rice paste. This allows the formed natural pregelatinized binder phase to more evenly coat the quicklime particles and quartz sand particles, and improves the smoothness of the coating application and the initial adhesion stability after the paint is applied to the wall.

[0020] In addition, natural plant fibers are used to form a dispersed anti-crack bridging network inside the lime-based slurry; the natural plant fibers can be one or more of cotton fiber, hemp fiber, bamboo fiber, and wood fiber; preferably, the natural plant fibers are short fibers with a length of 1 mm to 8 mm; after the natural plant fibers are dispersed in the slurry, they can block the propagation path of microcracks inside the coating, reducing the probability of through cracks in the wall coating under conditions of water loss shrinkage and temperature and humidity fluctuations.

[0021] It should be noted that, in order to make the natural plant fibers more evenly dispersed in the slurry, the natural plant fibers are preferably pre-wetted with lime water. Pre-wetting with lime water can reduce the possibility of agglomeration after the dry fibers directly enter the slurry, and can also improve the interfacial compatibility between the natural plant fibers and the lime-based slurry, making it easier for the natural plant fibers to embed into the composite matrix formed by quicklime and glutinous rice sugar solution.

[0022] Specifically, the lime-based coating in this embodiment preferably adopts the following proportions: 42 parts slaked lime, 16 parts first quartz sand, 12 parts second quartz sand, 12 parts glutinous rice flour, 6 parts white sugar, 2 parts natural plant fiber, and 30 parts water. The slaked lime is used to form a continuous inorganic matrix, the first and second quartz sands are used to form a graded skeleton, the glutinous rice flour and white sugar are used to form a natural pre-gelled binder phase, the natural plant fiber is used to improve the crack resistance stability of the slurry, and the water is used to adjust the fluidity and workability of the slurry.

[0023] Furthermore, the lime-based coating in this embodiment can be made into a base coat or a top coat. When made into a base coat, the proportion of the first quartz sand can be appropriately increased to enhance the skeletal support and the leveling ability of the base layer. When made into a top coat, the proportion of the second quartz sand can be appropriately increased, and the amount of natural plant fiber added can be controlled to improve the surface smoothness and uniformity of the finish. By combining the base coat and the top coat under the same natural system, the overall adhesion and decorative effect of the wall surface can be further improved.

[0024] Furthermore, the lime-based coating in this embodiment can be applied to wall substrates such as cement mortar substrates, brick wall substrates, lime mortar substrates, and rammed earth substrates. Before construction, the floating dust, oil stains, and loose particles on the substrate surface should be removed, and the substrate should be appropriately moistened according to its dryness. By moistening the substrate, the substrate can be prevented from absorbing the water in the lime-based slurry too quickly, thus avoiding localized powdering, hollowing, or surface cracking of the coating when it loses water too quickly in the initial stage.

[0025] Furthermore, in this embodiment, after the lime-based coating is applied to the wall, the quicklime gradually undergoes natural carbonization, which together with the organic bonding structure formed by the glutinous rice sugar solution constitutes an organic-inorganic composite consolidation layer. At the same time, the graded quartz sand provides internal support, and the natural plant fibers inhibit the propagation of microcracks, thereby enabling the wall surface to exhibit good hardness retention, moisture resistance stability, and durability during long-term use.

[0026] Example 2: Figure 2-3 As shown, a method for preparing a lime-based coating for walls includes a slaked lime pre-slaked step, a graded aggregate pretreatment step, a natural pre-gelled binder phase preparation step, a fiber pre-impregnation and dispersion step, a composite mixing step, and an aging and integration step. By forming a natural binder phase, aggregate structure, and crack-resistant fiber network in stages, the composite uniformity between the components can be improved, and the construction stability and film quality of the final lime-based coating can be enhanced.

[0027] Furthermore, the pre-slaking step of quicklime includes: mixing quicklime with a portion of clean water, stirring to form a lime slurry, and allowing it to stand for pre-slaking; preferably, quicklime and clean water are pre-mixed at a weight ratio of 1:0.5 to 1:1.2, stirred for 10 to 20 minutes, and then allowed to stand for 2 to 12 hours; through pre-slaking, the quicklime particles can reach a relatively stable wetted state before entering the composite mixing step, reducing local agglomeration during subsequent mixing and improving the uniformity of the lime slurry.

[0028] Specifically, the graded aggregate pretreatment steps include: screening the first and second quartz sands separately to remove excessively coarse particles and impurities; drying the quartz sand if necessary to reduce the impact of free water fluctuations on the surface of the quartz sand on the final slurry consistency; preferably, the quartz sand is dried at 80 to 120 degrees Celsius for 30 to 120 minutes and then cooled for later use; by pretreating the quartz sand, the subsequent batching and metering can be made more stable, and it is easier to control the slurry consistency and the workability.

