Dedicated deflocculating agent for flocculation washing machine-made sand concrete, preparation method and application

Abstract

The invention discloses a special deflocculating agent for flocculation washing machine-made sand concrete as well as a preparation method and application thereof.The special deflocculating agent for flocculation washing machine-made sand concrete is prepared from the following raw materials in percentage by mass: 10-20% of a nano-silica loaded chelating agent, 25-40% of a zwitterionic polymer and 45-60% of composite phosphate, respectively weighing the nano silicon dioxide loaded chelating agent, the zwitterionic polymer and the composite phosphate according to a specified weight ratio; the preparation method comprises the following steps: mixing the weighed three components in a mixing container for 30 minutes to obtain the special deflocculating agent for flocculating and washing machine-made sand concrete. Based on the synergistic effect of various mechanisms of the nano silicon dioxide loaded chelating agent, the zwitterionic polymer and the composite phosphate, the flocculation effect and the structure of a flocculating constituent are quickly destroyed; the anti-flocculation capability of the flocculation washing machine-made sand concrete is obviously improved, and the construction performance and the strength performance of the flocculation washing machine-made sand concrete are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of functional admixtures, in particular to a special anti-flocculant for flocculating water-washed machine-made sand concrete, a preparation method and an application thereof. Background Art

[0002] Currently, manufactured sand manufacturers often use PAM flocculants to wash manufactured sand, recycling the wastewater multiple times. This results in large amounts of PAM flocculants remaining in the manufactured sand. This leads to practical engineering problems such as poor concrete flowability and significant losses, seriously impacting the application and sustainable development of manufactured sand concrete.

[0003] In response to the problem that the performance of machine-made sand concrete deteriorates due to residual flocculants, domestic and foreign scholars have carried out research on the anti-flocculation technology of machine-made sand concrete. The Chinese patent with the announcement number CN115959848B discloses a concrete anti-flocculant and its preparation method. The technical solution is to use a high-valent cation neutralization method, which is only effective for anionic polyacrylamide. The Chinese patent with the announcement number CN116535127B discloses a concrete admixture of an anti-flocculant, its preparation method and application. The technical solution is to use a redox system (Fe 2+ / S2O8 2- However, this system has low reaction efficiency in the alkaline environment of concrete, and the persulfate oxidant can further oxidize the polycarboxylic acid-based water reducer, causing it to lose performance. Chinese Patent Publication No. CN115772010B discloses a deflocculant and its preparation method for efficiently treating flocculated material in water-washed sand used in building concrete. The technical solution involves encapsulating the flocculant with a polyether polyol, but this does not completely destroy its structure, leaving residue that affects concrete durability.

[0004] Therefore, there are problems with poor concrete fluidity and large losses in flocculated water-washed machine-made sand concrete. In view of the shortcomings of the existing technology, it is necessary to develop a deflocculant to solve the problems of the above-mentioned machine-made sand concrete. Summary of the Invention

[0005] The purpose of the present invention is to provide a special deflocculant for flocculating washed machine-made sand concrete, a preparation method and an application thereof, so as to solve the problems of poor concrete fluidity, rapid loss and reduced strength caused by residual flocculants such as PAM in machine-made sand.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The special anti-flocculant for flocculation water-washed machine-made sand concrete includes the following components and proportions in terms of mass percentage:

[0008] Nano-silica loaded chelating agent 10-20%

[0009] Zwitterionic polymer 25-40%

[0010] Complex phosphate 45-60%.

[0011] Furthermore, the nano-silica loaded chelating agent is nano-silica loaded hydroxyethylidene diphosphonic acid.

