阅读说明：本技术 一种混凝土用减水剂母液的制备方法 (Preparation method of water reducer mother liquor for concrete ) 是由 梅晶晶 马健 于 2021-10-11 设计创作，主要内容包括：本发明公开了一种混凝土用减水剂母液的制备方法,涉及水泥减水剂领域,包括酯化物原料合成及减水剂母液的制备等步骤,通过预先合成的大单体酯化中间体,使得聚羧酸减水剂母液具有良好的减水性能。本发明制备的减水剂在保持强度不变的条件下减少水泥用量,降低成本；在保证工作性能不变或增强的条件下,减少拌合水用量,降低水灰比,极大的提高了混凝土强度；在保证混凝土工作性能和强度不变的条件下,减少徐变、干缩、水泥水化热,提高混凝土耐久性,大大延长了混凝土制件本身的使用寿命。加入混凝土后,能够短时间内提高混凝土强度,利于喷射混凝土施工。(The invention discloses a preparation method of a mother liquor of a water reducing agent for concrete, which relates to the field of cement water reducing agents and comprises the steps of synthesizing an esterified raw material, preparing the mother liquor of the water reducing agent and the like. The water reducing agent prepared by the invention reduces the cement consumption and reduces the cost under the condition of keeping the strength unchanged; under the condition of ensuring that the working performance is unchanged or enhanced, the mixing water consumption is reduced, the water-cement ratio is reduced, and the concrete strength is greatly improved; under the condition of ensuring that the working performance and the strength of the concrete are not changed, creep, drying shrinkage and cement hydration heat are reduced, the durability of the concrete is improved, and the service life of a concrete part is greatly prolonged. After the concrete is added, the strength of the concrete can be improved in a short time, and the construction of spraying the concrete is facilitated.)

1. The preparation method of the water reducing agent mother liquor for concrete is characterized by comprising the following specific steps:

(1) synthesizing ester raw materials: sequentially adding polyethylene glycol and hydroquinone into a 250mL three-neck flask provided with a dropping device, a thermometer and a condenser, stirring and heating to 60 ℃, adding p-toluenesulfonic acid and silica gel, dropwise adding methacrylic acid after the hydroquinone and the p-toluenesulfonic acid are completely dissolved, heating to 110 ℃ within 2-3h, keeping the temperature, stopping heating after the required esterification rate is reached, continuously storing the product in an oil bath, slowly cooling to room temperature, pouring out an upper-layer ester liquid, taking a lower-layer faint yellow solid as solidified silica gel, extracting polyethylene glycol methyl acrylate monoester by a Weibull purification method, and adding the monoester into the upper-layer ester liquid to obtain an esterified material;

(2) adding a certain amount of distilled water into a three-mouth bottle provided with a condensation reflux device and two sets of dropping devices, introducing nitrogen, heating and stirring to 80 ℃, simultaneously slowly dropping a mercaptoacetic acid aqueous solution and hydrogen peroxide while dropping a mixed monomer containing an esterified material within 1-2h, continuously keeping constant temperature reaction for 2h, then finishing the reaction, adding a NaOH solution to adjust the pH value to 7, and obtaining the water reducer mother liquor.

2. The preparation method of the water reducer mother liquor for concrete according to claim 1, wherein the mixed monomer comprises 10 parts by weight of esterified material, 1 part by weight of methacrylic acid, 1 part by weight of sodium methallyl sulfonate and 0.5 part by weight of acrylamide, and the dripping amount of the thioglycolic acid is 4 per mill of the total amount of the mixed monomer, and the dripping amount of the hydrogen peroxide is 3 per mill of the total amount of the mixed monomer.

3. The preparation method of the mother liquor of the water reducing agent for concrete according to claim 1, wherein the Weibull purification method comprises the following specific operation methods: transferring the reaction solution to a separating funnel, adding ethyl acetate, dissolving, adding saturated sodium chloride, shaking, standing for about 20 minutes for layering, and separating two phases; mixing the upper layer ethyl acetate solution with the saturated sodium chloride solution, then repeatedly shaking, mixing the lower layer saturated sodium chloride solution with ethyl acetate, then repeatedly shaking, mixing the two parts of ethyl acetate solutions, then sequentially adding 10mL of distilled water solution for three times, and taking the lower layer solution to obtain the polyethylene glycol methacrylic acid monoester.

