Molasses fermentation concentrated solution copolymerization modified polycarboxylate superplasticizer, and preparation method and application thereof

Abstract

The invention provides a molasses fermentation concentrated solution copolymerization modified polycarboxylic acid water reducing agent, a preparation method and application. The preparation method comprises the following steps: under the action of a chain transfer agent for inhibiting miscellaneous sugar and an initiator, carrying out polymerization reaction on a molasses fermentation concentrated solution, an unsaturated polyoxyethylene ether monomer, an unsaturated carboxylic acid polymeric monomer and a reducing agent to obtain the molasses fermentation concentrated solution copolymerized and modified polycarboxylate superplasticizer, the chain transfer agent for inhibiting miscellaneous sugar is C16-C20 straight-chain or branched-chain mercaptan, and the density of the molasses fermentation concentrated solution is greater than or equal to 1.25 g / cm < 3 >. The synthesis method is simple and easy to implement, mild in reaction condition and short in reaction time. The molasses fermentation concentrated solution copolymerized and modified polycarboxylic acid high-performance water reducing agent prepared by the invention can effectively improve the workability and the flowability of concrete and improve the strength of the concrete.

Description

Technical Field

[0001] The invention relates to the field of fermentation, and in particular to a molasses fermentation concentrate copolymer-modified polycarboxylic acid water reducer, a preparation method and an application thereof. Background Art

[0002] The yeast produced in my country mainly uses fermentable sugars in molasses as a production carbon source, while a large amount of non-fermentable carbon sources in molasses cannot be used by yeast. The above non-fermentable carbon sources and organic matter newly produced by yeast during growth and metabolism enter the wastewater, resulting in high-concentration molasses fermentation wastewater containing residual sugar, caramel pigments, phenols and other substances (the main components are lignin, colloids, yeast proteins, nutrients that are not fully utilized in molasses, etc.). Fermentation wastewater with high molasses content has a deep chromaticity, a COD content of more than 100,000 mg / L, and also contains a certain amount of inorganic salts and sulfate ions. It is a high-concentration organic wastewater that is difficult to treat and has extremely high treatment costs, which brings a huge carbon emission burden to the yeast production industry. Using molasses fermentation concentrate as a renewable resource is an important means to build a carbon emission reduction system for the yeast industry and a circular economy system for industrial solid waste.

[0003] The main components of molasses fermentation concentrate are cellulose, lignin, colloidal substances and residual sugar in waste molasses that is not fully utilized. The cellulose, hemicellulose and residual sugar components have a certain retarding function, and have a certain effect on the segregation and bleeding of large-volume concrete, and can also improve the viscosity and plasticity of concrete. The lignin sulfonate component in the concentrate has the ability to dissolve quickly to form SO 4 2- , reducing the polycarboxylate water reducer being wrapped and consumed by cement hydration products, reducing the surface tension of the liquid solution, increasing surface activity, improving the micro-air entrainment effect and other advantages, which are beneficial to improving the dispersion performance of concrete and the fluidity of the slurry. Therefore, molasses fermentation concentrate can be used as an admixture in the construction industry. However, the water-reducing capacity of lignin sulfonate water reducer is limited, generally 5% to 10%, which cannot meet the requirements of high-performance concrete for water reducers.

[0004] The mainstream polycarboxylic acid water reducer on the market is widely used because of its high water reduction rate, excellent slump retention and good performance improvement of concrete. The main raw materials of polycarboxylic acid water reducer come from the petrochemical industry, which are expensive and non-renewable resources. Therefore, in actual application, lignin sulfonate and polycarboxylic acid are usually physically compounded. However, the water reduction effect of direct compounding is greatly affected by the season, cement production area and admixture type, and the water reduction performance is not satisfactory. Therefore, it is very meaningful and valuable to develop a lignin sulfonate modified polycarboxylic acid water reducer with good properties to ensure the strength and service life of large-volume concrete and improve the durability of concrete. Summary of the invention

[0005] The main purpose of the present invention is to provide a molasses fermentation concentrate copolymer modified polycarboxylic acid water reducer, a preparation method and an application thereof, so as to solve the problem of unstable water reducing performance in the process of preparing a water reducer by physically compounding lignin sulfonate and polycarboxylic acid.

