Acid and alkali resistant cement-based joint mixture and preparation method thereof

Abstract

The invention relates to the technical field of joint mixtures, in particular to an acid and alkali resistant cement-based joint mixture and a preparation method thereof. The mortar comprises the following components in percentage by weight: 40-55 wt% of quartz sand, 1-3 wt% of white silica fume, 1-8 wt% of semi-hydrated gypsum, 3-10 wt% of rubber powder, 0.5-5 wt% of an auxiliary agent and the balance of cement. By adding 1-8wt% of semi-hydrated gypsum, the wear resistance, the breaking strength and the compressive strength can be improved, and the shrinkage value can be reduced; by limiting the content of the semi-hydrated gypsum in the cement-based joint mixture to be 4.5-8 wt%, the anti-permeability pressure can be effectively improved; the content of the rubber powder in the cement-based joint mixture is limited to be 5-7.5 wt%, so that the stain resistance can be improved while the wear resistance is maintained; by limiting the weight ratio of the semi-hydrated gypsum to the rubber powder to be 1: (1-1.4), the compressive strength of the base material after freeze-thaw cycle can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of caulking agents, and in particular to an acid- and alkali-resistant cement-based caulking agent and a preparation method thereof. Background Art

[0002] In the construction and renovation industries, tile grout is a crucial filling material, and its quality directly impacts the final finish and lifespan of the tiles. However, traditional grout, composed of a mixture of ordinary cement, fine construction sand, and inorganic fillers, is susceptible to erosion by the elements after a period of use, such as wind, sun, rain, and freeze-thaw conditions. This can lead to quality issues and safety hazards such as whitening and alkali reversion on tiled walls, shrinkage cracks, mildew, and even tile loss. To address this issue, developing a grout with high wear resistance, strong stain resistance, alkali reversion resistance, and acid and alkali resistance has become a pressing technical challenge within the industry.

[0003] Chinese invention patent CN112341103B discloses a method for preparing a building tile caulking agent, which promotes deep hydration of cement by using polyvinyl alcohol glue and combines the molecular sieve effect of zeolite to adsorb Ca 2+ The zeolite is then calcined at 800°C to activate the zeolite, which fills the pores. However, polyvinyl alcohol must be pre-formulated into a colloidal solution, and the zeolite must be activated and calcined at 800°C to increase adsorption capacity, increasing the complexity of the process. Furthermore, polyvinyl alcohol has poor water resistance and may swell in long-term humid environments, affecting its durability. Summary of the Invention

[0004] The first aspect of the present invention provides an acid- and alkali-resistant cement-based caulking agent, which comprises, by weight percentage, 40-55wt% of quartz sand, 1-3wt% of white silica fume, 1-8wt% of hemihydrate gypsum, 3-10wt% of glue powder, 0.5-5wt% of additives, and the balance made up of cement.

[0005] This application improves wear resistance, flexural and compressive strength, and reduces shrinkage by adding 1-8wt% hemihydrate gypsum. Hemihydrate gypsum fills and reinforces cement-based caulking agents, filling the gaps between cement particles to form a tighter structure, thereby improving the overall density of the material and more effectively resisting wear, thereby enhancing wear resistance. Furthermore, when subjected to bending forces, hemihydrate gypsum acts as a "bridge" connecting cement particles, reducing the generation and expansion of cracks and thus improving flexural strength. Hemihydrate gypsum also regulates the hydration rate of cement, making the hydration process more uniform, helping to form a more stable and stronger structure, reducing shrinkage caused by water evaporation, and further reducing shrinkage.

[0006] Further research has revealed that a 4.5-8wt% hemihydrate gypsum content in cement-based caulking agents effectively improves impermeability. This is likely due to the specific proportion of hemihydrate gypsum providing an appropriate expansion source during cement hydration, offsetting shrinkage stress in the cement-based material due to drying shrinkage or temperature fluctuations, reducing the formation of shrinkage cracks. This reduced cracking blocks the permeation pathway, improving the overall impermeability of the system.

[0007] The weight ratio of the quartz sand to the cement is 1:(0.6-1).

[0008] Optionally, the weight ratio of the quartz sand to cement is 1:(0.8-1).

[0009] The applicant has found that the weight ratio of quartz sand to cement is 1: (0.6-1), which can further improve the wear resistance (wear resistance <500mm 3 , JC / T 1004-2017). Quartz sand has a high inherent hardness. At a high cement ratio, its particles bond more tightly with the cement paste, forming a composite system of "hard skeleton + high-strength gelling network." This optimizes aggregate packing density, reduces interfacial weak zones, avoids increased wear due to localized looseness, and significantly improves surface wear resistance. Furthermore, the specific cement ratio promotes hydration to generate more CSH-type gel, which fills the interfacial transition zone between the quartz sand and cement paste, reduces microcrack propagation, and further enhances wear resistance.

