Self-healing waterproof mortar

Abstract

The self-healing waterproof mortar is prepared from the following raw materials in parts by weight: 350 to 450 parts of low-heat cement, 10 to 30 parts of mineral powder, 20 to 30 parts of a plastic expanding agent, 550 to 650 parts of fine sand, 5 to 12 parts of a compound additive and 200 to 250 parts of water, the compound admixture is prepared from the following components in parts by weight: 1 to 2 parts of a polycarboxylic acid water reducing agent, 1 to 5 parts of a water repellent, 0.5 to 1.5 parts of white carbon black, 1 to 2 parts of a coagulant, 0.2 to 1.5 parts of a complexing agent, 0.3 to 1 part of a reinforcing agent, 0.01 to 0.05 part of a water-retaining agent and 0.05 to 0.1 part of a retarder. The self-healing waterproof mortar disclosed by the invention is applied to the field of building materials, and the purposes of cracking prevention and self healing are achieved by improving the grading of a cementing material particle group, improving the strength and durability of the mortar, reducing the porosity, improving the impermeability and complexing ions in the mortar into a stable compound.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly to a self-healing waterproof mortar. Background Art

[0002] Since the self-healing phenomenon of concrete was discovered by Abram in the 1820s, self-healing waterproof mortar has gradually developed into a new type of building material through the unremitting research of scientists.

[0003] Mortar is a typical brittle building material. During use, under the action of external forces or other factors, micro-cracks or local damages will occur, resulting in a reduction in mechanical properties and durability. It may even cause macroscopic cracks and brittle fractures, easily leading to accidents and causing significant losses to society. Currently, whether in road and bridge projects or building construction projects, mortar is widely used. The application of mortar in projects is becoming more and more common and important. Therefore, the repair of mortar cracks has become a research hotspot in the academic and engineering fields.

[0004] Currently, the repair methods for cracks can be roughly divided into two types: one is the traditional post-repair method or regular repair. Most of this type of repair is for cracks visible to the naked eye, and the repair location is generally where the mortar is easily damaged. Limited by the repair materials, secondary cracking is likely to occur. This repair method that stays in the passive and planned mode can no longer meet the current requirements for mortar materials. The other is self-healing and self-repair, which can control and repair mortar cracks in the early stage, avoid the generation of macroscopic cracks and the hazards brought by penetration, ensure the safety and durability of buildings, and thus solve the problems that are difficult or impossible to solve by traditional methods.

[0005] However, the self-healing mortars on the current market either achieve the self-healing purpose by adding microorganisms and nutrients, or use the addition of fibers to achieve the purpose of physical repair and crack prevention. Summary of the Invention

[0006] The technical problem to be solved by the present invention is: aiming at the deficiencies existing in the prior art, to provide a self-healing waterproof mortar with low production cost, high strength and good self-healing effect. By improving the gradation of the cementitious material particle group, the strength and durability of the mortar are improved, the porosity is reduced, and the anti-seepage performance is enhanced. At the same time, the ions in the mortar are complexed into stable compounds to achieve the purpose of crack prevention and self-healing.

[0007] To solve the above technical problem, the technical solution of the present invention is:

[0008] A self-healing waterproof mortar, comprising raw materials in the following parts by weight: 350-450 parts of low-heat cement, 10-30 parts of mineral powder, 20-30 parts of plastic expansion agent, 550-650 parts of fine sand, 5-12 parts of compound admixture, and 200-250 parts of water; the compound admixture comprises components in the following parts by weight: 1-2 parts of polycarboxylate water reducer, 1-5 parts of water repellent, 0.5-1.5 parts of white carbon black, 1-2 parts of coagulant, 0.2-1.5 parts of complexing agent, 0.3-1 part of strengthening agent, 0.01-0.05 part of water retention agent, and 0.05-0.1 part of retarder.

[0009] As a preferred technical solution, the self-healing waterproof mortar comprises raw materials in the following parts by weight: 400 parts of low-heat cement, 10 parts of mineral powder, 25 parts of plastic expansion agent, 600 parts of fine sand, 8.7 parts of compound admixture, and 230 parts of water; the compound admixture comprises components in the following parts by weight: 1.5 parts of polycarboxylate water reducer, 2.5 parts of water repellent, 1.0 part of white carbon black, 1.5 parts of coagulant, 1.5 parts of complexing agent, 0.6 part of strengthening agent, 0.02 part of water retention agent, and 0.08 part of retarder.

