Saltpetering-resistant cement-based impervious coating material and preparation method thereof

Abstract

The invention relates to the technical field of chemical engineering, in particular to an alkali efflorescence-resistant cement-based impervious coating material which comprises a base material and an active substance, and the base material comprises, by weight, 60-70 parts of a cementing material, 30-40 parts of an auxiliary cementing material and 40-60 parts of aggregate. The active substances comprise 1-1.5 parts of a precipitator, 2-3 parts of a complexing agent, 1-1.5 parts of an early strength agent, 4-6 parts of a calcium ion compensating agent, 1.5-2 parts of a dispersing agent and 1-1.5 parts of other auxiliaries. According to the method, alkali-aggregate reaction is reduced by means of not introducing alkali metal ions, the concentration of soluble calcium salt generated in the curing process is reduced through the pozzolanic effect generated when bulk industrial waste with high silicon content meets water, so that the adverse effect caused by saltpetering is reduced, and meanwhile, under the synergistic effect of various active substances, the curing effect is improved. The compactness and the impermeability of the coating are obviously improved.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to an alkali-resistant cement-based anti-seepage coating material and its preparation method. Background Technology

[0002] Efflorescence, or efflorescence, refers to the process by which soluble salts (such as calcium hydroxide, sodium hydroxide, and potassium hydroxide) migrate to the surface of concrete with moisture and crystallize. The resulting white powder or flocculent deposits not only damage the material's appearance but also pose multiple threats to the concrete's durability and structural integrity. The most direct impact of efflorescence is on the material's surface; the white crystals, after drying, form mottled stains, leading to uneven coloring, and causing irreversible damage, especially to the aesthetics of decorative concrete (such as exposed concrete walls and colored pavements). A deeper harm lies in the fact that efflorescence accelerates the deterioration of concrete durability. The expansion stress generated during salt crystallization can cause surface peeling or powdering, compromising the integrity of the protective layer. Simultaneously, the migration of salts increases the porosity of the concrete, significantly enhancing its permeability, allowing moisture, chloride ions, and harmful media to more easily penetrate the interior, thereby altering the internal chemical environment of the concrete and causing the decomposition of cementitious substances such as CSH. In cold regions, increased permeability can lead to freeze-thaw cycle damage; in humid environments, it accelerates steel corrosion, creating a vicious cycle of "corrosion-expansion-cracking," ultimately reducing the structural load-bearing capacity. Efflorescence can also induce chemical reactions, reducing the chemical stability of concrete. For example, alkaline substances migrating to the surface may trigger an alkali-aggregate reaction upon contact with reactive aggregates, causing internal expansion and cracking of the concrete; if the salts contain sulfate ions, they may induce sulfate attack, leading to a sharp drop in concrete strength. From an economic perspective, surface deterioration caused by efflorescence requires frequent cleaning or repair, significantly increasing subsequent maintenance costs. Furthermore, for large infrastructure or landmark buildings, repeated treatment of efflorescence not only consumes manpower and resources but also disrupts normal use due to construction interference.

[0003] Cement-based penetrating crystalline waterproofing material (CCCW) is a new type of rigid waterproofing material. Unlike traditional waterproofing materials that rely on a waterproofing layer, it reacts within the substrate through penetration to generate crystals or precipitates that plug cracks, thereby improving the substrate's own impermeability. Currently, CCCW is limited in its application due to its high construction requirements and drawbacks such as dependence on moisture activation, low early strength, and limited repair range.

[0004] The emissions of bulk industrial wastes such as fly ash, blast furnace slag ash, phosphorus slag powder, and phosphogypsum are showing a year-on-year increasing trend. However, as these are industrial by-products, the presence of numerous impurities greatly reduces their usability. Furthermore, these impurities contain trace amounts of toxic heavy metals and other substances. Direct dumping not only wastes a large amount of land resources but may also pollute the surrounding environment. Therefore, how to fully utilize these by-products has become a major challenge for many production enterprises.

