CN112940199B - Water-retaining internal curing anti-cracking concrete water reducer and preparation method thereof - Google Patents

Abstract

The invention discloses a water-retaining and internal-curing anti-cracking concrete water-reducing agent and a preparation method thereof. The concrete water-reducing agent is mainly prepared from the following materials: 22.28-22.85 parts of alcohol head, 301.13-309.28 parts of annular Monomer, 1.0-2.2 parts of catalyst, 47.59-58.87 parts of acids, 2.5-6.1 parts of reducing agent, 4.6-6.9 parts of initiator, 3.8-9.1 parts of neutralizer, 2.5-4.2 parts of chain transfer agent, and the rest are Ionized water. The invention prepares a concrete water-reducing agent with high water-retention performance, keeps free water inside the mortar, increases the fluidity of the mortar, delays the hydration process of the cement, reduces the drying shrinkage of the cement, and improves the crack resistance and the performance of the cement. work performance.

Description

A kind of water-retaining internal curing anti-cracking concrete water reducing agent and preparation method thereof

technical field

The invention belongs to the technical field of building materials and relates to cement admixture technology, in particular to a water-retaining and internal-curing anti-cracking concrete water reducing agent and a preparation method thereof.

Background technique

In recent years, with the continuous expansion of the project scale and the continuous improvement of the level of science and technology, the continuous emergence of important buildings with special functional requirements, such as skyscrapers, super-span bridges, high-speed railways and the construction of giant water conservancy projects, etc. High strength, better durability, better stability. Water reducing agent is one of the important components of high-performance concrete. Water reducing agent can reduce the water consumption of concrete during use, improve its durability, improve collapse resistance, and improve strength. Carboxylic acid-based high-performance water-reducing admixtures have the advantages of low dosage, high water-reducing rate, and good collapse retention performance, and have become the focus of research and development of concrete water-reducing admixtures at home and abroad. However, the existing polycarboxylate superplasticizers on the market have some shortcomings, such as poor adaptability to cement, insufficient collapse retention for concrete with high mud content, segregation and bleeding due to high water reduction rate, and The compatibility of different materials is not good, and the workability is poor. Therefore, it is imperative to study new polycarboxylate superplasticizers.

Patent CN108484897A discloses a polyoxyalkylene ether monomer and a method for preparing polycarboxylate water reducer with the same. The invention discloses a polyoxyolefin ether monomer and a method for preparing a polycarboxylate water reducer by using the same. Its preparation steps: 1. Preparation of polyoxyalkylene ether monomer: add initiator methallyl alcohol or prenyl alcohol or polyoxyethylene ether prepolymer and catalyst into the reaction vessel, and pass epoxy into the vessel. 1 mole of ethane, adjust the temperature to 105～130℃ for ring-opening polymerization reaction, adjust the temperature to 115～150℃, feed bl moles of propylene oxide to carry out ring-opening polymerization, repeatedly feed ethylene oxide polymerization reaction and propylene oxide polymerization After 1-2 cycles of the reaction, ethylene oxide is introduced for polymerization to obtain a polyoxyalkylene ether monomer a. 2. Preparation of polycarboxylate water-reducing agent: The monomer c and the auxiliary agent are added dropwise to the monomer a (polyoxyalkylene ether monomer), isobutenyl or isobutenyl by the normal temperature redox method or the heating-initiated free radical copolymerization method. The pentenyl polyoxyethylene ether monomer b and the bottom water of the kettle initiate free radical polymerization to obtain the final product.

