Cement-based capillary crystalline waterproofing coating, preparation method and application thereof

Abstract

The application discloses cement-based capillary crystalline waterproof coating and a preparation method and application thereof, and belongs to the technical field of cement compositions. The waterproof coating comprises the following raw materials in percentage by mass: cement 35-45%, standard sand 54-64%, calcium ion supplement 0.20-0.30%, crystallizing agent 0.4-0.6%, complex catalyst 0.05-0.10%, retarder 0.05-0.20% and anti-permeation aid 0.10-0.40%. The waterproof coating has the characteristics of low cost, environmental protection, no pollution and excellent anti-permeation performance. The application also provides a preparation method of the cement-based capillary crystalline waterproof coating, which can be realized by simple mixing, and the process is simple, fast and convenient. When applied to a concrete matrix, the waterproof coating has excellent waterproof and anti-permeation effects, and provides support for good application of waterproof materials in the field of building materials.

Description

Technical Field

[0001] This invention relates to the field of cement composition technology, and in particular to a cement-based penetrating crystalline waterproof coating, its preparation method, and its application. Background Technology

[0002] Concrete, as a porous and brittle material, contains numerous microcracks and pores. Harmful substances can enter the concrete through these pores along with moisture, altering the internal environment and causing the decomposition and loss of cement hydration products. Ultimately, this leads to a loss of the concrete's original strength. With age, concrete will crack and peel, posing a significant safety hazard to buildings and severely limiting their lifespan. This indirectly increases carbon emissions from the concrete industry and building operation and maintenance costs, creating a heavy burden for both the concrete industry and building users.

[0003] Since water is a medium for ion transport, reducing the permeability of concrete is an effective way to prevent ions from penetrating the concrete, thereby improving its resistance to erosion and durability. Building waterproofing materials can be classified according to their mechanism of action: surface film-forming type, silicone-permeable type, and pore-sealing type. Currently commonly used organic waterproofing materials are flexible materials, but their compatibility with the substrate is poor. They seal off the exchange of gas and moisture between the inside and outside of the concrete, easily leading to blistering and peeling. Furthermore, their durability is not strong; in areas with strong ultraviolet radiation, they are easily oxidized, causing cracking or peeling and thus losing their waterproofing effect.

[0004] Cement-based penetrating crystalline waterproofing materials use cement-based materials as the matrix. During construction, water is added and stirred to form a coating that is applied to the concrete surface or directly added as an admixture. It possesses both surface film-forming properties, forming a dense cement-based coating on the concrete surface, and pore-sealing effects, making the concrete structure denser and improving its impermeability from the inside out. Furthermore, the cement-based penetrating crystalline material and the concrete matrix have the same main components, exhibiting good compatibility and facilitating the exchange of gas and moisture between the concrete and the external environment, preventing blistering and cracking. In addition, cement-based penetrating crystalline materials also have advantages such as being environmentally friendly, providing longer-lasting protection, and achieving deeper penetration, making them promising for engineering applications. However, current research on the main components, mechanism of action, and protective performance of this material is insufficient, limiting its application scenarios. Moreover, most commercially available cement-based penetrating crystalline waterproofing materials are made from imported active masterbatches in different proportions, resulting in high prices.

[0005] Chinese patent CN102167547A discloses a penetrating crystalline waterproofing material that can quickly repair cracks. The material comprises the following components by weight percentage: 30%–50% cement, 5%–10% expanding agent, 8%–20% quartz sand, 5%–12% mineral additives, 20%–35% water-reducing agent, 0.2%–1.0% retarder, 1%–15% crystallizing precipitant, 1%–12% complexing agent, 1%–13% calcium ion compensator, and 0.1%–1.0% crystal growth agent. The cement-based penetrating crystalline waterproofing material provided by this invention possesses dual waterproofing, strong penetrating crystallization ability, rapid crack repair, and excellent chemical corrosion resistance. Chinese patent CN104446270A provides a building joint crystalline adhesive sealant, comprising component A and component B in a weight ratio of 1:1.0 to 1.6. Component A, by weight percentage, consists of 70-90% polyether polyol and 10%-30% polyisocyanate. Component B consists of 30%-38% cement, 5%-9% expanding agent, 8%-16% quartz sand, 5%-12% mineral additives, and other components. The NCO-terminated prepolymer obtained from the reaction in component A exhibits strong adhesion to numerous materials, and the addition of crystallizing materials allows for thorough mixing and reaction of the two types of materials. This not only enables crystallization within the joint but also results in highly adhesive crystals that maintain the joint sealant effect for an extended period. Currently, research on the formulation of cement-based penetrating crystalline waterproofing materials reveals that only a few products achieve the same anti-seepage effect as commercially available products at a lower price. To achieve the aforementioned technical objectives, existing technologies require a higher proportion of corresponding additives in the raw materials, which is detrimental to reducing usage costs. Therefore, research on this material is essential. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, in a first aspect of the present invention, a low-cost, environmentally friendly, pollution-free, and excellent seepage-proof cement-based penetrating crystalline waterproof coating is provided, the raw materials of which include the following components in weight percentage: cement 35%–45%, standard sand 54%–64%, calcium ion supplement 0.20%–0.30%, crystallizing agent 0.4%–0.6%, complexing catalyst 0.05%–0.10%, retarder 0.05%–0.20%, and anti-seepage aid 0.10%–0.40%.

