Cement-based joint mixture and preparation method thereof

Abstract

The invention relates to a cement-based joint mixture and a preparation method thereof, and belongs to the field of joint mixture material preparation, and the cement-based joint mixture comprises cement, fly ash, other alkali activation active materials, an activator, an expanding agent, a mineral thixotropic agent, inorganic fibers, a filler, cellulose ether and rubber powder. The prepared cement-based joint mixture overcomes the technical defects that an existing cement-based joint mixture technology is prone to cracking and falling off, alkali efflorescence and whitewashing are prone to occurring, attractiveness is affected, and the constructability is poor.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of caulking material, and particularly relates to a cement-based caulking agent and a preparation method thereof. Background Art

[0002] At present, the caulking materials mainly include cement-based caulking agents, beauty caulking agents and epoxy colored sands. The cement-based caulking agent has an irreplaceable position due to its excellent environmental protection performance, aging resistance performance and high cost performance. However, the cement-based caulking agent also has the following problems:

[0003] Firstly, because there is a large shrinkage stress in the curing process of the cement-based product itself, in actual application, affected by factors such as the aggregate gradation, water addition amount and construction environment in the cement-based caulking agent, if not properly treated, cracking or even peeling often occurs, and this hidden danger increases with the increase of the caulking width.

[0004] Secondly, after the construction of the cement-based caulking agent is completed, the cement hydration reaction is still ongoing. A large amount of Ca(OH)₂ generated by hydration migrates to the surface with the evaporation of water and reacts with CO₂ in the air to produce water-insoluble CaCO₃. This phenomenon of alkali return and white hanging will seriously affect the beauty.

[0005] In addition, the cement caulking agent product has a high content of fine powder and a large density, and generally has problems such as sticky scraping and unsmooth construction.

[0006] The problems of cracking and peeling of the cement-based caulking agent mainly come from the shrinkage during the cement hardening process. Reasonably adjusting the gradation, controlling the content of fine powder and controlling the construction water addition amount can reduce the shrinkage of the cement-based caulking agent, but cannot completely eliminate the shrinkage; at the same time, in the actual production of mortar, there are certain fluctuations in the aggregate gradation and the content of fine powder, and they cannot be well controlled; the water addition amount during construction is basically added according to the experience and habit of the construction personnel. Therefore, these measures reduce the probability of cracking and peeling to a certain extent, but there are still relatively large risks.

[0007] The problems of alkali return and white hanging come from the fact that a large amount of Ca(OH)₂ generated by cement hydration migrates to the surface with the evaporation of water. Therefore, to solve the problems of alkali return and white hanging, it is basically started from three aspects: the source of alkali generation, the channel of alkali output and the carrier of alkali output (water). Controlling the cement content can reduce the total content of free alkali in the product to a certain extent, but too low cement content affects the strength of the product, so this problem can only be slightly improved. Using low-alkali cement (such as high-aluminum cement) and adding an anti-alkali return agent are technical means to reduce the risk of alkali return by reducing the content of free alkali and filling the alkali return channel, but the costs of low-alkali cement and anti-alkali return agent are both relatively high, and the price of the product prepared is not competitive in the market.

[0008] Simply introducing various thixotropic agents can improve the construction performance of cement-based caulking agents, but it cannot change the essential nature of the thick consistency during scraping of cement-based caulking agents. At the same time, it increases the product cost. If the addition amount is relatively high, it will also affect other properties of the product, such as strength, water resistance, etc. Summary of the Invention

[0009] To solve the problems described above, the present invention provides a cement-based caulking agent and a preparation method thereof. The cement-based caulking agent prepared by the present invention overcomes the technical defects of the existing cement-based caulking agent technology, such as easy cracking and peeling, easy alkali return and white hanging, which affect the aesthetics and poor workability.

