Polymer modified low-carbon cementing material repair mortar and preparation method thereof

Abstract

The invention provides a polymer modified low-carbon cementing material repair mortar and a preparation method thereof. The repair mortar comprises the following components in percentage by mass: 10-30% of super sulfate cement, 10-20% of aluminate cement, 2-10% of desulfurized gypsum, 0.5-4% of polymer emulsion, less than or equal to 0.3% of fiber, 0.05-0.2% of a defoaming agent, 0.1-0.5% of a water reducing agent, less than or equal to 1% of an early strength agent and 54.5-70% of sand. According to the technical scheme, Portland cement is replaced by the super sulfate cement, so that the later strength of the aluminate cement is improved; the repairing mortar prepared by the invention contains the super sulfate cement, the aluminate cement and the polymer emulsion, wherein the super sulfate cement and the aluminate cement have good sulfate corrosion resistance.

Description

Technical Field

[0001] This application belongs to the field of repair mortar technology, and relates to a polymer-modified low-carbon cementitious material repair mortar and its preparation method. Background Technology

[0002] Repair mortar is a specialized mortar used for the repair and reinforcement of concrete. Existing repair materials include inorganic repair mortar and organic repair materials. Among them, organic repair materials have advantages such as high bonding strength and good durability, but poor compatibility with cement-based materials and high cost; inorganic repair materials have advantages such as high strength and good compatibility with cement-based materials, but have problems such as low bonding strength and easy detachment.

[0003] Aluminate cement is characterized by rapid hardening, early strength, and strong resistance to sulfate corrosion, and is commonly used for the repair and reinforcement of concrete structures. The hydration of calcium aluminate minerals in aluminate cement mainly occurs within the first 7 days. In the later stages of hydration, the hydration products of aluminate cement, CAH... 10 A crystal transformation can occur, leading to volume shrinkage and making it prone to cracking. In addition, the high cost of aluminate cement limits its use.

[0004] Patent application publication (CN111153670A) discloses a rapid repair material, mortar, and preparation method for cement concrete pavements. The raw materials for this rapid repair material include silicate cement, aluminate cement, hemihydrate gypsum, defoamer, water-reducing agent, and polymer emulsion. The silicate cement content is 50-70 parts, the aluminate cement content is 10-20 parts, the hemihydrate gypsum content is 5-15 parts, the defoamer content is 0.1-0.3 parts, the water-reducing agent content is 0.1-0.3 parts, and the polymer emulsion content is 10-20 parts. Although this silicate cement-aluminate cement-gypsum ternary system repair mortar utilizes silicate cement to address the issue of later strength reduction in aluminate cement, producing one ton of silicate cement clinker releases approximately 0.9 tons of carbon dioxide. With the advancement of low-carbon and green development, replacing silicate cement with low-carbon cement is one of the main ways to solve the "three highs" problem (high carbon dioxide, high pollution, and high energy consumption) in the cement industry. Furthermore, after silicate cement is hydrated, it contains a large amount of calcium hydroxide and hydrated calcium aluminate, which makes its resistance to sulfate attack poor. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the raw materials of the existing silicate cement-aluminate cement-gypsum ternary system repair mortar have high carbon emissions and high energy consumption. Furthermore, after silicate cement is hydrated, it contains a large amount of calcium hydroxide and hydrated calcium aluminate, which makes its resistance to sulfate attack poor.

[0006] To address the aforementioned problems, this invention provides a polymer-modified low-carbon cementitious material repair mortar. The components of this polymer-modified low-carbon cementitious material repair mortar, by mass percentage, include: 10%~30% supersulfate cement, 10%~20% aluminate cement, 2%~10% desulfurized gypsum, 0.5%~4% polymer emulsion, ≤0.3% fiber, 0.05%~0.2% defoamer, 0.1%~0.5% water-reducing agent, ≤1% early-strength agent, and 54.5%~70% sand.

[0007] The present invention utilizes supersulfate cement to replace silicate cement, thereby improving the later-stage strength of aluminate cement. The repair mortar prepared by the present invention comprises supersulfate cement, aluminate cement, and polymer emulsion, wherein the supersulfate cement and aluminate cement exhibit excellent resistance to sulfate attack. Furthermore, supersulfate cement is more carbon-efficient and energy-saving.

[0008] Optionally, according to the above technical solution of the present invention, the supersulfate cement is type 42.5 cement.

[0009] Optionally, according to the above technical solution of the present invention, the aluminate cement is CA-50 grade aluminate cement.