Patent CN 109880076 A discloses a preparation method and application of a powdered polycarboxylate water reducer. The invention discloses a mixed alcohol polyoxyethylene ether water reducing agent macromonomer and a preparation method and application thereof. The preparation process of the mixed alcohol polyoxyethylene ether water reducing agent macromonomer is as follows: in a nitrogen atmosphere , potassium hydroxide, sodium-based catalyst, methallyl alcohol, prenyl alcohol and ethylene oxide are mixed and stirred to react to synthesize mixed alcohol polyoxyethylene ether intermediates, mixed alcohol polyoxyethylene ether intermediates Then react with ethylene oxide under nitrogen atmosphere to synthesize the final product mixed alcohol polyoxyethylene ether, which is a macromonomer for preparing polycarboxylate water reducing agent. The mixed alcohol polyoxyethylene ether synthesized by the present invention has both the basic molecular skeleton structure of prenyl alcohol and methallyl alcohol, and the mixed alcohol polyoxyethylene ether product is used for preparing polycarboxylate water reducer. , Polycarboxylate water reducing agent can maintain the water reducing performance and have good dispersion retention when applied to cement.

Patent CN 109880019 A discloses a polycarboxylate water reducer with good workability and wide adaptability and its preparation method. The invention is a polycarboxylate water reducing agent with good workability and wide adaptability. Monomer, unsaturated carboxylic acid comonomer, initiator, reducing agent, chain transfer agent, liquid caustic soda and water; by introducing ethylene glycol monovinyl polyglycol ether (2+2 new active macromonomer), A high-performance polycarboxylate superplasticizer was synthesized by free radical polymerization at room temperature, and finally a product with higher polymerization activity, simple production process, excellent water-reducing and slump-retaining properties, and good workability can be used to meet the actual needs of different materials. A new type of high workability polycarboxylate superplasticizer.

Different from the above patents, the water reducing agent prepared by the present invention is a high adsorption rate polyether polycarboxylate water reducing agent. The invention adopts the polymerization of 3-allyloxy-1,2-propanediol, ethylene oxide and propylene oxide to prepare a polyether with a molecular weight of 2000. When this polyether is used as a side chain of a water reducing agent, the length is only half of the other 2000 molecular weight side chains, and a small amount of alcohol head is added in the form of a monomer during the preparation process, so that there are more molecular chains of the water reducing agent. The hydroxyl group enhances the complexing ability of the superplasticizer molecules to calcium ions in the cement and improves the adsorption performance of the superplasticizer, and the hydroxyl group is a hydrophilic group, which increases the water-retention capacity of the superplasticizer and reduces the drying shrinkage of concrete. , which enhances the crack resistance of concrete.

SUMMARY OF THE INVENTION

Aiming at the deficiencies of the existing water-reducing agents, the present invention provides a water-retaining and internal-curing anti-cracking concrete water-reducing agent and a preparation method thereof. Very good coating of cement particles.

The inventive concept of the present invention is as follows: what is prepared by the present invention is a water-retaining and internal-curing anti-cracking concrete water reducing agent and a preparation method thereof. The present invention selects 3-allyloxy-1,2-propanediol, ethylene oxide and propylene oxide to make the polyether, which reduces the cost of raw materials to a certain extent. The self-made polyether and acrylic acid are reacted to prepare water reducing agent molecules. The same polyether molecule can be used as two side chains, which improves the steric hindrance of the water reducing agent and enhances the water reducing effect.

For solving the above problems, the technical scheme of the present invention is as follows:

A method for preparing a water-retaining and internal-curing anti-cracking concrete water-reducing agent, characterized in that the following steps are included in sequence:

Step 1: Add 21.28-21.85 parts of alcohol head and 1.0-2.2 parts of catalyst to the autoclave equipped with stirrer and temperature control equipment, and after nitrogen replacement for 3 times, start vacuuming to gauge pressure-0.098MPa, then heat up to 120 ℃ start vacuum dehydration for 1-2h, then cool down to 115 ℃, start to pass cyclic monomer into the reaction kettle, feed 301.13-309.28 parts of cyclic monomer into the reaction kettle, control the pressure less than 0.4MPa, complete the cyclic monomer After the monomer, the nitrogen addition was stopped, and the high-pressure reaction kettle was kept at 110-120°C for thermal aging to a negative pressure, cooled and discharged to obtain crude polyether;