4. The preparation method of the water reducer mother liquor for concrete according to claim 1, wherein in the step (1), the molar ratio of methacrylic acid to polyethylene glycol is 1.2:1, the addition amount of hydroquinone is 0.5% of the total mass of methacrylic acid and polyethylene glycol, the addition amount of methyl benzenesulfonic acid is 1.0% of the total mass of methacrylic acid and polyethylene glycol, the addition amount of silica gel is 15% of the total mass of methacrylic acid and polyethylene glycol, and the constant temperature reaction time is 9 hours.

Technical Field

The invention relates to the field of cement water reducing agents, and particularly relates to a preparation method of a water reducing agent mother liquor for concrete.

Background

The polycarboxylate superplasticizers, also known as polycarboxylate high-performance (high-efficiency) water reducers, polycarboxylate superplasticizers and the like, gradually replace the former two water reducers (the first generation lignosulfonate common water reducer, the second generation naphthalene superplasticizer and the melamine superplasticizer) to become one of the main additives in the concrete mixing process at present.

The concrete without any additive has only a small part of mixing water which takes part in the hydration reaction of the cement as adsorption water during the mixing and hardening process, a part of mixing water which is free between cement groups makes the concrete have certain rheological property and thixotropy during the mixing process, and in addition, about 10 to 30 percent of water is wrapped by cement floc gel groups, which does not play any substantial role. The water reducing agent is added to break the colloid flocculation structure among cement molecules and release the internal wrapping water to form free water, so that the free water in a concrete system is increased and the fluidity is increased; or the amount of the added free water (namely the total mixing water) is reduced macroscopically, and the effect of reducing the water consumption is achieved under the condition of unchanged fluidity.

For polycarboxylic acid water reducing agents, the following four routes are mainly used for the function:

(1) electrostatic repulsion effect and steric hindrance effect: the main chain alkyl structure of the polycarboxylate superplasticizer has certain hydrophobicity, can be directionally adsorbed on the surfaces of cement particles or cement hydration product particles, and the anion groups carried on the side chain structure can enable the surfaces of the cement particles to form a special double electric layer structure, so that the cement particles are mutually dispersed due to the same charges, and the water wrapped in the cement flocculation structure can be released. The electrostatic repulsion effect plays an important role in the second-generation water reducing agent, but cement molecules cannot be dispersed to a greater extent due to the small thickness of the electric double layer, so that the effect no longer plays a dominant role in the structural design of the poly-carboxylic acid series water reducing agent.

After the main chain in the polycarboxylate superplasticizer molecule is anchored on the surface of cement particles, the long-chain macromonomer (mainly in an alkoxy structure) in the side chain has extremely strong hydrophilicity and can be randomly stretched in an aqueous solution, so that a hydrophilic three-dimensional layer with a considerable thickness is formed on the surface of the cement particles. When cement particles are close to each other, the respective hydrophilic three-dimensional layers are overlapped, so that the possibility of further close to the cement particles is prevented, and the water reducing effect of the water reducing agent is improved, and the action mode is called steric hindrance.

(2) Lubrication action

The polycarboxylate superplasticizer-cement particle group is spherical in an ideal state, the center is cement particles, and the periphery is a rigid water layer.

(3) Air entraining isolation ball function

The main chain of the polycarboxylate superplasticizer molecule is lipophilic, so that the solid-liquid interface energy on the surface of cement particles can be reduced, and the thermodynamic stability of a cement system is improved; and the liquid-air interfacial tension can be reduced, a large amount of air is introduced in the concrete mixing process, particularly the mechanical mixing process, and in fact, the air is mostly dispersed in the whole system in the form of micro bubbles, and a part of polycarboxylate superplasticizer molecules can be adsorbed and arranged on the bubbles, so that a layer of uniform hydration film is formed on the surface of the bubbles, and meanwhile, the charges carried by the bubbles can be the same as those on the surface of cement particles. In addition, the air bubbles can also isolate and float the cement particles, and the factors improve the dispersion and sliding capacity between the cement particles and the aggregate.