[0007] Preferably, the cement is P.O42.5 ordinary Portland cement, P.II42.5 Portland cement, or P.I42.5 Portland cement.

[0008] Preferably, the calcium ion supplement is calcium carbonate.

[0009] Preferably, the crystallizing agent is sodium silicate.

[0010] Preferably, the complexing catalyst is tetrasodium ethylenediaminetetraacetic acid.

[0011] Preferably, the retarder is glycine.

[0012] Preferably, the antipermeability agent is sodium acetate.

[0013] In a second aspect of the present invention, a simple method for preparing the cement-based penetrating crystalline waterproof coating of the first aspect of the present invention is provided, comprising the following steps:

[0014] (1) Preparation of active masterbatch: Prepare calcium ion supplement, crystallizing agent, complexing catalyst, retarder and anti-permeability additive in proportion, mix the above raw materials evenly to obtain active masterbatch;

[0015] (2) Preparation of coating: Prepare cement and standard sand in proportion, and then mix the cement, standard sand and the active masterbatch evenly to obtain cement-based penetrating crystalline waterproof coating.

[0016] In a third aspect of the invention, the application of a cement-based penetrating crystalline waterproof coating prepared by the method of the first aspect or the second aspect of the invention is provided, specifically its application as a waterproof material in concrete waterproofing and seepage prevention.

[0017] Cement-based penetrating crystalline waterproof coatings can be applied using methods commonly used in the field. Preferably, the cement-based penetrating crystalline waterproof coating is mixed with water to form a coating slurry, which is then applied to the concrete substrate requiring waterproofing and seepage resistance.

[0018] Based on the above technical solutions, the working mechanism of the waterproof coating of the present invention can be described as follows:

[0019] When applied, the cement-based penetrating crystalline waterproof coating is mixed with water. The active substances in the coating dissolve in the water, and the complexing agent, tetrasodium ethylenediaminetetraacetate, reacts with the Ca produced during cement hydration. 2+ The reaction produces a stable water-soluble complex, reducing the Ca2+ level during initial hydration. 2+ The concentration, along with the retarder glycine, reduces the early hydration rate of the coating, giving it good workability. When the coating is applied to the substrate, the active substances migrate into the concrete matrix with the water. The crystallizing agent sodium silicate in the active substances ensures that the resulting crystals are well-compatible with the concrete matrix itself, and that they react with the free Ca in the matrix. 2+ The reaction produces insoluble calcium silicate, which promotes the formation of CSH gel in the matrix, and the calcium ion supplement provides additional calcium ions for the reaction.

