Special additive for self-compacting concrete as well as preparation method and application of special additive
Through the compounding of polycarboxylic acid water-reducing agent and slump-retaining water-reducing agent and the synergistic effect of modified starch, the problems of fluidity loss and segregation of self-compacting concrete during construction are solved, and concrete performance with high fluidity and stability is achieved.
Patent Information
- Application Number
- CN202510851514.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-24
- Publication Date
- 2025-10-17
AI Technical Summary
Existing admixtures are difficult to provide sufficient suspension and cohesion in self-compacting concrete that maintains high fluidity to prevent coarse aggregate from sinking and paste from floating. In addition, the development of paste structure in the early stage of hydration leads to deterioration of construction performance.
The polycarboxylic acid water-reducing agent is compounded with the slump-retaining water-reducing agent, combined with modified starch, defoamer and air-entraining agent. Through synergistic effect, the slump-retaining performance and stability of concrete are improved, the paste structure in the initial stage of hydration is controlled, and segregation is prevented.
Maintain high fluidity of concrete while reducing water consumption, prevent deterioration of construction performance, improve anti-segregation and stability, and enhance frost resistance.
Smart Images
Figure BDA0005464962350000071 
Figure BDA0005464962350000081 
Figure BDA0005464962350000082
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of building materials, and particularly relates to a special admixture for self-compacting concrete and a preparation method and application thereof. BACKGROUND
[0002] Self-compacting concrete is a kind of high-performance concrete which can be compacted without vibration under the action of gravity. It is widely used in high-rise buildings, bridges and complex reinforced structures because it can significantly improve construction efficiency, improve structural durability and reduce labor costs. However, achieving excellent workability and ensuring its stability during transportation and pouring, as well as the durability after hardening, puts high requirements on the selection of raw materials and the design of mix proportion of concrete. Among them, high-efficiency admixtures are the core means to control the rheological properties, stability and durability of self-compacting concrete.
[0003] At present, in order to pursue high fluidity and low viscosity of concrete to meet the requirements of self-compacting, a higher water content is usually required, which limits the reduction of water-binder ratio, and is not conducive to the final strength and durability of concrete. Therefore, the water-binder ratio is reduced by adding admixtures. However, the existing admixtures often focus on the improvement of a single performance, and have limitations in improving the performance of self-compacting concrete. On the one hand, the hydration process of cement will cause the gradual formation of paste structure, which makes the fluidity of concrete lose rapidly with time. The existing admixtures cannot effectively inhibit the development of paste structure in the early stage of hydration, which leads to the significant deterioration of the workability of concrete during transportation or waiting for pouring, and affects the construction window period. On the other hand, in the high-fluidity self-compacting concrete system, the density difference between coarse aggregate and paste is large, and the segregation phenomenon of coarse aggregate sinking and paste floating and bleeding easily occurs. The existing admixture combination has limited or uneven effect on the improvement of yield stress and viscosity of the system, and it is difficult to provide enough “suspension force” and “cohesion” to stabilize the aggregate and paste while maintaining high fluidity. SUMMARY
[0004] In order to improve the flow stability of concrete during construction and maintain good construction performance, the present application provides a special admixture for self-compacting concrete and a preparation method and application thereof.