[0029] Furthermore, the preparation steps of the natural pregelatinized binder phase include: adding glutinous rice flour, white sugar, and a portion of water to a heating container and stirring and heating, so that the glutinous rice flour gradually gelatinizes under heating to form a viscoelastic natural glutinous rice syrup; preferably, the weight ratio of glutinous rice flour, white sugar, and water is 1:0.3 to 1:1:2 to 1:4; the heating temperature is 60 degrees Celsius to 95 degrees Celsius; the stirring time is 15 minutes to 40 minutes; to enhance the compatibility between the natural glutinous rice syrup and the lime system, during the preparation of the natural pregelatinized binder phase, a portion of pre-cooked lime slurry can also be introduced into it, so that the natural glutinous rice syrup forms a more stable pregelatinized binder phase in the lime environment.

[0030] It should be noted that the preparation of the natural pregelatinized binder phase is not simply adding glutinous rice flour and white sugar directly to the total slurry. Instead, heating and stirring are used to fully develop the binder structure of the glutinous rice flour, and then white sugar is used to improve the smoothness and dispersibility of the slurry. The natural pregelatinized binder phase formed by the above steps can more evenly coat the quicklime particles and quartz sand particles during subsequent compounding, thereby improving the overall bonding stability of the slurry and the continuity of wall application.

[0031] In addition, the fiber pre-impregnation and dispersion step includes: immersing and dispersing natural plant fibers in lime water to obtain pre-dispersed fiber slurry; preferably, the impregnation time is 10 to 60 minutes; through pre-impregnation, the surface of natural plant fibers can be fully wetted, reducing the floating, entanglement and agglomeration of natural plant fibers in the subsequent mixing process, so that natural plant fibers can be more evenly dispersed in lime-based slurry.

[0032] Specifically, the composite mixing steps include: first, adding the pre-hydrated lime slurry and the pre-treated first and second quartz sands into a mixing device for a first mixing; then, slowly adding the natural pre-gelled binder phase into the first mixed slurry and continuing to stir to form a composite slurry; finally, adding the pre-dispersed fiber slurry into the composite slurry for a second mixing to obtain the initial lime-based coating; preferably, the first mixing time is 10 to 25 minutes, the second mixing time after adding the natural pre-gelled binder phase is 10 to 20 minutes, and the final mixing time after adding the pre-dispersed fiber slurry is 5 to 15 minutes.

[0033] Furthermore, in the composite mixing step, the natural pregelatinized binder phase is preferably introduced into the slurry after one mixing by slowly adding it while stirring, so as to avoid local concentration of the natural pregelatinized binder phase causing agglomeration; the predispersed fiber slurry is preferably added after the slurry has reached a basically uniform state, so as to prevent the natural plant fibers from being subjected to excessive shearing during the coarse mixing stage and becoming entangled; by setting the above-mentioned sequence of inorganic phase first, then organic phase and then fiber phase, the skeleton structure, natural binder structure and crack-resistant bridging structure can be established in sequence, thereby improving the homogeneity of the final slurry.

[0034] Furthermore, the aging and integration steps include: allowing the initial lime-based coating to stand for aging before re-stirring; preferably, the standing aging time is 2 to 24 hours, and the re-stirring time is 3 to 10 minutes; through short-term aging, the interface between lime particles, natural pre-gelled binder phase, graded quartz sand and natural plant fibers can be further stabilized, the viscosity of the slurry tends to be uniform, and the slurry has good flow stability and continuous plastering when applied to the wall in subsequent construction.

[0035] Specifically, the lime-based coating prepared by the method of this embodiment can be applied in one or two coats during construction. When the substrate is relatively rough, it is preferable to apply the base coat of lime-based coating first, followed by the top coat. When the substrate is relatively smooth, the top coat can also be applied directly. After a single coat is applied, its natural water loss rate should be controlled to avoid rapid water loss under high temperature, strong wind, or sun exposure. By controlling the natural drying and carbonization process, the lime-based coating can gradually form a stable hardened layer without the need for chemically synthesized curing agents or external carbon dioxide strengthening devices.

[0036] In addition, during the curing stage after construction, the wall surface should be kept moderately ventilated and should be protected from continuous water rinsing, violent friction or strong thermal shock before it is fully hardened. As the quicklime gradually undergoes natural carbonization, a relatively stable composite consolidation relationship is formed between the natural pre-gelled binder phase and the lime hardened layer. The graded quartz sand provides internal skeleton support, and the natural plant fibers inhibit the propagation of microcracks, thereby giving the resulting lime-based wall coating good density, crack resistance, adhesion stability, mildew and moisture resistance and service durability.

[0037] Specifically, this embodiment provides a preferred preparation process: First, mix 42 parts of slaked lime with 18 parts of water and stir for 15 minutes, then let it stand for 6 hours to obtain a pre-slaked lime slurry; then, 16 parts of first quartz sand and 12 parts of second quartz sand are sieved, dried, and set aside; subsequently, 12 parts of glutinous rice flour, 6 parts of white sugar, and 12 parts of water are added to a heating container and stirred for 25 minutes at 75°C to 85°C to form a natural pre-gelatinized binder phase; then, 2 parts of cotton fiber are soaked in lime water for 20 minutes to obtain a pre-dispersed fiber slurry; next, the pre-slaked lime slurry is mixed with the first and second quartz sands for 15 minutes, then the natural pre-gelatinized binder phase is slowly added and stirred for another 15 minutes, followed by the addition of the pre-dispersed fiber slurry and final mixing for 8 minutes to obtain the initial slurry; finally, the initial slurry is allowed to stand for 8 hours and then stirred back for 5 minutes to obtain a lime-based coating for walls.