[0010] To solve the above problems, the present invention is achieved through the following technical solutions:

[0011] The first object of the present invention is:

[0012] Provide a cement-based caulking agent, which comprises the following components in parts by weight:

[0013] 10 - 60 parts of cement, 10 - 30 parts of fly ash, 2 - 15 parts of other alkali-activated active materials, 0.3 - 1.5 parts of activator, 0.05 - 2 parts of expansive agent, 0.1 - 1 part of mineral thixotropic agent, 0.2 - 2 parts of inorganic fiber, 0 - 60 parts of filler, 0.01 - 0.2 parts of cellulose ether, 0.1 - 10 parts of rubber powder;

[0014] The fly ash is Class F Grade 1 ash or Grade 2 ash required by GB / T1596 - 2017;

[0015] The other alkali-activated active materials are one or a combination of several of metakaolin, blast furnace slag powder, and silica fume;

[0016] The metakaolin is obtained by calcining kaolin, and the calcination process is calcining at 850 °C for 5 h;

[0017] The blast furnace slag powder is obtained by adding gypsum and grinding aids to blast furnace slag and through an ultrafine grinding process, and the specific surface area of the blast furnace slag powder ≥ 400 ㎡ / kg;

[0018] The silica fume has a silica content ≥ 85%, and a specific surface area ≥ 15000 ㎡ / kg.

[0019] Most of the existing technologies use single cement as the inorganic binder. The main technology of this technical solution is to upgrade the inorganic binder system to use a technical combination of cement + alkali-activated mixture + activator.

[0020] The alkali-activated mixture (a combination of fly ash and other alkali-activated active materials, there are many types of alkali-activated active materials, fly ash, slag powder, metakaolin, etc. are all alkali-activated active materials, but the performance varies greatly; the alkali-activated mixture mainly composed of fly ash adopted in this technical solution has small shrinkage and has the effect of spherical microbeads, and other alkali-activated active materials have the advantages of high activity, water immersion strength and high energy, and have better complementary effects) contains spherical microbeads, which act as ball bearings. This morphological effect makes the product more smooth and easy to construct.

[0021] The technical solution of this invention is to upgrade the inorganic cementitious material system. The alkali-activated mixture introduced has inherent shrinkage properties superior to cement. Introducing it into cement-based caulking agents can significantly reduce the cement dosage, thereby reducing the shrinkage of the entire system. The introduction of an expansive agent further compensates for the product's shrinkage. The introduction of inorganic fibers dispersed in the mortar effectively restricts the mortar's deterioration. The compensation of the expansive agent and inorganic fibers greatly reduces the product's shrinkage rate, thereby reducing the risk of cracking and falling off during use. The synergistic effect of the alkali-activated mixture, expansive agent, and inorganic fibers ultimately ensures the safety of the product, preventing it from cracking or falling off.

[0022] The alkali activation mixture acts simultaneously on the alkali return source and the alkali return channel, greatly reducing the risk of alkali return.

[0023] The introduction of mineral thixotropic agents can reduce the dosage of cellulose ether, thereby reducing the water consumption of the product, reducing the carrier of alkali backflow, and further reducing the risk of alkali backflow.

[0024] At the same time, mineral thixotropic agents have obvious advantages in improving workability. Combined with the spherical microbead materials contained in the alkali-activated mixture, the workability of the product is significantly improved, making it more easily accepted by construction workers.

[0025] The cement-based sealant of the present invention is further optimized as follows:

[0026] The fly ash is Class F primary ash or secondary ash required by GB / T1596-2017;

[0027] The other alkali-activated active materials are one or a combination of metakaolin, slag and silica fume.

[0028] The cement-based sealant of the present invention is further optimized as follows:

[0029] The activator is one or a combination of chloride, sulfate and silicate.

[0030] The cement-based sealant of the present invention is further optimized as follows:

[0031] The mineral thixotropic agent is one of magnesium aluminum silicate and bentonite or a combination of the two.