[0012] Furthermore, the preparation method of the nano-silica-loaded hydroxyethylidene diphosphonic acid is as follows:

[0013] S1: Nano-silica pretreatment: Disperse nano-SiO2 in anhydrous ethanol and ultrasonicate for 30 minutes to remove surface impurities; centrifuge the mixture, discard the supernatant, and repeat washing three times; place the washed SiO2 in a vacuum drying oven at 60°C for 12 hours;

[0014] S2: Preparation of chelating agent solution: Weigh a certain amount of hydroxyethylidene diphosphonic acid and dissolve it in deionized water to prepare a 20% chelating agent solution; adjust the pH value of the chelating agent solution to 3-5 to promote the condensation of hydroxyl groups on the SiO2 surface with the phosphate groups of the chelating agent;

[0015] S3: Loading process: Mix the nano-SiO2 pretreated by S1 with the chelating agent solution prepared by S2, where the mass ratio of nano-SiO2 to chelating agent is 1:17.5; heat to 70°C and continue stirring for 12 hours to form Si-OP covalent bonds between the hydroxyl groups and the phosphate groups;

[0016] S4: Post-treatment: Centrifuge the mixed solution after S3 loading and collect the precipitate; wash the precipitate with deionized water three times to remove the unloaded free chelating agent; place the precipitate after washing with deionized water in a vacuum drying oven and dry it at 60°C for 24 hours to obtain a white powder of nano-silica loaded with chelating agent.

[0017] Furthermore, the mass ratio of the nano-SiO2 to anhydrous ethanol is 1:10.

[0018] Furthermore, the zwitterionic polymer is an acrylic acid-sodium methacrylic acid sulfonate-vinylimidazole terpolymer, the polymer molecular weight is 8000-12000, and the molar ratio of sulfonic acid group to imidazole group is 1:1.2-1.5.

[0019] Furthermore, the composite phosphate is a complex of sodium hexametaphosphate and sodium tripolyphosphate, and the mass ratio is 3:1.

[0020] A method for preparing a special deflocculant for flocculating water-washed machine-made sand concrete, comprising the following steps:

[0021] The nano-silica loaded chelating agent, the zwitterionic polymer and the composite phosphate are weighed respectively according to the prescribed weight ratio; the weighed three components are mixed in a mixing container for 30 minutes to obtain a special anti-flocculant for flocculating water-washed machine-made sand concrete.

[0022] The invention discloses an application of a special anti-flocculant for flocculating water-washed machine-made sand concrete in flocculating water-washed machine-made sand concrete, wherein the amount of the anti-flocculant used is 0.3% to 0.5% of the total mass of the cementitious material.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The nano-silica loaded chelating agent introduced in the present invention has a high specific surface area and can directly adsorb the flocculant PAM molecular chain through van der Waals force, hydrogen bond and electrostatic effect, directly reducing the concentration of free PAM in the solution and weakening its bridging flocculation ability; secondly, the surface of nano-silica is rich in hydroxyl groups, which can form hydrogen bonds with PAM amide groups, resulting in the contraction of the PAM molecular chain conformation and reducing its ductility and adsorption efficiency; thirdly, the chelating agent has a multi-dentate coordination group, which can bind to the metal ions (such as Ca2+) in the PAM chain. 2+ 、Al 3+ ) combines with the suspended particles, destroying the charge neutralization bridge between PAM and suspended particles.

[0025] 2. The zwitterionic polymer introduced in the present invention has the following characteristics: first, the sulfonic acid group in the polymer has strong negative charge, which neutralizes the positive charge of cationic PAM or repels the negative charge of anionic PAM through electrostatic interaction, thereby weakening the charge adsorption bridge between it and the suspended particles; second, the imidazole ring of vinyl imidazole is protonated in an alkaline environment (such as concrete) to form a cationic group (-NH + ), which can specifically bind to the carboxylic acid group (-COO-) of anionic PAM, further disrupting its flocculation network. This shows that the zwitterionic properties of the polymer can achieve a broad spectrum of deflocculation for PAMs of different charge types.

[0026] 3. The composite phosphate introduced in the present invention, first, the sodium hexametaphosphate in the composite coordinates with the metal ions through the phosphate groups in the ring structure to form a stable water-soluble complex, destroying the floc structure formed by PAM through metal ion bridging; second, the sodium tripolyphosphate in the composite has a particularly outstanding complexing ability for calcium ions, and its chelation effect further weakens the charge neutralization effect between PAM and particles; third, the introduction of phosphorus-containing inorganic salts significantly increases the solution ionic strength, compresses the diffuse double layer of the PAM molecular chain, causing it to transform from an extended state (effective bridging) to a curled state (ineffective conformation), reducing the flocculation efficiency.