[0020] Regarding the technical objective of achieving long-term anti-seepage effects and reducing the proportion of additives used, the concept of this invention lies in that, when free Ca... 2+When the concentration of the anion is insufficient for the reaction to proceed, the excess anion will capture the CaO from the tetrasodium ethylenediaminetetraacetate complex. 2+ The reaction continues, and the complexing agent returns to its initial state, migrating to Ca. 2+ At higher concentrations, complexes form again, creating a cyclical process that allows crystallization to continue. Furthermore, the tetrasodium ethylenediaminetetraacetate (EDTA-4Na) used in this coating is employed in chemical analysis for titrating calcium ions; it forms a stable, colorless, water-soluble complex with calcium ions, and the reaction is rapid and complete. Simultaneously, the Ca in the matrix liquid phase... 2+ The large-scale consumption disrupted the original reaction equilibrium, thereby catalyzing the hydration of unhydrated cement particles to generate more Ca. 2+ This accelerates the hydration process of cement, generating more hydration products such as hydrated calcium silicate and hydrated calcium aluminate. As the reaction proceeds, pores are gradually sealed, increasing overall impermeability and making it increasingly difficult for water to penetrate the matrix. The matrix gradually dries, and the active substances enter a dormant state. When concrete experiences seepage damage, water re-enters the concrete. The damaged area is washed away by water, causing the concentration of active substances to be lower than in other areas. Under the influence of the concentration gradient, the active substances accumulate at the damaged area, continuing to react and generate insoluble crystals that fill cracks. Even when the crystallizing agent and calcium ion supplement are completely consumed, the complexing agent can still remove excess calcium. 2+ When transported to the crack, it reacts with CO2 in the air to generate calcium carbonate crystals to repair the crack, thus achieving self-repair and long-term protection.

[0021] Compared to existing technologies, the key components selected in the active masterbatch of this invention are inexpensive. The more expensive complexing agent, tetrasodium ethylenediaminetetraacetate, is present in only 0.05 wt.% to 0.15 wt.%, having a minimal impact on coating costs. Furthermore, sodium acetate, a crystallization aid, is introduced into this coating. Its strong hygroscopic properties promote the growth of insoluble crystals within the concrete, while simultaneously forming hydrophobic organosilicon bonds within the coating and substrate, further ensuring and enhancing the coating's waterproofing capabilities. Therefore, this coating maintains excellent impermeability while requiring less active masterbatch compared to similar products, further reducing usage costs.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] This invention provides a cement-based penetrating crystalline waterproof coating, which is characterized by low cost, environmental friendliness and pollution-free properties, and excellent seepage prevention performance.

[0024] This invention provides a method for preparing a cement-based penetrating crystalline waterproof coating, which can be achieved through simple mixing and is a simple and quick process.

[0025] This invention also provides an application of a cement-based penetrating crystalline waterproof coating, which has excellent waterproof and seepage-resistant effects on concrete substrates. Attached Figure Description

[0026] Figure 1 The images are scanning electron microscope (SEM) images of uncoated blank mortar specimens, where image a is at 7500 magnification and image b is at 25000 magnification.

[0027] Figure 2 The images are scanning electron microscope (SEM) images of mortar specimens taken at a depth of 10 mm from the coating formed by the cement-based penetrating crystalline waterproofing coating of Example 3. Image a is at 7500 magnification and image b is at 25000 magnification.

[0028] Figure 3 The images are scanning electron microscope (SEM) images of mortar specimens at a depth of 20 mm from the coating formed by the cement-based penetrating crystalline waterproofing coating of Example 3. Image a is at 7500 magnification and image b is at 25000 magnification.

[0029] Figure 4 The images are scanning electron microscope (SEM) images of mortar specimens taken at a depth of 30 mm from the coating formed by the cement-based penetrating crystalline waterproofing coating of Example 3. Image a is at 7500 magnification and image b is at 25000 magnification.

[0030] Figure 5 The images are scanning electron microscope (SEM) images of mortar specimens at a depth of 40 mm from the coating formed by the cement-based penetrating crystalline waterproofing coating of Example 3. Image a is at 7500 magnification and image b is at 25000 magnification. Detailed Implementation

[0031] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0032] Example 1

[0033] A cement-based penetrating crystalline waterproof coating is prepared using the following method:

[0034] (1) Preparation of active masterbatch: Prepare raw materials, in terms of mass percentage, the proportions are: 38.85% P.O42.5 ordinary Portland cement, 60.00% standard sand, 0.20% calcium carbonate, 0.40% sodium silicate, 0.05% tetrasodium ethylenediaminetetraacetate, 0.10% glycine, and 0.40% sodium acetate; put the other components except P.O42.5 ordinary Portland cement and standard sand into a dry powder mixer, stir and mix for 30 minutes to make it uniform, then weigh and measure the mixture, package and seal it for later use as active masterbatch;

[0035] (2) Preparation of coating: P.O42.5 ordinary silicate cement, standard sand and the active masterbatch are added to the mixer at intervals according to the ratio and stirred for 30 minutes to make it uniform. Then the mixture is weighed, packaged and sealed for later use as cement-based penetrating crystalline waterproof coating.

