Composite concrete water-retaining agent and preparation method thereof

Abstract

The invention relates to a composite concrete water-retaining agent and a preparation method thereof. The composite concrete water-retaining agent comprises the following components: 200-400 parts of unsaturated acid monomer; 1100 to 1400 parts of acrylamide and / or a derivative thereof; 2-7 parts of a water retention functional monomer; 2 to 14 parts of a polyol functional monomer; 20-30 parts of an oxidizing agent; 5-10 parts of a reducing agent; and water; the water-retaining functional monomer is prepared from long-chain boric acid ester and unsaturated acyl chloride, and the molecular formula of the water-retaining functional monomer is CH2 = CHCOOCH2-(CH2) n-B (OH) 2. According to the invention, a polyol functional monomer is also introduced into the composite water-retaining agent, a boric acid group in the water-retaining functional monomer and a polyol structure of the polyol functional monomer form dynamic crosslinking, a flexible network structure is constructed, and the network structure can lock moisture to form gel in a humid environment; and under a dry or high-alkali condition, the network structure gradually releases water, so that the dynamic adjustment of the water retention performance is realized.

Description

Technical Field

[0001] The invention relates to the technical field, in particular to a composite concrete water retaining agent and a preparation method thereof. Background Art

[0002] With the continuous development of construction technology, the performance requirements of mortar and concrete are increasing. As a key admixture to improve its bleeding, segregation and workability, water retaining agent plays an important role in concrete engineering.

[0003] At present, traditional water-retaining agents are mainly based on cellulose ether materials, which achieve water-retaining properties by increasing the viscosity of the system. However, this type of water-retaining agent has some significant defects:

[0004] 1. Decreased fluidity: Although high viscosity enhances water retention, it causes a significant decrease in concrete fluidity and increased slump loss.

[0005] 2. Insufficient stability: In an alkaline environment, cellulose ether water-retaining agents are easily affected by divalent metal ions, and their water-retaining properties are unstable, which increases the difficulty of operation and adjustment at the construction site.

[0006] In order to overcome the shortcomings of cellulose ether water retaining agents, new biopolysaccharide thickeners (such as xanthan gum and Wenlun gum) are used in concrete. This type of thickener shows high stability in acid and alkali environments and has excellent suspension and fluidity. However, these biopolysaccharide thickeners also have the following problems:

[0007] 1. Insufficient water retention performance: Compared with cellulose ethers, its water retention performance is relatively inferior.

[0008] 2. Limitations of using large amounts: When used in large amounts, the fluidity of the concrete will decrease, limiting its scope of application.

[0009] In addition, it is difficult for existing water-retaining agents to dynamically adjust their water-retaining properties according to specific needs during the construction process, which limits their adaptability under complex construction conditions. Therefore, developing a water-retaining agent that can dynamically adjust its water-retaining properties and take into account both concrete workability and water-retaining properties has become the key to solving the above problems. Summary of the invention

[0010] Based on this, it is necessary to provide a composite concrete water-retaining agent and a preparation method thereof that takes into account both concrete workability and water retention.

[0011] To achieve the above object, the present invention provides a technical solution:

[0012] A composite concrete water retaining agent, measured in parts by weight, comprising:

[0013]

[0014] The water-retaining functional monomer is prepared from long-chain boric acid ester and unsaturated acyl chloride, and the molecular formula of the water-retaining functional monomer is as follows:

[0015] CH 2 =CHCOOCH 2 -(CH 2 ) n -B(OH) 2 .

[0016] The present invention provides a composite concrete water-retaining agent with dynamic adjustment capability, which can not only achieve a balance between water retention and fluidity by adjusting the intermolecular forces, but also maintain stability within a wide pH range and flexibly adjust the water retention performance by external conditions, thereby meeting the comprehensive requirements of concrete engineering for workability, water seepage resistance and durability, and providing a more superior solution for the application of modern building materials.

[0017] Furthermore, the long-chain boric acid ester is prepared by esterification of long-chain alcohol and boric acid. The specific preparation steps of the water-retaining functional monomer are as follows:

[0018] S100, Preparation of long-chain borate esters

[0019] Boric acid and long-chain alcohol are reacted in an anhydrous solvent, and an acid catalyst is used to heat to 50-100° C. to promote esterification reaction to generate long-chain boric acid esters, and the generated water is removed.