[0005] Patent CN 117025009 A discloses a protective coating based on the principle of crystallization repair and its preparation method. By not using soluble sodium salts, the alkali-aggregate reaction is avoided. However, the main factor causing efflorescence is the migration of soluble calcium salts such as Ca(OH)2 to the concrete surface to form calcium carbonate and other substances. Therefore, even without the use of alkali metal salts, it is still difficult to effectively reduce the occurrence of efflorescence.

[0006] Patent CN 117602895 A discloses a fly ash-based anti-seepage material and its application. It uses moderately or highly alkaline fly ash as the main cementing material and the main precursor for alkali-activated materials, and uses calcium-ion-containing alkaline substances as activators to prepare an environmentally friendly fly ash-based anti-seepage material, greatly improving the utilization rate of fly ash. However, as an anti-seepage and waterproof material, relying solely on the density of the coating itself is insufficient to achieve long-term anti-seepage goals. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention provides an alkali-resistant cement-based anti-seepage coating material, which aims to improve the anti-seepage and waterproof performance of the material.

[0008] To achieve its objectives, the present invention employs the following technical solution: An alkali-resistant cement-based anti-seepage coating material includes a substrate and active substances. The substrate, by weight, comprises 60-70 parts of cementitious material, 30-40 parts of auxiliary cementitious material, and 40-60 parts of aggregate. The active substances include 1-1.5 parts of precipitant, 2-3 parts of complexing agent, 1-1.5 parts of early-strength agent, 4-6 parts of calcium ion compensator, 1.5-2 parts of dispersant, and 1-1.5 parts of other additives.

[0009] In one feasible embodiment, the cementing material is at least one of ordinary silicate cement and sulfoaluminate cement, preferably a mixture of ordinary silicate cement and sulfoaluminate cement as the cementing material.

[0010] In one feasible solution, the auxiliary cementing material is at least one of fly ash, blast furnace slag ash, and phosphorus slag powder, preferably a mixture of fly ash, blast furnace slag ash, and phosphorus slag powder as the auxiliary cementing material.

[0011] In one feasible approach, the aggregate is refined quartz sand.

[0012] In one feasible approach, the precipitant is phosphogypsum.

[0013] In one feasible approach, the complexing agent is at least one of glycine and tartaric acid, preferably a combination of glycine and tartaric acid as the complexing agent.

[0014] In one feasible approach, the early-strength agent is calcium formate.

[0015] In one feasible embodiment, the calcium ion compensator is at least one of calcium hydroxide and calcium oxide, preferably a combination of calcium hydroxide and calcium oxide as the calcium ion compensator. Calcium formate, which acts as an early strength agent, and phosphogypsum, which acts as a precipitant, also serve as calcium ion compensators.

[0016] In one feasible approach, the dispersant is polyvinylpyrrolidone.

[0017] In one feasible approach, the other additives include at least one of hydroxypropyl methylcellulose, polycarboxylate superplasticizer, and redispersible latex powder, preferably a combination of hydroxypropyl methylcellulose, polycarboxylate superplasticizer, and redispersible latex powder as other additives.

[0018] As the most preferred embodiment, the anti-alkali efflorescence cement-based anti-seepage coating material of the present invention includes a substrate and an active substance, in parts by weight: the substrate includes 70 parts of cementitious material (60 parts of ordinary silicate cement (such as P.II 52.5 grade silicate cement), 10 parts of sulfoaluminate cement (such as 62.5 grade sulfoaluminate cement), 30 parts of auxiliary cementitious material (10 parts of fly ash, 5 parts of blast furnace slag ash, 15 parts of phosphorus slag powder) and 50 parts of aggregate (refined quartz sand).

[0019] The active substances include 1 part precipitant (phosphogypsum), 2.25 parts complexing agent (1.25 parts glycine, 1 part tartaric acid), 1 part early strength agent (calcium formate), 5 parts calcium ion compensator (4 parts calcium hydroxide, 1 part calcium oxide), 1.75 parts dispersant (polyvinylpyrrolidone), and 1.3 parts other additives (1 part hydroxypropyl methylcellulose, 0.2 parts polycarboxylate superplasticizer, 0.1 parts redispersible latex powder).