[0010] Optionally, according to the above technical solution of the present invention, the polymer emulsion is a styrene-butadiene rubber emulsion or a styrene-acrylate emulsion; Preferably, the styrene-butadiene emulsion has a pH value of 7.0-8.5 and a solid content of 45%. Preferably, the styrene-acrylic emulsion has a pH value of 5-7 and a solid content of 45%.

[0011] Optionally, according to the above technical solution of the present invention, the fiber is a polypropylene fiber.

[0012] According to the above technical solution of the present invention, optionally, the defoamer is an organosilicon, which is a milky white viscous liquid with a pH value of 6-8 and a solid content of 30%.

[0013] Optionally, according to the above technical solution of the present invention, the water-reducing agent is a powdered polycarboxylate high-efficiency water-reducing agent.

[0014] Optionally, according to the above technical solution of the present invention, the early strength agent is powdered sodium sulfate.

[0015] According to the above technical solution of the present invention, optionally, the sand is medium-grade sand with a fineness modulus of 2.3 to 3.0.

[0016] Based on the above-mentioned polymer-modified low-carbon cementitious material repair mortar, the present invention also provides a method for preparing the above-mentioned polymer-modified low-carbon cementitious material repair mortar, comprising: The polymer emulsion is diluted with water at a volume ratio of 1:2 to 20.

[0017] Mix sand, supersulfate cement, aluminate cement, desulfurized gypsum, fiber, water-reducing agent, and early-strength agent and stir for 3-5 minutes. While stirring, slowly add polymer diluted emulsion and continue stirring for 3-5 minutes. Add defoamer 30 seconds to 1 minute before the end of stirring to obtain polymer-modified low-carbon cementitious material repair mortar.

[0018] The beneficial effects of this application are as follows: 1. Supersulfate cement can replace silicate cement to improve the later strength of aluminate cement. Compared with traditional silicate cement, supersulfate cement eliminates the "one grinding and one firing" process, which can achieve a 95% utilization rate of industrial solid waste, a 90% reduction in carbon emissions, and an 85% reduction in energy consumption, resulting in significant ecological and environmental benefits. 2. Environmentally friendly and low-cost. The repair mortar prepared by this invention contains 95% supersulfate cement and desulfurized gypsum, which effectively solves the problem of high-value utilization of solid waste, and at the same time solves the problem of high cost of using aluminate cement alone, thus realizing the low-cost preparation of repair mortar; 3. Excellent resistance to sulfate attack: The repair mortar prepared by this invention contains supersulfate cement, aluminate cement and polymer emulsion. Supersulfate cement and aluminate cement have good resistance to sulfate attack. At the same time, the addition of polymer emulsion can form a polymer mold inside the mortar, which further improves the corrosion resistance of the repair mortar.

[0019] 4. The repair mortar prepared by this invention combines the advantages of inorganic and organic repair materials, possessing advantages such as high early strength, high bonding strength, and good compatibility with cement-based materials. Preferably, the fibers form a dense network structure within the cement paste, and together with the formed polymer film, the two combine to form a spatially continuous polymer network structure within the mortar. This effectively prevents crack formation, improves the toughness of the repair mortar, and enhances its bonding performance and shrinkage resistance. Detailed Implementation

[0020] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0021] This invention provides a polymer-modified low-carbon cementitious repair mortar and its preparation method. The polymer-modified low-carbon cementitious repair mortar comprises, by mass percentage: 10%–30% persulfate cement, 10%–20% aluminate cement, 2%–10% desulfurized gypsum, 0.5%–4% polymer emulsion, ≤0.3% fiber, 0.05%–0.2% defoamer, 0.1%–0.5% water-reducing agent, ≤1% early-strength agent, and 54.5%–70% sand. Preferably, the persulfate cement used in this invention is type 42.5 cement. In the following specific embodiments, the type 42.5 persulfate cement used is produced by Ningxia Jiaheng Green Low-Carbon New Material Technology Co., Ltd. The aluminate cement is CA-50 grade aluminate cement.

[0022] In this invention, the polymer emulsion is a styrene-butadiene rubber (SBR) emulsion or a styrene-acrylate emulsion; wherein the SBR emulsion used has a pH value of 7.0-8.5 and a solid content of 45%; the styrene-acrylate emulsion used has a pH value of 5-7 and a solid content of 45%. In the following specific embodiments, the SBR emulsion was purchased from Shenzhen Yoshida Chemical Co., Ltd. as F106# SBR emulsion, with a measured solid content of 45%. The styrene-acrylate emulsion was purchased from Qingdao Dayang Haiderun Building Materials Co., Ltd. as 888# styrene-acrylate emulsion, with a measured solid content of 45%.