[0036] The performance of the cement-based penetrating crystalline waterproof coating prepared in this embodiment was tested according to the provisions and methods provided in GB 18445-2012 "Cement-based Penetrating Crystalline Waterproofing Materials". The uncoated group was used as a control. The seepage resistance pressure of the uncoated control group after 28 days was measured to be 0.4 MPa. In contrast, the seepage resistance pressure of the mortar with the coating of this embodiment after 28 days reached 1.4 MPa, with a seepage resistance pressure ratio of 350%. This indicates that the cement-based penetrating crystalline waterproof coating of this invention still has excellent waterproof and seepage-resistant effects on concrete substrates even with a lower proportion of additives.

[0037] Example 2

[0038] A cement-based penetrating crystalline waterproof coating is prepared using the following method:

[0039] (1) Preparation of active masterbatch: Prepare raw materials, in terms of mass percentage, the proportions are: 38.75% P.O42.5 ordinary Portland cement, 60.00% standard sand, 0.20% calcium carbonate, 0.60% sodium silicate, 0.10% tetrasodium ethylenediaminetetraacetate, 0.05% glycine, and 0.30% sodium acetate; put the other components except P.O42.5 ordinary Portland cement and standard sand into a dry powder mixer, stir and mix for 30 minutes to make it uniform, then weigh and measure the mixture, package and seal it for later use as active masterbatch;

[0040] (2) Preparation of coating: P.O42.5 ordinary silicate cement, standard sand and the active masterbatch are added to the mixer at intervals according to the ratio and stirred for 30 minutes to make it uniform. Then the mixture is weighed, packaged and sealed for later use as cement-based penetrating crystalline waterproof coating.

[0041] The impermeability of the cement-based penetrating crystalline waterproof coating prepared in this example was tested using the same method as in Example 1. The impermeability pressure of the uncoated blank group was 0.4 MPa after 28 days, while the impermeability pressure of the mortar with the coating of this example was 1.3 MPa after 28 days, with an impermeability pressure ratio of 325%, still maintaining excellent waterproof and impermeable performance.

[0042] Example 3

[0043] A cement-based penetrating crystalline waterproof coating is prepared using the following method:

[0044] (1) Preparation of active masterbatch: Prepare raw materials, in terms of mass percentage, the proportions are: 38.90% P.O42.5 ordinary Portland cement, 60.00% standard sand, 0.20% calcium carbonate, 0.40% sodium silicate, 0.10% tetrasodium ethylenediaminetetraacetate, 0.10% glycine, and 0.30% sodium acetate; put the other components except P.O42.5 ordinary Portland cement and standard sand into a dry powder mixer, stir and mix for 30 minutes to make it uniform, then weigh and measure the mixture, package and seal it for later use as active masterbatch;

[0045] (2) Preparation of coating: P.O42.5 ordinary silicate cement, standard sand and the active masterbatch are added to the mixer at intervals according to the ratio and stirred for 30 minutes to make it uniform. Then the mixture is weighed, packaged and sealed for later use as cement-based penetrating crystalline waterproof coating.

[0046] The impermeability of the cement-based penetrating crystalline waterproof coating prepared in this example was tested using the same method as in Example 1. The impermeability pressure of the uncoated blank group was 0.4 MPa after 28 days, while the impermeability pressure of the mortar with the coating of this example was 1.5 MPa after 28 days, with an impermeability pressure ratio of 375%, indicating better waterproof and impermeable performance.

[0047] The microstructure of the uncoated blank group and the coated mortar specimens of this embodiment at different depths (10 mm, 20 mm, 30 mm, and 40 mm from the coating) was observed using scanning electron microscopy. Figure 1 It can be clearly observed that the electron micrographs of the uncoated blank group contain a large number of plate-like crystals and amorphous CSH gel, and the microstructure contains a large number of micropores and microcracks, with a relatively high overall porosity. The crystals are loosely distributed in space, and the connections between the crystals are weak. Figures 2-5 It can be clearly observed that the surface microstructure of the coating of this invention is obviously more compact, the crystals are more closely connected, the number of plate-like crystals is significantly reduced, a large number of needle-like and block-like crystals are generated in the pores, the volume of the pores is significantly reduced, and the number of macropores is significantly reduced.