[0005] In a first aspect, the present application provides a special admixture for self-compacting concrete, which adopts the following technical scheme: A special admixture for self-compacting concrete is prepared from the following raw materials by weight parts: polycarboxylic acid water reducing agent 110-130 parts, slump retaining water reducing agent 65-75 parts, modified starch 1-3 parts, defoaming agent 0.4-0.6 parts, air entraining agent 0.16-0.24 parts, and water 230-270 parts; The preparation raw materials of the polycarboxylic acid water reducing agent include, by weight parts, methyl allyl polyoxyethylene ether 12-15 parts, hydroxy polyethylene glycol acrylate 3.6-4.2 parts, Tween-80 2.1-3.3 parts, sulfosalicylic acid 0.9-1.5 parts, mercapto acetic acid 0.3-0.6 parts, ammonium persulfate 0.15-0.21 parts; The preparation raw materials of the polycarboxylic acid water reducing agent include, by weight parts, methyl allyl polyoxyethylene ether 12-15 parts, hydroxy polyethylene glycol acrylate 3.6-4.2 parts, Tween-80 2.1-3.3 parts, sulfosalicylic acid 0.9-1.5 parts, mercapto acetic acid 0.3-0.6 parts, ammonium persulfate 0.15-0.21 parts;
[0006] By adopting the above technical scheme, the water reducing agent component composed of the polycarboxylic acid water reducing agent and the slump retaining water reducing agent makes the freshly mixed concrete maintain good construction performance within a certain time and improves the slump retaining capacity of the concrete itself. The polycarboxylic acid water reducing agent has both water reducing and initial slump retaining performance. The polycarboxylic acid water reducing agent has a large density and a long side chain, and also has a certain amount of sulfonic acid groups. Through the steric hindrance effect of the side chain, the polycarboxylic acid water reducing agent prevents cement particles from agglomerating and maintains the dispersion effect. However, due to the continuous hydration of cement, the polycarboxylic acid water reducing agent molecules adsorbed on the surface of the cement are continuously consumed, which causes the slump and spread loss of the freshly mixed concrete over time. At this time, the slow release effect of the slump retaining water reducing agent molecules makes the water reducing agent molecules continuously supplement the concrete slurry. The ester groups in the structure of the slump retaining water reducing agent molecules can be continuously converted into adsorption groups of the water reducing agent molecules over time, so that the water reducing agent molecules in the water are slowly adsorbed, the cement slurry in the concrete is kept in a dispersed state, and the flow stability of the concrete in the construction process is ensured. Therefore, the polycarboxylic acid water reducing agent and the slump retaining water reducing agent have a synergistic effect. In addition, the modified starch can expand and swell in water, has a tackifying effect, helps to increase the water retaining capacity of the concrete, and also has molecular crosslinking, entanglement and bridging of the hydrogen bonds between molecules and between the modified starch and water molecules, and forms a colloidal film on the surface of the cement particles to prevent the migration of water in the concrete, thereby improving the water retention of the concrete and enhancing the anti-segregation and stability of the concrete.
[0007] Preferably, the preparation method of the polycarboxylic acid water reducing agent comprises the following steps: At 30-40℃, the methyl allyl polyoxyethylene ether is added into water, stirred uniformly, and then the hydroxy polyethylene glycol acrylate, Tween-80 and sulfosalicylic acid are added and stirred. The temperature is raised to 80-90℃, the mercapto acetic acid and ammonium persulfate are added, and the mixture is stirred and reacted for 3-4h. The solution is cooled to room temperature, the pH of the solution is adjusted to 6-8, and the polycarboxylic acid water reducing agent is obtained.
[0008] Preferably, the preparation method of the polycarboxylic acid water reducing agent comprises the following steps: At 30-40℃, isoprenol polyoxyethylene ether is added into water, stirred uniformly, then acrylic acid, ester monomer is mixed and stirred, heated to 80-90℃, then mercapto propionic acid and potassium persulfate are added, stirred and reacted for 3-4h, cooled to room temperature, then the solution pH is adjusted to 6-8, to obtain a slump retaining water reducing agent.
[0009] Preferably, the ester monomer is selected from one or more of dimethyl maleate, dimethyl itaconate and dimethyl fumarate.