[0032] In the prior art, cellulose ether is usually used for water retention and viscosity adjustment. In this technical solution, a mineral thixotropic agent is used to assist in controlling the water retention performance and viscosity, thereby controlling the water addition amount.

[0033] While introducing the mineral thixotropic agent, the dosage of cellulose ether is reduced. On the one hand, the workability of the product is improved; on the other hand, the water consumption of the product is reduced, increasing the density of the product and thus improving various strengths.

[0034] A further optimization of the cement-based caulking agent of the present invention is as follows:

[0035] The expansion agent is a calcium sulfoaluminate-based expansion agent.

[0036] A further optimization of the cement-based caulking agent of the present invention is as follows:

[0037] The inorganic fiber is glass fiber or ceramic fiber.

[0038] The prior art does not add an expansion agent and inorganic fiber. In this technical solution, a combination of an expansion agent and inorganic fiber is used to further control shrinkage.

[0039] A further optimization of the cement-based caulking agent of the present invention is as follows:

[0040] The cement is ordinary portland cement.

[0041] A further optimization of the cement-based caulking agent of the present invention is as follows:

[0042] The cellulose ether is one or a combination of several of methyl cellulose ether, hydroxypropyl methyl cellulose ether, hydroxymethyl cellulose ether, and carboxymethyl cellulose;

[0043] A further optimization of the cement-based caulking agent of the present invention is as follows:

[0044] It includes a combination of one or several of the following features:

[0045] The filler is sand or calcium powder. The sand is one or a combination of manufactured sand, river sand, and tailings sand; the calcium powder is 200 mesh to 400 mesh;

[0046] The rubber powder is water-soluble rubber powder;

[0047] The rubber powder is one or a combination of several of ethylene / vinyl acetate copolymer, vinyl acetate / vinyl versatate copolymer, acrylic copolymer, waterborne epoxy resin rubber powder, polyvinyl alcohol rubber powder, acrylic rubber powder, and starch-modified rubber powder.

[0048] The second object of the present invention is as follows:

[0049] Provided is a preparation method of the aforementioned cement-based caulking agent, which comprises the following preparation steps:

[0050] S1. Mix fly ash, other alkali-activated active materials, an activator, an expansion agent, a mineral thixotropic agent, inorganic fibers, a cellulose ether, and a rubber powder evenly in proportion;

[0051] S2. Then, add cement, a filler, and the mixture obtained in step S1 into a blender in sequence and stir for three minutes to obtain the cement-based caulking agent.

[0052] The cement-based caulking agent and its preparation method of the present invention have the following technical characteristics and advantages:

[0053] 1. The inorganic cementitious material of ordinary caulking agents is cement, and the shrinkage performance is relatively large. The technical solution of the present invention reduces the cement dosage and introduces an alkali-activated mixture. The performances of different alkali-activated active materials vary greatly. The technical solution of the present invention preferably uses a combination of fly ash and at least one or several of metakaolin, slag, and silica fume. This is because fly ash has relatively low activity compared with other alkali-activated active materials, but its economic performance is obvious and its shrinkage performance is excellent. Metakaolin, slag, silica fume, etc. have relatively high strength and large shrinkage performance differences. The alkali-activated mixture after appropriate proportioning, combined with an activator, can take into account relatively high compressive strength and low shrinkage performance.

[0054] Meanwhile, an expansion agent and inorganic fibers are further introduced:

[0055] The expansion agent can further compensate for the shrinkage of the inorganic cementitious material;

[0056] The inorganic fibers are dispersed in the mortar to strongly restrict the deformation of the material, playing a role in reducing shrinkage and preventing cracking.

[0057] The synergistic effect of the above three points greatly reduces the shrinkage performance of the cement-based caulking agent of the present invention, and takes into account the advantages of cost and environmental protection.