Step 2: Put the crude polyether in the reactor, replace it with nitrogen negative pressure for 3 times, heat up to 125-135°C and stir for 2.5-3.5h, cool down to 85°C, then add distilled water and stir for 0.5-1.5h, while vacuuming. The temperature is raised to 120°C to obtain the finished polyether;

Step 3: Add the obtained finished polyether into the reaction kettle, heat it up to 45°C using a water bath, and prepare 2.5-6.1 parts of reducing agent, 4.6-6.9 parts of initiator, 2.5-4.2 parts of chain transfer agent and water into A liquid, 47.59-58.87 parts of acid substances, 0.5-1.0 parts of alcohol head and water are prepared into B liquid, and A liquid and B are added dropwise to the reaction kettle with a drip pump, wherein A is added dropwise 0.5-1 hours, B was added dropwise for 2-2.5 hours. After dripping A and B liquids, keep the water for 1 hour to obtain a concrete water reducing agent;

Step 4: adding 3.8-9.1 parts of neutralizer to the prepared concrete water-reducing agent, and replenishing water to the required solid content to obtain a concrete water-reducing agent solution, which is a water-retaining internal curing anti-cracking concrete water-reducing agent.

Further, the solid content of the water-retaining internal curing anti-cracking concrete water-reducing agent is 37-43%, and the optimum is 40%.

Preferably, the alcohol head is 3-allyloxy-1,2-propanediol.

Preferably, the cyclic monomers are ethylene oxide and propylene oxide.

Preferably, the catalyst is anhydrous aluminum chloride, boron trifluoride, concentrated sulfuric acid, hydrogen halide, arylsulfonic acid, inorganic phosphorus compound, carboxylic acid, organic cation exchange resin and aluminum phenolate, sodium hydroxide, hydrogen Any one or more compositions of potassium oxide, sodium cyanide, lithium aluminum tetrahydrogen, boron trifluoride vinyl ether, DMC, most preferably a composition of sodium hydroxide and sodium cyanide whose mass ratio is 2:1 .

Preferably, the acid substance is acrylic acid.

Preferably, the acid-to-ether ratio (molar ratio) is 3.8-4.3:1, most preferably 4.1:1

Preferably, the molecular weight of the polyether obtained in step 1 is 2000.

As preferably, the reducing agent is any one or several compositions in sodium hydrosulfite, ascorbic acid, sodium formaldehyde sulfoxylate, maltodextrin, sodium bisulfite, sodium metabisulfite, sodium hypophosphite, most preferably It is a composition of ascorbic acid and sodium metabisulfite with a mass ratio of 2:3.

Preferably, the initiator is ammonium persulfate, azobisisobutyronitrile, diisopropyl peroxydicarbonate, benzoyl peroxide, di-tert-butyl peroxide, dicyclohexyl peroxydicarbonate Any one or several of the compositions, the most preferably a composition of azobisisobutyronitrile and di-tert-butyl peroxide in a mass ratio of 1:1.

Preferably, the chain transfer agent is composed of any one or more of mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol, and mercaptopropanol, and most preferably, the mass ratio is 1:3 of mercaptoacetic acid and mercaptopropanol. combination.

Preferably, the neutralizing agent is any of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, sodium methoxide, sodium ethoxide, ethanolamine, diethanolamine, triethanolamine and triisopropanolamine One or more compositions, most preferably a composition of potassium carbonate and potassium hydroxide in a mass ratio of 3:5.

The preparation of water-retaining and internal-curing anti-cracking concrete water reducing agent is mainly prepared from the following components. The total mass of the raw materials is 1000 parts, and the mass parts are 40%.

Alcohol head 22.28-22.85 copies;

301.13-309.28 copies of cyclic monomers;

1.0-2.2 parts of catalyst;

Acid substances 47.59-58.87 copies;

2.5-6.1 parts of reducing agent;

4.5-6.9 parts of initiator;

2.5-4.2 copies of chain transfer agent;

3.8-9.1 copies of neutralizer;

The rest is water, and the total mass is 1000 parts.