[0020] The present invention also provides a method for preparing the alkali-resistant cement-based anti-seepage coating material, specifically: mixing the substrate and the active substance evenly according to the formula to prepare the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0021] This invention also provides a method for using the aforementioned alkali-resistant cement-based anti-seepage coating material, specifically: adding water (dry material to water mass ratio of 2:1) to the dry material of the alkali-resistant cement-based anti-seepage coating material and stirring evenly to form a slurry, which is then brushed onto the mortar or concrete surface (based on dry material mass, the preferred brushing amount is 1.5 kg / m²). 2 This forms an alkali-resistant cement-based impermeable coating.

[0022] Compared with the prior art, the beneficial effects of the present invention are reflected in: 1. The coating material of this invention reduces the alkali-aggregate reaction by not introducing alkali metal ions, and utilizes the pozzolanic reaction generated when high-silicon-content bulk industrial waste (such as fly ash, phosphorus slag powder, etc.) comes into contact with water (i.e., the reaction of active silica, alumina, etc. with calcium hydroxide to form hydrated calcium silicate, hydrated calcium aluminate, and ettringite). This reduces the concentration of soluble calcium salts during the curing process, thereby reducing efflorescence.

[0023] 2. The coating material of the present invention uses a variety of bulk industrial wastes (such as fly ash, blast furnace slag ash, and phosphorus slag powder) as auxiliary cementitious materials, which can reduce the use of high carbon emission cement in the base material and realize the resource recycling of waste.

[0024] 3. The coating material of this invention uses phosphogypsum as a precipitant instead of gypsum dihydrate, realizing the reuse of phosphogypsum and providing a new approach for the high-value recycling of phosphogypsum. Furthermore, the main component of phosphogypsum, CaSO4·2H2O, works synergistically with sulfoaluminate cement in the matrix to promote the formation of ettringite, reducing microcracks caused by cement shrinkage in mortar and concrete.

[0025] 4. The addition of calcium formate as an early-strength agent to the coating material of the present invention can shorten the curing cycle of the coating, and at the same time, it can provide complexing anions together with glycine and other substances to improve the resistance to Ca. 2+ The ability of metal ions to "transport".

[0026] 5. Polyvinylpyrrolidone (PVP), as a dispersant, contains amide groups that can react with Ca... 2+ Plasma chelation, coupled with its inherent hydrophilicity, makes it suitable as an active component of CCCW. This invention enhances the chelating ability of the complexing agent in the active material through the incorporation of PVP, achieving microcrack repair. Simultaneously, the dispersion ability of PVP on cement particles reduces porosity defects in the substrate, further improving the substrate's density and impermeability. Attached Figure Description

[0027] Figure 1 This is a camera photograph of the sample from Example 1 after 30 cycles in the anti-alkali cycling experiment.

[0028] Figure 2 XRD patterns of cured coated cement paste, coated cement paste, and reference cement paste.

[0029] Figure 3 The DTG spectrum of the coating after 28 days of standard curing.

[0030] Figure 4 This is a SEM image magnified 1000 times after 28 days of standard curing.

[0031] Figure 5 This is a SEM image of the coating magnified 5000 times after 28 days of standard curing.

[0032] Figure 6 This is a SEM image magnified 5000 times after 28 days of standard curing.

[0033] Figure 7 This is a SEM image of the coating magnified 10,000 times after 28 days of standard curing. Detailed Implementation

[0034] To provide a better understanding of the technical features, objectives, and beneficial effects of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the present invention is not limited to the following embodiments.

[0035] Unless otherwise specified, all raw materials used in this invention are purchased from the market.