[0010] The content of the hemihydrate gypsum in the cement-based caulking agent is 4.5-8 wt %.

[0011] Optionally, the content of the hemihydrate gypsum in the cement-based caulking agent is 4.5-6 wt %.

[0012] The content of the rubber powder in the cement-based sealant is 5-7.5 wt%.

[0013] The applicant's research has found that a 5-7.5wt% content of rubber powder in cement-based caulk can improve stain resistance while maintaining wear resistance. This is likely due to the rubber powder strengthening the interfacial adhesion between the cement matrix and aggregate through chemical bonding and physical adsorption, reducing microcracks and maintaining a foundation for wear resistance. Simultaneously, its polymer components fill the pores between cement hydration products, reducing surface roughness and physical attachment points for stain particles. Furthermore, the continuous polymer film formed by the rubber powder covers the caulk surface, sealing open pores and effectively blocking the infiltration pathways for contaminants.

[0014] The weight ratio of the hemihydrate gypsum to the rubber powder is 1:(1-1.4).

[0015] The auxiliary agent includes at least one of a mildew preventer, an anti-eluviation agent, a defoamer, an early strength agent, a water reducer, a retarder, a hydrophobic agent, a suspending agent, and a thixotropic agent.

[0016] Optionally, the auxiliary agent further comprises a viscosity modifier, and the viscosity modifier comprises wood fiber and cellulose ether.

[0017] Optionally, the mildew inhibitor includes at least one of BBIT (n-butyl-1,2-benzisothiazolin-3-one), Bropol, tribromophenol, diiodomethyl-p-methylphenyl sulfone, organic amines, and chlorine dioxide.

[0018] Optionally, the rubber powder includes at least one of ethylene-vinyl laurate-vinyl chloride copolymer, EVA resin, ABS resin, and polyurethane resin.

[0019] Optionally, the defoaming agent comprises a mixture of a polyoxyalkylene derivative and a non-mineral oil.

[0020] Optionally, the early strength agent includes at least one of lithium sulfate, calcium formate, calcium chloride, calcium nitrate, and sodium thiosulfate.

[0021] Optionally, the water reducer includes at least one of melamine-based, naphthalene-based, polycarboxylic acid-based, fatty acid-based, and acrylic acid graft copolymers.

[0022] Optionally, the wood fiber includes at least one of cellulose, lignin, and hemicellulose.

[0023] Optionally, the retarder includes at least one of tartaric acid, citric acid monohydrate, sodium gluconate, sodium phosphate, and zinc salt.

[0024] Optionally, the hydrophobic agent includes at least one of sodium stearate, silane hydrophobic agent, calcium stearate, silicone emulsion, and paraffin-based hydrophobic agent.

[0025] Optionally, the suspending agent includes at least one of silicon dioxide, bentonite, and xanthan gum.

[0026] Optionally, the cellulose ether includes at least one of polypropylene, hydroxypropyl methylcellulose (HPMC), carboxymethyl cellulose (CMC), methyl cellulose (MC), and ethyl cellulose (EC).

[0027] Optionally, the thixotropic agent includes at least one of fumed silica, bentonite, polyamide wax, hydrogenated castor oil, and organic clay.

[0028] The weight ratio of the quartz sand to the white silica fume is (22-25):1.

[0029] Optionally, the weight ratio of the quartz sand to the white silica fume is (22-23):1.

[0030] The mesh number of the quartz sand is 300-500 meshes.

[0031] Optionally, the mesh size of the quartz sand is 300-400 mesh.

[0032] The second aspect of the present invention provides a method for preparing an acid- and alkali-resistant cement-based caulking agent, comprising the following steps: mixing cement, quartz sand, white silica fume, and semi-hydrated gypsum evenly, then adding glue powder and additives, and mixing evenly.

[0033] Beneficial effects

[0034] 1. Adding 1-8 wt% of hemihydrate gypsum can improve wear resistance, flexural strength and compressive strength and reduce shrinkage value.

[0035] 2. By limiting the content of hemihydrate gypsum in the cement-based caulking agent to 4.5-8wt%, the anti-seepage pressure can be effectively improved.

[0036] 3. By limiting the weight ratio of quartz sand and cement to 1: (0.6-1), the wear resistance can be further improved (wear resistance < 500mm 3 , JC / T 1004-2017).

