Environment-friendly anti-flocculating functional additive for machine-made sand in concrete and preparation method thereof

Abstract

The application provides an environment-friendly anti-flocculation functional additive for concrete and a preparation method thereof. The environment-friendly anti-flocculation functional additive for concrete contains an esterified modification of an organic acid group grafted on a hydroxyl group of beta-cyclodextrin. The environment-friendly anti-flocculation functional additive for concrete can effectively reduce the viscosity of concrete, shorten the pouring time and improve the workability of concrete.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of concrete building materials, in particular to an environment-friendly anti-flocculating agent for machine-made sand for concrete, and a preparation method of the environment-friendly anti-flocculating agent. BACKGROUND

[0002] In recent years, with the continuous expansion of the market demand for concrete, the amount of sand used has rapidly increased, and the natural sand resources are decreasing year by year. The exploitation of natural sand cannot meet the demand of construction, and machine-made sand has become the main raw material for the production of ready-mixed concrete. A large amount of soil and stone powder is produced in the process of mining and crushing of machine-made sand, and the soil in the machine-made sand has a great negative impact on the performance of concrete. Therefore, measures should be taken to control the content of soil and stone powder in machine-made sand. The water washing method is commonly used to treat machine-made sand, but it will produce a large amount of washing wastewater. In order to reduce the production water and meet the environmental protection requirements, the sand washing water is treated by using a flocculating agent to accelerate the settlement, purification and clarification, and to speed up the recycling. However, the upper clear water is recycled to wash the sand again, and a certain amount of flocculating agent is left on the surface of the machine-made sand particles and in the water contained in the machine-made sand. The recycling of sand washing water will cause the accumulation of residual flocculating agent in the machine-made sand. The residual amount of soluble polyacrylamide in the recycled sand washing machine-made sand is 0.0002% to 0.0020% (based on the mass of machine-made sand). The existing research and test of the content of polyacrylamide are often 10 to 100 times higher than the actual value, which seriously affects the performance of concrete. In recent years, this has led to quality accidents of concrete.

[0003] At present, the flocculating agents used by sand and gravel enterprises are mostly anionic polyacrylamide PAM (molecular weight 1200 million, 1800 million, etc.), non-ionic polyacrylamide, and cationic polyacrylamide flocculating agent. In the process of concrete production, the flocculating agent left in the machine-made sand will cause competition adsorption and dispersion performance interference of polycarboxylic acid water reducing agent on the cement particles due to its high molecular weight, which will cause a large increase in the dosage of admixtures, increase the cohesiveness of concrete mixture, and accelerate the loss of slump, etc. The adjustment difficulty and cost of concrete admixtures are increased, which is one of the common problems in the industry.

[0004] CN113773441A proposes an anti-flocculating agent, which is mainly copolymerized by several cationic monomers and styrene, and can reduce the influence of flocculating agent on fluidity when used with water reducing agent. However, the anti-flocculating agent is based on the positive charge branch of cationic monomers, which is attracted to the opposite charge of the negative charge flocculating agent, and the flocculating agent is firmly adsorbed together to form a large group, so as to be precipitated out of the cement slurry solution. It can only effectively precipitate anionic polyacrylamide, and cannot overcome nonionic and cationic polyacrylamide. Patent CN112661913A uses imide, unsaturated carboxylic acid and macromonomer to synthesize a functional polycarboxylic acid water reducing agent for resisting flocculating agent in machine-made sand. Compared with the commonly used polycarboxylic acid water reducing agent, it has better resistance to flocculating agent, but the preparation process is complex and uses expensive monomers such as imide, which has high use cost and does not have practical application value.

[0005] Therefore, it is of great significance to research and develop an anti-flocculating agent functional additive for machine-made sand to prevent the influence of flocculating agent on the quality of concrete for the popularization and application of machine-made sand. SUMMARY

[0006] Therefore, the present application proposes an environmentally friendly anti-flocculating agent functional additive for machine-made sand for concrete, which can effectively reduce the viscosity of concrete prepared by machine-made sand containing flocculating agent and improve the workability of concrete.