[0036] Example 1 This embodiment provides an alkali-resistant cement-based anti-seepage coating material, the specific raw material composition of which is: 70 parts of cementitious materials: 60 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 30 parts of auxiliary cementitious materials: 10 parts fly ash, 5 parts blast furnace slag ash, and 15 parts phosphorus slag powder; 50 parts refined quartz sand; 1 part precipitant phosphogypsum; 2.25 parts complexing agent: 1.25 parts glycine, 1 part tartaric acid; 1 dose of calcium formate, an early-strength agent; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.75 parts dispersant polyvinylpyrrolidone; 1.3 parts other additives: 1 part hydroxypropyl methylcellulose, 0.2 parts polycarboxylate superplasticizer and 0.1 parts redispersible latex powder.

[0037] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0038] Example 2 The alkali-resistant cement-based anti-seepage coating material provided in this embodiment differs from that in Embodiment 1 only in that the cementitious material in the raw materials is 60 parts (50 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement), and the auxiliary cementitious material is 40 parts (10 parts of fly ash, 10 parts of blast furnace slag ash, and 20 parts of phosphorus slag powder). The specific raw material composition is as follows: 60 parts of cementitious materials: 50 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 40 parts of auxiliary cementitious materials: 10 parts fly ash, 10 parts blast furnace slag ash, and 20 parts phosphorus slag powder; 50 parts refined quartz sand; 1 part precipitant phosphogypsum; 2.25 parts complexing agent: 1.25 parts glycine, 1 part tartaric acid; 1 dose of calcium formate, an early-strength agent; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.75 parts dispersant polyvinylpyrrolidone; 1.3 parts other additives: 1 part hydroxypropyl methylcellulose, 0.2 parts polycarboxylate superplasticizer and 0.1 parts redispersible latex powder.

[0039] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0040] Example 3 The alkali-resistant cement-based anti-seepage coating material provided in this embodiment differs from that in Embodiment 1 only in that the cementitious material in the raw materials is 65 parts (55 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement), and the auxiliary cementitious material is 35 parts (10 parts of fly ash, 10 parts of blast furnace slag ash, and 15 parts of phosphorus slag powder). The specific raw material composition is as follows: 65 parts of cementitious materials: 60 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 35 parts of auxiliary cementitious materials: 10 parts fly ash, 10 parts blast furnace slag ash, and 15 parts phosphorus slag powder; 50 parts refined quartz sand; 1 part precipitant phosphogypsum; 2.25 parts complexing agent: 1.25 parts glycine, 1 part tartaric acid; 1 dose of calcium formate, an early-strength agent; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.75 parts dispersant polyvinylpyrrolidone; 1.3 parts other additives: 1 part hydroxypropyl methylcellulose, 0.2 parts polycarboxylate superplasticizer and 0.1 parts redispersible latex powder.

[0041] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0042] Example 4 The alkali-resistant cement-based anti-seepage coating material provided in this embodiment differs from that in Example 1 only in that the content of the precipitant phosphogypsum in the raw materials is 1.5 parts. The specific raw material composition is as follows: 70 parts of cementitious materials: 60 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 30 parts of auxiliary cementitious materials: 10 parts fly ash, 5 parts blast furnace slag ash, and 15 parts phosphorus slag powder; 50 parts refined quartz sand; 1.5 parts precipitant phosphogypsum; 2.25 parts complexing agent: 1.25 parts glycine, 1 part tartaric acid; 1 dose of calcium formate, an early-strength agent; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.75 parts dispersant polyvinylpyrrolidone; 1.3 parts other additives: 1 part hydroxypropyl methylcellulose, 0.2 parts polycarboxylate superplasticizer and 0.1 parts redispersible latex powder.

[0043] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0044] Example 5 The alkali-resistant cement-based anti-seepage coating material provided in this embodiment differs from that in Example 1 only in that the complexing agent in the raw materials is 2 parts (1 part glycine and 1 part tartaric acid). The specific raw material composition is as follows: 70 parts of cementitious materials: 60 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 30 parts of auxiliary cementitious materials: 10 parts fly ash, 5 parts blast furnace slag ash, and 15 parts phosphorus slag powder; 50 parts refined quartz sand; 1 part precipitant phosphogypsum; Two parts complexing agent: 1 part glycine and 1 part tartaric acid; 1 dose of calcium formate, an early-strength agent; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.75 parts dispersant polyvinylpyrrolidone; 1.3 parts other additives: 1 part hydroxypropyl methylcellulose, 0.2 parts polycarboxylate superplasticizer and 0.1 parts redispersible latex powder.

