Anti-crack plastering mortar and preparation method thereof

Abstract

The application relates to the field of mortar, and particularly discloses a crack-resistant plastering mortar and a preparation method thereof. The mortar comprises the following raw materials in parts by weight: cement 70-100 parts, sodium alginate 5-9 parts, latex powder 3-7 parts, machine-made sand 100-155 parts, gypsum 80-180 parts, diatomite 10-25 parts, fly ash 3-6 parts, an additive 1-3 parts and anti-crack fiber 15-35 parts. The preparation method comprises the following steps: gypsum pretreatment: homogenizing sodium alginate and gypsum under the condition of ultrasonic coupling mechanical stirring; machine-made sand pretreatment: dissolving the additive in water to form an additive solution, and mixing and grinding the latex powder and the machine-made sand; mixing: uniformly mixing the cement, the pretreated gypsum and machine-made sand, diatomite, fly ash and anti-crack fiber, and uniformly stirring the mixture by adding appropriate water. The application has the advantages of improving the crack resistance of the plastering mortar and improving the bonding strength with a concrete base.

Description

Technical Field

[0001] This application relates to the field of mortar, and more specifically, to a crack-resistant plastering mortar and its preparation method. Background Technology

[0002] Plastering mortar is a type of building mortar that is applied to building surfaces to level them or meet decoration and finishing requirements. It is mainly divided into premixed dry plastering mortar and wet plastering mortar. Premixed dry plastering mortar is a material made by mixing aggregates, cementitious materials such as cementitious materials and admixtures in a certain proportion. It can be used directly after adding water and stirring. It has the characteristics of convenient transportation and high construction efficiency, and is widely used. With the continuous acceleration of urbanization, the demand for plastering mortar in both basic and high-rise buildings is gradually increasing. However, cement-based plastering mortar has a relatively fast hydration rate in the early stage, generating a large number of small molecular bubbles that are difficult to expel in time. After the water evaporates completely in the later stage, it is easy to cause severe shrinkage inside the mortar. This uneven hydration process can easily lead to hollowing and cracking. In addition, the large number of pores in the plastering mortar matrix can also easily lead to cracking. At present, the residential building structure in my country is mainly based on shear wall and frame-shear structure. With the promotion and application of large formwork and the improvement of construction technology, the concrete surface after demolding is generally relatively smooth. Therefore, when applying the plaster layer, the bonding problem between cement mortar and smooth concrete base is easy to occur. Summary of the Invention

[0003] In order to improve the crack resistance of plastering mortar and enhance its bond strength with concrete substrate, this application provides a crack-resistant plastering mortar and its preparation method.

[0004] Firstly, the crack-resistant plastering mortar provided in this application adopts the following technical solution:

[0005] A crack-resistant plastering mortar comprises the following raw materials in parts by weight: 70-100 parts cement, 5-9 parts sodium alginate, 3-7 parts latex powder, 100-155 parts manufactured sand, 80-180 parts gypsum, 10-25 parts diatomaceous earth, 3-6 parts fly ash, 1-3 parts additives, and 15-35 parts crack-resistant fiber.

[0006] The crack-resistant fiber is prepared by the following steps: the fiber is placed in an excess of acidic solution and stirred, a silane coupling agent is added, a neutralizing agent is added under stirring conditions, and a thickener is added and stirred evenly after the reaction is completed.

[0007] Furthermore, the cement grade is P.O42.5 silicate cement, and the fly ash is grade II fly ash.

[0008] By employing the above technical solution, the fibers are first acid-treated with an acidic solution to alter their morphology. After adding a silane coupling agent, the agent hydrolyzes under acidic conditions, causing the silicon-oxygen bonds in the silane molecules to break easily. This generates silicate ions and corresponding organic groups, allowing the organic groups in the silane coupling agent to connect with other functional groups. The added neutralizing agent neutralizes the acidic solution and generates corresponding salts, which, under the action of a thickener, adhere and fix to the fibers. The resulting crack-resistant fibers not only effectively improve the crack resistance of plastering mortar but also participate in cement hydration, combine with gypsum, and improve the mechanical properties of the mortar after molding, as well as its bond strength with the concrete substrate.

[0009] Preferably, the acidic solution includes at least one of calcium acetate solution and magnesium acetate solution.

[0010] Furthermore, the acidic solution can be a calcium acetate solution, a magnesium acetate solution, or a mixture of calcium acetate and magnesium acetate solutions.

[0011] As a further preferred acidic solution, the acidic solution is a mixture of calcium acetate solution with a mass concentration of 15-25% and magnesium acetate solution with a mass concentration of 10-18%.