[0010] As a preferred technical solution, the fine sand is 100-200 mesh.

[0011] As a preferred technical solution, the fine sand is recycled fine aggregate; or fine aggregate obtained by separating, crushing, shaping, and screening natural river sand, quartz sand, or stone.

[0012] As an improved technical solution, the heat of hydration of the low-heat cement < 300 J / g.

[0013] The low-heat cement selects cement with the physical property indexes as shown in Table 1.

[0014] Table 1

[0015]

[0016] As an improved technical solution, the mineral powder is S95 grade steel slag micro powder, and the residue on 45-micron sieve ≤ 1%. The performance indexes are shown in Table 2. The mineral powder has a finer fineness and has better effects of increasing viscosity, retaining water, and enhancing strength.

[0017] Table 2

[0018]

[0019] As an improved technical solution, the plastic expansion agent is HEA expansion agent. The HEA expansion agent has a good effect of improving early strength and increasing the structural density. It has a good synergistic effect with the high-performance polycarboxylate water reducer, and preferably solves the problems of fluidity and time-dependent loss, creating conditions for improving the performance and strength of the mortar.

[0020] As an improved technical solution, the water retention agent uses hydroxypropyl methyl cellulose ether with a viscosity of 150,000 Pa·S, which can make the mortar reach an appropriate cohesiveness and greatly improve the water retention of the mortar.

[0021] As an improved technical solution, the water repellent is one or more of polysiloxane, silicone resin, and polyacrylamide. Organosilicon-based and polysiloxane additives can prevent liquid water from penetrating into the cured cement-based material through the surface or capillary action in the mortar, significantly reducing the water absorption of the material.

[0022] As a preferred technical solution, the water repellent is one or more of polysiloxane, silicone resin, and polyacrylamide.

[0023] As an optimized choice, the white carbon black has a good filling effect, which can fill the voids between the mortar particles and hydration products, improving the density of the internal structure.

[0024] As an improved technical solution, the coagulant is one or a mixture of phosphates, magnesium fluorosilicate, polyacrylamide, or lithium carbonate.

[0025] As an improved technical solution, the complexing agent uses a combination of tripolyphosphate and EDTA.

[0026] As a preferred technical solution, the tripolyphosphate is sodium tripolyphosphate.

[0027] As a further improved technical solution, the complexing agent further includes at least one of sodium tetraborate or citric acid.

[0028] As an improved technical solution, the strengthening agent is at least one of aluminum sulfate, sodium carbonate, and sodium silicate.

[0029] As an improved technical solution, the retarder uses at least one of citric acid, tartaric acid, or sodium gluconate.

[0030] It should be noted that the inventors of this application have been long-term committed to the research work in this technical field. Through a large number of repeated theoretical analyses and experimental verifications in long-term practice, the technical solution of this invention has been determined. In this invention: Mineral admixtures have a great influence on the early strength of mortar. As a self-healing waterproof mortar, the selection of mineral admixtures is even more crucial. The inventors found in the research that when S95-grade blast furnace slag powder is selected, it can effectively improve the compactness and compressive and flexural properties of the cementitious material particle group, achieving the purpose of improving the mortar performance. Among the compound admixtures, the dosage of the water retention agent has a very significant impact on the water retention effect of the mortar. According to the proportion in the mortar, when the dosage is lower than the minimum weight part of this invention, the mortar has a certain viscosity, the water-cement ratio has little influence, but there is a sagging phenomenon during construction, the leveling and finishing effect is poor, affecting the workability, and there is a phenomenon of insufficient surface strength after 24 hours. When the dosage is greater than the maximum weight part of this invention, the fluidity and time-dependent loss are relatively large, seriously affecting the construction progress. Therefore, through a large number of studies and repeated experiments, the inventors determined the addition amount of the water retention agent to meet the requirements of fluidity, water retention, no bleeding, and no segregation.