[0023] In this invention, the fiber is polypropylene fiber. The water-reducing agent is powdered polycarboxylate superplasticizer. The early-strength agent is powdered sodium sulfate. The sand is medium-grade sand with a fineness modulus of 2.3~3.0.

[0024] In this invention, the defoamer is an organosilicon, which is a milky white viscous liquid with a pH value of 6-8 and a solid content of 30%.

[0025] It should be noted that the pH values ​​of the above-mentioned styrene-butadiene emulsion, styrene-acrylic emulsion, and organosilicon are not fixed values. Fluctuations in pH value within the above range are normal and can all be used in the polymer-modified low-carbon cementitious material repair mortar of this application.

[0026] The method for preparing polymer-modified low-carbon cementitious repair mortar provided by this invention includes: The polymer emulsion is diluted with water at a volume ratio of 1:2 to 20.

[0027] Mix sand, supersulfate cement, aluminate cement, desulfurized gypsum, fiber, water-reducing agent, and early-strength agent and stir for 3-5 minutes. While stirring, slowly add polymer diluted emulsion and continue stirring for 3-5 minutes. Add defoamer 30 seconds to 1 minute before the end of stirring to obtain polymer-modified low-carbon cementitious material repair mortar.

[0028] The present invention will be illustrated below through specific embodiments.

[0029] Example 1: Preparation method of polymer-modified low-carbon cementitious material repair mortar Dilute 0.5 parts of styrene-butadiene rubber latex with 20 times the volume of water according to the weight ratio of styrene-butadiene rubber latex. Then mix 58 parts of sand, 10 parts of supersulfate cement, 20 parts of aluminate cement, 10 parts of desulfurized gypsum, 0.4 parts of water-reducing agent, and 1 part of early strength agent and stir for 4 minutes. While stirring, slowly add the diluted polymer latex and continue stirring for 5 minutes. Add 0.1 parts of defoamer within 40 seconds before the end of stirring to obtain polymer-modified low-carbon cementitious material repair mortar.

[0030] Examples 2-5: The difference from Example 1 is that the proportions of each component are different, as detailed in Table 1.

[0031] Comparative Example 1: The difference from Example 5 is that the supersulfate cement in Comparative Example 1 is replaced with 42.5 type silicate cement. Otherwise, it is the same as Example 5. See Table 1 for details.

[0032] Comparative Example 2: The difference from Example 5 is that it does not contain aluminate cement, but is otherwise the same as Example 5, as detailed in Table 1.

[0033] Comparative Example 3: The difference from Example 5 is that the polymer emulsion diluent in Example 5 was replaced with 14 parts of water, and no polymer emulsion was present. Otherwise, it was the same as Example 5, as detailed in Table 1.

[0034] Comparative Example 4: The difference from Example 5 is that the proportion of supersulfate cement is too high. Otherwise, it is the same as Example 5. See Table 1 for details.

[0035] Table 1. Comparative composition ratio of each embodiment

[0036] The performance of the repair mortars obtained in the above embodiments and comparative examples was tested: The fluidity was tested in accordance with GB / T 8077-2012 Test Method for Homogeneity of Concrete Admixtures.

[0037] The initial setting time and final setting time were determined in accordance with GB / T 1346-2011 Standard Consistency Water Requirement, Setting Time and Soundness Test Method for Cement.

[0038] Mechanical properties were tested in accordance with GB / T 17671-1999 Cement Mortar Strength Test Method (ISO Method).

[0039] The sulfate resistance performance was evaluated by the number of wet-dry cycles. The test method was based on the "Sulfate Resistance Test" in the national standard GB / T50082-2024 Standard for Test Methods of Long-Term Performance and Durability of Concrete.

[0040] According to the requirements of the "DBJ61 / T112-2016 Technical Specification for Application of High-Ductility Concrete", 40*40*160mm cement mortar test blocks were prepared. The equivalent flexural toughness of the test specimens (kJ / m) was tested. 3 The bonding performance is evaluated by using the bond strength.

[0041] According to the requirements of "JC / C 603-2004 Cement Mortar Dry Shrinkage Test Method", the shrinkage rate is tested and the shrinkage rate is used to evaluate the shrinkage resistance.