[0058] 2. The main mineral components of ordinary cement are tricalcium silicate and dicalcium silicate, and a large amount of Ca(OH)2 is generated during their hydration. The reaction equations are as follows:

[0059] 3CaO·SiO2 + nH2O → xCaO·SiO2·yH2O + (3 - x)Ca(OH)2

[0060] 2CaO·SiO2 + mH2O → xCaO·SiO2·yH2O + (2 - x)Ca(OH)2

[0061] The generated Ca(OH)2 will migrate to the surface with water and form crystals, resulting in efflorescence and white stains, affecting the appearance.

[0062] The technical solution of the present invention effectively controls in three aspects: the source of alkali, the channel of alkali output, and the carrier of alkali output (water), effectively reducing the risk of alkali return and white spots.

[0063] Source of alkali: The introduced alkali activation mixture contains a large amount of reactive silica and alumina, which can react with Ca(OH)2 produced by cement hydration to produce stronger C-S-H or C-A-H, etc. This not only improves the strength of the hydration products but also reduces the alkali content of the products from the source, greatly reducing the risk of alkali return. The reaction equations are as follows:

[0064] xCa(OH)2 + SiO2 + (n - 1)H2O → xCaO·SiO2·nH2O

[0065] xCa(OH)2 + Al2O3 + mH2O → xCaO·Al2O3·nH2O

[0066] 3Ca(OH)2 + Al2O3 + 2SiO2 + mH2O → 3CaO·Al2O3·2SiO2·nH2O

[0067] Channel of alkali output: The pozzolanic reaction in the alkali activation mixture is relatively dense. Therefore, the pozzolanic reaction of activated silica and reactive alumina produces relatively hard cement stones in the pores, playing a role in blocking and sealing the pores. At the same time, superimposing the micro-aggregate effect of the alkali activation mixture (fine particles are evenly distributed in the cement paste, just like fine aggregates (aggregates). These fine particles will become the core of the deposition of a large amount of hydrates. As the hydration age progresses, these fine particles and their hydration reaction products can continuously fill the pores of the cement stone.), the density of the joint filler in the new system of the present invention is greatly increased, becoming more dense, reducing the capillary pores of the product, that is, greatly reducing the channel of alkali output, thereby reducing the risk of alkali return and white spots from the output channel aspect.

[0068] Carrier of alkali return (water): Ordinary joint fillers use cellulose ether for water retention and consistency control. The technical solution of the present invention introduces a mineral thixotropic agent to assist cellulose ether for water retention and consistency control. Compared with ordinary joint fillers, the technical solution of the present invention can significantly reduce the water addition amount to achieve the same water retention and consistency control effect. The introduction of the mineral thixotropic agent in the joint filler can effectively control the viscosity of the product, reduce the dosage of cellulose ether, and thus reduce the water addition amount of the whole product. Therefore, it hinders the precipitation of alkali from the aspect of the alkali output carrier and enhances the alkali resistance performance.

[0069] 3. Ordinary cement-based caulking agents are divided into sanded and non-sanded types. The non-sanded type is all fine powder, and the sanded type has a fine powder content of about 30% (cement and fine fillers) or more. The fine powder content is relatively high, and the cement-based products themselves have problems with poor viscosity and workability during construction. The alkali-activated mixture introduced in the technical solution of the present invention can not only reduce the cement dosage, but also the spherical microbead-containing material in it plays the role of a ball and a bearing, making the caulking agent prepared by the present invention have smoother workability. Detailed implementation mode

[0070] In order to make the application, technical solution and advantages of the present invention clearer, the content of the present invention will be described in detail in combination with specific embodiments. It should be understood that the embodiments are only used to illustrate the present invention, rather than limiting the protection scope of the present invention. Any simple improvement to the preparation method of the present invention under the premise of the inventive concept belongs to the protection scope of the present invention.