[0038] Furthermore, the lime-based wall coating prepared by the above method exhibits improved initial adhesion of the slurry to the substrate during construction due to the natural pre-gelled binder phase, reduced shrinkage of the pure lime slurry by graded quartz sand, and suppressed crack propagation caused by drying shrinkage by natural plant fibers. The dual-stage curing and short-term aging processes enhance the overall stability of the slurry. Therefore, without the addition of chemically synthesized additives, it can still meet the comprehensive requirements for construction performance and durability in wall decoration and protection applications.

[0039] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A lime-based coating for walls, characterized in that, It includes quicklime, graded quartz sand, natural pre-gelled binder phase, natural plant fiber and water; The graded quartz sand includes first quartz sand and second quartz sand with different particle sizes. The first quartz sand is used to form a supporting skeleton, and the second quartz sand is used to fill the gaps between the first quartz sand. The natural pregelatinized binder phase is formed by pregelatinizing glutinous rice flour and white sugar in a lime water environment, and together with quicklime, it constitutes the binder matrix for coating graded quartz sand. The natural plant fibers are dispersed in the composite slurry formed by the binder matrix and graded quartz sand to inhibit coating shrinkage and cracking.

2. The lime-based coating for walls according to claim 1, characterized in that, By weight, it includes: 35 to 50 parts quicklime, 20 to 35 parts graded quartz sand, 8 to 18 parts glutinous rice flour, 3 to 10 parts white sugar, 0.5 to 5 parts natural plant fiber, and 20 to 40 parts water.

3. A lime-based coating for walls according to claim 2, characterized in that, The natural pregelatinized binder phase is formed by heating and gelatinizing glutinous rice flour, white sugar and lime water, with the weight ratio of glutinous rice flour to white sugar being 1:0.3 to 1:

1.

4. A lime-based coating for walls according to claim 2, characterized in that, The first quartz sand has a particle size of 0.15 mm to 0.60 mm, the second quartz sand has a particle size of 0.03 mm to 0.15 mm, and the weight ratio of the first quartz sand to the second quartz sand is 1:0.5 to 1:

2.

5. A lime-based coating for walls according to claim 2, characterized in that, The natural plant fiber is one or more of cotton fiber, hemp fiber, bamboo fiber, and wood fiber. The length of the natural plant fiber is 1 mm to 8 mm. The natural plant fiber is introduced into the composite slurry after being pre-impregnated and dispersed with lime water.

6. A method for preparing a lime-based coating for walls, characterized in that, Includes the following steps: S1. Mix quicklime with some water and pre-hydrate it to obtain pre-hydrated lime slurry; S2. The first and second quartz sands are pre-treated by screening to obtain graded quartz sand; S3. Mix glutinous rice flour, white sugar and lime water and heat to gelatinize to obtain a natural pregelatinized binder phase; S4. Natural plant fibers are pre-impregnated and dispersed in lime water to obtain pre-dispersed fiber pulp. S5. After mixing the pre-hydrated lime slurry with graded quartz sand, add the natural pre-gelled binder phase and mix, then add the pre-dispersed fiber slurry and mix to obtain the initial slurry. S6. After allowing the initial slurry to stand and age, stir it again to obtain a lime-based coating for walls.

7. The method for preparing a lime-based coating for walls according to claim 6, characterized in that, The weight ratio of quicklime to water is 1:0.5 to 1:1.2, and the pre-slaking time is 2 to 12 hours.

8. The method for preparing a lime-based coating for walls according to claim 6, characterized in that, The weight ratio of glutinous rice flour, white sugar and water is 1:0.3 to 1:1:2 to 1:4, the heating temperature is 60 degrees Celsius to 95 degrees Celsius, and the heating and stirring time is 15 minutes to 40 minutes.

9. The method for preparing a lime-based coating for walls according to claim 6, characterized in that, The particle size of the first quartz sand is 0.15 mm to 0.60 mm, the particle size of the second quartz sand is 0.03 mm to 0.15 mm, and the weight ratio of the first quartz sand to the second quartz sand is 1:0.5 to 1:

2. The pre-impregnation time of the natural plant fiber is 10 to 60 minutes.

10. A method for preparing a lime-based coating for walls according to claim 6, characterized in that, First, the pre-hydrated lime slurry and graded quartz sand are mixed once, then the natural pre-gelled binder phase is slowly added for a second mixing, and finally the pre-dispersed fiber slurry is added for final mixing. The settling and aging time is 2 to 24 hours, and the stirring time is 3 to 10 minutes.

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