[0010] By adopting the technical scheme, the polycarboxylate superplasticizer prepared by the method and the slump retaining water reducing agent have a synergistic effect. The polycarboxylate superplasticizer has long side chains and sulfonic acid groups introduced by Tween-80 and sulfosalicylic acid. Tween-80 has polyoxyethylene chain structure and long aliphatic chain structure, which can increase the length of the side chains of the polycarboxylate superplasticizer. The sulfosalicylic acid contains sulfonic acid groups. The two together increase the steric hindrance effect of the polycarboxylate superplasticizer, so that the polycarboxylate superplasticizer has excellent water reducing and initial slump retaining performance in the self-compacting concrete. The slump retaining water reducing agent has ester groups introduced by the ester monomer, and the ester monomer has double ester groups in the molecular structure, which has good slow-release dispersion effect. The ester groups are gradually hydrolyzed in the alkaline environment of the cement paste, producing anion groups that have dispersion effect on the concrete, which are adsorbed on the hydrated concrete particles, thereby achieving good slump retaining performance.
[0011] Preferably, the defoaming agent is selected from one or both of organosilicon defoaming agent and polyether modified silicone oil defoaming agent.
[0012] By adopting the technical scheme, the defoaming agent mainly functions to quickly reduce the surface tension of the concrete, take away the bubble molecules on the surface of the concrete, and take away the surface solution near the bubble molecules, so as to reduce the surface viscosity, elasticity and strength of the liquid film.
[0013] Preferably, the air entraining agent is selected from one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate and sodium dodecyl benzene sulfonate.
[0014] By adopting the technical scheme, a large number of uniformly distributed, stable and closed micro bubbles are introduced by the air entraining agent, so as to effectively improve the workability of the concrete, and improve the frost resistance and durability of the concrete.
[0015] In a second aspect, the application provides a preparation method of a special admixture for self-compacting concrete, which adopts the following technical scheme: The preparation method of the special admixture for self-compacting concrete comprises the following steps: Mix polycarboxylic acid water reducing agent, slump retaining water reducing agent, modified starch and water, stir uniformly, add defoaming agent, stir until dispersed uniformly, add air entraining agent, stir until dispersed uniformly, to obtain self-compacting concrete special admixture.
[0016] By adopting the above technical scheme, in the preparation method, the polycarboxylic acid water reducing agent and the slump retaining water reducing agent play a synergistic role, reduce the loss of the fluidity of the concrete in the construction process, and guarantee the good construction performance of the concrete. The modified starch improves the paste viscosity and enhances the segregation resistance and stability of the concrete. In addition, the application adopts the method of first defoaming and then introducing small bubbles, and the defoaming agent and the air entraining agent synergistically eliminate the poor bubbles in the concrete and then introduce bubbles with small diameter and uniform distribution, so that the quality of the bubbles in the concrete reaches the best state, and the apparent quality and the frost resistance of the concrete are improved.
[0017] In the third aspect, the application provides a self-compacting concrete special admixture, which is prepared by the following technical scheme: a self-compacting concrete special admixture is prepared by mixing polycarboxylic acid water reducing agent, slump retaining water reducing agent, modified starch and water, stirring uniformly, adding defoaming agent, stirring until dispersed uniformly, and adding air entraining agent, stirring until dispersed uniformly.
[0018] Preferably, the content of the self-compacting concrete special admixture is 1.3%-1.7%; Preferably, after the self-compacting concrete special admixture is mixed with the concrete, the water-binder ratio is 0.3-0.35.
[0019] By adopting the above technical scheme, the admixture prepared by the application is added to the concrete, and the content and the water-binder ratio are controlled, so that the high fluidity of the concrete can be maintained while reducing the water consumption, the development of the slurry structure in the early hydration stage is controlled, the working performance of the concrete is prevented from deteriorating during transportation or waiting for pouring, sufficient "suspension force" and "cohesion" are provided to stabilize the aggregate and the slurry while maintaining high fluidity, and the post-set bleeding phenomenon is reduced.