[0071] Example 1

[0072] A preparation method of a cement-based caulking agent, which comprises the following components in parts by weight:

[0073] 10 - 60 parts of cement, 10 - 30 parts of fly ash, 2 - 15 parts of other alkali-activated active materials, 0.3 - 1.5 parts of activator, 0.05 - 2 parts of expansive agent, 0.1 - 1 part of mineral thixotropic agent, 0.2 - 2 parts of inorganic fiber, 0 - 60 parts of filler, 0.01 - 0.2 parts of cellulose ether, 0.1 - 10 parts of rubber powder; (See the specific dosage in Table 1 for the raw material composition of each experimental group in each example)

[0074] The fly ash is Class F Grade I or Grade II ash required by GB / T1596-2017;

[0075] The other alkali-activated active materials are one or a combination of metakaolin, blast furnace slag powder, and silica fume;

[0076] The metakaolin is obtained by calcining kaolin, and the calcination process is calcining at 850°C for 5 hours;

[0077] The blast furnace slag powder is obtained by adding gypsum and grinding aids to blast furnace slag and subjecting it to an ultrafine grinding process, and the specific surface area of the blast furnace slag powder ≥ 400㎡ / kg;

[0078] The silica fume has a silicon dioxide content ≥ 85% and a specific surface area ≥ 15000㎡ / kg.

[0079] The preparation method of the cement-based caulking agent includes the following preparation steps:

[0080] S1. Mix fly ash, other alkali-activated active materials, activators, expansive agents, mineral thixotropic agents, inorganic fibers, cellulose ethers, and rubber powders evenly in proportion.

[0081] S2. Then, add cement, fillers, and the mixture obtained in step S1 to a mixer in sequence and stir for three minutes to obtain the cement-based caulking agent.

[0082] The preparation methods of the comparative examples and the examples are basically the same, and the main difference lies in the differences in the composition of some raw materials. For details, see the following table.

[0083] Table 1 Composition of raw materials for each experimental group in the examples and comparative examples (parts by weight)

[0084]

[0085]

[0086] Table 2 Test results of experimental groups of Example 1# and Comparative Examples 1# - 3#

[0087]

[0088] In Comparative Example 1#, the alkali-activated mixture (fly ash + other alkali-activated active materials) was not selected to replace part of the cement, and its shrinkage rate increased significantly, the water absorption increased, and it was particularly prone to alkali return and blooming.

[0089] In Comparative Example 2#, adding alkali-activated active materials to replace part of the cement can improve the alkali-return resistance performance. Compared with Comparative Example 1#, the shrinkage performance has also been better improved; however, compared with Example 1#, adding an appropriate amount of expansive agent in Example 1# can significantly improve the compensated shrinkage.

[0090] By comparing Example 1# with Comparative Example 3#, it can be seen that inorganic fibers have a certain effect on increasing the flexural strength performance and also have a certain performance of compensated shrinkage.

[0091] In summary, the three-point synergistic effect of the alkali-activated mixture, expansive agent, and inorganic fibers greatly reduces the shrinkage performance of the cement-based caulking agent of the present invention, and also takes into account the advantages of cost and environmental protection.

[0092] Table 3 Test results of experimental groups of Examples 2# - 4# and Comparative Example 4#

[0093] Test items Water addition% Compressive strength MPa Shrinkage rate mm / m Anti-alkali performance Example 2# 30 19.8 0.51 No alkali back Example 3# 29 21 0.48 No alkali back Example 4# 28 21.5 0.45 No alkali back Comparative Example 4# 34 19.5 0.9 Some alkali back

[0094] From the comparison of the experimental groups of Examples 2# to 4# and Comparative Example 4#, it can be seen that when introducing a mineral thixotropic agent and simultaneously reducing the dosage of cellulose ether, the water consumption can be significantly reduced, while the compressive strength is increased, the shrinkage rate is decreased, and the anti-alkali return performance is significantly improved, without affecting other properties at the same time.