[0042] The test results are shown in Table 2.

[0043] Table 2. Performance test table of repair mortar obtained from the comparative examples of each embodiment.

[0044] As can be seen from Tables 1 and 2, the repair mortars obtained in Examples 1 to 5 have good overall performance. The decreased fluidity in Example 5 is due to the addition of fibers.

[0045] By comparing Example 5 and Comparative Example 1, Comparative Example 1 showed poor resistance to sulfate attack because silicate cement has poor resistance to sulfate attack.

[0046] Comparing Example 5 and Comparative Example 2, it can be seen that Comparative Example 2 has a longer setting time and poorer early strength. This is because Comparative Example 2 does not contain aluminate cement, and the hydration rate of pure persulfate cement is slow. In contrast, Example 5, with the addition of aluminate cement, can react rapidly with gypsum to produce ettringite, providing early strength and shortening the setting time. The low 7-day bond strength of the repair mortar obtained in Comparative Example 2 is also due to the slow hydration reaction of persulfate cement.

[0047] Comparing Example 5 and Comparative Example 3, it can be seen that in Example 5, compared to Comparative Example 3, the fibers form a dense network structure inside the cement paste. Combined with the polymer film formed by the polymer, the two work together to form a spatially continuous polymer network structure within the mortar. This effectively prevents crack formation, improves the toughness of the repair mortar, and enhances its bonding performance and shrinkage resistance. In Example 5, the supersulfate cement and aluminate cement exhibit good resistance to sulfate attack. Furthermore, the addition of the polymer emulsion forms a polymer film within the mortar, further improving the corrosion resistance of the repair mortar.

[0048] By comparing Example 5 and Comparative Example 4, it can be seen that the excessive amount of supersulfate cement and the insufficient amount of aluminate cement in Comparative Example 4 will result in a low early production of ettringite, which cannot provide sufficient early strength.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A polymer-modified low-carbon cementitious material repair mortar, characterized in that, The components of the repair mortar, by mass percentage, are as follows: 10%~30% supersulfate cement, 10%~20% aluminate cement, 2%~10% desulfurized gypsum, 0.5%~4% polymer emulsion, ≤0.3% fiber, 0.05%~0.2% defoamer, 0.1%~0.5% water-reducing agent, ≤1% early-strength agent, and 54.5%~70% sand.

2. The polymer-modified low-carbon cementitious material repair mortar according to claim 1, characterized in that, The supersulfate cement is type 42.5 cement.

3. The polymer-modified low-carbon cementitious material repair mortar according to claim 1, characterized in that, The aluminate cement is CA-50 grade aluminate cement.

4. The polymer-modified low-carbon cementitious material repair mortar according to claim 1, characterized in that, The polymer emulsion is a styrene-butadiene rubber emulsion or a styrene-acrylate emulsion; Preferably, the styrene-butadiene emulsion has a pH value of 7.0-8.5 and a solid content of 45%. Preferably, the styrene-acrylic emulsion has a pH value of 5-7 and a solid content of 45%.

5. The polymer-modified low-carbon cementitious material repair mortar according to claim 1, characterized in that, The fiber is polypropylene fiber.

6. The polymer-modified low-carbon cementitious material repair mortar according to claim 1, characterized in that, The defoamer is an organosilicon, which appears as a milky white viscous liquid with a pH of 6-8 and a solid content of 30%.

7. The polymer-modified low-carbon cementitious material repair mortar according to claim 1, characterized in that, The water-reducing agent is a powdered polycarboxylate high-efficiency water-reducing agent.

8. The polymer-modified low-carbon cementitious material repair mortar according to claim 1, characterized in that, The early strength agent mentioned is powdered sodium sulfate.

9. The polymer-modified low-carbon cementitious material repair mortar according to claim 1, characterized in that, The sand is medium-grade sand with a fineness modulus of 2.3 to 3.

0.

10. A method for preparing the polymer-modified low-carbon cementitious material repair mortar according to any one of claims 1 to 9, characterized in that, include: The polymer emulsion is diluted with water, and the volume ratio of polymer emulsion to water is 1:2~20; Mix sand, supersulfate cement, aluminate cement, desulfurized gypsum, fiber, water-reducing agent, and early-strength agent and stir for 3-5 minutes. While stirring, slowly add polymer diluted emulsion and continue stirring for 3-5 minutes. Add defoamer 30 seconds to 1 minute before the end of stirring to obtain polymer-modified low-carbon cementitious material repair mortar.

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