[0006] In order to achieve the above object, the present invention provides a method for preparing a molasses fermentation concentrate copolymer-modified polycarboxylic acid water reducer, the method comprising: under the action of a chain transfer agent and an initiator for inhibiting heterocarboxylates, a molasses fermentation concentrate, an unsaturated polyoxyethylene ether monomer, an unsaturated carboxylic acid polymer monomer and a reducing agent are polymerized to obtain a molasses fermentation concentrate copolymer-modified polycarboxylic acid water reducer, wherein the chain transfer agent for inhibiting heterocarboxylates is C 16 ~C 20 Straight-chain or branched-chain thiols, density of molasses fermentation concentrate ≥1.25g / cm 3 .

[0007] Furthermore, the polymerization reaction includes: mixing molasses fermentation concentrate, unsaturated polyoxyethylene ether monomer and initiator to obtain a mixed solution; at a stirring rate of 100 to 300 r / min and a temperature of 55 to 90° C., dripping unsaturated carboxylic acid polymerization monomer, chain transfer agent for inhibiting foreign sugars and reducing agent into the mixed solution in sequence, and after maturation, obtaining a molasses fermentation concentrate copolymer-modified polycarboxylic acid water reducer.

[0008] Furthermore, the unsaturated polymerizable monomer is selected from one or more of isopentanol polyoxyethylene ether, methpropylene polyoxyethylene ether, allyl polyoxyethylene ether and methyl allyl polyoxyethylene ether; preferably, the hydroxyl value of isopentanol polyoxyethylene ether is 22.5±5 mgKOH / g, the degree of unsaturation is ≥0.35 mol / Kg, and the double bond retention rate is ≥80%.

[0009] Furthermore, the polymerization reaction temperature is 55 to 90° C., and the reaction time is 4 to 8 hours.

[0010] Furthermore, the initiator is selected from one or more of tert-amyl peroxy ester, peracetic acid, hydrogen peroxide and ammonium persulfate; the reducing agent is selected from one or more of oxalic acid, hydroxylamine hydrochloride, ascorbic acid and citric acid.

[0011] Furthermore, the molasses fermentation concentrate is a concentrate obtained by subjecting sugarcane molasses and / or beet molasses to a yeast fermentation process.

[0012] Furthermore, the molasses fermentation concentrate includes cellulose, lignin, colloidal substances and residual sugar that is not fully utilized in the waste molasses, has a moisture content of 40wt%, and a content of unsaturated lignin organic matter of ≥10wt%.

[0013] Furthermore, the weight ratios of the chain transfer agent for inhibiting miscellaneous sugars, the reducing agent, the initiator, the molasses fermentation concentrate with a high molasses content, the unsaturated polyoxyethylene ether monomer and the unsaturated carboxylic acid polymerization monomer are (0.05% to 2%): (0.05% to 2%): (0.3% to 5%): (10% to 90%): (5% to 80%): (2.5% to 45%).

[0014] The second aspect of the present application also provides a molasses fermentation concentrate copolymer-modified polycarboxylic acid water reducer having a comb-like structure and a degree of polymerization of 6 to 12. The molasses fermentation concentrate copolymer-modified polycarboxylic acid water reducer is prepared by the above-mentioned preparation method.

[0015] The third aspect of the present application also provides an application of a molasses fermentation concentrate copolymer-modified polycarboxylic acid water reducer in the field of concrete preparation.

[0016] By applying the technical solution of the present invention, lignin sulfonate in molasses fermentation concentrate is used to prepare high-performance polycarboxylate water reducer, which can realize full resource utilization of lignin sulfonate in waste liquid, and at the same time digest the high COD yeast wastewater that is difficult to treat in industry, meeting the requirements of current green environmental protection chemical industry; the modified polycarboxylate water reducer prepared by the above method has the advantages of good dispersibility and slump retention, can prolong the setting time of concrete, improve the 28-day compressive strength of concrete, and reduce the water bleeding rate. The above method is simple, the equipment occupies a small area; the raw materials used are small, and no raw materials harmful to the environment are added. DETAILED DESCRIPTION