[0007] To achieve the above purpose, the technical scheme of the present application is as follows:

[0008] An environmentally friendly anti-flocculating agent functional additive for machine-made sand for concrete, which contains an esterified modification of organic acid groups grafted on the hydroxyl groups of beta-cyclodextrin.

[0009] Further, the organic acid includes maleic anhydride, sulfamic acid, gluconic acid or citric acid.

[0010] Further, the esterification degree of the esterified modification is 0.5-0.7.

[0011] The present application also proposes a preparation method of the above-mentioned environmentally friendly anti-flocculating agent functional additive for machine-made sand for concrete, which comprises the following steps:

[0012] Beta-cyclodextrin is added to a solvent for dissolution, organic acid and catalyst are added, heated, and solid is precipitated out with acetone. The solid is filtered and dried, the solid is dissolved in anhydrous methanol and filtered, the product is precipitated out with acetone, and then vacuum dried after crystallization with distilled water and acetone, to obtain the environmentally friendly anti-flocculating agent functional additive for machine-made sand for concrete.

[0013] Further, the solvent includes N,N-dimethylformamide.

[0014] Further, the catalyst comprises at least one of concentrated sulfuric acid, zinc oxide, stannous chloride, and dibutyltin dilaurate.

[0015] Further, the heating temperature is controlled at 60-70 DEG C.

[0016] The environment-friendly anti-machine-sand-in-flocculant functional additive for concrete of the present application is prepared by chemically esterifying and modifying beta-cyclodextrin (beta-CD) with organic acid groups grafted. The modified beta-cyclodextrin has a unique structure, which can be adsorbed on the polyacrylamide molecular chain in preference to polycarboxylic acid molecules, and at the same time, increases the distance between polycarboxylic acid molecules and polyacrylamide molecules, thereby reducing the probability of polycarboxylic acid molecules being adsorbed, embedded and bound by polyacrylamide, weakening the flocculation of polyacrylamide flocculants, reducing the viscosity of concrete, and improving the workability of concrete containing machine-made sand. The environment-friendly anti-machine-sand-in-flocculant functional additive for concrete of the present application is prepared by using natural beta-cyclodextrin as raw material, which has the advantages of environmental protection and low cost, and is conducive to industrial use. DETAILED DESCRIPTION

[0017] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0018] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials used in the following examples are all commercially available from conventional biochemical reagent stores unless otherwise specified. In addition, the terms and processes involved in the present examples are understood according to the general knowledge and conventional methods in the prior art unless otherwise specified in the present examples.

[0019] An environment-friendly anti-machine-sand-in-flocculant functional additive for concrete includes an esterified and modified product of beta-cyclodextrin with organic acid groups grafted on the hydroxyl groups of the beta-cyclodextrin.

[0020] The environment-friendly anti-machine-sand-in-flocculant functional additive for concrete of the present application is prepared by chemically esterifying and modifying beta-cyclodextrin (beta-CD) with organic acid groups grafted. The modified beta-cyclodextrin has a unique structure, which can be adsorbed on the polyacrylamide molecular chain in preference to polycarboxylic acid molecules, and at the same time, increases the distance between polycarboxylic acid molecules and polyacrylamide molecules, thereby reducing the probability of polycarboxylic acid molecules being adsorbed, embedded and bound by polyacrylamide, weakening the flocculation of polyacrylamide flocculants, reducing the viscosity of concrete, and improving the workability of concrete containing machine-made sand. The environment-friendly anti-machine-sand-in-flocculant functional additive for concrete of the present application is prepared by using natural beta-cyclodextrin as raw material, which has the advantages of environmental protection and low cost, and is conducive to industrial use.

[0021] The organic acid preferably includes maleic anhydride, sulfamic acid, gluconic acid, or citric acid. More preferably, the degree of esterification of the esterified modified product is 0.5-0.7. 。 This degree of substitution in esterification modification can not only ensure the strong adsorption of negatively charged carboxylic acid adsorption groups, but also give β-cyclodextrin good solubility and prevent the reduction in cement strength caused by excessive carboxyl groups.