[0012] Preferably, the neutralizing agent is ammonia.

[0013] By adopting the above technical solution, calcium acetate solution and magnesium acetate solution can provide a corresponding acidic environment for acid treatment of fibers, which is also conducive to the hydrolysis reaction of silane coupling agent. At the same time, under the action of neutralizing agent ammonia water, calcium hydroxide and magnesium hydroxide can be generated and attached to the fibers, further reinforcing the fibers. This allows the crack-resistant fibers to further improve the microstructure of mortar, resist the damage of the external environment, disperse stress, reduce the generation of cracks, and improve the strength and bonding ability of mortar.

[0014] Preferably, the thickener is one of carbomer, gelatin, and xanthan gum.

[0015] Furthermore, carbomer is preferred as a thickener.

[0016] By adopting the above technical solution, the thickener can effectively absorb a large amount of water and adjust the consistency of the system, so that the substance obtained from the reaction of the acidic solution and the neutralizing agent can effectively adhere to the fiber. When the crack-resistant fiber is mixed with materials such as cement and water, the water in the mortar is easily evaporated during the construction process, resulting in the mortar drying too quickly. The thickener can improve the water retention rate of the mortar, slow down the drying rate of the mortar, give construction workers enough time to carry out construction operations, extend the construction time, improve construction efficiency, and retain the moisture in the mortar can also improve the bonding performance of the mortar, making it stronger and more reliable.

[0017] Preferably, the fiber includes one of basalt fiber, polyester fiber, polyvinyl alcohol fiber, and polypropylene fiber.

[0018] Furthermore, polyvinyl alcohol fibers are preferred.

[0019] By adopting the above technical solution, the random distribution of fibers and their overlapping to form a network entanglement in the mixture can absorb and disperse the pressure of the load-bearing material and disperse stress, effectively reducing the generation of cracks. Furthermore, the polyvinyl alcohol fibers contain hydroxyl groups, which can be further connected with the organic groups after hydrolysis of silane coupling agents, further enhancing the performance of crack-resistant fibers.

[0020] Preferably, the components used in the crack-resistant fiber are as follows, by weight: 5-10 parts fiber, 15-25 parts acidic solution, 0.3-0.8 parts coupling agent, 6-11 parts neutralizing agent, and 1-2 parts thickener.

[0021] By adopting the above technical solution, optimizing the dosage of each component is beneficial to obtaining crack-resistant fibers with better performance. The acid solution is in excess so that the crack-resistant fibers also contain free calcium ions and make the crack-resistant fibers weakly acidic as a whole. When the crack-resistant fibers are mixed with cement, water and sodium alginate, they can not only adjust the cement hydration and setting time, but also crosslink with sodium alginate, promote the bonding ability between the raw material components, improve the mechanical properties of mortar, reduce the generation of cracks, and further improve the bonding ability of mortar.

[0022] Preferably, the gypsum comprises calcined gypsum and raw gypsum, wherein the mass ratio of calcined gypsum to raw gypsum is 1:(0.7-1.5).

[0023] By adopting the above technical solution and using a mixture of calcined gypsum and raw gypsum, the strength and crack resistance of the mortar can be further improved, as well as its workability, making it easier to construct and control. When calcined gypsum and raw gypsum are mixed in a mass ratio of 1:(0.7-1.5), the resulting mortar exhibits even better performance.

[0024] Preferably, the additives include one or two of lignin sulfonate, sodium rosinate, and polycarboxylate superplasticizer.

[0025] Furthermore, the preferred additives are sodium rosinate and polycarboxylate superplasticizer, wherein the polycarboxylate superplasticizer has a water reduction rate of 20-30%.

[0026] By adopting the above technical solutions and optimizing the selection of additives, the compound of polycarboxylate superplasticizer and sodium rosinate can better improve the dispersion of each raw material component, improve the fluidity of the material, improve the workability of mortar, and at the same time help improve the mechanical properties of mortar.

[0027] Secondly, this application provides a method for preparing crack-resistant plastering mortar, which adopts the following technical solution:

[0028] A method for preparing crack-resistant plastering mortar includes the following steps:

[0029] Gypsum pretreatment: Sodium alginate and gypsum are homogenized under ultrasonic-coupled mechanical stirring.

[0030] Pretreatment of manufactured sand: Dissolve the additives in water to form an additive solution, mix and grind the manufactured sand;

[0031] Mixing: Mix cement, pretreated gypsum, manufactured sand, diatomaceous earth, fly ash, and crack-resistant fiber evenly, and add an appropriate amount of water and stir evenly.

