Multifunctional anti-cracking material with cooling and shrinkage reducing functions and preparation method of multifunctional anti-cracking material

Abstract

The invention discloses a multifunctional anti-cracking material with cooling and shrinkage reducing functions and a preparation method of the multifunctional anti-cracking material. The multifunctional anti-cracking material comprises the following components in parts by weight: a water-soluble monomer, a micromolecular retarder, an initiator and a cross-linking agent in a ratio of 100: (20-300): (0.5-1.5): (0.1-1), and the micromolecular retarder is at least one of glucose, sodium gluconate, cane sugar, sorbitol and mannitol. According to the multifunctional anti-cracking material, internal curing is achieved through water release of the hydrogel, self-constriction is reduced, meanwhile, the small-molecule retarder is slowly released to regulate and control the hydration rate and reduce temperature rise, the multifunctional anti-cracking material has wide application prospects in the fields of mass concrete, high-performance concrete, severe environment construction and the like, the durability of a concrete structure can be remarkably improved, and the service life of the concrete structure can be remarkably prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to a functional material with the functions of inhibiting the temperature rise of concrete and reducing the shrinkage of concrete and a preparation method thereof, and belongs to the field of building materials, BACKGROUND

[0002] Concrete cracks are the most common engineering diseases in civil, water conservancy, bridge and other engineering projects, and more than 80% of the cracks are deformation cracks, such as autogenous shrinkage, dry shrinkage, temperature shrinkage and the like. Among them, in high-grade concrete, temperature shrinkage superimposed on autogenous shrinkage causes the main inducement of concrete cracking.

[0003] Retarder is a commonly used additive in the concrete industry. Common retarders include sugar, sucrose, sodium sugar and other sugar derivatives. The main purpose is to prolong the setting time of concrete and prolong the construction time of concrete, which cannot significantly reduce the temperature rise of concrete structure and cannot solve the problem of temperature cracks. Concrete hydration temperature rise inhibitor or hydration heat regulating material, this kind of material is mainly starch and its incomplete hydrolysis dextrin and other derivatives. This kind of substance can reduce the reaction rate of cement hydration acceleration period, reduce the temperature rise and reduce the temperature cracking.

[0004] At present, there are also various additives for reducing the shrinkage of concrete. CN101143770A discloses a concrete internal curing agent and a preparation method thereof, which reduces shrinkage by absorbing water resin internal curing. CN111377648A discloses a magnesium-based, temperature and humidity controlled high-efficiency anti-cracking agent for cement concrete, a preparation method and application thereof, which is a magnesium-based, temperature and humidity controlled high-efficiency anti-cracking agent. Through the expansion of magnesium-based shrinkage compensation, the internal curing shrinkage reduction effect of zeolite and the phase change endothermic of temperature sensitive material, the compensation shrinkage and temperature control coordination effect are realized, and the anti-cracking property of concrete is improved. CN103739722A discloses a hydration heat regulating material, a preparation method and application thereof, which controls the temperature rise by regulating the hydration of cement, thereby reducing the temperature shrinkage. CN103342494A discloses a hydration heat inhibition type concrete expansion material and a preparation method and application thereof. The hydration heat inhibition type concrete expansion material is a composite of the first two of the expansion agent, the hydration heat inhibitor and the internal curing agent, or a composite of the three, which is a three-function anti-cracking material. In summary, the above-mentioned functional materials either only have one shrinkage reduction and anti-cracking effect, or achieve the shrinkage reduction and anti-cracking function through the compounding of multiple materials. SUMMARY

[0005] Invention purposes: In view of the increase of concrete grade and the increase of structure volume, the use of such concrete engineering is increasing, and the cracking problem caused by the superposition of self-shrinkage and temperature shrinkage is becoming more and more serious. One of the purposes of the present application is to provide a multifunctional anti-cracking functional material with hydration temperature rise regulation function and certain self-shrinkage reduction function, and another purpose of the present application is to provide a preparation method of the multifunctional anti-cracking functional material.