[0020] S200, reacting a long-chain boric acid ester with an unsaturated acyl chloride in an anhydrous organic solvent, adding an alkaline catalyst to neutralize HCl, generating an acrylic acid-esterified long-chain boric acid ester, and finally obtaining a water-retaining functional monomer containing a polymerizable double bond.

[0021] Specifically, the acidic catalyst includes concentrated sulfuric acid and p-toluenesulfonic acid.

[0022] Basic catalysts include pyridine.

[0023] Furthermore, the long-chain alcohol includes at least one of dodecanol, hexadecanol and stearyl alcohol.

[0024] Furthermore, the unsaturated acid chloride includes at least one of acryloyl chloride and methacryloyl chloride.

[0025] Furthermore, the unsaturated acid monomer includes at least one of acrylic acid, methacrylic acid and maleic anhydride.

[0026] Furthermore, the acrylamide and / or its derivative B includes at least one of acrylamide, 2-acrylamido-2-phenylethanesulfonic acid, N-isobutylacrylamide and N-hydroxyacrylamide.

[0027] Furthermore, the hydroxyl functional polyol functional monomer includes at least one of 1,2-ethylene glycol, glycerol and 1,2-propylene glycol.

[0028] Furthermore, the oxidant includes at least one of sodium persulfate and ammonium persulfate.

[0029] Furthermore, the reducing agent includes sodium hypophosphite.

[0030] The present invention also provides a method for preparing a composite concrete water retaining agent, comprising the steps of:

[0031] Mix unsaturated acid monomers, polyol functional monomers, acrylamide and / or its derivatives and water to prepare a base material, and adjust the pH value of the base material to 9-10.5;

[0032] The reducing agent, the water-retaining monomer and water are prepared into solution A;

[0033] Prepare solution B by mixing oxidant and water;

[0034] The initial reaction temperature is 40-70°C, and solution A and solution B are added dropwise to the base material for 2-3 hours. After the addition is completed, the mixture is aged at a constant temperature for 1-3 hours, and water is added to prepare the mixture to obtain a concrete water retaining agent with a desired specific solid content.

[0035] Beneficial effects of the present invention:

[0036] 1. The composite concrete water-retaining agent prepared by the present invention introduces a water-retaining functional monomer, which is prepared from a long-chain borate and an unsaturated acyl chloride. The long-chain borate is a long-chain alkyl group, which can form a microscopic hydrophobic interface inside the concrete, reduce the free migration speed of water, thereby reducing water evaporation and improving the water retention effect.

[0037] At the same time, long-chain alkyl groups can adjust the distribution and morphology of pores in the concrete system, forming a more uniform and stable bubble and pore structure. This optimized pore structure not only improves the concrete's resistance to water seepage, but also improves its crack resistance and durability.

[0038] 2. The present invention also introduces a polyol functional monomer into the composite concrete water-retaining agent. The boric acid group in the water-retaining functional monomer forms a dynamic crosslink with the polyol structure of the polyol functional monomer to construct a flexible network structure. In a humid environment, the network structure can lock in moisture to form a gel; in dry or high-alkali conditions, the network structure gradually releases moisture, thereby achieving dynamic adjustment of the water-retaining performance.

[0039] 3. The composite concrete water retaining agent prepared in this application not only has excellent water retaining effect, but also significantly improves the workability of concrete. In addition, its production process is completed at room temperature, which is green, low-carbon, environmentally friendly and efficient. DETAILED DESCRIPTION

[0040] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0041] In the examples, the test methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0042] 1. Preparation of water-retaining functional monomer

[0043] 1. Preparation of water-retaining functional monomer A1

[0044] S100, Preparation of long-chain borate esters

[0045] Boric acid and dodecanol are reacted in anhydrous toluene, and concentrated sulfuric acid is used to heat to 50°C to promote the esterification reaction to generate long-chain boric esters, and the generated water is removed.

[0046] S200, reacting a long-chain borate ester with acryloyl chloride in an anhydrous organic solvent, adding an alkaline catalyst pyridine to neutralize HCl, generating an acrylic acid-esterified long-chain borate ester, and finally obtaining a water-retaining functional monomer containing a polymerizable double bond.

[0047] 2. Preparation of water-retaining functional monomer A2

[0048] S100, Preparation of long-chain borate esters

[0049] Boric acid and hexadecanol are reacted in anhydrous dichloromethane, and concentrated sulfuric acid is used to heat to 100°C to promote the esterification reaction to generate long-chain boric acid esters, and the generated water is removed.