[0037] 4. By limiting the content of rubber powder in the cement-based caulking agent to 5-7.5wt%, the stain resistance can be improved while maintaining the wear resistance.

[0038] 5. By limiting the weight ratio of hemihydrate gypsum to rubber powder to 1: (1-1.4), the compressive strength of the substrate after freeze-thaw cycles can be improved. DETAILED DESCRIPTION

[0039] Examples 1-2, Comparative Examples 1-8

[0040] An acid and alkali resistant cement-based caulking agent, the components by weight percentage are shown in Table 1, and the specific sources of the components are shown in Table 2, where " / " indicates that the manufacturer is not disclosed.

[0041] Table 1

[0042]

[0043]

[0044] Table 2

[0045]

[0046] A preparation method of an acid- and alkali-resistant cement-based caulking agent comprises the following steps: uniformly stirring cement, quartz sand, white silica fume and semi-hydrated gypsum for 15 minutes, then adding the remaining components and stirring for 30 minutes.

[0047] Comparative Example 9

[0048] Mapei caulk (Mapei color anti-mold caulk 2801).

[0049] Performance testing methods

[0050] The performance of the sealants prepared in the examples and comparative examples was tested, and the test data are listed in Table 3.

[0051] Wear resistance / mm 3 Refer to JC / T 1004-2017.

[0052] For flexural strength, refer to JC / T 1004-2017.

[0053] The flexural strength after freeze-thaw cycles shall refer to JC / T 1004-2017.

[0054] Under standard test conditions, compressive strength refers to JC / T 1004-2017.

[0055] The compressive strength after freeze-thaw cycles refers to JC / T 1004-2017.

[0056] Shrinkage value / (mm / m) refers to JC / T 1004-2017.

[0057] Water absorption in 30 minutes refers to JC / T 1004-2017.

[0058] Water absorption in 240 minutes refers to JC / T 1004-2017.

[0059] For stain resistance, refer to GB / T 9780-2013.

[0060] The resistance to alkali reversion shall refer to JC / T 1024-2019. If there is no visible trace of alkali reversion and no powdering, it is qualified, otherwise it is unqualified.

[0061] Alkali resistance refers to GB / T 9265-2009. It is qualified if there is no blistering, peeling, powdering or softening. Otherwise, it is unqualified.

[0062] Transverse deformation / mm refers to JC / T 1004-2017.

[0063] For the impermeability pressure / MPa, please refer to JC / T 2090-2011.

[0064] The " / " is not tested.

[0065] Performance test data

[0066] Table 3

[0067]

[0068]

Claims

1. An acid and alkali resistant cement-based sealant, characterized in that: Calculated by weight percentage, the components include: 40-55wt% of quartz sand, 1-3wt% of white silica fume, 1-8wt% of semi-hydrated gypsum, 3-10wt% of rubber powder, 0.5-5wt% of additives, and the balance is made up of cement.

2. The acid and alkali resistant cement-based sealant according to claim 1, characterized in that: The weight ratio of the quartz sand to the cement is 1:(0.6-1).

3. The acid and alkali resistant cement-based sealant according to claim 2, characterized in that: The content of the hemihydrate gypsum in the cement-based caulking agent is 4.5-8 wt %.

4. The acid and alkali resistant cement-based sealant according to claim 3, characterized in that: The content of the rubber powder in the cement-based caulking agent is 5-7.5 wt %.

5. The acid and alkali resistant cement-based sealant according to claim 4, characterized in that: The weight ratio of the hemihydrate gypsum to the rubber powder is 1:(1-1.4).

6. The acid and alkali resistant cement-based sealant according to claim 1, characterized in that: The auxiliary agent includes at least one of a mildew preventer, an anti-eluviation agent, a defoamer, an early strength agent, a water reducer, a retarder, a hydrophobic agent, a suspending agent, and a thixotropic agent.

7. The acid and alkali resistant cement-based sealant according to claim 1, characterized in that: The weight ratio of the quartz sand to the white silica fume is (22-25):

1.

8. The acid and alkali resistant cement-based caulking agent according to claim 7, characterized in that: The weight ratio of the quartz sand to the white silica fume is (22-23):

1.

9. The acid and alkali resistant cement-based sealant according to claim 1, characterized in that: The mesh number of the quartz sand is 300-500 meshes.

10. A method for preparing the acid- and alkali-resistant cement-based caulking agent according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: mixing cement, quartz sand, white silica fume and semi-hydrated gypsum evenly, then adding rubber powder and additives and mixing evenly.

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