[0095] At the same time, adding a mineral thixotropic agent can better improve the construction performance, and well solve the problems of sticky scraping and non-smooth construction of the cement-based caulking agent.

[0096] In summary, the above are only the preferred examples of the present invention, and there is no any form of limitation to the present invention; any equivalent changes, modifications and evolutions made by those skilled in the art within the scope of the technical solution of the present invention by using the disclosed technical content are regarded as the equivalent examples of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments according to the essential technology of the present invention still fall within the protection scope of the technical solution of the present invention.

[0097] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0098] The experimental methods without specific conditions noted in the present invention are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0099] For the various optimized technical solutions in the present invention, unless otherwise stated, the various optimized technical solutions can be combined with each other.

[0100] Unless otherwise stated, the percentages and parts are weight percentages and weight parts.

[0101] The experimental methods without specific conditions noted in the specification and the embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0102] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the method of the present invention.

Claims

1. A cement-based caulking agent, characterized in that: It comprises the following components in parts by weight: 10-60 parts of cement, 10-30 parts of fly ash, 2-15 parts of other alkali-activated active materials, 0.3-1.5 parts of activator, 0.05-2 parts of expansive agent, 0.1-1 part of mineral thixotropic agent, 0.2-2 parts of inorganic fiber, 0-60 parts of filler, 0.01-0.2 parts of cellulose ether, 0.1-10 parts of rubber powder; The fly ash is Class F Grade 1 ash or Grade 2 ash required by GB / T1596-2017; The other alkali-activated active materials are one or a combination of several of metakaolin, granulated blast furnace slag powder, and silica fume; The metakaolin is obtained by calcining kaolin, and the calcination process is calcining at 850 °C for 5 h; The granulated blast furnace slag powder is obtained by adding gypsum and grinding aid to granulated blast furnace slag and through an ultrafine grinding process, and the specific surface area of the granulated blast furnace slag powder ≥ 400 ㎡ / kg; The silica fume has a silica content ≥ 85% and a specific surface area ≥ 15000 ㎡ / kg.

2. The cement-based caulking agent according to claim 1, characterized in that: The activator is one or a combination of several of chloride salts, sulfate salts, and silicate salts. The cement-based caulking agent according to claim 1, characterized in that: The mineral thixotropic agent is one or a combination of two of magnesium aluminum silicate and bentonite. The cement-based caulking agent according to claim 1, characterized in that: The expansive agent is a calcium sulfoaluminate-based expansive agent. The cement-based caulking agent according to claim 1, characterized in that: The inorganic fiber is glass fiber or ceramic fiber. The cement-based caulking agent according to claim 1, characterized in that: The cement is ordinary Portland cement. The cement-based caulking agent according to claim 1, characterized in that: The cellulose ether is one or a combination of several of methyl cellulose ethers, hydroxypropyl methyl cellulose ethers, hydroxymethyl cellulose ethers, and carboxymethyl cellulose. The cement-based caulking agent according to claim 1, characterized in that: It comprises a combination of one or more of the following features: The filler is sand or calcium powder, and the sand is one or a combination of several of machine-made sand, river sand, and tailings sand; the calcium powder is 200 mesh - 400 mesh; The rubber powder is water-soluble rubber powder; The rubber powder is one or a combination of several of ethylene / vinyl acetate copolymer, vinyl acetate / vinyl versatate copolymer, acrylic copolymer, water-based epoxy resin rubber powder, polyvinyl alcohol rubber powder, acrylic rubber powder, and starch-modified rubber powder.

9. A preparation method of the cement-based caulking agent according to claim 1, characterized in that: It comprises the following preparation steps: S1. Mix fly ash, other alkali-activated active materials, activator, expansive agent, mineral thixotropic agent, inorganic fiber, cellulose ether, and rubber powder evenly in proportion; S2. Then add cement, filler, and the mixture obtained in step S1 to a mixer in sequence and stir for three minutes to obtain the cement-based caulking agent.

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