[0020] The application has the following beneficial effects: The polycarboxylic acid water reducing agent and the slump retaining water reducing agent are compounded to form a water reducing agent component, so that the freshly mixed concrete maintains good construction performance within a certain time, and the slump retaining capacity of the concrete itself is improved. The polycarboxylic acid water reducing agent has water reducing and initial slump retaining performance. The polycarboxylic acid water reducing agent has a high side chain density and a long side chain, and also has a certain amount of sulfonic acid groups. Through the steric hindrance effect of the side chain, the cement particle agglomeration is prevented, and the dispersion effect is maintained. However, due to the continuous hydration of the cement, the polycarboxylic acid water reducing agent molecules adsorbed on the surface of the cement are continuously consumed, which causes the slump and the spread of the freshly mixed concrete to be lost over time. At this time, the slow release of the slump retaining water reducing agent molecules makes the water reducing agent molecules continuously supplement the concrete slurry. The ester groups in the slump retaining water reducing agent molecule structure can be continuously converted into the adsorption groups of the polycarboxylic acid molecules over time, so that the polycarboxylic acid molecules in the water are slowly adsorbed, so that the cement slurry in the concrete continues to maintain a dispersed state, and the flow stability of the concrete in the construction process is ensured. Therefore, the polycarboxylic acid water reducing agent and the slump retaining water reducing agent have a synergistic effect.
[0021] In addition, the modified starch can expand and expand in water, play a viscosity increasing role, help to increase the water retaining capacity of the concrete, and at the same time, the hydrogen bonds between the molecules of the modified starch, the intramolecular hydrogen bonds and the hydrogen bonds between the water molecules interact to form molecular crosslinking, entanglement and bridge the cement particles, form a colloidal film in water, and adsorb on the surface of the cement particles to prevent the migration of water in the concrete, thereby improving the water retention of the concrete and enhancing the anti-segregation and stability of the concrete. DETAILED DESCRIPTION
[0022] The application will be further described in detail below in combination with examples.
[0023] In the following detailed description, some of the substances are shown in Table 1.
[0024] Table 1: Methylallyl polyoxyethylene ether Nantong Runfeng Petroleum Chemical Co., Ltd. Hydroxypolyethylene glycol acrylate Shaanxi Xingbei Aike Biological Technology Co., Ltd. Isopentenol polyoxyethylene ether Wuhan Kemik Biological Medicine Technology Co., Ltd. Modified starch Lingshou Judian Mining Co., Ltd. Polydimethylsiloxane Dow Corning 63148-62-9 Polyether-modified polydimethylsiloxane Hubei Langbowan Biological Medicine Co., Ltd. Preparation Example Preparation Example 1 Preparation of the polycarboxylic acid water reducing agent: At 30°C, 12 kg of methylallyl polyoxyethylene ether was added to 50 kg of water, stirred uniformly, and then 3.6 kg of hydroxyl polyethylene glycol acrylate, 2.1 kg of Tween-80, 0.9 kg of sulfosalicylic acid were added and stirred, the temperature was raised to 80°C, 0.3 kg of mercaptoacetic acid and 0.15 kg of ammonium persulfate were added, and stirred for 3 h, and then cooled to room temperature. The pH of the solution was adjusted to 6 to obtain the polycarboxylic acid water reducing agent.
[0025] Preparation Example 2 Preparation of the polycarboxylic acid water reducing agent: At 35°C, 13.5 kg of methyl allyl polyoxyethylene ether was added to 50 kg of water, stirred uniformly, then 3.9 kg of hydroxyl polyethylene glycol acrylate, 2.7 kg of Tween-80, 1.2 kg of sulfosalicylic acid were mixed and stirred, heated to 85°C, 0.45 kg of mercaptoacetic acid and 0.18 kg of ammonium persulfate were added, stirred for 3.5 h, cooled to room temperature, and the solution pH was adjusted to 7 to obtain a polycarboxylic acid water reducer.
[0026] Preparation Example 3 Preparation of polycarboxylic acid water reducer: At 40°C, 15 kg of methyl allyl polyoxyethylene ether was added to 50 kg of water, stirred uniformly, then 4.2 kg of hydroxyl polyethylene glycol acrylate, 3.3 kg of Tween-80, 1.5 kg of sulfosalicylic acid were mixed and stirred, heated to 90°C, 0.6 kg of mercaptoacetic acid and 0.21 kg of ammonium persulfate were added, stirred for 4 h, cooled to room temperature, and the solution pH was adjusted to 8 to obtain a polycarboxylic acid water reducer.