[0022] This invention also proposes a method for preparing the above-mentioned environmentally friendly anti-flocculation functional additive for concrete manufactured sand, which specifically includes the following steps:

[0023] Dissolve 10-20 parts of β-cyclodextrin in a solvent, add 10-15 parts of organic acid and 1-5 parts of catalyst, heat, precipitate the solid with acetone, filter and dry the solid, dissolve the solid in anhydrous methanol, filter, precipitate the product with acetone, crystallize with distilled water and acetone, and then vacuum dry to obtain an environmentally friendly anti-flocculation functional additive for concrete-grade manufactured sand. The solvent can be N,N-dimethylformamide (DMF), with the amount of DMF being 9-11 times the weight of β-cyclodextrin. The catalyst can be at least one of concentrated sulfuric acid, zinc oxide, stannous chloride, and dibutyltin dilaurate. Controlling the heating temperature at 60℃~70℃ can improve efficiency.

[0024] All of the above-mentioned reaction reagents can be purchased from the market. The specific implementation scheme of the present invention will be described in detail below.

[0025] Example 1

[0026] In a 100ml three-necked flask, 15 parts of β-CD were dissolved in an appropriate amount of DMF, followed by 10 parts of maleic anhydride (MA) and 1.5 parts of concentrated sulfuric acid. The mixture was heated to 60℃ and stirred at low speed for 24 hours. After cooling to room temperature, β-CD-CAS and unreacted β-CD were precipitated with acetone. The precipitate was filtered, dried, and dissolved in 60ml of anhydrous methanol. A small amount of β-CD was filtered off, and the product was precipitated with acetone. After repeated crystallization with distilled water and acetone several times, the product was dried under vacuum to obtain the esterified product of β-cyclodextrin with organic acid groups. The degree of esterification of the anti-flocculation functional aid in manufactured sand prepared in this example was 0.6.

[0027] Example 2

[0028] In a 100ml three-necked flask, 10 parts of β-CD were dissolved in an appropriate amount of DMF, followed by 10 parts of aminosulfonic acid (ACS) and 2.5 parts of dibutyltin dilaurate. The mixture was heated to 65℃ and stirred at low speed for 20 hours. After cooling to room temperature, β-CD-ACS and unreacted β-CD were precipitated with acetone. The precipitate was filtered, dried, and dissolved in 70ml of anhydrous methanol. A small amount of β-CD was filtered off, and the product was precipitated with acetone. After repeated crystallization with distilled water and acetone several times, the product was dried under vacuum to obtain the esterified product of β-cyclodextrin with organic acid groups. The degree of esterification of the anti-flocculation functional aid in manufactured sand prepared in this example was 0.7.

[0029] Example 3

[0030] In a 100ml three-necked flask, 20 parts of β-CD were dissolved in an appropriate amount of DMF, followed by 10 parts of citric acid (CA) and 3 parts of stannous chloride. The mixture was heated to 70℃ and stirred at low speed for 30 hours. After cooling to room temperature, β-CD-CA and unreacted β-CD were precipitated with acetone. The precipitate was filtered, dried, and dissolved in 80ml of anhydrous methanol. A small amount of β-CD was filtered off, and the product was precipitated with acetone. After repeated crystallization with distilled water and acetone several times, the product was dried under vacuum to obtain the esterified product of β-cyclodextrin with organic acid groups. The degree of esterification of the anti-flocculation functional aid in manufactured sand prepared in this example was 0.4.

[0031] Example 4

[0032] In a 100ml three-necked flask, 20 parts of β-CD were dissolved in an appropriate amount of DMF, followed by 10 parts of gluconic acid (GLCA) and 5 parts of zinc oxide. The mixture was heated to 70℃ and stirred at low speed for 35 hours. After cooling to room temperature, β-CD-GLCA and unreacted β-CD were precipitated with acetone. The precipitate was filtered, dried, and dissolved in 80ml of anhydrous methanol. A small amount of β-CD was filtered off, and the product was precipitated with acetone. After repeated crystallization with distilled water and acetone several times, the product was dried under vacuum to obtain the esterified product of β-cyclodextrin with organic acid groups. The degree of esterification of the anti-flocculation functional aid in manufactured sand prepared in this example was found to be 0.5.