[0045] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0046] Example 6 The alkali-resistant cement-based anti-seepage coating material provided in this embodiment differs from that in Example 1 only in that the complexing agent in the raw materials is 3 parts (2 parts glycine and 1 part tartaric acid). The specific raw material composition is as follows: 70 parts of cementitious materials: 60 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 30 parts of auxiliary cementitious materials: 10 parts fly ash, 5 parts blast furnace slag ash, and 15 parts phosphorus slag powder; 50 parts refined quartz sand; 1 part precipitant phosphogypsum; 3 parts complexing agent: 2 parts glycine, 1 part tartaric acid; 1 dose of calcium formate, an early-strength agent; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.75 parts dispersant polyvinylpyrrolidone; 1.3 parts other additives: 1 part hydroxypropyl methylcellulose, 0.2 parts polycarboxylate superplasticizer and 0.1 parts redispersible latex powder.

[0047] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0048] Example 7 The alkali-resistant cement-based anti-seepage coating material provided in this embodiment differs from that in Example 1 only in that the other additives in the raw materials are 1.5 parts (1 part hydroxypropyl methylcellulose, 0.4 parts polycarboxylate superplasticizer, and 0.1 parts redispersible latex powder). The specific raw material composition is as follows: 70 parts of cementitious materials: 60 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 30 parts of auxiliary cementitious materials: 10 parts fly ash, 5 parts blast furnace slag ash, and 15 parts phosphorus slag powder; 50 parts refined quartz sand; 1 part precipitant phosphogypsum; 2.25 parts complexing agent: 1.25 parts glycine, 1 part tartaric acid; 1 dose of calcium formate, an early-strength agent; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.75 parts dispersant polyvinylpyrrolidone; 1.5 parts other additives: 1 part hydroxypropyl methylcellulose, 0.4 parts polycarboxylate superplasticizer and 0.1 parts redispersible latex powder.

[0049] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0050] Example 8 The alkali-resistant cement-based anti-seepage coating material provided in this embodiment differs from that in Example 1 only in that the other additives in the raw materials are 1 part each (0.5 parts hydroxypropyl methylcellulose, 0.4 parts polycarboxylate superplasticizer, and 0.1 parts redispersible latex powder). The specific raw material composition is as follows: 70 parts of cementitious materials: 60 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 30 parts of auxiliary cementitious materials: 10 parts fly ash, 5 parts blast furnace slag ash, and 15 parts phosphorus slag powder; 50 parts refined quartz sand; 1 part precipitant phosphogypsum; 2.25 parts complexing agent: 1.25 parts glycine, 1 part tartaric acid; 1 dose of calcium formate, an early-strength agent; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.75 parts dispersant polyvinylpyrrolidone; 1 part of other additives: 0.5 parts of hydroxypropyl methylcellulose, 0.4 parts of polycarboxylate superplasticizer and 0.1 parts of redispersible latex powder.

[0051] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0052] Comparative Example 1 The cement-based anti-seepage coating material provided in this comparative example differs from that in Example 1 only in the amount of cementitious material: 100 parts (90 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement) and 0 parts of auxiliary cementitious material. The specific raw material composition is as follows: 100 parts of cementitious materials: 90 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 50 parts refined quartz sand; 1 part precipitant phosphogypsum; 2.25 parts complexing agent: 1.25 parts glycine, 1 part tartaric acid; 1 dose of calcium formate, an early-strength agent; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.75 parts dispersant polyvinylpyrrolidone; 1.3 parts other additives: 1 part hydroxypropyl methylcellulose, 0.2 parts polycarboxylate superplasticizer and 0.1 parts redispersible latex powder.