[0032] Preferably, in the gypsum pretreatment step, the ultrasonic wave is 0.1-0.3MHz and the stirring rate is 1000-1500rpm.

[0033] By adopting the above technical solution, sodium alginate is premixed with gypsum, and ultrasonic coupling mechanical stirring is used. During the propagation of ultrasound, mechanical, thermal, cavitation, and chemical effects are generated, which can modify the gypsum to a certain extent and further improve its bonding strength. First, additives are mixed and ground with manufactured sand to improve the bonding force between the manufactured sand and other raw material components, reducing mortar segregation and cracking. All raw materials are then blended together, and an appropriate amount of water is added to obtain a mortar with excellent comprehensive performance.

[0034] In summary, this application has the following beneficial effects:

[0035] The fibers are first acid-treated with an acidic solution to alter their morphology. After adding a silane coupling agent, the agent hydrolyzes under acidic conditions, causing the silicon-oxygen bonds in the silane molecules to break easily. This generates silicate ions and corresponding organic groups, allowing the organic groups in the silane coupling agent to connect with other functional groups. Calcium acetate and magnesium acetate solutions are used as the acidic solution. The added neutralizing agent, ammonia, reacts with the solution to generate calcium hydroxide and magnesium hydroxide, which adhere to and are fixed onto the fibers under the action of a thickener. An excess of acidic solution ensures that the crack-resistant fibers also contain free calcium ions, making the overall fiber slightly acidic. When the crack-resistant fibers are mixed with cement, water, and sodium alginate, they not only regulate the cement hydration and setting time but also crosslink with sodium alginate, promoting the bonding ability between the various raw material components. The obtained crack-resistant fibers can not only effectively improve the crack resistance of plastering mortar, but also participate in cement hydration and work with gypsum to improve the mechanical properties of the mortar after molding and the bond strength between it and the concrete substrate. Attached Figure Description

[0036] Figure 1 This is a flowchart illustrating the process for preparing the crack-resistant plastering mortar of this application. Detailed Implementation

[0037] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Specific conditions not specified in the examples shall be carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0038] Example of Crack-Resistant Fiber Preparation

[0039] Preparation Example 1

[0040] The crack-resistant fiber is prepared by the following steps: 0.5 kg of basalt fiber is placed in 1.5 kg of acidic solution and stirred, 0.03 kg of silane coupling agent is added, and 0.6 kg of neutralizing agent ammonia is added under stirring conditions. After the reaction is completed, 0.1 kg of thickener is added and stirred evenly; wherein the acidic solution is a 15% magnesium acetate solution; and the thickener is gelatin.

[0041] Preparation Example 2

[0042] The difference from Preparation Example 1 is that the fiber used is polypropylene fiber, the acidic solution is a 20% calcium acetate solution, and the thickener is xanthan gum; all other aspects are the same as Preparation Example 1.

[0043] Preparation Example 3

[0044] The crack-resistant fiber is prepared by the following steps: 1 kg of polyester fiber is placed in 2.5 kg of acidic solution and stirred, 0.08 kg of silane coupling agent is added, and 1.1 kg of neutralizing agent ammonia is added under stirring conditions. After the reaction is completed, 0.2 kg of thickener is added and stirred evenly.

[0045] The acidic solution consists of 1 kg of 15% calcium acetate solution and 1.5 kg of 10% magnesium acetate solution; the thickener is carbomer.

[0046] Preparation Example 4

[0047] The crack-resistant fiber is prepared by the following steps: 0.8 kg of polyvinyl alcohol fiber is placed in 2 kg of acidic solution and stirred, 0.05 kg of silane coupling agent is added, and 1 kg of neutralizing agent ammonia is added under stirring conditions. After the reaction is completed, 0.16 kg of thickener is added and stirred evenly. The acidic solution is 1.5 kg of 15% calcium acetate solution and 0.5 kg of 10% magnesium acetate solution. The thickener is carbomer.

[0048] Comparative Preparation Example 1

[0049] The crack-resistant fiber is prepared by the following steps: 0.8 kg of polyvinyl alcohol fiber is placed in 0.05 kg of silane coupling agent and stirred, and then 0.16 kg of thickener is added and mixed evenly.

[0050] Example

[0051] Example 1

[0052] The crack-resistant plastering mortar includes the following raw materials: 7 kg of cement, 0.5 kg of sodium alginate, 0.3 kg of latex powder, 10 kg of manufactured sand, 18 kg of gypsum, 2.5 kg of diatomaceous earth, 0.3 kg of fly ash, 0.1 kg of additives, and 1.5 kg of crack-resistant fiber prepared in Example 1.