(4) Other effects

The electric double layer can "trap" Ca in the system²⁺Limiting Ca²⁺The cement is invaded into the inner core of the polycarboxylate superplasticizer-cement particle group, so that the hardening speed of the cement is delayed. In addition, some special poly carboxylic acid water reducing agent molecules have a certain slow release function, so that the water reducing agent has a slow setting effect and can effectively control slump loss.

Disclosure of Invention

The invention aims to provide a preparation method of a mother liquor of a water reducing agent for concrete, which solves the problem that the strength of concrete cannot be improved in a short time after the mother liquor of a polycarboxylic acid high-efficiency water reducing agent is mixed.

A preparation method of a water reducing agent mother liquor for concrete comprises the following specific steps:

(1) synthesizing ester raw materials: sequentially adding polyethylene glycol and hydroquinone into a 250mL three-neck flask provided with a dropping device, a thermometer and a condenser, stirring and heating to 60 ℃, adding p-toluenesulfonic acid and silica gel, dropwise adding methacrylic acid after the hydroquinone and the p-toluenesulfonic acid are completely dissolved, heating to 110 ℃ within 2-3h, keeping the temperature, stopping heating after the required esterification rate is reached, continuously storing the product in an oil bath, slowly cooling to room temperature, pouring out an upper-layer ester liquid, taking a lower-layer faint yellow solid as solidified silica gel, extracting polyethylene glycol methyl acrylate monoester by a Weibull purification method, and adding the monoester into the upper-layer ester liquid to obtain an esterified material;

(2) adding a certain amount of distilled water into a three-mouth bottle provided with a condensation reflux device and two sets of dropping devices, introducing nitrogen, heating and stirring to 80 ℃, simultaneously slowly dropping a mercaptoacetic acid aqueous solution and hydrogen peroxide while dropping a mixed monomer containing an esterified material within 1-2h, continuously keeping constant temperature reaction for 2h, then finishing the reaction, adding a NaOH solution to adjust the pH value to 7, and obtaining the water reducer mother liquor.

Preferably, the mixed monomer comprises 10 parts by weight of esterified material, 1 part by weight of methacrylic acid, 1 part by weight of sodium methallyl sulfonate and 0.5 part by weight of acrylamide, and the dripping amount of the thioglycolic acid is 4 per mill of the total amount of the mixed monomer, and the dripping amount of the hydrogen peroxide is 3 per mill of the total amount of the mixed monomer.

Preferably, the detailed operation method of the Weibull purification method comprises the following steps: transferring the reaction solution to a separating funnel, adding ethyl acetate, dissolving, adding saturated sodium chloride, shaking, standing for about 20 minutes for layering, and separating two phases; mixing the upper layer ethyl acetate solution with the saturated sodium chloride solution, then repeatedly shaking, mixing the lower layer saturated sodium chloride solution with ethyl acetate, then repeatedly shaking, mixing the two parts of ethyl acetate solutions, then sequentially adding 10mL of distilled water solution for three times, and taking the lower layer solution to obtain the polyethylene glycol methacrylic acid monoester.

Preferably, in the step (1), the molar ratio of the methacrylic acid to the polyethylene glycol is 1.2:1, the addition amount of hydroquinone is 0.5 percent of the total mass of the methacrylic acid and the polyethylene glycol, the addition amount of the toluenesulfonic acid is 1.0 percent of the total mass of the methacrylic acid and the polyethylene glycol, the addition amount of the silica gel is 15 percent of the total mass of the methacrylic acid and the polyethylene glycol, and the constant temperature reaction time is 9 hours.