[0048] from Figures 2-4 It can be clearly observed that for the microstructure of samples at different depths in the coating group, there is no significant difference in the microstructure and the number of crystals in the pores among the three groups of samples with depths ranging from 10mm to 30mm. This indicates that the coating penetrated to depths above 30mm, altering the microporous structure at that depth. Figure 5 It can be clearly observed that the overall structure of the sample at a depth of 40 mm has more pores, and the overall structure tends to be similar to Figure 1 The uncoated blank group showed a more porous crystal distribution than the other coated groups, but a certain number of crystals could still be observed in the pores. This indicates that the active material in the coating penetrated to a depth of 40 mm, but the amount of active material penetrating to that depth was relatively small.

[0049] Based on the changes in microstructure, it can be concluded that the coating prepared by this invention can penetrate to a depth of 40mm, and alters the microstructure at the penetration point, effectively sealing harmful pores and significantly improving the impermeability within the surface 40mm, forming a three-dimensional impermeable barrier. After application, the coating promotes the reaction of unhydrated cement clinker, generating more hydration products. Simultaneously, active substances crystallize within the pores; the combined effect of these two factors makes the microstructure of the coated concrete more compact.

[0050] Example 4

[0051] A cement-based penetrating crystalline waterproof coating is prepared using the following method:

[0052] (1) Preparation of active masterbatch: Prepare raw materials, in terms of mass percentage, the proportions are: 38.90% P.O42.5 ordinary Portland cement, 60.00% standard sand, 0.30% calcium carbonate, 0.40% sodium silicate, 0.10% tetrasodium ethylenediaminetetraacetate, 0.20% glycine, and 0.10% sodium acetate; put the other components except P.O42.5 ordinary Portland cement and standard sand into a dry powder mixer, stir and mix for 30 minutes to make it uniform, then weigh and measure the mixture, package and seal it for later use as active masterbatch;

[0053] (2) Preparation of coating: P.O42.5 ordinary silicate cement, standard sand and the active masterbatch are added to the mixer at intervals according to the ratio and stirred for 30 minutes to make it uniform. Then the mixture is weighed, packaged and sealed for later use as cement-based penetrating crystalline waterproof coating.

[0054] The impermeability of the cement-based penetrating crystalline waterproof coating prepared in this example was tested using the same method as in Example 1. The 28-day impermeability pressure of the uncoated blank group was 0.4 MPa, while the 28-day impermeability pressure of the mortar with the coating from this example was 1.1 MPa, achieving an impermeability pressure ratio of 275%.

[0055] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A cement-based penetrating crystalline waterproof coating, characterized in that, Its raw materials consist of the following components by mass percentage: cement 35%~45%, standard sand 54%~64%, calcium ion supplement 0.20%~0.30%, crystallizing agent 0.40%~0.60%, complexing catalyst 0.05%~0.10%, retarder 0.05%~0.20%, and anti-permeability aid 0.10%~0.40%; The cement is P.O42.5 ordinary Portland cement, P.II42.5 Portland cement, or P.I42.5 Portland cement; the calcium ion supplement is calcium carbonate; the crystallizing agent is sodium silicate; the complexing catalyst is tetrasodium ethylenediaminetetraacetate; the retarder is glycine; and the antipermeability aid is sodium acetate.

2. A method for preparing a cement-based penetrating crystalline waterproof coating as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of active masterbatch: Prepare calcium ion supplement, crystallizing agent, complexing catalyst, retarder and anti-permeability agent in proportion, mix the above raw materials evenly to obtain active masterbatch; (2) Preparation of coating: Prepare cement and standard sand in proportion, and then mix the cement, standard sand and the active masterbatch evenly to obtain cement-based penetrating crystalline waterproof coating.

3. The application of a cement-based penetrating crystalline waterproof coating as described in claim 1 or a cement-based penetrating crystalline waterproof coating prepared by the method described in claim 2, characterized in that: Its application as a waterproofing material in concrete waterproofing and seepage prevention.

4. The application according to claim 3, characterized in that: Cement-based penetrating crystalline waterproof coatings are mixed with water to form a coating slurry, which is then applied to concrete substrates requiring waterproofing and seepage resistance.

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