[0017] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0018] As described in the background art, the process of preparing a water reducer by physically compounding lignin sulfonate with polycarboxylic acid has the problem of unstable water reducing performance. In order to solve the above technical problems, the present application provides a method for preparing a polycarboxylic acid water reducer copolymerized with molasses fermentation concentrate, comprising: under the action of a chain transfer agent and an initiator that inhibits miscellaneous sugars, molasses fermentation concentrate, an unsaturated polyoxyethylene ether monomer, an unsaturated carboxylic acid polymerization monomer and a reducing agent are polymerized to obtain a polycarboxylic acid water reducer copolymerized with molasses fermentation concentrate, wherein the chain transfer agent that inhibits miscellaneous sugars is C 16 ~C 20 Straight-chain or branched-chain thiols, density of molasses fermentation concentrate ≥1.25g / cm 3 .

[0019] In addition to a portion of lignin sulfonate, molasses fermentation concentrate also contains residual sugar in waste molasses that is not fully utilized. If molasses fermentation concentrate is directly used as a raw material to prepare a water reducer, the water reducing performance of the water reducer is poor and cannot meet the industry standards. Therefore, there is no research in the art on the application of molasses fermentation concentrate in the preparation of water reducers.

[0020] In order to overcome the above defects and improve the economic value of molasses fermentation concentrate, the applicant has conducted a lot of research. It was found that when the water reducer is prepared by polymerization reaction using molasses fermentation concentrate as raw material, the residual sugar in the molasses fermentation concentrate will also participate in the polymerization reaction, which will lead to the deterioration of the performance of the water reducer. Based on the above theory, a chain transfer agent (such as hexadecyl mercaptan, etc.) with large steric hindrance that can inhibit the participation of miscellaneous sugars in the reaction is added to the raw material. During the polymerization process, the chain transfer agent that inhibits miscellaneous sugars can inhibit the participation of residual sugars in the molasses fermentation concentrate in the copolymerization reaction, thereby improving the water-reducing effect of the final water reducer (such as water bleeding rate and slump retention performance). At the same time, the unsaturated lignin sulfonate in the molasses fermentation concentrate is used as a polymerization monomer to copolymerize with unsaturated polyoxyethylene ether monomers and unsaturated carboxylic acid polymerization monomers, which can effectively improve the dispersibility of polycarboxylic acid water reducer. In addition, molasses fermentation concentrate also contains retarding components such as cellulose, hemicellulose and residual sugar. The above components can effectively prolong the setting time of concrete, improve the 28-day compressive strength of concrete, and reduce the water seepage rate of concrete when used in the concrete preparation process.

[0021] In summary, the use of lignin sulfonate in molasses fermentation concentrate to prepare high-performance polycarboxylate water reducer can achieve full resource utilization of lignin sulfonate in waste liquid, while digesting high COD yeast wastewater that is difficult to treat in industry, which meets the requirements of current green environmental protection chemical industry; the modified polycarboxylate water reducer prepared by the above method has the advantages of good dispersibility and slump retention, can prolong the setting time of concrete, improve the 28-day compressive strength of concrete, and reduce the water bleeding rate. The above method is simple, the equipment occupies a small area, and the raw materials used are small, and no raw materials harmful to the environment are added.

[0022] In order to further improve the effective content and water reducing performance of the polycarboxylate water reducer in the product, preferably, the polymerization reaction includes: mixing molasses fermentation concentrate, unsaturated polyoxyethylene ether monomer and initiator to obtain a mixed solution; at a stirring rate of 100 to 300 r / min and a temperature of 55 to 90° C., dripping unsaturated carboxylic acid polymerization monomer, chain transfer agent for inhibiting miscellaneous sugars and reducing agent into the mixed solution in sequence, and after aging, obtaining a molasses fermentation concentrate copolymer-modified polycarboxylate water reducer.

[0023] In a preferred embodiment, the unsaturated polyoxyethylene ether monomer can be selected from commonly used types in the art, including but not limited to one or more of isopentanol polyoxyethylene ether (TPEG), methacrylic polyoxyethylene ether (HPEG), allyl polyoxyethylene ether (APEG) and methyl allyl polyoxyethylene ether (VPEG). More preferably, the hydroxyl value of isopentanol polyoxyethylene ether is 22.5±5mgKOH / g, the unsaturation is ≥0.35mol / Kg, and the double bond retention rate is ≥80%.