[0053] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0054] Comparative Example 2 The cement-based anti-seepage coating material provided in this comparative example differs from that in Example 1 only in that it does not contain a precipitant (phosphogypsum). The specific raw material composition is as follows: 70 parts of cementitious materials: 60 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 30 parts of auxiliary cementitious materials: 10 parts fly ash, 5 parts blast furnace slag ash, and 15 parts phosphorus slag powder; 50 parts refined quartz sand; 2.25 parts complexing agent: 1.25 parts glycine, 1 part tartaric acid; 1 dose of calcium formate, an early-strength agent; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.75 parts dispersant polyvinylpyrrolidone; 1.3 parts other additives: 1 part hydroxypropyl methylcellulose, 0.2 parts polycarboxylate superplasticizer and 0.1 parts redispersible latex powder.

[0055] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0056] Comparative Example 3 The cement-based anti-seepage coating material provided in this comparative example differs from that in Example 1 only in that it does not contain an early-strength agent (calcium formate). The specific raw material composition is as follows: 70 parts of cementitious materials: 60 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 30 parts of auxiliary cementitious materials: 10 parts fly ash, 5 parts blast furnace slag ash, and 15 parts phosphorus slag powder; 50 parts refined quartz sand; 1 part precipitant phosphogypsum; 2.25 parts complexing agent: 1.25 parts glycine, 1 part tartaric acid; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.75 parts dispersant polyvinylpyrrolidone; 1.3 parts other additives: 1 part hydroxypropyl methylcellulose, 0.2 parts polycarboxylate superplasticizer and 0.1 parts redispersible latex powder.

[0057] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0058] Comparative Example 4 The cement-based anti-seepage coating material provided in this comparative example differs from that in Example 1 only in that it does not contain a dispersant (polyvinylpyrrolidone). The specific raw material composition is as follows: 70 parts of cementitious materials: 60 parts of P.II 52.5 grade silicate cement and 10 parts of 62.5 grade sulfoaluminate cement; 30 parts of auxiliary cementitious materials: 10 parts fly ash, 5 parts blast furnace slag ash, and 15 parts phosphorus slag powder; 50 parts refined quartz sand; 1 part precipitant phosphogypsum; 2.25 parts complexing agent: 1.25 parts glycine, 1 part tartaric acid; 1 dose of calcium formate, an early-strength agent; 5 parts calcium ion compensator: 4 parts calcium hydroxide and 1 part calcium oxide; 1.3 parts other additives: 1 part hydroxypropyl methylcellulose, 0.2 parts polycarboxylate superplasticizer and 0.1 parts redispersible latex powder.

[0059] Mix the above raw materials evenly to produce the dry material of the alkali-resistant cement-based anti-seepage coating material.

[0060] The anti-permeability and anti-efflorescence properties of the coating materials obtained in the above embodiments and comparative examples were verified using the following method: Impermeability performance: Mortar test blocks were formed using a frustum-shaped metal impermeability test mold (70×80×30 mm) according to GB18445-2012. The pre-curing conditions were a temperature of 20°C. 1℃, 95%RH, for 1 day. After pre-curing, roughen the back surface of the mortar test block, then apply the cement-based anti-seepage coating material. Ensure the surface is moist before application to fix the water-cement ratio (the dry material to water mass ratio of the cement-based anti-seepage coating material is 2:1, and the application rate is 1.5 kg / m²). 2 Apply the coating to the back surface of the test block to form an impermeable coating. After the coating dries, immerse the test block in water (saturated calcium hydroxide solution) for curing at a temperature of 20°C. The curing time was 28 days at 1℃, and the water level was maintained at 3 / 4 of the test block. The mortar test blocks (6 specimens for each example and comparative example) with or without coating were sealed in molds with paraffin and rosin. The molds were then screwed into the permeability tester. The instrument pressure was increased from 0.2 MPa, maintained for 2 hours, and then increased by 0.1 MPa every hour. When water seepage appeared on the surface of 3 specimens, the mortar permeability tester was shut off, and the machine pressure at that moment was recorded (accurate to 0.1 MPa). The permeability pressure value of the mortar was calculated according to formula (1): P=H-0.1 (1) In the formula: P is the impermeability pressure of the mortar, in MPa; H is the pressure when water seepage occurs on the surface of the third specimen, in MPa.