[0050] S200, reacting a long-chain borate ester with methacryloyl chloride in an anhydrous organic solvent, adding an alkaline catalyst such as pyridine to neutralize HCl, generating an acrylic acid-esterified long-chain borate ester, and finally obtaining a water-retaining functional monomer containing a polymerizable double bond.

[0051] 3. Preparation of water-retaining functional monomer A3

[0052] S100, Preparation of long-chain borate esters

[0053] Boric acid and octadecyl alcohol are reacted in an anhydrous solvent, concentrated sulfuric acid is used to heat to 80° C., an esterification reaction is promoted to generate a long-chain boric acid ester, and the generated water is removed.

[0054] S200, reacting a long-chain borate ester with acryloyl chloride in an anhydrous organic solvent, adding an alkaline catalyst pyridine to neutralize HCl, generating an acrylic acid-esterified long-chain borate ester, and finally obtaining a water-retaining functional monomer containing a polymerizable double bond.

[0055] 2. Preparation of water retaining agent

[0056] The preparation steps are as follows:

[0057] S100, mixing unsaturated acid A, functional polyol functional monomer, acrylamide and / or its derivative B aqueous solution to prepare a base material, adding sodium hydroxide solution into the base material, and adjusting the pH value of the base solution to 9-10.5;

[0058] S200, preparing solution A by mixing sodium hypophosphite, a homemade water-retaining functional monomer and water;

[0059] S300, preparing solution B with oxidant and water;

[0060] S400, the initial reaction temperature is 40-70°C, the dripping time of solution A and solution B is 2h, after the dripping is completed, the mixture is kept at a constant temperature for 1.5h, and water is added to obtain a composite concrete water retaining agent with a solid content of 20wt.%.

[0061] Example 1

[0062] S100, 300 parts of acrylic acid A, 2 parts of functional polyol functional monomer, 1200 parts of acrylamide and water are mixed to prepare a base material, sodium hydroxide solution is added to the base material, and the pH value of the base liquid is adjusted to 9;

[0063] S200, preparing solution A by mixing 6 parts of sodium hypophosphite, 30 parts of water-retaining functional monomer and water;

[0064] S300, preparing solution B by mixing 30 parts of potassium persulfate with water;

[0065] S400, the initial reaction temperature is 45°C, the dripping time of solution A and solution B is 2h, the dripping is completed, the temperature is kept constant for 1.5h, and water is added to obtain a composite concrete water retaining agent with a solid content of 20wt.%

[0066] In addition, the steps for preparing the composite water-retaining agent in Examples 2 to 4 are the same as those in Example 1, except for the amount of each raw material used. The material list of Examples 1 to 4 is shown in Table 1.

[0067] Table 1 Materials list of Examples 1 to 4

[0068]

[0069] Comparative Example 1

[0070] Comparative Example 1 is a commercially available concrete water retaining agent, and its solid content is configured to be the same as that of Example 1;

[0071] Comparative Example 2

[0072] Comparative Example 2 The steps for preparing the composite water-retaining agent are the same as those of Example 1, except that:

[0073] 0 parts of water-retaining functional monomer;

[0074] 0 parts of polyol functional monomer;

[0075] In addition, the amount of water used was changed so that the solid content of the prepared composite water-retaining agent remained consistent with that in Example 1.

[0076] Comparative Example 3

[0077] Comparative Example 3 The steps for preparing the composite water-retaining agent are the same as those in Example 1, except that:

[0078] Without adding water-retaining functional monomer, the solid content of the composite water-retaining agent prepared was kept consistent with that in Example 1 by changing the amount of water.

[0079] Comparative Example 4

[0080] Comparative Example 4 The steps for preparing the composite water-retaining agent are the same as those in Example 1, except that:

[0081] Without adding polyol functional monomer, the amount of water is changed so that the solid content of the composite water-retaining agent prepared is consistent with that in Example 1.

[0082] In order to verify the effects of the above embodiments and comparative examples, C30 concrete mix ratio was used:

[0083] Cement 330kg / m 3 , sand 750kg / m 3 、Stone (1) 825kg / m 3 、Stone (2) 195kg / m 3 , water 175kg / m 3 , try mixing 15L of concrete.