Compared with the prior art, the advantages and beneficial effects of the present invention are:

1. The alcohol head used in the self-made polyether of the present invention is 3-allyloxy-1,2-propanediol, the alcohol head has 2 reactive hydroxyl groups, and the synthesized polyether molecular chain with a molecular weight of 2000 is composed of Compared with the side chain of 1000 molecular weight with 2 times the density, the final prepared water reducing agent molecule has both good steric hindrance and high adsorption.

2. The present invention adds part of the alcohol head in the form of a monomer, which increases the hydroxyl density on the molecular side chain of the water reducing agent, and the hydroxyl group can well complex the calcium ions in the cement particles and enhance the effect of the water reducing agent on the cement particles. adsorption. And the hydroxyl group is a hydrophilic group, which can form a hydrogen bond with the water molecule, which can effectively retain the water molecule, delay the hydration time of the cement, give the cement time to release the heat of hydration, reduce the drying shrinkage of the cement and reduce the cement water. The internal stress generated due to the untimely release of the hydration heat during crystallization improves the crack resistance of the concrete.

3. The present invention appropriately increases the consumption of the initiator and the chain transfer agent in the process of preparing the water-reducing agent, so as to obtain a water-reducing agent molecule with a high hydroxyl density and short main chain, and the molecular configuration of such a water-reducing agent can be Better increase the adsorption performance of the superplasticizer molecules and improve the water reducing rate of the superplasticizer.

Description of drawings

Fig. 1 is the SEM of the concrete sample added with TC-900J water reducer for 28d hydration in the comparative example of the present invention.

Fig. 2 is the SEM of the concrete sample hydrated for 28d by adding the water reducing agent of Example 1 in the comparative example of the present invention.

Detailed ways

Below, the applicant will further describe the technical solutions and beneficial effects of the present invention in detail in conjunction with specific embodiments, but it should be understood that the following embodiments should not be construed as limiting the scope of protection claimed in the claims of the application to any extent .

Example 1

The invention provides a preparation method of a water-retaining and internal-curing anti-cracking concrete water-reducing agent.

Alcohol head: 22.37 parts of 3-allyloxy-1,2-propanediol;

Cyclic monomers: 60.95 parts of ethylene oxide, 244.11 parts of propylene oxide;

Catalyst: 1.3 parts of the composition of sodium hydroxide and sodium cyanide with a mass ratio of 2:1;

Acid substances: 47.65 parts of acrylic acid;

Reducing agent: 2.8 parts of the composition of ascorbic acid and sodium metabisulfite with a mass ratio of 2:3;

Initiator: 6.5 parts of compositions of azobisisobutyronitrile and di-tert-butyl peroxide whose mass ratio is 1:1;

Chain transfer agent: 4.2 parts of the composition of thioglycolic acid and mercaptopropanol with a mass ratio of 1:3;

Neutralizer: 5.1 parts of compositions of potassium carbonate and potassium hydroxide whose mass ratio is 3:5;

The rest is water, the total mass is 1000 parts, and the solid content of the prepared water reducing agent is about 40%.

The preparation process includes the following operation steps in turn:

Step 1: Add 21.37 parts of 3-allyloxy-1,2-propanediol and 1.3 parts of sodium hydroxide and sodium cyanide with a mass ratio of 2:1 to the autoclave equipped with a stirrer and temperature control equipment. For the composition, after nitrogen replacement for 3 times, vacuum was started to gauge pressure -0.098MPa, then the temperature was raised to 120°C and dehydration was started for 1.9h, and then the temperature was lowered to 115°C. Start to feed the cyclic monomer into the reaction kettle, feed 60.95 parts of ethylene oxide and 244.11 parts of propylene oxide into the reaction kettle, and control the pressure to be less than 0.4MPa. After the cyclic monomer is passed through, stop adding nitrogen and react at high pressure. The kettle is kept at 115°C and aged to negative pressure (the cyclic monomer is gaseous at this temperature, when the reaction pressure no longer drops or is negative pressure, it indicates that the cyclic monomer has basically reacted completely), cooled and discharged to obtain the crude polyether .