[0027] Preparation Example 4 The difference between this preparation example and Preparation Example 2 is that an equal amount of oleic acid is used instead of Tween-80.
[0028] Preparation Example 5 The difference between this preparation example and Preparation Example 2 is that no sulfosalicylic acid is added.
[0029] Preparation Example 6 Preparation of slump retention type water reducer: At 30°C, 9 kg of isopentenyl alcohol polyoxyethylene ether was added to 50 kg of water, stirred uniformly, then 7.5 kg of acrylic acid, 3 kg of maleic acid dimethyl ester were mixed and stirred, heated to 80°C, 0.18 kg of mercaptopropionic acid and 0.09 kg of potassium persulfate were added, stirred for 3 h, cooled to room temperature, and the solution pH was adjusted to 6 to obtain a slump retention type water reducer.
[0030] Preparation Example 7 Preparation of slump retention type water reducer: At 35°C, 10.5 kg of isopentenyl alcohol polyoxyethylene ether was added to 50 kg of water, stirred uniformly, then 9 kg of acrylic acid, 3.6 kg of itaconic acid dimethyl ester were mixed and stirred, heated to 85°C, 0.21 kg of mercaptopropionic acid and 0.12 kg of potassium persulfate were added, stirred for 3.5 h, cooled to room temperature, and the solution pH was adjusted to 7 to obtain a slump retention type water reducer.
[0031] Preparation Example 8 Preparation of slump retention type water reducer: At 40℃, 12kg of isopentenyl alcohol polyoxyethylene ether was added into 50kg of water, stirred uniformly, then 10.5kg of acrylic acid, 4.5kg of dimethyl fumarate were mixed and stirred, heated to 90℃, 0.24kg of mercaptopropionic acid and 0.15kg of potassium persulfate were added, stirred for 4h, cooled to room temperature, the solution pH was adjusted to 8, to obtain a slump retaining water reducing agent.
[0032] Preparation Example 9 The difference between this preparation example and Preparation Example 7 is that an equal amount of monomethyl itaconate is used instead of dimethyl itaconate.
[0033] Preparation Example 10 The difference between this preparation example and Preparation Example 7 is that an equal amount of acrylic acid is used instead of dimethyl itaconate. Example
[0034] Example 1 A self-compacting concrete special additive, comprising: 11kg of polycarboxylate superplasticizer (prepared in Preparation Example 1), 6.5kg of slump retaining water reducing agent (prepared in Preparation Example 6), 0.1kg of modified starch, 0.04kg of polydimethylsiloxane, 0.016kg of sodium dodecyl sulfate, 23kg of water.
[0035] The preparation method of the self-compacting concrete special additive in this example comprises the following steps: The polycarboxylate superplasticizer, the slump retaining water reducing agent, the modified starch, and the water are mixed and stirred uniformly, the polydimethylsiloxane is added and stirred until dispersed uniformly, the sodium dodecyl sulfate is added and stirred until dispersed uniformly, to obtain the self-compacting concrete special additive.
[0036] Example 2 A self-compacting concrete special additive, comprising: 12kg of polycarboxylate superplasticizer (prepared in Preparation Example 2), 7kg of slump retaining water reducing agent (prepared in Preparation Example 7), 0.2kg of modified starch, 0.05kg of polyether modified polydimethylsiloxane, 0.02kg of sodium dodecyl sulfate, 25kg of water.
[0037] The preparation method of the self-compacting concrete special additive in this example comprises the following steps: The polycarboxylate superplasticizer, the slump retaining water reducing agent, the modified starch, and the water are mixed and stirred uniformly, the polyether modified polydimethylsiloxane is added and stirred until dispersed uniformly, the sodium dodecyl sulfate is added and stirred until dispersed uniformly, to obtain the self-compacting concrete special additive.