[0053] Gypsum includes calcined gypsum and raw gypsum in a mass ratio of 1:0.7;

[0054] The additive is sodium lignosulfonate;

[0055] The preparation method of crack-resistant plastering mortar includes the following steps:

[0056] Gypsum pretreatment: Sodium alginate and gypsum were homogenized under ultrasonic conditions of 0.1 MHz coupled with mechanical stirring at a stirring rate of 1000 rpm.

[0057] Pretreatment of manufactured sand: Dissolve the additives in water to form an additive solution, mix and grind the latex powder and manufactured sand;

[0058] Mixing: Mix cement, pretreated gypsum, manufactured sand, diatomaceous earth, fly ash, and crack-resistant fiber evenly, and add an appropriate amount of water and stir evenly.

[0059] Example 2

[0060] The crack-resistant plastering mortar includes the following raw materials: 10 kg of cement, 0.9 kg of sodium alginate, 0.7 kg of latex powder, 15 kg of manufactured sand, 8 kg of gypsum, 1 kg of diatomaceous earth, 0.6 kg of fly ash, 0.3 kg of additives, and 3.5 kg of crack-resistant fiber prepared in Preparation Example 2.

[0061] Gypsum includes calcined gypsum and raw gypsum in a mass ratio of 1:1.5;

[0062] The additive is sodium lignosulfonate;

[0063] The preparation method of crack-resistant plastering mortar includes the following steps:

[0064] Gypsum pretreatment: Sodium alginate and gypsum were homogenized under ultrasonic conditions of 0.3MHz and coupled mechanical stirring at a stirring rate of 1500rpm.

[0065] Pretreatment of manufactured sand: Dissolve the additives in water to form an additive solution, mix and grind the latex powder and manufactured sand;

[0066] Mixing: Mix cement, pretreated gypsum, manufactured sand, diatomaceous earth, fly ash, and crack-resistant fiber evenly, and add an appropriate amount of water and stir evenly.

[0067] Example 3

[0068] The difference from Example 1 is that the following are the same as in Example 1: 9 kg of cement, 0.7 kg of sodium alginate, 0.5 kg of latex powder, 13.5 kg of manufactured sand, 15 kg of gypsum, 2 kg of diatomaceous earth, 0.4 kg of fly ash, 0.2 kg of additives, and 3 kg of crack-resistant fiber; the rest are the same as in Example 1.

[0069] Example 4

[0070] The difference from Example 3 is that the gypsum includes calcined gypsum and raw gypsum in a mass ratio of 1:1; the additives are 0.15 kg of polycarboxylate superplasticizer and 0.05 kg of sodium rosinate, and the water reduction rate of polycarboxylate superplasticizer is 30%. All other aspects are the same as in Example 3.

[0071] Example 5

[0072] The difference from Example 4 is that the gypsum is calcined gypsum; the additive is polycarboxylate superplasticizer with a water reduction rate of 20%, and the rest are the same as in Example 4.

[0073] Example 6

[0074] The difference from Example 4 is that the crack-resistant fiber prepared in Preparation Example 3 was used, while the rest are the same as in Example 4.

[0075] Example 7

[0076] The difference from Example 4 is that the crack-resistant fiber prepared in Example 4 was used, while the rest are the same as in Example 4.

[0077] Comparative Example

[0078] Comparative Example 1

[0079] The difference from Example 7 is that polyvinyl alcohol fiber is used to replace the crack-resistant fiber in an equal amount, while the rest is the same as in Example 7.

[0080] Comparative Example 2

[0081] The difference from Example 7 is that the crack-resistant fiber prepared in Comparative Preparation Example 1 was used, while the rest were the same as in Example 7.

[0082] Comparative Example 3

[0083] The difference from Example 7 is that no pretreatment is performed on the gypsum and manufactured sand; instead, the raw material components are directly mixed and stirred evenly according to the formula.

[0084] Performance testing

[0085] The tensile bond strength of the specimens prepared in Examples 1-7 and Comparative Examples 1-3 was determined according to JGJ / T70-2009 "Standard for Test Methods of Basic Performance of Building Mortar". After curing for 28 days, the specimens were placed in an environment with a temperature of 50℃ and a humidity of 60%RH. The number of cracks and the maximum crack width of the specimens after 90 days were recorded. The results are shown in Table 1.

[0086] Table 1

[0087]

[0088]

[0089] As can be seen from Examples 1-7 and Table 1, using the raw material components of this application and the corresponding preparation methods, mortars with excellent bonding strength and good crack resistance can be obtained.