[0027] 4. The three functional components introduced in the present invention have a rapid destructive effect on the bridging flocculation effect of polyacrylamide of different ionic types through the synergistic effect of multiple mechanisms, and can significantly improve the initial fluidity and slump retention performance of flocculated water-washed machine-made sand concrete.

[0028] 5. The technical solution involved in the present invention has simple components, simple process and obvious anti-flocculation effect. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] Example 1: A special deflocculant for flocculating water-washed machine-made sand concrete, the components and proportions of which are: 10% of nano-silica-loaded hydroxyethylidene diphosphonic acid, 30% of acrylic acid-sodium methyl propylene sulfonate-vinyl imidazole terpolymer, and 60 parts of composite phosphate.

[0031] The dosage of antiflocculant is 0.3% of the total mass of concrete cementitious materials.

[0032] Example 2: A special deflocculant for flocculating water-washed machine-made sand concrete, the components and proportions of which are: 10% of nano-silica-loaded hydroxyethylidene diphosphonic acid, 40% of acrylic acid-sodium methyl propylene sulfonate-vinyl imidazole terpolymer, and 50% of composite phosphate.

[0033] The dosage of antiflocculant is 0.3% of the total mass of concrete cementitious materials.

[0034] Example 3: A special deflocculant for flocculating water-washed machine-made sand concrete, the components and proportions of which are: 15% of nano-silica-loaded hydroxyethylidene diphosphonic acid, 25% of acrylic acid-sodium methyl propylene sulfonate-vinyl imidazole terpolymer, and 60% of composite phosphate.

[0035] The dosage of antiflocculant is 0.3% of the total mass of concrete cementitious materials.

[0036] Example 4: A special antiflocculant for flocculating water-washed machine-made sand concrete

[0037] The composition and proportion of the invention are as follows: 15% of nano-silica-loaded hydroxyethylidene diphosphonic acid, 35% of acrylic acid-sodium methyl propylene sulfonate-vinyl imidazole terpolymer, and 50% of composite phosphate.

[0038] The dosage of antiflocculant is 0.3% of the total mass of concrete cementitious materials.

[0039] Example 5: A special antiflocculant for flocculating water-washed machine-made sand concrete

[0040] The composition and proportion are as follows: 15% of nano-silica-loaded hydroxyethylidene diphosphonic acid, 40% of acrylic acid-sodium methyl propylene sulfonate-vinyl imidazole terpolymer, and 45% of composite phosphate.

[0041] The dosage of antiflocculant is 0.3% of the total mass of concrete cementitious materials.

[0042] Example 6: A special deflocculant for flocculating water-washed machine-made sand concrete, the components and proportions of which are: 20% of nano-silica-loaded hydroxyethylidene diphosphonic acid, 25% of acrylic acid-sodium methyl propylene sulfonate-vinyl imidazole terpolymer, and 55% of composite phosphate.

[0043] The dosage of antiflocculant is 0.3% of the total mass of concrete cementitious materials.

[0044] Example 7: A special deflocculant for flocculating water-washed machine-made sand concrete, the components and proportions of which are: 20% of nano-silica-loaded hydroxyethylidene diphosphonic acid, 35% of acrylic acid-sodium methyl propylene sulfonate-vinyl imidazole terpolymer, and 45% of composite phosphate.

[0045] The dosage of antiflocculant is 0.3% of the total mass of concrete cementitious materials.

[0046] Example 8: A special deflocculant for flocculating water-washed machine-made sand concrete, the components and proportions of which are: 10% of nano-silica-loaded hydroxyethylidene diphosphonic acid, 30% of acrylic acid-sodium methyl propylene sulfonate-vinyl imidazole terpolymer, and 60% of composite phosphate.

[0047] The dosage of antiflocculant is 0.5% of the total mass of concrete cementitious materials.

[0048] Comparative Example 1: The product prepared by the present invention is not added to the concrete, and the sand used in the concrete is natural sand without flocculant, and the amount of natural sand is the same as the amount of machine-made sand in the mix ratio.

[0049] Comparative Example 2: a benchmark group, i.e., the concrete was not mixed with the product prepared by the present invention.