[0024] In a preferred embodiment, the polymerization temperature is 55-90°C and the reaction time is 4-8h. The polymerization temperature and reaction time include but are not limited to the above ranges, and limiting them within the above ranges is beneficial to further improve the yield of the water reducing agent.

[0025] The initiator, reducing agent and chain transfer agent for inhibiting miscellaneous sugars can be selected from the types commonly used in the preparation process of water reducer. The initiator includes but is not limited to one or more of tert-amyl peroxy ester, peracetic acid, hydrogen peroxide and ammonium persulfate; the reducing agent includes but is not limited to one or more of oxalic acid, hydroxylamine hydrochloride, ascorbic acid and citric acid.

[0026] The molasses fermentation concentrate is a concentrate obtained by yeast fermentation of sugarcane molasses and / or beet molasses. Preferably, it is sugarcane molasses fermentation concentrate, which includes cellulose, lignin, colloidal substances, and residual sugar that is not fully utilized in waste high-sugar molasses, with a moisture content of 40wt%, and a content of unsaturated lignin organic matter ≥10wt%. When the content of lignin in the molasses fermentation concentrate is low, the improvement of water reducing performance is limited. When its content is ≥10%, the water reducing performance of the water reducer can be further improved.

[0027] In order to further improve the yield and water reducing performance of the water reducing agent, preferably, the weight ratio of the chain transfer agent for inhibiting miscellaneous sugars, the reducing agent, the initiator, the molasses fermentation concentrate, the unsaturated polyoxyethylene ether monomer and the unsaturated carboxylic acid polymerization monomer is (0.05% to 2%): (0.05% to 2%): (0.3% to 5%): (10% to 90%): (5% to 80%): (2.5% to 45%).

[0028] The second aspect of the present application also provides a molasses fermentation concentrate copolymer-modified polycarboxylic acid water reducer having a comb-like structure and a degree of polymerization of 6 to 12. The molasses fermentation concentrate copolymer-modified polycarboxylic acid water reducer is prepared by the above-mentioned preparation method.

[0029] The modified polycarboxylic acid water-reducing agent prepared by the above method has the advantages of good dispersibility and slump retention, can prolong the setting time of concrete, and reduce the water bleeding rate. Therefore, the application of it in the field of concrete preparation can effectively improve the 28-day compressive strength of concrete. At the same time, the water-reducing agent has a certain retarding effect, which is convenient for the transportation of commercial concrete.

[0030] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0031] Example 1

[0032] The three-necked flask equipped with a stirrer was placed in a temperature-controlled electric heating mantle and a 1.25 g / cm 3 The molasses fermentation concentrate was added with isopentanol polyoxyethylene ether, an initiator (tert-amyl peroxy ester) and a mixed solution of water (weight ratio of 6:6:1:7), and the temperature was raised to 60°C to prepare a precursor solution.

[0033] 20g of acrylic acid was mixed with 20g of water to prepare a monomer solution; 0.15g of oxalic acid was mixed with 10g of water to prepare a reducing agent solution; 0.3g of hexadecyl mercaptan was mixed with 10g of water to prepare a chain transfer agent solution for inhibiting heterocarboxylation.

[0034] At a stirring speed of 100 r / min and a temperature of 60°C, the weight ratio of molasses fermentation concentrate, isopentanol polyoxyethylene ether, initiator, monomer (acrylic acid), reducing agent (oxalic acid) and miscellaneous sugar inhibitor (hexadecyl mercaptan) is 6:6:0.5:7:3:0.1:0.2. The monomer solution, reducing agent solution and miscellaneous sugar inhibitor solution are added dropwise to the precursor solution, and the mixture is kept warm and matured for 5 hours to obtain a polycarboxylic acid water reducer, which is recorded as P1.

[0035] Example 2

[0036] The difference from Example 1 is that the sugar inhibitor is eicosyl mercaptan. A polycarboxylate water reducer is obtained, which is recorded as P2.