[0038] Example 3 A special admixture for self-compacting concrete, comprising: 13 kg of polycarboxylate superplasticizer (prepared in Preparation Example 3), 7.5 kg of slump retaining superplasticizer (prepared in Preparation Example 8), 0.3 kg of modified starch, 0.06 kg of polyether modified polydimethylsiloxane, 0.024 kg of sodium dodecyl benzene sulfonate, 27 kg of water.
[0039] In the present embodiment, the preparation method of the special admixture for self-compacting concrete comprises the following steps: The polycarboxylate superplasticizer, the slump retaining superplasticizer, the modified starch, and the water are mixed and stirred uniformly, the polyether modified polydimethylsiloxane is added and stirred until dispersed uniformly, the sodium dodecyl benzene sulfonate is added and stirred until dispersed uniformly, and the special admixture for self-compacting concrete is obtained.
[0040] Example 4 The difference between the present embodiment and Example 2 is that the slump retaining superplasticizer prepared in Preparation Example 9 is used.
[0041] Comparative Example Comparative Example 1 A special admixture for self-compacting concrete, which differs from Example 2 in that the polycarboxylate superplasticizer prepared in Preparation Example 4 is used.
[0042] Comparative Example 2 A special admixture for self-compacting concrete, which differs from Example 2 in that the polycarboxylate superplasticizer prepared in Preparation Example 5 is used.
[0043] Comparative Example 3 A special admixture for self-compacting concrete, which differs from Example 2 in that the slump retaining superplasticizer prepared in Preparation Example 10 is used.
[0044] Comparative Example 4 A special admixture for self-compacting concrete, which differs from Example 2 in that no polycarboxylate superplasticizer is added.
[0045] Comparative Example 5 A special admixture for self-compacting concrete, which differs from Example 2 in that no slump retaining superplasticizer is added.
[0046] Comparative Example 6 A special admixture for self-compacting concrete, which differs from Example 2 in that no polyether modified polydimethylsiloxane is added.
[0047] Comparative Example 7 A special admixture for self-compacting concrete, which differs from Example 2 in that no sodium dodecyl sulfonate is added.
[0048] Performance detection test The self-compacting concrete special additive prepared in Examples 1-4 and Comparative Examples 1-7 is applied to the concrete, and the corresponding concrete is detected.
[0049] 1. Cement paste fluidity test: The cement paste fluidity test is prepared according to the relevant standards of GB / T 8077-2023. Among them, the cement used is 100 kg, PO.42.5, Hebei Yannian Building Material Company Drilling Brand; the water-binder ratio is 0.32; the self-compacting concrete special additive dosage is 1.5%. The test results are shown in Table 2.
[0050] Table 2: 1. Concrete test: The reference concrete is prepared according to the relevant provisions of GB / T 8077-2023, and the proportioning meets the requirements of JGJ55. The cement used is PO.42.5, Hebei Yannian Building Material Company Drilling Brand; the apparent density of the sand used is 2.61g / cm3, the fineness modulus is 2.53, and the clay content is 1.7%; the selected stone is 5mm-24mm crushed stone, the apparent density is 2.68g / cm 3 , the bulk density is 1.44g / cm 3 , the two gradations of small stones (5mm-10mm) and large stones (10mm-24mm) are used, and the fly ash used is grade II fly ash. The mixing of the concrete meets the requirements of JG 3036.
[0051] Among them, the mix proportion of the reference concrete in this test is as follows Table 3: Table 3: Reference concrete proportioning Water-binder ratio: 0.32 Self-compacting concrete special additive dosage: 1.5%.
[0052] The self-compacting concrete special additive prepared in Examples 1-4 and Comparative Examples 1-7 is applied to the concrete prepared above, and the corresponding concrete is detected, and the results are recorded in Table 4.