[0050] Comparative Example 3: is basically the same as Example 1, except that nano-silica loaded hydroxyethylidene diphosphonic acid is not compounded, and the amount of nano-silica loaded hydroxyethylidene diphosphonic acid is replaced by an equal amount of cement, and the addition amount is the same as Example 1.

[0051] Comparative Example 4: is basically the same as Example 1, except that the acrylic acid-sodium methacrylic acid sulfonate-vinylimidazole terpolymer is not compounded, and the amount of acrylic acid-sodium methacrylic acid sulfonate-vinylimidazole terpolymer is replaced by an equal amount of cement, and the addition amount is the same as Example 1.

[0052] Comparative Example 5: is basically the same as Example 1, except that the composite phosphate is not compounded, and the amount of composite phosphate is replaced by an equal amount of cement, and the addition amount is the same as Example 1.

[0053] The present invention addresses the problems of poor concrete fluidity and large concrete loss in flocculated water-washed machine-made sand concrete. A deflocculant based on the synergistic action of multiple mechanisms is introduced to effectively and quickly destroy the flocculation effect of flocculants such as PAM, thereby improving the fluidity, slump retention and strength properties of flocculated water-washed machine-made sand concrete.

[0054] The prepared product is evaluated by technical parameters of the machine-made sand concrete, such as initial slump, initial expansion, 1h slump, 1h expansion, and 28d compressive strength.

[0055] Comparative test of flocculation water-washed machine-made sand concrete performance: The amount of each raw material in the concrete mix ratio is Xinning P·O42.5 cement 288kg / m 3 , Jianbi II fly ash 72kg / m 3 、Changjiu machine-made sand in Chizhou, Anhui Province 781kg / m 3 (flocculant PAM content 0.022%), 5mm to 31.5mm continuously graded crushed stone 1079kg / m 3 , water 170kg / m 3 , the dosage of polycarboxylic acid high performance water reducer is 1.0%.

[0056] The slump and expansion tests are carried out in accordance with the provisions of GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures";

[0057] The 28d compressive strength test was conducted in accordance with the provisions of GB / T 50081-2019 Standard for Test Methods of Mechanical Properties of Ordinary Concrete; the specific performance test results are shown in Table 1.

[0058] Table 1 Flocculation and washing machine-made sand concrete performance test results

[0059]

[0060]

[0061] As shown in Table 1, compared to Comparative Example 1, the use of flocculant-containing manufactured sand in Comparative Example 2 significantly impacted the workability of the concrete mix. Initial slump decreased by nearly 50%, initial spread completely lost, and fluidity was lost. The 1-hour slump loss rate increased by nearly 8 times, and the 28-day compressive strength decreased by 8.7%. This indicates that flocculant-containing manufactured sand significantly impacted the workability of fresh concrete and had a certain impact on the 28-day compressive strength of hardened concrete. Compared to Comparative Example 2, the initial slump and initial spread of the concrete in Examples 1 through 8 were significantly improved. Initial slump increased by a minimum of 79.2% and a maximum of 91.7%. Initial spread increased by a minimum of 1.6 times and a maximum of 1.85 times. The 1-hour slump loss rate decreased by a minimum of 84.4% and a maximum of 96.1%. The 28-day compressive strength increased by a minimum of 10.1% and a maximum of 15.2%. This indicates that the workability and strength properties of Examples 1 through 8 were significantly improved. Compared with Comparative Example 3, Example 1 shows that the initial slump of Comparative Example 3 decreased by 18.6%, the initial expansion decreased by 20%, the 1-hour slump loss rate increased by 1.7 times, the 1-hour expansion loss rate increased by 5.1 times, and the 28-day compressive strength decreased by 5.3%. This is because the strong adsorption effect of the nano-silica-loaded chelating agent reduces the concentration of free flocculant in the solution to weaken its bridging flocculation ability, and its chelating effect destroys the charge neutralization and bridging between the flocculant and suspended particles. Compared with Comparative Example 4, Example 1 shows that the initial slump of Comparative Example 4 decreased by 9.3%, the initial expansion decreased by 10.5%, the 1-hour slump loss rate increased by 82.9%, the 1-hour expansion loss rate increased by 97.7%, and the 28-day compressive strength decreased by 3.1%. This is because the sulfonic acid group and imidazole group in the zwitterionic polymer neutralize the anionic and cationic polyacrylamide, respectively, to destroy the flocculation effect and broaden its applicability. Compared with Comparative Example 5, Example 1 shows that the initial slump of Comparative Example 5 decreases by 4.7%, the initial expansion decreases by 5.8%, the 1-h slump loss rate increases by 74.3%, the 1-h expansion loss rate increases by 39.5%, and the 28-d compressive strength is equivalent. This is because the strong complexing effect of the composite phosphate consumes the high-valent metal cations in the solution to further weaken the bridging flocculation ability of the flocculant.