[0037] Example 3

[0038] The difference from Example 1 is that the weight ratio of the amount of the miscellaneous sugar inhibitor to the molasses fermentation concentrate is 1:40.

[0039] The polycarboxylate water reducer was obtained and recorded as P3.

[0040] Example 4

[0041] The difference from Example 1 is that the weight ratio of the amount of the miscellaneous sugar inhibitor to the molasses fermentation concentrate is 1:60.

[0042] The polycarboxylate water reducer was obtained and recorded as P4.

[0043] Example 5

[0044] The difference from Example 1 is that the reaction conditions are different. Specifically, at a stirring rate of 100 r / min and a temperature of 80° C., unsaturated carboxylic acid polymerization monomers, a chain transfer agent for inhibiting impurities and a reducing agent are sequentially dropped into the mixed solution, and after aging, a molasses fermentation concentrate copolymer modified polycarboxylic acid water reducer is obtained, which is recorded as P5.

[0045] Example 6

[0046] The difference from Example 1 is that the reaction temperature is 40° C. A polycarboxylate water-reducing agent is obtained, which is recorded as P6.

[0047] Comparative Example 1

[0048] The difference from Example 1 is that a three-necked flask equipped with a stirrer is placed in a temperature-controlled electric heating mantle, molasses fermentation concentrate is not added, isopentanol polyoxyethylene ether, an initiator (tert-amyl peroxy ester) and a mixed solution of water (weight ratio of 12:0.5:7) are added to prepare a precursor solution. The rest is the same as Example 1.

[0049] The prepared polycarboxylate water-reducing agent is recorded as blank.

[0050] Comparative Example 2

[0051] The difference from Example 1 is that no sugar inhibitor is added, but the chain transfer agent is mercaptoethanol. The obtained polycarboxylate water reducer is recorded as D2.

[0052] Performance Test:

[0053] The cement used in this application is PI425 cement specially used for experiments, the river sand is medium sand with a fineness modulus of 2.7, the crushed stone is a continuously graded stone of 5mm to 31.5mm, and the water is deionized water.

[0054] The water reducing agent mother liquor synthesized in Examples 1 to 6 and Comparative Examples 1 to 3 was used in the production of commercial concrete, the weight ratio of cement, water, river sand and crushed stone was 1.0:0.67:3.21:5.10, and the amount of the synthesized water reducing agent accounted for 0.8% of the total weight of the raw materials. The concrete strength grade was C40.

[0055] The water reduction rate, water bleeding rate, slump, air content, setting time and compressive strength of concrete were all carried out in accordance with the relevant operations in GB8076-2008 and GB50081-2002. The test results are shown in Table 1.

[0056] Table 1

[0057]

[0058] Comparison of Example 1 with Comparative Example 1 shows that after the addition of molasses fermentation concentrate, the harmful components therein will slightly weaken the water reducing property of the product, increase the air content of concrete, and prolong the setting time of concrete.

[0059] Comparison between Example 1 and Comparative Example 2 shows that: compared with the case where no sugar inhibitor is added, the water reduction rate and compressive strength are significantly improved after the addition of the sugar inhibitor, and at the same time, the setting time is advanced.

[0060] Compared with Example 1, Example 6 has an incomplete reaction of the system due to the lowered reaction temperature, resulting in poor performance of the prepared polycarboxylate water-reducing agent.

[0061] Compared with Example 4, Example 3 increases the ratio of the sugar inhibitor to the sugar, thereby increasing the content of the sugar inhibitor in the raw material, effectively improving the water reduction rate and compressive strength of the polycarboxylate water reducer, and reducing the gas content of the product.

[0062] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: From Table 1, it can be seen that the synthesized water-reducing agent product is applied to commercial concrete, and the detected concrete performance is significantly better than the national standard, and the initial setting time is long, which is convenient for commercial concrete transportation. At the same time, adding a chain transfer agent that inhibits miscellaneous sugars not only improves the reaction efficiency, but also improves the performance of the copolymerized modified polycarboxylic acid water-reducing agent of molasses fermentation concentrate.

