Concrete slow-release slump retaining agent and preparation method thereof

Abstract

The invention relates to the technical field of concrete admixtures, in particular to a concrete slow-release slump retaining agent and a preparation method thereof, and the concrete slow-release slump retaining agent comprises the following raw materials: 320-430 parts of an isopentenol polyoxyethylene ether macromonomer, 15-20 parts of a general monomer, 0.5-1.0 part of a reducing agent, 40-70 parts of a slump retaining functional monomer, 2.5-4.5 parts of an oxidizing agent, 2.0-3.5 parts of a chain transfer agent and 620-471 parts of deionized water. An initial free radical is generated through an electron transfer reaction between an oxidizing agent and a reducing agent by utilizing a composite initiation system composed of the oxidizing agent and the reducing agent, the initial free radical is combined with monomer molecules to form a chain growth free radical, and then the chain growth free radical is continuously increased to connect a plurality of monomers to form macromolecules, so that a steric hindrance effect is provided; the agglomeration of cement particles is delayed, and the slump retaining performance is high.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and particularly to a concrete slow-release slump retention agent and a preparation method thereof. Background Art

[0002] Since the distance between the concrete mixing plant and the construction site is relatively long, the slow-release slump retention agent delays the initial setting and final setting of concrete by slowing down the cement hydration reaction, prolongs the setting time, enables the concrete to maintain its workability during high-temperature or long-distance transportation, is easier to operate during construction, and reduces quality problems caused by too fast setting.

[0003] Chinese patent application for invention with publication number CN107474195A discloses a polycarboxylate slump retention agent and a preparation method thereof, which is prepared by polymerizing isopentenyl alcohol polyoxyethylene ether (TPEG), acrylic acid (AA), slump retention aid a, and slump retention aid b in the presence of an initiator and a chain transfer agent. The slump retention aid a is octavinyl-POSS (CAS No. 69655-76-1), that is, octavinyl-octasilsequioxane, and the slump retention aid b is divinylbenzene (DVB); the molar ratio of TPEG, AA, slump retention aid a, and slump retention aid b is: 1∶(1-3)∶(0.01-0.05)∶(0.1-0.5); the dosage of the chain transfer agent is 0.1-0.5% of the total weight of the monomers, and the dosage of the initiator is 0.1-2% of the total weight of the monomers; it includes the following steps: (1) Add TPEG, slump retention aid b, and deionized water into a reactor, heat up and stir to completely dissolve TPEG; (2) Prepare material A by adding water to AA and slump retention aid a; (3) Prepare material B by adding water to the chain transfer agent and the initiator; (4) When the temperature rises to 50-70°C, simultaneously dropwise add material A and material B, and material B is dropped more than material A for 30-40 minutes, and keep warm for 0.5-1.5 hours after dropping; (5) Wait for the reactant to cool to room temperature, and adjust the pH to neutral with an alkali to obtain the target product. This prior art can further improve the slump, spread, and compressive strength of concrete, but its slump retention effect still cannot meet the requirements of existing construction projects.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the Invention

[0005] In order to solve the problems raised in the above background art, the present invention provides a concrete slow-release slump retention agent and a preparation method thereof.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present invention is as follows:

[0007] A concrete slow-release slump-keeping agent, comprising the following raw materials: 320-430 parts of isopentenol polyoxyethylene ether macromonomer, 15-20 parts of general monomer, 0.5-1.0 part of reducing agent, 40-70 parts of slump-keeping functional monomer, 2.5-4.5 parts of oxidizing agent, 2.0-3.5 parts of chain transfer agent, and 620-471 parts of deionized water.

[0008] According to the above method, the molecular weight of the isopentenol polyoxyethylene ether macromonomer is 3000.

[0009] According to the above method, the general monomer is one or more of methacrylic acid and acrylic acid.

[0010] According to the above method, the reducing agent is one or more of ascorbic acid, Rongalite, ferrous sulfate, and sulfite.