[0053] 3. Compressive strength test: The influence of polycarboxylate superplasticizer in Examples 1-4 and Comparative Examples 1-7 on the strength of concrete is tested. Among them, the dosage of self-compacting concrete special additive is 1.5%, which is added to the reference concrete, and the specific test method is tested according to the provisions in GB / T50081-2019, and the test results of compressive strength are recorded in Table 4.
[0054] Table 4: According to the comparison of Example 2 and Example 4 and the data in Table 2 and Table 4, it can be known that the hydrolysis rate of carboxylic acid diglyceride is lower than that of carboxylic acid monoglyceride, and the slow-release dispersion effect of dimethyl itaconate is better than that of monomethyl itaconate, so the fluidity retention effect and slump retention performance in Example 2 are better than those in Example 4.
[0055] According to the comparison of Example 2 and Comparative Example 1 and the data in Table 2 and Table 4, it can be known that Tween-80 has a long polyoxyethylene chain in the molecular structure, has strong polarity, and can form hydrogen bonds with water, while the oil acid molecule only contains one carboxyl group as the hydrophilic end, but the hydrophobic effect of the long hydrocarbon chain dominates, resulting in the molecule tending to aggregate or float on the water surface, and being difficult to disperse in water, so the water-reducing performance and slump retention performance are poor. The Tween-80 of the application has a polyoxyethylene chain structure and a long fatty chain structure, which can increase the side chain length of the polycarboxylic acid water reducer molecule, and has a synergistic effect with sulfosalicylic acid, increasing the steric hindrance effect of the polycarboxylic acid water reducer, so that the polycarboxylic acid water reducer has excellent water-reducing and initial slump retention performance in self-compacting concrete.
[0056] According to the comparison of Example 2 and Comparative Example 2 and the data in Table 2 and Table 4, it can be known that the sulfosalicylic acid molecule contains a sulfonic acid group, which is negatively charged in water and adsorbed on the surface of cement particles, causing electrostatic repulsion between particles, and the sulfonic acid group has a synergistic effect with the polyether side chain, forming a physical barrier between the cement particles through the long chain molecules, reducing the re-aggregation of particles, effectively maintaining the dispersion state of the cement slurry, and reducing the loss of concrete fluidity during construction.
[0057] According to the comparison of Example 2 and Comparative Example 3 and the data in Table 2 and Table 4, it can be known that acrylic acid does not contain an ester group, and dimethyl itaconate molecule contains a double ester group. The ester group can continuously change into the adsorption group of the water reducing agent molecule over time, so that the free water reducing agent molecule in water is slowly adsorbed, so that the cement slurry in concrete continues to maintain a dispersed state, ensuring the flow stability of concrete during construction.
[0058] According to the comparison of the embodiment 2 and the comparative examples 4-5 and the data in the table 2 and the table 4, it can be known that the polycarboxylic water reducing agent and the slump retaining water reducing agent have a synergistic effect. The polycarboxylic water reducing agent has water reducing and initial slump retaining performance. The polycarboxylic water reducing agent has a large side chain density, a long side chain and a certain sulfonic acid group. Through the steric hindrance effect of the side chain, the cement particle agglomeration is prevented and the dispersion effect is maintained. The slow release effect of the slump retaining water reducing agent molecule makes the water reducing agent molecules released by itself constantly supplement the concrete slurry. The ester group in the slump retaining water reducing agent molecule structure can be constantly converted into the adsorption group of the water reducing agent molecule with time, so that the free water reducing agent molecules in the water are slowly adsorbed, the cement slurry in the concrete is kept in a dispersed state, and the flow stability of the concrete in the construction process is ensured.
[0059] According to the comparison of the embodiment 2 and the comparative examples 6-7 and the data in the table 2 and the table 4, it can be known that the defoaming agent and the air entraining agent have a synergistic effect. The method of eliminating large bubbles first and then introducing small bubbles is adopted. The poor quality bubbles in the concrete are eliminated, and the bubbles with small diameter and uniform distribution are introduced, so that the quality of the bubbles in the concrete reaches the best state.