[0006] Technical scheme: The multifunctional anti-cracking material with cooling and shrinkage reduction according to the present application comprises the following components by weight: water-soluble monomer: small molecule retarder: initiator: crosslinking agent is 100:(20-300):(0.5-1.5):(0.1-1), wherein the small molecule retarder is at least one of glucose, sodium gluconate, sucrose, sorbitol and mannitol.

[0007] Further, the following components are included by weight: water-soluble monomer: small molecule retarder: initiator: crosslinking agent is 100:(150-300):(0.8-1.5):(0.5-1). The water-soluble monomer is divided into ionic monomer and non-ionic monomer, wherein the ionic monomer is (meth) acrylic acid or its salt, and the non-ionic monomer is acrylamide. The mass ratio of non-ionic monomer to total water-soluble monomer is less than 90%. The initiator is one or both of potassium sulfate and ammonium persulfate. The crosslinking agent is one or several of N,N'-methylenebis(meth)acrylamide and ethylene glycol diacrylate.

[0008] The preparation method of the multifunctional anti-cracking material with cooling and shrinkage reduction according to the present application comprises the following steps:

[0009] (1) Preparation of reaction solution: dissolve water-soluble monomer, small molecule retarder, initiator and crosslinking agent in water, and mix to form a uniform reaction solution;

[0010] (2) Heating reaction of the reaction solution, crushing to obtain a gel, or heating reaction of the reaction solution, drying and crushing to obtain a powder.

[0011] Further, in step (1), the total amount of water-soluble monomer, small molecule retarder, initiator and crosslinking agent is 10-50% of the mass of the reaction solution. In step (2), the heating reaction temperature is 50-75℃, and the heating reaction time is 3-10h. The particle size of the gel is controlled to be less than 1mm during crushing. The particle size of the powder is less than 300um during crushing.

[0012] The present application researches and finds that when the traditional retarder has a slow-release function, it can have a function similar to that of a hydration temperature inhibitor. The main reason is that a certain amount of retarder can only slightly inhibit the hydration of cement, but as the retarder is consumed, it can no longer inhibit hydration, and the cement hydration enters the normal hydration stage. However, if the retarder is in a slow and low amount of slow-release state, there is always a low amount of retarder in the system to work, which can continuously and slowly inhibit the hydration of cement, thereby dispersing the early hydration heat dissipation, and playing a role in reducing the temperature rise and reducing temperature cracks of concrete. The multifunctional anti-cracking functional material of the present application is composed of a hydrogel containing small molecule retarder. When the hydrogel is added to the concrete, due to the osmotic pressure and humidity gradient, the water in the gel will be released into the concrete matrix as the hydration proceeds, and the small molecule retarder contained therein will also be released into the matrix. On the one hand, the release of water in the gel plays a role in internal curing, which can reduce the autogenous shrinkage, and on the other hand, more importantly, due to the slow release of small molecule retarder, the hydration of cement can be continuously slowed down, thereby reducing the early hydration heat, and achieving the effect of reducing the temperature rise of concrete structure and reducing temperature cracking.

[0013] Advantages: Compared with the prior art, the present application has the following remarkable advantages: in the present application, the small molecule retarder is absorbed in the gel during the synthesis of the gel; when the gel is added to the concrete, as the gel releases water, the small molecule retarder contained therein is also released, on the one hand, the release of water in the gel plays a role in internal curing, which reduces the autogenous shrinkage, and on the other hand, the release of small molecule retarder achieves the effect of hydration temperature inhibitor, and reduces the early hydration heat, thereby achieving the purpose of reducing the temperature rise of concrete structure and reducing temperature cracking, and the material has the effect of regulating the hydration rate in the acceleration period of cement hydration. Since the gel can be directly used as the final product, the drying step is also reduced, which is more energy-saving. DETAILED DESCRIPTION

[0014] The technical solutions of the present application will be further described below in combination with examples.

[0015] In the present application, the product performance detection method: the test method for evaluating the internal curing and shrinkage reduction performance of the material refers to JC / T2551-2019-“Concrete High Water Absorbency Resin Internal Curing Agent”, and the test method for evaluating the performance of regulating the hydration rate of the material refers to JC / T 2608-2021“Concrete Hydration Temperature Inhibitor”. The amount of functional material used in the test is 0.3% of the mass of cement (the gel is converted into dry matter); when the powder product is used, the water-binder ratio of the paste is additionally increased by 0.02.