[0011] According to the above method, the slump-keeping functional monomer is one or more of hydroxypropyl acrylate and hydroxyethyl acrylate.

[0012] According to the above method, the oxidizing agent is one or more of hydrogen peroxide, ammonium persulfate, and potassium permanganate.

[0013] According to the above method, the chain transfer agent is one or more of mercaptoethanol, mercaptopropionic acid, and mercaptoacetic acid.

[0014] The present invention also provides a preparation method of a concrete slow-release slump-keeping agent, comprising the following steps:

[0015] a. Add 150-300 parts of deionized water with a temperature of 5-15°C into a reaction kettle, and then sequentially add 320-430 parts of isopentenyl polyoxyethylene ether macromonomer, and start a stirrer to stir and dissolve for 30 minutes;

[0016] b. Prepare Material A: Weigh 15-20 parts of general monomer, 40-70 parts of slump-keeping functional monomer, and 90-120 parts of deionized water, and mix the three evenly for standby;

[0017] c. Prepare Material B: Weigh 0.5-1.0 part of reducing agent, 2.0-3.5 parts of chain transfer agent, and 80-110 parts of deionized water, and mix the three evenly for standby;

[0018] d. Add 2.5-4.5 parts of oxidizing agent into the reaction kettle and stir for 3 minutes;

[0019] e. Dropwise add Material A and Material B into the reaction kettle simultaneously. The dropping time of Material A is 120 minutes, and the dropping time of Material B is 150 minutes. Control the temperature of the reaction kettle at 15-25°C. After the dropping is completed, keep the temperature for 60 minutes; finally, add deionized water to make the total amount of the sample 1000 parts, and a concrete slow-release slump-keeping agent is obtained.

[0020] The beneficial effects of the present invention are as follows:

[0021] The synthesis reaction of the present invention utilizes a composite initiation system composed of an oxidant and a reductant. Through the electron transfer reaction between the two, initial free radicals are generated. The initial free radicals combine with monomer molecules to form chain growth free radicals, and a polymerization reaction occurs with the continuous growth of the chain growth free radicals. Specifically, unsaturated double bond-containing vinyl monomers are used as raw materials. By opening the double bonds in the monomer molecules, repeated addition reactions are carried out between molecules to connect many monomers to form macromolecules, providing steric hindrance effects to delay the agglomeration of cement particles, thereby maintaining the slump.

[0022] The concrete slow-release slump retaining agent of the present invention reacts in an alkaline environment (such as the environment generated during cement hydration) to form negatively charged hydroxyl groups, which are combined with the positively charged surface of cement particles through electrostatic adsorption, thereby dispersing the cement particles and reducing the slump loss of concrete during the mixing and pouring processes. Its core function is to improve the workability of concrete and extend the transportation and retention time of concrete through electrostatic adsorption and steric hindrance effects. Specific embodiments

[0023] The technical solutions of the present invention will be described below in conjunction with examples and comparative examples.

[0024] Example 1

[0025] It is prepared by the following steps:

[0026] a. Add 150 parts of deionized water with a temperature of 5 - 15°C to the reaction kettle, and then add 320 parts of isopentenyl polyoxyethylene ether macromonomer in sequence. Start the stirrer and stir for 30 minutes to dissolve.

[0027] b. Prepare Material A: Weigh 15 parts of general monomer, 40 parts of slump retaining functional monomer, and 90 parts of deionized water, and mix the three evenly for later use.

[0028] c. Prepare Material B: Weigh 0.5 part of reductant, 2.0 parts of chain transfer agent, and 80 parts of deionized water, and mix the three evenly for later use.

[0029] d. Add 2.5 parts of oxidant to the reaction kettle and stir for 3 minutes.