[0033] Comparative Example 1

[0034] This comparative example uses a commercially available product, model X007, from Sichuan Luhua Lingtuo Building Materials Co., Ltd.

[0035] Comparative Example 2

[0036] This comparative example uses β-cyclodextrin that has not been modified with organic acids.

[0037] The antiflocculating agents prepared in the above embodiments and comparative examples were used in concrete tests. To simulate the effect of polyacrylamide flocculant on the workability of concrete, 0.15% anionic polyacrylamide (molecular weight 1200w) by weight of water was added to the concrete mixing water. According to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the initial and 1-hour spread, slump, and lift-off time of the concrete were tested. The cement used in the concrete preparation was P.O42.5 Esheng cement, the fly ash was Mingxiang Grade I fly ash, and the water-reducing agent was GK-3000 polycarboxylate high-performance water-reducing agent (product of Shijiazhuang Chang'an Yucai Building Materials Co., Ltd.). The water-reducing agent dosage was 1.0% of the cementitious material weight, and the antiflocculating agent dosage prepared in each embodiment and comparative example was 0.05% of the cementitious material weight. The concrete reference mix is ​​shown in Table 1, and the test results are shown in Table 2. The blank group was concrete without the addition of antiflocculating agent.

[0038] Table 1 Concrete Mix Proportions

[0039]

[0040] Table 2 Concrete Test Results

[0041]

[0042] By comparing the test results of each embodiment, Comparative Example 1 (commercially available product), Comparative Example 2 and the blank group, the present invention's environmentally friendly anti-flocculation sand functional additive for concrete can effectively reduce concrete viscosity, shorten the lifting time, and improve the workability of concrete.

[0043] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0044] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. An environmentally friendly functional additive for concrete that resists flocculants in manufactured sand, characterized in that: The aforementioned environmentally friendly anti-fragmented sand for concrete contains an esterified modified product with organic acid groups grafted onto the hydroxyl groups of β-cyclodextrin. The organic acid includes gluconic acid; The degree of esterification of the esterified modified product is 0.5-0.

7.

2. A method for preparing an environmentally friendly anti-flocculation functional additive for concrete manufactured sand according to claim 1, characterized in that: The method includes the following steps: β-Cyclodextrin was dissolved in a solvent, organic acid and catalyst were added, and the mixture was heated. The solid was precipitated with acetone, filtered and dried, dissolved in anhydrous methanol and filtered again. The product was precipitated with acetone, crystallized by distilled water and acetone, and then dried under vacuum to obtain the environmentally friendly anti-flocculation functional additive for concrete-grade manufactured sand.

3. The preparation method of the environmentally friendly anti-flocculation functional additive for concrete manufactured sand according to claim 2, characterized in that: The solvent includes N,N-dimethylformamide.

4. The preparation method of the environmentally friendly anti-flocculation functional additive for concrete manufactured sand according to claim 2, characterized in that, The catalyst includes at least one of concentrated sulfuric acid, zinc oxide, stannous chloride, and dibutyltin dilaurate.

5. The preparation method of the environmentally friendly anti-flocculation functional additive for concrete sand according to any one of claims 2-4, characterized in that: The heating temperature is controlled at 60℃~70℃.

6. The application of an esterified product of β-cyclodextrin with organic acid groups grafted onto its hydroxyl groups in a functional additive for environmentally friendly anti-flocculation sand used in concrete, characterized in that: The organic acids in the esterified modified β-cyclodextrin with organic acid groups grafted onto its hydroxyl groups include maleic anhydride, aminosulfonic acid, gluconic acid, or citric acid, and the degree of esterification is 0.5-0.7.

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