[0031] The selection and dosage of the water repellent and the complexing agent are also the optimized selection of the entire technical solution, which can well meet the requirements of hydrophobicity and healing of the self-healing waterproof mortar. The dosage of the water repellent can play a key role in the waterproof performance of the mortar. For example, if the dosage is too small, the waterproof effect will be poor; if the dosage exceeds the range, the overall performance of the mortar will be reduced, such as the reduction of properties such as compressive strength, flexural strength, frost resistance, and durability, and even there will be cracking phenomena. The selection and dosage of the complexing agent are also the optimized selection of the entire technical solution. It can not only form stable complexes with metal ions in the mortar to achieve the effect of crack healing, but also reduce the ion dissolution and improve the durability of the mortar. At the same time, the admixtures can play a synergistic role. For example, the complexing agent reacts with metal ions such as sodium, magnesium, and aluminum in the coagulant and the strengthening agent to form stable complexes, improving the overall performance and self-healing effect of the mortar.

[0032] Due to the adoption of the above technical solution, the beneficial effects of this invention are:

[0033] The self-healing waterproof mortar of the present invention comprises raw materials in the following parts by weight: 350-450 parts of low-heat cement, 10-30 parts of mineral powder, 20-30 parts of plastic expansion agent, 550-650 parts of fine sand, 5-12 parts of compound admixture, and 200-250 parts of water; the compound admixture comprises components in the following parts by weight: 1-2 parts of polycarboxylate water reducer, 1-5 parts of water repellent, 0.5-1.5 parts of white carbon black, 1-2 parts of coagulant, 0.2-1.5 parts of complexing agent, 0.3-1 part of strengthening agent, 0.01-0.05 part of water retaining agent, 0.05-0.1 part of retarder. The present invention optimizes the selection and proportion of raw materials, can effectively improve the compactness and compressive and flexural properties of the cementitious material particle group, and achieves the purpose of improving the performance of the mortar; by filling the internal micropores and capillary pores of the mortar, the porosity is reduced, and the impermeability of the mortar is improved. At the same time, by adding a complexing agent, the ions in the mortar are complexed into stable compounds to prevent the penetration and erosion of water and chemical substances, and the chemical corrosion resistance of the mortar is improved; by adding a water repellent, the water absorption rate of the mortar is reduced to prevent water penetration, achieving waterproofness and healing effects.

[0034] The mortar prepared by the present invention by adding a compound admixture compounded with a polycarboxylate superplasticizer, hydroxypropyl methyl cellulose ether with a viscosity of 150000 Pa·S, etc. does not bleed water and has high strength. By adding white carbon black and S95 grade mineral powder, the grading of the cementitious material particle group is improved, the cement consumption is reduced, and the strength and durability of the mortar are improved. By adding HEA expansion agent to compensate for the shrinkage generated during the hydration of cement, the cracks appearing during the hardening process of the mortar are reduced. By adding a water repellent and a complexing agent, the waterproof performance and crack self-healing performance of the mortar are effectively improved.

[0035] The complexing agent of the present invention adopts a combination of tripolyphosphate and EDTA. The functions of tripolyphosphate are as follows: First, it undergoes a complexation reaction with metal ions such as calcium ions (Ca2+) on the surface of cement particles to form a protective film, hindering the normal hydration process of cement, thereby delaying the setting time of concrete. This retarding effect helps to extend the workable time of mortar, facilitating construction, and at the same time will not have an adverse impact on the later performance of mortar. Second, it can improve the fluidity of mortar, reduce the friction between particles, promote the dispersion and filling effect of cement particles, and increase the compactness and strength of mortar. It can also fill the internal micropores and capillary pores of mortar, reduce the porosity, improve the impermeability of mortar, and at the same time can complex with chemical substances to form compounds insoluble in water, preventing the penetration and erosion of water and chemical substances, and improving the chemical corrosion resistance, waterproofness and healing effect of mortar. And EDTA among them: First, it can also form stable complexes with metal ions in mortar, reduce ion dissolution, avoid efflorescence, and enhance the durability of mortar. Second, it can promote the cement hydration reaction, accelerate the hardening process of mortar, and improve the strength of mortar. Through a large number of studies by the inventors of this application, it is found that when the two are used simultaneously, they can play a mutually enhancing role, and the complexing effect is more than doubled compared with the use of any one of them, achieving the effect of 1 + 1 > 2.