[0030] e. Add Material A and Material B to the reaction kettle simultaneously. The dropping time of Material A is 120 minutes, and the dropping time of Material B is 150 minutes. Control the temperature of the reaction kettle at 15 - 25°C. After the dropping is completed, keep it warm for 60 minutes; finally, supplement deionized water to make the total amount of the sample 1000 parts, and a concrete slow-release slump retaining agent is obtained.

[0031] Example 2

[0032] Prepared by the following steps:

[0033] a. Add 225 parts of deionized water at a temperature of 5 - 15°C into the reaction kettle, then successively add 375 parts of isopentenyl polyoxyethylene ether macromonomer, and start the stirrer to stir and dissolve for 30 minutes;

[0034] b. Prepare Material A: Weigh 17.5 parts of general monomer, 55 parts of slump - retaining functional monomer and 105 parts of deionized water, mix the three evenly for standby;

[0035] c. Prepare Material B: Weigh 0.75 part of reducing agent, 2.75 parts of chain transfer agent and 95 parts of deionized water, mix the three evenly for standby;

[0036] d. Add 3.5 parts of oxidizing agent into the reaction kettle and stir for 3 minutes;

[0037] e. Add Material A and Material B into the reaction kettle simultaneously. The dropping time of Material A is 120 minutes, and the dropping time of Material B is 150 minutes. Control the temperature of the reaction kettle at 15 - 25°C. After the dropping is completed, keep warm for 60 minutes; finally, add deionized water to make the total amount of the sample 1000 parts, and a concrete slow - release slump - retaining agent is obtained.

[0038] Example 3

[0039] Prepared by the following steps:

[0040] a. Add 300 parts of deionized water at a temperature of 5 - 15°C into the reaction kettle, then successively add 430 parts of isopentenyl polyoxyethylene ether macromonomer, and start the stirrer to stir and dissolve for 30 minutes;

[0041] b. Prepare Material A: Weigh 20 parts of general monomer, 70 parts of slump - retaining functional monomer and 120 parts of deionized water, mix the three evenly for standby;

[0042] c. Prepare Material B: Weigh 1 part of reducing agent, 3.5 parts of chain transfer agent and 110 parts of deionized water, mix the three evenly for standby;

[0043] d. Add 4.5 parts of oxidizing agent into the reaction kettle and stir for 3 minutes;

[0044] e. Add Material A and Material B into the reaction kettle simultaneously. The dropping time of Material A is 120 minutes, and the dropping time of Material B is 150 minutes. Control the temperature of the reaction kettle at 15 - 25°C. After the dropping is completed, keep warm for 60 minutes; finally, add deionized water to make the total amount of the sample 1000 parts, and a concrete slow - release slump - retaining agent is obtained.

[0045] Comparative Example 1

[0046] Purchase a concrete slump - retaining agent produced by a certain manufacturer on the market.

[0047] Experiment 1

[0048] The concrete slow-release slump-retention agent prepared in Comparative Example 1 and Examples 1-3 was diluted to a solid content of 10% and then the cement paste test was carried out to test the fluidity of the cement paste. The test method refers to the national standard GB / T8077-2023 "Test Method for Uniformity of Concrete Admixtures". The cement is P.O42.5 cement produced by Anhui Conch Group Co., Ltd. Among them, each sample includes 600 g of P.O42.5 cement, 174 g of water, and the addition amount of the diluted slow-release slump-retention agent is 1% of the cement dosage. The test results are shown in Table 1 below.

[0049] Table 1

[0050]

[0051] Through the comparison of the cement paste fluidity results in Table 1, it can be concluded that the slow-release slump-retention performance of the concrete slow-release slump-retention agent of the present invention is good. The water-reducing performance reaches the peak at 2.5 h, and the fluidity loss over time is small, meeting the expected effect of the slow-release slump-retention performance.