[0063] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a polycarboxylic acid water reducer copolymerized and modified by molasses fermentation concentrate, characterized in that: The preparation method of the molasses fermentation concentrate copolymerized modified polycarboxylic acid water reducer comprises: Under the action of a chain transfer agent for inhibiting miscellaneous sugars and an initiator, molasses fermentation concentrate, unsaturated polyoxyethylene ether monomer, unsaturated carboxylic acid polymerization monomer and a reducing agent are polymerized to obtain the molasses fermentation concentrate copolymer modified polycarboxylic acid water reducer, wherein the chain transfer agent for inhibiting miscellaneous sugars is C 16 ~C 20 The density of the molasses fermentation concentrate is ≥1.25 g / cm 3 .

2. The method for preparing the molasses fermentation concentrate copolymer modified polycarboxylic acid water reducer according to claim 1, characterized in that: The polymerization reaction comprises: Mixing the molasses fermentation concentrate, the unsaturated polyoxyethylene ether monomer and the initiator to obtain a mixed solution; At a stirring rate of 100 to 300 r / min and a temperature of 55 to 90° C., the unsaturated carboxylic acid polymerization monomer, the chain transfer agent for inhibiting heterocarboxyls and the reducing agent are sequentially dripped into the mixed solution, and after ripening, a molasses fermentation concentrate copolymer-modified polycarboxylic acid water reducer is obtained.

3. The method for preparing the molasses fermentation concentrate copolymer modified polycarboxylic acid water reducer according to claim 1 or 2, characterized in that: The unsaturated polymerizable monomer is selected from one or more of isopentanol polyoxyethylene ether, methpropylene polyoxyethylene ether, allyl polyoxyethylene ether and methyl allyl polyoxyethylene ether; Preferably, the hydroxyl value of the isopentanol polyoxyethylene ether is 22.5±5 mgKOH / g, the unsaturation degree is ≥0.35 mol / Kg, and the double bond retention rate is ≥80%.

4. The method for preparing the molasses fermentation concentrate copolymer modified polycarboxylate water reducer according to claim 2, characterized in that: The polymerization reaction temperature is 55-90° C., and the reaction time is 4-8 hours.

5. The method for preparing a molasses fermentation concentrate copolymer modified polycarboxylic acid water reducer according to any one of claims 1 to 4, characterized in that: The initiator is selected from one or more of tert-amyl peroxy ester, peracetic acid, hydrogen peroxide and ammonium persulfate; The reducing agent is selected from one or more of oxalic acid, hydroxylamine hydrochloride, ascorbic acid and citric acid.

6. The method for preparing the molasses fermentation concentrate copolymer modified polycarboxylic acid water reducer according to claim 1, characterized in that: The molasses fermentation concentrate is a concentrate obtained by subjecting sugarcane molasses and / or beet molasses to a yeast fermentation process.

7. The method for preparing the molasses fermentation concentrate copolymer modified polycarboxylic acid water reducer according to claim 6, characterized in that: The molasses fermentation concentrate comprises cellulose, lignin, colloidal substances and residual sugar that is not fully utilized in waste molasses, has a water content of 40wt%, and a content of unsaturated lignin organic matter of ≥10wt%.

8. The method for preparing the molasses fermentation concentrate copolymer modified polycarboxylic acid water reducer according to claim 7, characterized in that: The weight ratio of the chain transfer agent for inhibiting foreign sugars, the reducing agent, the initiator, the molasses fermentation concentrate with a high molasses content, the unsaturated polyoxyethylene ether monomer and the unsaturated carboxylic acid polymerization monomer is (0.05% to 2%): (0.05% to 2%): (0.3% to 5%): (10% to 90%): (5% to 80%): (2.5% to 45%).

9. A molasses fermentation concentrate copolymer modified polycarboxylic acid water reducer, characterized in that: The polycarboxylic acid water reducer has a comb-like structure and a polymerization degree of 6 to 12. The molasses fermentation concentrate copolymerized modified polycarboxylic acid water reducer is prepared by the preparation method described in any one of claims 1 to 8.

10. Application of a molasses fermentation concentrate copolymer modified polycarboxylic acid water reducer in the field of concrete preparation.

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