[0062] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. Flocculation water washing machine sand concrete special antiflocculant, characterized by, In terms of mass percentage, it includes the following components and proportions: Nano-silica loaded chelating agent 10-20% Zwitterionic polymer 25-40% Complex phosphate 45-60%.

2. The special antiflocculant for flocculation and washing machine-made sand concrete according to claim 1, characterized in that: The nano-silica loaded chelating agent is nano-silica loaded hydroxyethylidene diphosphonic acid.

3. The special antiflocculant for flocculation and washing machine-made sand concrete according to claim 2, characterized in that: The preparation method of the nano-silica-loaded hydroxyethylidene diphosphonic acid is as follows: S1: Nano-silica pretreatment: Disperse nano-SiO2 in anhydrous ethanol and ultrasonicate for 30 minutes to remove surface impurities; centrifuge the mixture, discard the supernatant, and repeat washing three times; place the washed SiO2 in a vacuum drying oven at 60°C for 12 hours; S2: Preparation of chelating agent solution: Weigh a certain amount of hydroxyethylidene diphosphonic acid and dissolve it in deionized water to prepare a 20% chelating agent solution; adjust the pH value of the chelating agent solution to 3-5 to promote the condensation of hydroxyl groups on the SiO2 surface with the phosphate groups of the chelating agent; S3: Loading process: Mix the nano-SiO2 pretreated by S1 with the chelating agent solution prepared by S2, where the mass ratio of nano-SiO2 to chelating agent is 1:17.5; heat to 70°C and continue stirring for 12 hours to form Si-OP covalent bonds between the hydroxyl groups and the phosphate groups; S4: Post-treatment: Centrifuge the mixed solution after S3 loading and collect the precipitate; wash the precipitate with deionized water three times to remove the unloaded free chelating agent; place the precipitate after washing with deionized water in a vacuum drying oven and dry it at 60°C for 24 hours to obtain a white powder of nano-silica loaded with chelating agent.

4. The special antiflocculant for flocculation and washing machine-made sand concrete according to claim 3, characterized in that: The mass ratio of the nano-SiO2 to anhydrous ethanol is 1:

10.

5. The special antiflocculant for flocculation and washing machine-made sand concrete according to claim 1, characterized in that: The zwitterionic polymer is an acrylic acid-sodium methacrylic acid sulfonate-vinyl imidazole terpolymer, the polymer molecular weight is 8000-12000, and the molar ratio of sulfonic acid group to imidazole group is 1:1.2-1.

5.

6. The special antiflocculant for flocculation and washing machine-made sand concrete according to claim 1, characterized in that: The composite phosphate is a compound of sodium hexametaphosphate and sodium tripolyphosphate, and the mass ratio is 3:

1.

7. A method for preparing the special deflocculant for flocculation and washing machine-made sand concrete according to any one of claims 1 to 6, characterized in that: Here are the steps: The nano-silica loaded chelating agent, the zwitterionic polymer and the composite phosphate are weighed respectively according to the prescribed weight ratio; the weighed three components are mixed in a mixing container for 30 minutes to obtain a special anti-flocculant for flocculating water-washed machine-made sand concrete.

8. Application of the special deflocculant for flocculation and washing machine-made sand concrete prepared according to claim 7 in flocculation and washing machine-made sand concrete, characterized in that: The dosage of the anti-flocculant is 0.3% to 0.5% of the total mass of the gelling material.

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