[0061] Anti-efflorescence cycle test: Test blocks were formed using a (40×40×40)mm cubic steel mold. Pre-curing conditions were: temperature 20±1℃, 95%RH, and time 1 day. After pre-curing, the back surface of the mortar test block was roughened with a brush before coating. The surface must be moistened before coating to fix the water-cement ratio (dry material to water mass ratio of 2:1, coating amount 1.5kg / m²). 2 Apply the coating to the back surface of the test block to form an impermeable coating. After the coating dries, immerse the test block in water (saturated calcium hydroxide solution) for curing at a temperature of 20±1℃, a humidity of 95%RH, and a curing time of 28 days, maintaining the water level at 3 / 4 of the test block's height. Immerse the cured coated mortar test block in water for 12 hours, then remove it and place it in a 60℃ oven to dry for 12 hours. Repeat the immersion / drying steps 30 times, observing whether a white substance precipitates on the surface (stop the experiment if a white substance precipitates).

[0062] Table 1 shows the permeability test results of coated and uncoated test blocks of Examples 1-8 and Comparative Examples 1-4. The permeability pressure of the reference test block is 0.3 MPa.

[0063] Table 1 Results of the anti-permeability test

[0064] As shown in the table above, the alkali-resistant and impermeable coating prepared by this invention can improve the impermeability of mortar test blocks, meeting the impermeability requirements of the national standard GB18445-2012 for cement-based penetrating crystalline impermeable materials. According to the impermeability test results of Examples 1-3 and Comparative Example 1, the addition of 30% auxiliary cementitious material has no significant effect on impermeability performance, but the impermeability performance decreases with the increase of the amount of bulk waste added. According to the impermeability test results of Examples 1 and Comparative Examples 2 and 4, the addition of phosphogypsum and polyvinylpyrrolidone (PVP) improves the impermeability of the coating. Firstly, the combined action of phosphogypsum and sulfoaluminate cement in the matrix promotes the formation of ettringite, reducing microcracks caused by cement shrinkage in the reference block. Secondly, the addition of PVP not only enhances the chelating ability of the complexing agent in the active material, achieving the repair of microcracks, but also reduces pore defects due to the dispersion effect of PVP on cement particles, further improving the density and impermeability of the coating.

[0065] Table 2 Results of Anti-alkali Cycling Experiment

[0066] Table 2 shows the results of the anti-efflorescence cycling test for Examples 1-8 and Comparative Examples 1-4. The results from Comparative Example 1 and Example 1 demonstrate that the incorporation of auxiliary cementitious materials significantly improves the material's anti-efflorescence ability. Figure 1 As shown, the anti-permeability coating prepared in Example 1 of the present invention showed no visible efflorescence marks or powdering on the coating surface after 30 anti-efflorescence cycles, indicating that it has good anti-efflorescence performance.

[0067] To verify the effect of the coating on the composition and content of hydration substances in mortar samples, two groups of cement paste samples without standard sand were prepared and pre-cured (at 20°C). (11℃, 95%RH, for 1 day), one group was coated with a cement-based anti-seepage coating material (same composition as Example 1, except without quartz sand), while the other group served as a reference sample was not coated. Both groups of materials were subjected to water immersion curing (curing temperature 20℃). The temperature was 11℃, the curing time was 28 days, and the water level was maintained at 3 / 4 of the test block.