[0036] The polysiloxane in the water repellent of the present invention forms organosilicon water repellent groups in mortar, which can effectively prevent liquid water from penetrating into the cured mortar through the surface or capillary action, thereby improving the waterproof performance of mortar. At the same time, it can significantly improve the water repellency of mortar, greatly reduce its water absorption rate, and maintain excellent performance even when the mortar is in long-term contact with water. The organosilicon resin can penetrate into the microporous walls of mortar to form a water repellent film to prevent water penetration. Polyacrylamide can slow down the dry shrinkage rate of the cement matrix, reduce the internal stress of mortar, and improve the crack resistance. At the same time, polyacrylamide can fill the micropores and cracks in mortar, reduce the permeability, and improve the compactness. Specific Embodiments

[0037] The following specific embodiments are used to further illustrate the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0038] In the following examples and comparative examples, low-heat cement is selected as the cement with the physical property indexes shown in Table 3.

[0039] Table 3

[0040]

[0041] The mineral powder is S95 grade steel slag powder, with a residue on 45-micron sieve not exceeding 1%, and the performance indicators are shown in Table 4. The mineral powder has a finer fineness and has good effects of increasing viscosity, retaining water, and enhancing strength.

[0042] Table 4

[0043]

[0044] The recycled fine aggregate needs to meet the technical indicators in Table 5.

[0045] Table 5

[0046]

[0047] Example 1

[0048] A self-healing waterproof mortar is prepared from the following raw materials in parts by weight: 365 parts of low-heat cement, 11 parts of S95 grade steel slag powder, 20 parts of HEA expansive agent, 560 parts of fine sand with a mesh size of 100-200, 8 parts of compound admixture, and 220 parts of water.

[0049] The compound admixture is prepared from the following components in parts by weight: 1.2 parts of polycarboxylate water reducer, 0.6 parts of hydrophobic agent polysiloxane, 0.8 parts of polyacrylamide, 0.6 parts of white carbon black, 1.0 parts of coagulant magnesium fluorosilicate, 0.2 parts of complexing agent sodium tripolyphosphate and 0.2 parts of EDTA, 0.4 parts of strengthening agent aluminum sulfate, 0.02 parts of hydroxypropyl methyl cellulose ether with a viscosity of 150,000 Pa·S, and 0.06 parts of retarder citric acid.

[0050] Example 2

[0051] A self-healing waterproof mortar is prepared from the following raw materials in parts by weight: 380 parts of low-heat cement, 14 parts of S95 grade steel slag powder, 24 parts of HEA expansive agent, 580 parts of recycled fine aggregate with a mesh size of 100-200, 7 parts of compound admixture, and 220 parts of water.

[0052] The compound admixture is prepared from the following components in parts by weight: 1.3 parts of polycarboxylate water reducer, 1 part of hydrophobic agent silicone resin, 1.2 parts of polyacrylamide, 0.8 parts of white carbon black, 1.3 parts of coagulant polyacrylamide, 0.5 parts of complexing agent sodium tripolyphosphate and 0.5 parts of EDTA, 0.4 parts of strengthening agent sodium carbonate, 0.02 parts of hydroxypropyl methyl cellulose ether with a viscosity of 150,000 Pa·S, and 0.07 parts of retarder tartaric acid.

[0053] Example 3

[0054] A self-healing waterproof mortar is prepared from the following raw materials in parts by weight: 420 parts of low-heat cement, 28 parts of steel slag powder of S95 grade, 28 parts of HEA expansion agent, 620 parts of recycled fine aggregate with a mesh size of 100-200, 11 parts of compound admixture, and 250 parts of water.

[0055] The compound admixture is prepared from the following components in parts by weight: 1.8 parts of polycarboxylate water reducer, 2.2 parts of hydrophobic agent polysiloxane, 2.4 parts of polyacrylamide, 1.4 parts of white carbon black, 1.8 parts of coagulant lithium carbonate, 0.7 part of complexing agent sodium tripolyphosphate and 0.7 part of EDTA, 0.9 part of strengthening agent sodium silicate, 0.05 part of hydroxypropyl methyl cellulose ether with a viscosity of 150000 Pa·S, and 0.1 part of retarder sodium gluconate.

[0056] Example 4

[0057] A self-healing waterproof mortar is prepared from the following raw materials in parts by weight: 400 parts of low-heat cement, 20 parts of steel slag powder of S95 grade, 25 parts of HEA expansion agent, 600 parts of recycled fine aggregate with a mesh size of 100-200, 8 parts of compound admixture, and 230 parts of water.