The invention has the advantages that:

the water reducing agent prepared by the invention has the following advantages: 1. the cement consumption is reduced under the condition of keeping the strength unchanged, and the cost is reduced; 2. under the condition of ensuring that the working performance is unchanged or enhanced, the mixing water consumption is reduced, the water-cement ratio is reduced, and the concrete strength is greatly improved; 3. under the condition of ensuring that the working performance and the strength of the concrete are not changed, creep, drying shrinkage and cement hydration heat are reduced, the durability of the concrete is improved, and the service life of a concrete part is greatly prolonged. 4. After the concrete is added, the strength of the concrete can be improved in a short time, and the construction of spraying the concrete is facilitated.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.

Example 1: a preparation method of a water reducing agent mother liquor for concrete comprises the following specific steps:

(1) synthesizing ester raw materials: sequentially adding polyethylene glycol and hydroquinone into a 250mL three-neck flask provided with a dropping device, a thermometer and a condenser, stirring and heating to 60 ℃, adding p-toluenesulfonic acid and silica gel, dropwise adding methacrylic acid after hydroquinone and p-toluenesulfonic acid are completely dissolved, wherein the molar ratio of methacrylic acid to polyethylene glycol is 1.2:1, heating to 110 ℃ within 2-3h, keeping the temperature, reacting at the constant temperature for 9h, keeping the esterification rate at 95%, continuously storing the product in an oil bath, slowly cooling to room temperature, pouring out the upper-layer ester liquid, and taking the lower-layer light yellow solid as solidified silica gel. The addition of hydroquinone is 0.5 percent of the total mass of methacrylic acid and polyethylene glycol, the addition of methyl benzene sulfonic acid is 1.0 percent of the total mass of methacrylic acid and polyethylene glycol, and the addition of silica gel is 15 percent of the total mass of methacrylic acid and polyethylene glycol;

(2) transferring the reaction solution to a separating funnel, adding ethyl acetate, dissolving, adding saturated sodium chloride, shaking, standing for about 20 minutes for layering, and separating two phases; mixing the upper layer ethyl acetate solution with the saturated sodium chloride solution, then repeatedly shaking, mixing the lower layer saturated sodium chloride solution with ethyl acetate, then repeatedly shaking, mixing the two parts of ethyl acetate solutions, then sequentially adding 10mL of distilled water solution for three times, taking the lower layer solution to obtain polyethylene glycol methacrylic acid monoester, and adding the polyethylene glycol methacrylic acid monoester into the upper layer ester solution to obtain an esterified material raw material;

(3) adding a certain amount of distilled water into a three-mouth bottle provided with a condensation reflux device and two sets of dropping devices, introducing nitrogen, heating and stirring to 80 ℃, simultaneously slowly dropping a mercaptoacetic acid aqueous solution and hydrogen peroxide while dropping a mixed monomer containing an esterified material within 1-2h, continuously keeping constant temperature reaction for 2h, then finishing the reaction, adding a NaOH solution to adjust the pH value to 7, and obtaining the water reducer mother liquor.

The mixed monomer is formed by mixing 10 parts by weight of esterified material raw materials, 1 part by weight of methacrylic acid, 1 part by weight of sodium methallyl sulfonate and 0.5 part by weight of acrylamide according to a proportion, wherein the dripping amount of thioglycolic acid is 4 per mill of the total amount of the mixed monomer, and the dripping amount of hydrogen peroxide is 3 per mill of the total amount of the mixed monomer.

According to the test method of the homogeneity of the GB8077-2000 concrete admixture and the cement paste fluidity method, the water-cement ratio is determined to be 0.26, the mixing amount is set to be 0.39 wt% by taking a commercial polycarboxylic acid water reducing agent as a control, and the following tests are carried out:

cement paste fluidity test

The specific experimental steps are as follows:

the method comprises placing a stainless steel cone section mold with an upper opening diameter of 36mm, a lower opening diameter of 60mm and a height of 60mm and smooth inner wall without seams on a horizontally placed 400mm x 400mm glass plate, wiping an instrument used for testing the fluidity of the net slurry with standard wet paper to ensure that the instrument has certain humidity and prevents water from forming a strand, placing the cone section mold meeting the requirement at the center of the glass plate, covering the instrument with the standard wet paper for standby, adding 300g of cement into a net slurry stirring pot, sequentially adding 87g or 105g of water and a certain amount of water reducing agent (measured by solid mass), mixing for three minutes, quickly transferring the slurry to the cone section mold after stirring, lifting up the cone section mold vertically and stably once, starting a stopwatch, measuring the diameters of the slurry in the mutually vertical directions by using a vernier caliper when the slurry flows on the glass plate for 30 seconds, wherein the average value of the measured diameters is the fluidity of the net slurry, each sample was tested in triplicate and the average was taken.