[0084] By adjusting the adhesive and sand ratio to make the concrete bleed, keeping the same mix ratio, adding water retaining agent to the admixture, testing the concrete slump expansion, workability, water bleeding rate, compressive strength and other performance indicators, the experimental results are shown in Table 2:

[0085] Table 2 Concrete performance test results

[0086]

[0087] It can be seen from the data of the examples and comparative examples in Table 2 that the introduction of water-retaining functional monomers and polyol functional monomers can improve the workability, flow rate, collapse retention performance, water bleeding rate and compressive strength of concrete.

[0088] Comparative Example 1 is a concrete prepared using a conventional water-retaining agent, which exhibits problems of poor fluidity, weak water-retaining capacity, and insufficient working performance;

[0089] Comparative Example 2 is a water-retaining agent produced by the same process without introducing water-retaining functional monomers and polyol functional monomers, and has the defects of poor encapsulation and high water bleeding rate.

[0090] Comparative Example 3 is a water-retaining agent produced by the same process without introducing a water-retaining functional monomer, and has the defects of poor encapsulation and high water seepage rate.

[0091] Comparative Example 4 is a water-retaining agent of the same process without the introduction of polyol functional monomers, and has the defect of large loss of expansion.

[0092] In contrast, Examples 1-4, which introduced water-retaining functional monomers and polyol functional monomers, significantly improved the performance of concrete. While the dosage was significantly reduced, the concrete water bleeding rate after 2 hours and 3 hours dropped significantly, indicating that the water-retaining performance was significantly improved.

[0093] From the expansion test results, the collapse retention performance of the embodiment is better than that of the comparative example, which verifies that the dynamic cross-linking structure gradually releases moisture under dry conditions and effectively delays the loss of expansion.

[0094] In terms of workability, the examples show good paste fullness, indicating that the introduction of long-chain alkyl groups improves the workability of concrete.

[0095] In addition, the compressive strength test results show that the compressive strength of the embodiment is relatively high, further proving the superiority of its comprehensive performance.

[0096] It should be noted that the specific parameters or some reagents in the above embodiments are specific embodiments or preferred embodiments of the present invention, rather than limiting the present invention; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

Claims

1. A composite concrete water retaining agent, characterized in that: In parts by weight, the composite concrete water retaining agent comprises: The water-retaining functional monomer is prepared from long-chain boric acid ester and unsaturated acyl chloride, and the molecular formula of the water-retaining functional monomer is as follows: CH2=CHCOOCH2-(CH2) n -B(OH)2。 2. The composite concrete water retaining agent according to claim 1, characterized in that: Long-chain borate esters are prepared by esterification of long-chain alcohols and boric acid.

3. The composite concrete water retaining agent according to claim 1, characterized in that: The long-chain alcohol includes at least one of dodecanol, hexadecanol and stearyl alcohol.

4. The composite concrete water retaining agent according to claim 1, characterized in that: The unsaturated acid chloride includes at least one of acryloyl chloride and methacryloyl chloride.

5. The composite concrete water retaining agent according to claim 1, characterized in that: The unsaturated acid monomer includes at least one of acrylic acid, methacrylic acid and maleic anhydride.

6. The composite concrete water retaining agent according to claim 1, characterized in that: The acrylamide and / or its derivative B includes at least one of acrylamide, 2-acrylamido-2-phenylethanesulfonic acid, N-isobutylacrylamide and N-hydroxyacrylamide.

7. The composite concrete water retaining agent according to claim 1, characterized in that: The hydroxyl functional polyol functional monomer includes at least one of 1,2-ethylene glycol, glycerol and 1,2-propylene glycol.

8. The composite concrete water retaining agent according to claim 1, characterized in that: The oxidant includes at least one of barium persulfate, sodium persulfate and ammonium persulfate.

9. The composite concrete water retaining agent according to claim 1, characterized in that: The reducing agent includes at least one of ascorbic acid and sodium hypophosphite.

10. A method for preparing the composite concrete water retaining agent according to any one of claims 1 to 9, characterized in that: Includes steps: Mix unsaturated acid monomers, polyol functional monomers, acrylamide and / or its derivatives and water to prepare a base material, and adjust the pH value of the base material to 9-10.5; The reducing agent, the water-retaining monomer and water are prepared into solution A; Prepare solution B by mixing oxidant and water; The initial reaction temperature is 40-70° C. The solution A and the solution B are added dropwise to the base material. After the addition is completed, the constant temperature reaction is continued. After the reaction is completed, the composite concrete water retaining agent can be obtained.

Images