[0016] Example 1

[0017] 1) 88 g of acrylic acid, 12 g of acrylamide, 80 g of sodium gluconate, 0.1 g of N,N'-methylenebisacrylamide, 0.5 g of potassium persulfate were added to 450 g of water, and stirred to prepare a uniform reaction solution.

[0018] 2) The above reaction solution was moved into a 75°C reaction box, and reacted for 4 h.

[0019] 3) The gel obtained by the above reaction was stirred and crushed by a high-speed tissue homogenizer to obtain a multifunctional anti-cracking functional material gel, and the particle size of the gel was about 0.5 mm.

[0020] Example 2

[0021] 1) 65 g of acrylic acid, 35 g of acrylamide, 100 g of sorbitol, 0.2 g of N,N'-methylenebisacrylamide, 1.5 g of potassium persulfate were added to 450 g of water, and stirred to prepare a uniform reaction solution.

[0022] 2) The above reaction solution was moved into a 75°C reaction box, and reacted for 4 h.

[0023] 3) The gel obtained by the above reaction was stirred and crushed by a high-speed tissue homogenizer to obtain a multifunctional anti-cracking functional material gel, and the particle size of the gel was about 0.5 mm.

[0024] Example 3

[0025] 1) 30 g of acrylic acid, 70 g of acrylamide, 150 g of sucrose, 0.5 g of N,N'-methylenebisacrylamide, 0.8 g of potassium persulfate were added to 450 g of water, and stirred to prepare a uniform reaction solution.

[0026] 2) The above reaction solution was moved into a 75°C reaction box, and reacted for 4 h.

[0027] 3) The gel obtained by the above reaction was stirred and crushed by a high-speed tissue homogenizer to obtain a multifunctional anti-cracking functional material gel, and the particle size of the gel was about 0.5 mm.

[0028] Example 4

[0029] 1) 25 g of acrylic acid, 85 g of acrylamide, 200 g of glucose, 1 g of N,N'-methylenebisacrylamide, 1 g of potassium persulfate were added to 450 g of water, and stirred to prepare a uniform reaction solution.

[0030] 2) The above reaction solution was moved into a 75°C reaction box, and reacted for 4 h.

[0031] 3) The gel obtained by the above reaction was stirred and crushed by a high-speed tissue homogenizer to obtain a multifunctional anti-cracking functional material gel, and the particle size of the gel was about 0.5 mm.

[0032] Example 5

[0033] 1) 10 g of acrylic acid, 90 g of acrylamide, 300 g of mannitol, 0.8 g of ethylene glycol diacrylate, 1.5 g of ammonium persulfate were added to 1200 g of water, and stirred to prepare a uniform reaction solution.

[0034] 2) The above reaction solution was moved into a 75°C reaction box, and reacted for 4 h.

[0035] 3) The gel obtained by the above reaction was stirred and crushed by a high-speed tissue homogenizer to obtain a multifunctional anti-cracking functional material gel, and the particle size of the gel was about 0.5 mm.

[0036] Example 6

[0037] 1) 70 g of methacrylic acid, 30 g of acrylamide, 20 g of sucrose, 0.8 g of N,N'-methylenebisacrylamide, 1.2 g of potassium persulfate were added to 900 g of water, and stirred to prepare a uniform reaction solution.

[0038] 2) The above reaction solution was moved into a 50°C reaction box, and reacted for 10 h.

[0039] 3) The gel obtained by the above reaction was stirred and crushed by a high-speed tissue homogenizer to obtain a multifunctional anti-cracking functional material gel, and the particle size of the gel was about 0.5 mm.

[0040] Example 7

[0041] 1) 80 g of methacrylic acid, 20 g of acrylamide, 40 g of glucose, 0.4 g of N,N'-methylenebisacrylamide, 1 g of potassium persulfate were added to 650 g of water, and stirred to prepare a uniform reaction solution.