[0068] Figure 2 The XRD patterns are shown for the coated cement paste, the coated cement paste, and the reference cement paste after curing. After 28 days of standard curing, compared with the reference cement, the intensity of the calcium silicate diffraction peak in the coated cement sample decreased, while the intensity of the characteristic diffraction peaks of ettringite and hydrated calcium silicate increased significantly. This indicates that the brush-coated layer promotes cement hydration, forming more hydrated calcium silicate and ettringite crystals, thus reducing efflorescence caused by calcium ion dissolution. Furthermore, the generated ettringite fills internal pores, increasing internal density and improving the impermeability of the matrix.

[0069] like Figure 3 The DTG spectrum of the coating paste, as shown, corroborates the fact that the coating lost weight at 70-200℃ and 400-450℃ after 28 days of standard curing. Figure 2 The XRD pattern of the intermediate coating cement paste shows that the coating contains a large amount of hydrated calcium silicate and calcium hydroxide, and monosulfate calcium sulfoaluminate (AFm) was also observed. In addition, the weight loss at 450-800℃ corresponds to the decomposition of calcium carbonate (including amorphous calcium carbonate ACC and calcite). This indicates that the coating contains a certain amount of calcium carbonate, which, together with monosulfate calcium sulfoaluminate, can fill the internal pores, reduce porosity, and increase internal density. At the same time, appropriate carbonation can reduce cement alkalinity, thereby reducing the occurrence of efflorescence.

[0070] like Figure 4-7 The SEM images show that after 28 days of standard curing, the coating has a relatively dense microstructure, with a large amount of gel-like substances (such as calcium silicate hydrate) and blocky substances (such as calcium carbonate), as well as a small amount of flaky substances (calcium hydroxide).

[0071] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art who makes analogous substitutions or changes based on the technical solution and concept of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An alkali-resistant cement-based anti-seepage coating material, comprising a substrate and an active substance, characterized in that, By weight, the base material comprises 60-70 parts of cementitious material, 30-40 parts of auxiliary cementitious material and 40-60 parts of aggregate, and the active substance comprises 1-1.5 parts of precipitant, 2-3 parts of complexing agent, 1-1.5 parts of early strength agent, 4-6 parts of calcium ion compensator, 1.5-2 parts of dispersant and 1-1.5 parts of other additives.

2. The alkali-resistant cement-based anti-seepage coating material according to claim 1, characterized in that, The cementing material is at least one of ordinary silicate cement and sulfoaluminate cement; the auxiliary cementing material is at least one of fly ash, blast furnace slag ash and phosphorus slag powder.

3. The alkali-resistant cement-based anti-seepage coating material according to claim 1, characterized in that, The aggregate is refined quartz sand.

4. The alkali-resistant cement-based anti-seepage coating material according to claim 1, characterized in that, The precipitant is phosphogypsum.

5. The alkali-resistant cement-based anti-seepage coating material according to claim 1, characterized in that, The complexing agent is at least one of glycine and tartaric acid.

6. The alkali-resistant cement-based anti-seepage coating material according to claim 1, characterized in that, The early strength agent is calcium formate.

7. The alkali-resistant cement-based anti-seepage coating material according to claim 1, characterized in that, The calcium ion compensator is at least one of calcium hydroxide and calcium oxide.

8. The alkali-resistant cement-based anti-seepage coating material according to claim 1, characterized in that, The dispersant is polyvinylpyrrolidone.

9. The alkali-resistant cement-based anti-seepage coating material according to claim 1, characterized in that, The other additives include at least one of hydroxypropyl methylcellulose, polycarboxylate superplasticizer, and redispersible latex powder.

10. A method for preparing an alkali-resistant cement-based anti-seepage coating material according to any one of claims 1 to 9, characterized in that: Mix the base material and active substance evenly according to the formula to prepare the dry material of the alkali-resistant cement-based anti-seepage coating material.

11. A method of using the anti-alkali efflorescence cement-based anti-seepage coating material according to any one of claims 1 to 9, characterized in that: Water is added to the dry material of the alkali-resistant cement-based anti-seepage coating material and stirred evenly to make a slurry, which is then brushed onto the mortar or concrete surface to form an alkali-resistant cement-based anti-seepage coating.

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