[0090] Combining Example 7 and Comparative Example 1 with Table 1, it can be seen that in Comparative Example 1, the polyvinyl alcohol fibers were used directly without any treatment, while in Comparative Example 2, only a simple treatment with a silane coupling agent and a thickener was performed. The bonding strength and crack resistance of the mortars prepared in Comparative Examples 1 and 2 decreased significantly. This is because the polyvinyl alcohol fibers were first treated with an acidic solution to change the morphology of the fibers. After adding the silane coupling agent, the silane coupling agent hydrolyzed under acidic conditions, and the silicon-oxygen bonds in the silane molecules were easily broken under acidic conditions, generating silicate ions and corresponding organic groups. This allowed the organic groups in the silane coupling agent to connect with the hydroxyl groups contained in the polyvinyl alcohol fibers, further enhancing the crack resistance of the fibers. Calcium acetate solution and magnesium acetate solution, as acidic solutions, reacted with the added neutralizing agent ammonia to generate calcium hydroxide and magnesium hydroxide, which, under the action of the thickener, adhered and fixed onto the fibers. Simultaneously, an excess of acidic solution is used to ensure that the crack-resistant fibers contain free calcium ions, making the fibers generally weakly acidic. When the crack-resistant fibers are mixed with cement, water, and sodium alginate, they not only regulate the cement hydration and setting time but also crosslink with sodium alginate, promoting the bonding ability between the various raw material components. The resulting crack-resistant fibers not only effectively improve the crack resistance of plastering mortar but also participate in cement hydration and, when combined with gypsum, improve the mechanical properties of the mortar after molding and its bond strength with the concrete substrate.

[0091] Based on Examples 7 and 3, and referring to Table 1, it can be seen that in Comparative Example 3, no pretreatment was performed on the gypsum and manufactured sand; the raw material components were directly mixed and used. The resulting mortar exhibited poor bonding strength and crack resistance. This is because sodium alginate was premixed with gypsum, and ultrasonic coupling mechanical stirring was employed. During the propagation of ultrasound, mechanical, thermal, cavitation, and chemical effects were generated, which could modify the gypsum to a certain extent, further improving its bonding strength. By first mixing and grinding the manufactured sand with additives, the bonding force between the manufactured sand and other raw material components was improved, reducing mortar segregation and cracking. By blending all raw materials and adding an appropriate amount of water, a mortar with excellent overall performance was obtained.

[0092] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A crack-resistant rendering mortar, characterized in that, The raw materials include the following parts by weight: 70-100 parts cement, 5-9 parts sodium alginate, 3-7 parts latex powder, 100-155 parts manufactured sand, 80-180 parts gypsum, 10-25 parts diatomaceous earth, 3-6 parts fly ash, 1-3 parts additives, and 15-35 parts crack-resistant fiber. Crack-resistant fibers are prepared through the following steps: Place the fiber in an excess of calcium acetate or magnesium acetate solution and stir. Add silane coupling agent and let stand. Add neutralizing agent under stirring. After the reaction is complete, add thickener and stir evenly. The neutralizing agent is ammonia. The thickener is one of carbomer, gelatin, and xanthan gum; The components used in the anti-crack fiber are as follows, by weight: 5-10 parts fiber, 15-25 parts calcium acetate or magnesium acetate solution, 0.3-0.8 parts coupling agent, 6-11 parts neutralizing agent, and 1-2 parts thickener.

2. Anti-crack plastering mortar according to claim 1, characterized in that: The fiber includes one of basalt fiber, polyester fiber, polyvinyl alcohol fiber, and polypropylene fiber.

3. Anti-crack plastering mortar according to claim 1, characterized in that: The gypsum includes calcined gypsum and raw gypsum, and the mass ratio of calcined gypsum to raw gypsum is 1:(0.7-1.5).

4. Anti-crack plastering mortar according to claim 1, characterized in that: The additives include one or two of lignin sulfonate, sodium rosinate, and polycarboxylate superplasticizer.

5. Process for the preparation of an anti-crack plastering mortar according to any one of claims 1-4, characterized in that: Includes the following steps: Gypsum pretreatment: Sodium alginate and gypsum are homogenized under ultrasonic-coupled mechanical stirring. Pretreatment of manufactured sand: Dissolve the additives in water to form an additive solution, mix and grind the latex powder and manufactured sand; Mixing: Mix cement, pretreated gypsum, manufactured sand, diatomaceous earth, fly ash, and crack-resistant fiber evenly, and add an appropriate amount of water and stir evenly.

6. The method for preparing the anti-cracking rendering mortar according to claim 5, characterized in that: In the gypsum pretreatment step, the ultrasonic wave is 0.1-0.3MHz and the stirring rate is 1000-1500rpm.

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