[0042] 2) The above reaction solution was moved into a 60°C reaction box, and reacted for 7 h.

[0043] 3) The gel obtained by the above reaction was stirred and crushed by a high-speed tissue homogenizer to obtain a multifunctional anti-cracking functional material gel, and the particle size of the gel was about 0.5 mm.

[0044] Example 8

[0045] 1) 75 g of sodium methacrylate, 25 g of acrylamide, 150 g of glucose, 0.8 g of N,N'-methylenebisacrylamide, 1.5 g of potassium persulfate were added to 1000 g of water, and stirred to prepare a uniform reaction solution.

[0046] 2) The above reaction solution was moved into a 65°C reaction box, and reacted for 6 h.

[0047] 3) The gel obtained by the above reaction was stirred and crushed by a high-speed tissue homogenizer to obtain a multifunctional anti-cracking functional material gel, and the particle size of the gel was about 0.5 mm.

[0048] Example 9

[0049] The preparation process is the same as that of Example 4. The gel obtained in Example 4 is dried at 75°C for 4h, crushed, and sieved to obtain a multifunctional anti-cracking functional material powder. The particle size of the powder is about 200μm.

[0050] Comparative Example 1

[0051] The preparation process is the same as that of Example 4, except that no small molecule retarder glucose is added, and a prepared gel is obtained.

[0052] Comparative Example 2

[0053] The preparation process is the same as that of Example 4, except that only 200g of glucose is dissolved in 450g of water to form a solution, and no water-soluble monomer molecules, initiators, and crosslinking agents are used.

[0054] The test of the present application uses three standardized performance evaluation methods to comprehensively evaluate the comprehensive performance of the multifunctional anti-cracking material. The setting time difference test is performed by preparing a cement paste containing a functional material and a blank control group, and the initial setting and final setting times are measured according to the standard method, and the time difference between the two is calculated to evaluate the influence of the material on the setting time of concrete. A positive value indicates that the setting time is prolonged to produce a retarding effect, and a negative value indicates that the setting time is shortened. This index reflects the degree of influence of the material on the operability of construction. The 24-hour hydration heat reduction rate test is strictly performed according to the JC / T 2608-2021 “Concrete Hydration Temperature Rise Inhibitor” standard. The hydration heat meter or adiabatic calorimeter is used to continuously monitor the hydration heat of the test group containing the functional material and the blank control group within 24 hours. The larger the value of this index, the more significant the hydration temperature rise inhibition effect of the material. The 7-day self-shrinkage ratio test refers to the JC / T 2551-2019 “Concrete High Water Absorption Resin Internal Curing Agent” standard, and uses a shrinkage deformation tester to continuously monitor the 7-day self-shrinkage deformation of the test group and the blank group. A negative value indicates that the material produces expansion and completely inhibits self-shrinkage, and a positive value less than 100% indicates that it has a shrinkage reduction effect. This index evaluates the internal curing and shrinkage reduction performance of the material. The comprehensive evaluation of these three test indexes can fully reflect the balanced performance of the material in terms of temperature reduction, shrinkage reduction, and construction operability, providing a scientific evaluation basis for the performance optimization and practical application of multifunctional anti-cracking materials.

[0055] The test results are shown in Table 1. The larger the 24h hydration heat reduction rate, the smaller the difference in setting time, indicating that the product has better control over the hydration performance of cement in the acceleration period, better temperature rise reduction effect, and weaker negative effect of retarding. The larger the 7d self-shrinkage ratio, the worse the shrinkage reduction performance. When the value is negative, it indicates that it can completely inhibit self-shrinkage and produce a certain amount of expansion.