[0058] The compound admixture is prepared from the following components in parts by weight: 1.5 parts of polycarboxylate water reducer, 1.5 parts of hydrophobic agent polysiloxane, 1.5 parts of polyacrylamide, 0.9 part of white carbon black, 1.5 parts of coagulant magnesium fluorosilicate, 0.5 part of complexing agent sodium tripolyphosphate and 0.5 part of EDTA, 0.7 part of strengthening agent sodium silicate, 0.03 part of hydroxypropyl methyl cellulose ether with a viscosity of 150000 Pa·S, and 0.08 part of retarder citric acid.

[0059] Comparative Example 1

[0060] Comparative Example 1 is different from Example 4 in that the complexing agent in the compound admixture is 1.0 part of sodium tripolyphosphate, and EDTA is not added, and the rest are the same.

[0061] Comparative Example 2

[0062] Comparative Example 2 is different from Example 4 in that the complexing agent in the compound admixture is 1.0 part of EDTA, and sodium tripolyphosphate is not added, and the rest are the same.

[0063] Comparative Example 3

[0064] Comparative Example 3 is different from Example 4 in that the addition amount of hydroxypropyl methyl cellulose ether with a viscosity of 150000 Pa·S in the compound admixture is 0.08 part, and the rest are the same.

[0065] The tests were conducted in accordance with the provisions of GB / T 25181-2010 "Ready-mixed Mortar", JC / T 984-2011 "Polymer Cement Waterproof Mortar", and JGJ / T 70-2009 "Standard for Test Methods of Basic Properties of Building Mortar". The mortar performance data is shown in Table 6 below:

[0066] Table 6

[0067]

[0068] From the comparison of the mortar performance data of the above examples and comparative examples, it can be seen that in Comparative Example 1 and Comparative Example 2, on the premise of adding only one of the complexing agents sodium tripolyphosphate and EDTA, although the total addition amount is the same, the comprehensive performance of the mortar is reduced a lot, especially the final cracks cannot heal themselves. In Comparative Example 3, the addition amount of the water-retaining agent hydroxypropyl methyl cellulose ether is 0.08 parts, and the dosage is greater than the protection scope of the present invention. Although the addition amount is more, the performance of the mortar is lower instead, especially the impermeability performance is relatively poor and the self-healing effect is not ideal.

Claims

1. A self-healing waterproof mortar, characterized in that The invention comprises the following raw materials in parts by weight: 350-450 parts of low-heat cement, 10-30 parts of mineral powder, 20-30 parts of plastic expansion agent, 550-650 parts of fine sand, 5-12 parts of compound admixture and 200-250 parts of water; the compound admixture comprises the following components in parts by weight: 1-2 parts of polycarboxylic acid water reducer, 1-5 parts of water repellent, 0.5-1.5 parts of white carbon black, 1-2 parts of accelerator, 0.2-1.5 parts of complexing agent, 0.3-1 parts of reinforcing agent, 0.01-0.05 parts of water retaining agent and 0.05-0.1 parts of retarder.

2. The self-healing waterproof mortar according to claim 1, characterized in that: The hydration heat of the low-heat cement is less than 300 J / g.

3. The self-healing waterproof mortar according to claim 1, characterized in that: The mineral powder is S95 grade steel slag powder; the 45 micron sieve residue is ≤1%.

4. The self-healing waterproof mortar according to claim 1, characterized in that: The plastic expansion agent is a HEA expansion agent.

5. The self-healing waterproof mortar according to claim 1, characterized in that: The water retaining agent is hydroxypropyl methylcellulose ether with a viscosity of 150000 Pa·S.

6. The self-healing waterproof mortar according to claim 1, characterized in that: The water repellent is one or more of polysiloxane, silicone resin and polyacrylamide.

7. The self-healing waterproof mortar according to claim 1, characterized in that: The coagulant is a mixture of one or more of phosphate, magnesium fluorosilicate, polyacrylamide or lithium carbonate.

8. The self-healing waterproof mortar according to claim 1, characterized in that: The complexing agent is a combination of tripolyphosphate and EDTA.

9. The self-healing waterproof mortar according to claim 8, characterized in that: The complexing agent also includes at least one of sodium tetraborate or citric acid.

10. The self-healing waterproof mortar according to claim 1, characterized in that: The reinforcing agent is at least one of aluminum sulfate, sodium carbonate and sodium silicate.

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