Determination of Water-reducing Rate of mortar

The specific experimental steps are as follows:

determination of water consumption for standard mortar fluidity

Putting water into a pot, adding 450g of cement, putting the pot on an unopened stirrer, adjusting to a proper stirring height, immediately starting the stirrer, stirring at a low speed for 30 seconds, adding sand by using the intermediate idle time, wherein the second 30 seconds do not start, adjusting to a high-speed stirring for 30 seconds after 30 seconds, pausing for 90 seconds, immediately scraping mortar on the wall of the stirrer and blades into the pot by using the time, continuously stirring for 60 seconds in a high-speed stirring state, and controlling the stirring time of each stage not to exceed 1 second.

During the blending of mortar, the mortar fluidity measuring instrument and the inner wall of the jacket mold were wet-wiped with standard wet paper, and they were placed at the center of a diving table, covered with standard wet paper, and the like before use. The mixed mortar is transferred to a cutting die in batches quickly, the first loading amount is about sixty percent of that of the truncated cone round die, the orthogonal positions are respectively scribed for 5 times by using a spatula, the mortar is finely scribed in the truncated cone round die by using a tamping bar, the task is completed, the next batch of mortar is immediately placed, the loading amount is determined to be 2cm higher than that of the truncated cone round die, the mortar is scribed for 10 times by using the spatula, and the truncated cone round die is pressed by hand while the mortar is loaded and tamped, so that the truncated cone round die is not moved. And after tamping is finished, removing the mortar which exceeds the cutting die by 2cm by using a spatula, strickling, quickly lifting the cutting die on the table top of the jump table in a direction vertical to the direction of the jump table, and starting the jump table immediately to keep the jump table jumping for twenty-five seconds for twenty-five times.

And (3) finishing a jumping instruction by the jumping table, measuring the maximum diameter of the mortar in the mutually orthogonal directions by using a vernier caliper, and taking the average value of two measured values in the orthogonal directions as the fluidity of the mortar under the measuring condition, wherein the average value is represented by mm.

Repeating the steps until the fluidity reaches 180 +/-5 mm, taking the water consumption under the measured value as the standard mortar fluidity water demand compared with other samples, and taking m as the water demand₀And (4) showing.

The water consumption of the water reducing agent and the sample is m₀Adding the water into a mortar fluidity measuring pot, starting a machine to mix uniformly, operating according to the steps, and changing the water consumption until the water consumption of the mortar is within the range of 180 +/-5 mm, wherein the water consumption is m.

The calculation method comprises the following steps:

water reducing rate of mortar (m)₀-m)/m₀*100％

The marks, names and models of the cement are noted, and the indoor allowable error is 1.0%.

TABLE 1 characterization of the Properties of different polycarboxylic acid Water-reducing Agents

Group of	Fluidity/mm of cement paste	Water reduction of mortar%
			Example 1	243.1	25
Commercial polycarboxylic acid water reducing agent	208.3	20

The concrete grade is evaluated according to the standard of ordinary concrete mechanical property test method GB/T50081-2002 and GB50010-2010 concrete structure design Specification, so that the influence of the water reducing agent on the concrete strength in a short time after mixing is judged.

TABLE 2 Effect of polycarboxylate superplasticizer on post-mix strength of concrete

As can be seen from the results in Table 2, the water reducer prepared by the invention can rapidly promote the solidification of concrete and improve the strength of the concrete.

It will be appreciated by those skilled in the art that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed above are therefore to be considered in all respects as illustrative and not restrictive. All changes which come within the scope of or equivalence to the invention are intended to be embraced therein.