Step 2: Place the crude polyether in the reaction kettle, replace it with nitrogen negative pressure 3 times, heat up to 127°C and stir for 2.5h, cool down to 85°C, then add distilled water and stir for 0.8h, and heat up to 120°C while vacuuming to obtain Finished polyether.

Step 3: add the prepared polyether into the reaction kettle, and heat it up to 45°C using a water bath. 2.8 parts of the composition of ascorbic acid and sodium metabisulfite with a mass ratio of 2:3, 6.5 parts of a composition of azobisisobutyronitrile and di-tert-butyl peroxide with a mass ratio of 1:1, and 4.2 parts of a mass ratio of 1 The composition of : 3 thioglycolic acid and mercaptopropanol and water are prepared into A liquid, 47.65 parts of acrylic acid, 1.0 parts of 3-allyloxy-1,2-propanediol and water are prepared into B liquid, respectively. Liquid A and B were added dropwise to the reaction kettle, wherein A was added dropwise for 0.7 hours and B was added dropwise for 2.2 hours. After dripping A and B liquids, keep the water for 1 hour to obtain a concrete water reducing agent.

Step 4: adding 5.1 parts of the composition of potassium carbonate and potassium hydroxide with a mass ratio of 3:5 to the prepared concrete water-reducing agent, and replenishing water to a total mass of 1000, that is, to obtain a concrete with a solid content of about 40% The water-reducing agent solution is a water-retaining and internal-curing anti-cracking concrete water-reducing agent.

The specific raw materials of Example 2-6 and the specific parameters (steps are the same) in the preparation method are different from those in Example 1, as shown in Table 1 and Table 2 below (Table 1 is the raw material, and Table 2 is the raw material in the preparation method). parameters), the expressions not listed in Table 2 are the same as those in Example 1.

Table 1 is a comparison table of the raw material components of Examples 1-6 of the present invention

Table 2 is a comparison table of the reaction parameters of Examples 1-6 of the present invention

The product of the present invention and Hubei Tengchen TC-900J water reducer were prepared into C50 concrete samples, and the following table was obtained after testing. (The 28d chloride ion diffusion coefficient is tested according to the standard of GB/T 50082-2009, the alkali aggregate reaction destructiveness is tested according to the chemical method of alkali aggregate activity detection in "Hydraulic Concrete Test Regulations", and the crack resistance of the flat plate method is tested. The maximum crack width is tested according to the standard of dynamic crack resistance in JG/T157-2004 industry standard.)

Table 3 is the performance comparison table of implementations 1-6 of the present invention and comparative examples

It can be seen from the above table that the high adsorption rate polyether polycarboxylate water reducing agent of the present invention has many excellent practical properties. Combining with example 1, it can be clearly seen that the present invention has excellent performance, excellent water reduction rate and corrosion resistance. At the same time, the preparation method is simple, the production process and equipment requirements are low, and it is suitable for production and use in various environments.

The sample of TC-900J water reducing agent hydrated for 28d and the sample of Example 1 were examined by SEM to observe the morphology and structure. The results are shown in Figures 1 and 2. It is obvious that the structure of the hydration product in Figure 2 is relatively dense, because the content of hydrated CSH gel increases continuously with the progress of hydration, and at the same time, due to the incorporation of Example 1, the hydration of cement is promoted, which consumes Part of the CH crystallizes, making the hydration products more tightly bound.

The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that various combinations, modifications or equivalent replacements to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and should cover within the scope of the claims of the present invention.