[0056] Table 1: Setting time difference, 24h hydration heat reduction rate, and 7d self-shrinkage ratio of each example

[0057] Setting time difference / min 24 h hydration heat reduction rate / % 7d autogenous shrinkage ratio / % Comparative Example 1 -24 1.2 3 Comparative Example 2 1562 3.8 102 Example 1 239 35.4 35 Example 2 295 42.8 29 Example 3 346 48.1 6 Example 4 413 56.3 -7 Example 5 527 58.2 -15 Example 6 168 31.3 18 Example 7 215 33.6 21 Example 8 326 45.2 25 Example 9 395 54.3 -3

[0058] From Table 1, it can be seen that 1) in Comparative Example 2, directly adding the retarder can only greatly prolong the setting time, and cannot significantly improve the 24h hydration heat reduction rate index; but in Comparative Example 1, the retarder is not a small molecule retarder, and the setting time and the hydration heat reduction rate are significantly decreased, and in Examples 1-9, the use of the gel adsorbed small molecule retarder can significantly improve the 24h hydration heat reduction rate, but the retarding effect is greatly inhibited; 2) in general, for appropriately increasing the amount of the small molecule retarder, it is beneficial to improve the hydration heat regulation effect, but it will also increase the setting time to a certain extent. It can be seen that, by the hydrogel slow-release carrier technology, the controlled release of the small molecule retarder is successfully realized, the problem of excessive retarding caused by directly adding the retarder (the setting time of Comparative Example 2 is prolonged by 1562min) is avoided, the hydration heat regulation effect is significantly improved (the 24h hydration heat reduction rate is improved to 31.3%-58.2%, far more than 1.2% of Comparative Example 1 and 3.8% of Comparative Example 2), and good internal curing and shrinkage reduction functions are simultaneously achieved. The technical route effectively solves the technical problem that the traditional retarder cannot balance the cooling effect and the construction operability, realizes the organic unity of the cooling and shrinkage reduction dual functions, and the performance of Examples 1-9 is ranked as Example 4>Example 9>Example 3>Example 5>Example 8>Example 2>Example 7>Example 6>Example 1.

Claims

1. A multifunctional anti-cracking material with reduced shrinkage and cooling, characterized in that: The components include water-soluble monomers, small molecule retarder, initiator and crosslinking agent by weight parts as 100:(20-300):(0.5-1.5):(0.1-1), wherein the small molecule retarder is at least one of glucose, sodium gluconate, sucrose, sorbitol and mannitol. ​ 2. The multifunctional anti-cracking material with temperature reduction and shrinkage reduction according to claim 1, characterized in that: The components include water-soluble monomers, small molecule retarder, initiator and crosslinking agent by weight parts as 100:(150-300):(0.8-1.5):(0.5-1).

3. The multifunctional anti-cracking material with temperature reduction and shrinkage reduction according to claim 1, characterized in that: The water-soluble monomers are divided into ionic monomers and non-ionic monomers, wherein the ionic monomers are (meth) acrylic acid or its salt, and the non-ionic monomers are acrylamide.

4. The multifunctional anti-cracking material with the functions of temperature reduction and shrinkage according to claim 3, characterized in that: The non-ionic monomers account for less than 90% of the total mass of the water-soluble monomers.

5. The multifunctional anti-cracking material with the functions of temperature reduction and shrinkage according to claim 1, characterized in that: The initiator is one or both of potassium sulfate and ammonium persulfate, and the crosslinking agent is one or more of N,N'-methylenebis(meth)acrylamide and ethylene glycol diacrylate.

6. The method for preparing the multifunctional anti-cracking material with the functions of temperature reduction and shrinkage reduction according to any one of claims 1-5, characterized in that, The method includes the following steps: (1) preparing a reaction solution: dissolving the water-soluble monomers, small molecule retarder, initiator and crosslinking agent in water in sequence to form a uniform reaction solution; (2) heating the reaction solution to react, crushing to obtain a gel, or heating the reaction solution to react, drying and crushing to obtain a powder.

7. The production method according to claim 6, wherein In step (1), the total amount of the water-soluble monomers, small molecule retarder, initiator and crosslinking agent is 10-50% of the mass of the reaction solution.

8. The preparation method according to claim 6, characterized in that, In step (2), the heating reaction temperature is 50-75℃, and the heating reaction time is 3-10h.

9. The preparation method according to claim 6, characterized in that, In step (2), the particle size of the gel is controlled to be less than 1mm during crushing.

10. The method of claim 6, wherein, In step (2), the particle size of the powder is less than 300um during crushing.