[0060] The specific embodiment is only an explanation of the application, and is not a limitation of the application. Those skilled in the art can make modifications to the specific embodiment without creative contribution after reading the specification, but as long as the modifications are within the scope of the claims of the application, they are protected by the patent law.
Claims
1. A special admixture for self-compacting concrete, characterized in that: The invention is prepared from the following raw materials in parts by weight: 110-130 parts of polycarboxylate water reducer, 65-75 parts of slump-retaining water reducer, 1-3 parts of modified starch, 0.4-0.6 parts of defoamer, 0.16-0.24 parts of air entraining agent, 230-270 parts of water; The raw materials for preparing the polycarboxylate water reducer include, by weight: 12-15 parts of methyl allyl polyoxyethylene ether, 3.6-4.2 parts of hydroxy polyethylene glycol acrylate, 2.1-3.3 parts of Tween-80, 0.9-1.5 parts of sulfosalicylic acid, 0.3-0.6 parts of thioglycolic acid, and 0.15-0.21 parts of ammonium persulfate; The raw materials for preparing the slump-retaining water reducer include, by weight, 9-12 parts of isopentanol polyoxyethylene ether, 7.5-10.5 parts of acrylic acid, 3-4.5 parts of ester monomers, 0.18-0.24 parts of mercaptopropionic acid, and 0.09-0.15 parts of potassium persulfate.
2. A special admixture for self-compacting concrete according to claim 1, characterized in that: The preparation method of the polycarboxylate water-reducing agent comprises the following steps: At 30-40°C, add methyl allyl polyoxyethylene ether into water, stir evenly, then add hydroxy polyethylene glycol acrylate, Tween-80, and sulfosalicylic acid, mix and stir, heat to 80-90°C, add thioglycolic acid and ammonium persulfate, stir and react for 3-4 hours, cool to room temperature, and adjust the pH of the solution to 6-8 to obtain a polycarboxylate water reducer.
3. A special admixture for self-compacting concrete according to claim 1, characterized in that: The preparation method of the slump-retaining water-reducing agent comprises the following steps: At 30-40°C, add isopentanol polyoxyethylene ether into water, stir evenly, then add acrylic acid and ester monomers and mix and stir. Heat to 80-90°C, add mercaptopropionic acid and potassium persulfate, stir and react for 3-4 hours, cool to room temperature, adjust the solution pH to 6-8, and obtain a slump-retaining water reducer.
4. A special admixture for self-compacting concrete according to claim 1, characterized in that: The ester monomer is selected from one or more of dimethyl maleate, dimethyl itaconate, and dimethyl fumarate.
5. A special admixture for self-compacting concrete according to claim 1, characterized in that: The defoaming agent is selected from one or both of an organic silicon defoaming agent and a polyether modified silicone oil defoaming agent.
6. A special admixture for self-compacting concrete according to claim 1, characterized in that: The air entraining agent is one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate.
7. A method for preparing a special admixture for self-compacting concrete according to any one of claims 1 to 6, characterized in that: The following steps are involved: The polycarboxylate water reducer, the slump-retaining water reducer, the modified starch and water are mixed and stirred evenly. A defoamer is added and stirred until the mixture is evenly dispersed. An air entraining agent is added and stirred until the mixture is evenly dispersed to obtain a special admixture for self-compacting concrete.
8. Application of a special admixture for self-compacting concrete, characterized in that: The special admixture for self-compacting concrete according to any one of claims 1 to 6 is mixed with concrete for use.
9. The use of a special admixture for self-compacting concrete according to claim 8, characterized in that: The dosage of the special admixture for self-compacting concrete is 1.3%-1.7%.
10. The use of a special admixture for self-compacting concrete according to claim 8, characterized in that: After the self-compacting concrete special admixture is mixed with concrete, the water-binder ratio is 0.3-0.35.