Claims (6)

1. The preparation method of the water-retaining internal curing anti-cracking concrete water reducer is characterized by sequentially comprising the following operation steps of:

the method comprises the following steps: adding 21.28-21.85 parts of alcohol head and 1.0-2.2 parts of catalyst into a high-pressure reaction kettle provided with a stirrer and a temperature control device, performing nitrogen replacement for 3 times, starting vacuumizing to gauge pressure of-0.098 MPa, heating to 120 ℃, starting vacuum dehydration for 1-2h, cooling to 115 ℃, starting introducing an annular monomer into the reaction kettle, introducing 301.13-309.28 parts of the annular monomer into the reaction kettle, controlling the pressure to be less than 0.4MPa, stopping adding nitrogen after the annular monomer is introduced, performing heat preservation and aging at the temperature of 110-35120 ℃ to negative pressure in the high-pressure reaction kettle, cooling and discharging to obtain crude polyether;

step two: placing the crude polyether in a reaction kettle, replacing for 3 times by nitrogen under negative pressure, heating to 125-phase 135 ℃, stirring for 2.5-3.5h, cooling to 85 ℃, adding distilled water, stirring for 0.5-1.5h, and heating to 120 ℃ while vacuumizing to obtain a finished polyether product;

step three: adding the prepared finished polyether into a reaction kettle, heating to 45 ℃ by adopting water bath, preparing A solution from 2.5-6.1 parts of reducing agent, 4.6-6.9 parts of initiator, 2.5-4.2 parts of chain transfer agent and water, preparing B solution from 47.59-58.87 parts of acid substance, 0.5-1.0 part of alcohol head and water, and respectively adding the A solution and the B solution into the reaction kettle by using a dropping pump, wherein the A solution is dropped for 0.5-1 hour, and the B solution is dropped for 2-2.5 hours; after the A, B liquid is dripped, the temperature is kept for 1 hour to prepare the concrete water reducing agent;

step four: adding 3.8-9.1 parts of neutralizer to the prepared concrete water reducing agent, and supplementing water to required solid content to obtain a concrete water reducing agent solution, namely the water-retaining internal curing anti-cracking concrete water reducing agent;

the alcohol head is 3-allyloxy-1, 2-propylene glycol; the cyclic monomer is ethylene oxide and propylene oxide;

the catalyst is composed of one or more of anhydrous aluminum chloride, boron trifluoride, concentrated sulfuric acid, hydrogen halide, aryl sulfonic acid, an inorganic phosphorus compound, carboxylic acid, organic cation exchange resin, aluminum phenoxide, sodium hydroxide, potassium hydroxide, sodium cyanide, lithium aluminum hydride, boron trifluoride vinyl ether and DMC; the acid substance is acrylic acid;

the molecular weight of the polyether obtained in the step one is 2000, the molecular chain of the synthesized polyether with the molecular weight of 2000 is composed of a molecular chain with the molecular weight of 1000 on the 2 side, and the finally prepared water reducing agent molecules have the molecular weight of 1000 with the density of 2 times.

2. The preparation method of the water reducer for water-retaining internal curing anti-cracking concrete of claim 1 is characterized by comprising the following steps: the reducing agent is any one or more of sodium hydrosulfite, ascorbic acid, sodium formaldehyde sulfoxylate, maltodextrin, sodium hydrosulfite, sodium metabisulfite and sodium hypophosphite.

3. The preparation method of the water reducer for water-retaining internal curing anti-cracking concrete according to claim 1, characterized by comprising the following steps: the initiator is any one or more of ammonium persulfate, azobisisobutyronitrile, diisopropyl peroxydicarbonate, benzoyl peroxide, di-tert-butyl peroxide and dicyclohexyl peroxydicarbonate.

4. The preparation method of the water reducer for water-retaining internal curing anti-cracking concrete according to claim 1, characterized by comprising the following steps: the chain transfer agent is any one or more of thioglycolic acid, mercaptopropionic acid, mercaptoethanol and mercaptopropanol.

5. The preparation method of the water reducer for water-retaining internal curing anti-cracking concrete according to claim 1, characterized by comprising the following steps: the neutralizing agent is any one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, sodium methoxide, sodium ethoxide, ethanolamine, diethanolamine, triethanolamine and triisopropanolamine.

6. The water-retaining internal curing anti-cracking concrete water reducer is characterized in that: prepared by the preparation method of any one of claims 1 to 5.

Images