[0052] Experiment 2

[0053] The performance of the prepared concrete slow-release slump-retention agent mother liquor was further verified through concrete mix proportion design. In this experiment, C30 concrete mix proportion design was adopted. The C30 concrete mix proportion is 200 g of cement, 60 g of mineral powder, 70 g of fly ash, 840 g of sand, 200 g of 1-3 stone, 800 g of 1-2 stone, and 150 g of water. Among them, the cement is Conch P.O42.5 cement, the mineral powder is S95 grade slag powder, the fly ash is secondary ash, and the sand is manufactured sand. The final measured slump and spread of the concrete are shown in Table 2, and the test results of the compressive strength are shown in Table 3.

[0054] Table 2

[0055]

[0056] Through the comparison of the slump and spread test results of each sample in Table 2, it can be further concluded that the slow-release slump-retention performance of the concrete slow-release slump-retention agent of the present invention is good.

[0057] Table 3

[0058]

[0059]

[0060] Through the comparison of the compressive strength test results of each sample in Table 3, it can be seen that the compressive strength of the concrete added with the concrete slow-release slump-retention agent of the present invention is slightly higher than that of the concrete added with the commercially available concrete slump-retention agent.

[0061] The above are only the preferred embodiments of the present invention. Therefore, all equivalent changes or modifications made according to the structures, features, and principles described in the scope of the present invention patent application are included in the scope of the present invention patent application.

Claims

1. A concrete slow-release slump retainer, characterized in that, It includes the following raw materials: 320 - 430 parts of isopentenol polyoxyethylene ether macromonomer, 15 - 20 parts of general monomer, 0.5 - 1.0 part of reducing agent, 40 - 70 parts of slump retaining functional monomer, 2.5 - 4.5 parts of oxidizing agent, 2.0 - 3.5 parts of chain transfer agent, and 620 - 471 parts of deionized water.

2. The concrete slow-release slump retaining agent according to claim 1, wherein The molecular weight of the isopentenol polyoxyethylene ether macromonomer is 3000.

3. The concrete slow-release slump retaining agent according to claim 1, wherein, The general monomer is one or more of methacrylic acid and acrylic acid.

4. The concrete slow-release slump-retaining agent according to claim 1, characterized in that, The reducing agent is one or more of ascorbic acid, Rongalite, ferrous sulfate, and sulfite.

5. The concrete slow-release slump retention agent according to claim 1, characterized in that The slump retaining functional monomer is one or more of hydroxypropyl acrylate and hydroxyethyl acrylate.

6. The concrete slow-release slump retaining agent according to claim 1, wherein The oxidizing agent is one or more of hydrogen peroxide, ammonium persulfate, and potassium permanganate.

7. The concrete slow-release slump-retention agent according to claim 1, wherein, The chain transfer agent is one or more of mercaptoethanol, mercaptopropionic acid, and mercaptoacetic acid.

8. A preparation method of a concrete slow-release slump retaining agent, characterized in that, It includes the following steps: a. Add 150 - 300 parts of deionized water with a temperature of 5 - 15°C into the reaction kettle, and then successively add 320 - 430 parts of isopentenyl polyoxyethylene ether macromonomer, and start the stirrer to stir and dissolve for 30 minutes; b. Prepare Material A: Weigh 15 - 20 parts of general monomer, 40 - 70 parts of slump retaining functional monomer, and 90 - 120 parts of deionized water, and mix the three evenly for standby; c. Prepare Material B: Weigh 0.5 - 1.0 part of reducing agent, 2.0 - 3.5 parts of chain transfer agent, and 80 - 110 parts of deionized water, and mix the three evenly for standby; d. Add 2.5 - 4.5 parts of oxidizing agent into the reaction kettle and stir for 3 minutes; e. Add Material A and Material B into the reaction kettle dropwise simultaneously. The dropping time of Material A is 120 minutes, and the dropping time of Material B is 150 minutes. Control the temperature of the reaction kettle at 15 - 25°C. After the dropping is completed, keep warm for 60 minutes; finally, add deionized water to make the total amount of the sample reach 1000 parts, and a concrete slow-release slump retaining agent is obtained.

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