Concrete viscosity modifier as well as preparation method and application thereof

Abstract

The invention relates to a concrete viscosity modifier as well as a preparation method and application of the concrete viscosity modifier. Comprising 15-20 parts of an agricultural waste-based water reducing agent, 1-3 parts of a polycarboxylic acid water reducing agent, 5-8 parts of polyacrylamide, 3-7 parts of silica fume, 5-10 parts of fly ash, 12-18 parts of superfine limestone powder, 2-8 parts of calcium sulfate and 40-50 parts of deionized water. Wherein the agricultural waste-based water reducing agent is obtained by taking pistachio nut shells as raw materials, performing solvent extraction to obtain an extract, and performing sulfonation modification treatment on the extract. The agricultural waste-based water reducing agent is obtained by taking pistachio shells as a raw material, extracting the pistachio shells with the propyl alcohol-ethyl alcohol mixed solvent and performing sulfonation modification treatment, so that the bleeding rate is reduced, the working performance of concrete is effectively improved, good balance of water retention and fluidity is realized, and the water-retaining property and the flowability of the concrete are improved. And the compressive strength and freeze-thaw resistance of the concrete can be improved, and the concrete is durable.

Description

Technical Field

[0001] This invention belongs to the field of concrete additives technology, specifically relating to a concrete viscosity modifier, its preparation method, and its application. Background Technology

[0002] Concrete, as one of the most important building materials in modern construction engineering, directly affects the quality and service life of projects due to its workability, mechanical properties, and durability. With the rapid development of construction technology, high-rise, large-span, and high-performance concrete structures place higher demands on the fluidity, water retention, volume stability, and hardened strength and durability of concrete mixtures. Concrete viscosity modifiers, as key functional admixtures, can effectively regulate the rheological properties of mixtures, improving workability while significantly influencing the mechanical and durability properties of hardened concrete. Currently, concrete viscosity modifiers mainly rely on traditional water-reducing agent systems, including naphthalene-based, melamine-based, and polycarboxylate-based water-reducing agents. Among them, polycarboxylate-based water-reducing agents have become the mainstream product in the market due to their high water reduction rate, low dosage, and good slump retention performance. However, polycarboxylate-based water-reducing agents have a high air content during production, which can affect the strength of concrete when used directly. Currently, a complex process of "defoaming first, then air induction" is required to control this, increasing the technical difficulty. To overcome these problems, this invention provides a concrete viscosity modifier, its preparation method, and its application. Summary of the Invention

[0003] The purpose of this invention is to provide a concrete viscosity modifier, its preparation method, and its application in order to solve the above-mentioned problems.

[0004] The present invention achieves the above objectives through the following technical solutions: A concrete viscosity modifier, wherein the raw materials for preparing the concrete viscosity modifier, by weight, include 15-20 parts of agricultural waste-based water-reducing agent, 1-3 parts of polycarboxylate-based water-reducing agent, 5-8 parts of polyacrylamide, 3-7 parts of silica fume, 5-10 parts of fly ash, 12-18 parts of ultrafine limestone powder, 2-8 parts of calcium sulfate, and 40-50 parts of deionized water. The agricultural waste-based water-reducing agent is obtained by solvent extraction of pistachio shells, followed by sulfonation modification of the extract.

[0005] As a further optimization of the present invention, the method for obtaining the agricultural waste-based water-reducing agent includes soaking the cleaned, dried, crushed and sieved pistachio shells in a propanol-ethanol mixed solvent or deionized water, extracting them at 200-260℃ and 10-25MPa for 30-60 minutes to obtain an extract solution, evaporating and concentrating the extract solution to 10-20% of its original volume, and then freeze-drying it under vacuum to obtain extract one. The propanol-ethanol mixed solvent is obtained by mixing propanol and ethanol in a volume ratio of 7:3.

[0006] As a further optimization of the present invention, the method for obtaining the agricultural waste-based water-reducing agent further includes collecting the solid residue after extraction, grinding it evenly, adding 0.1-0.3M sulfuric acid solution, with a solid-liquid ratio of 1:10-20, keeping it at 80-90°C for 2-4 hours with continuous stirring, and after the reaction is completed, obtaining the filtrate by vacuum filtration, adjusting the pH of the filtrate to 1.5-2.0, letting it stand at 2-6°C for 18-24 hours, centrifuging, washing, and vacuum freeze-drying to obtain extract two.

[0007] As a further optimization of the present invention, the sulfonation modification treatment specifically involves preparing a 50-60wt% lignin aqueous solution by mixing the above-mentioned extract one / extract one and extract two at a mass ratio of (1-2):(1-2), adjusting the pH of the lignin aqueous solution to 12-14, adding dihydroxyacetone, reacting at 70-95℃ for 1-2 hours, adding a sulfonating agent, reacting at 80-100℃ for 3-5 hours, adjusting its pH to 7-8, and cooling to room temperature to obtain an agricultural waste-based water-reducing agent.

[0008] As a further optimization of the present invention, the mass ratio of lignin to dihydroxyketone is 1:3-5, and the mass ratio of lignin to sulfonating agent is 1:0.5-2.

[0009] As a further optimization of the present invention, the sulfonating agent is at least one of sodium sulfite and sodium metabisulfite.

[0010] As a further optimization of the present invention, the diameter of the ultrafine limestone powder is 5-10µm.

[0011] This invention also provides a method for preparing a concrete viscosity modifier, wherein an agricultural waste-based water-reducing agent, a polycarboxylate-based water-reducing agent, polyacrylamide, silica fume, fly ash, ultrafine limestone powder, calcium sulfate, and deionized water are mixed evenly and then sprayed and granulated to obtain the concrete viscosity modifier.

[0012] The present invention also provides an application of a concrete viscosity modifier in concrete, wherein the amount of the concrete viscosity modifier added to the concrete system is 0.3-6% of the cement content.

[0013] The beneficial effects of this invention are as follows: 1) This invention adds an agricultural waste-based water-reducing agent obtained by extracting pistachio shells with a propanol-ethanol mixed solvent and sulfonating them to a concrete viscosity modifier system. This can reduce the bleeding rate while effectively improving the workability (slump and spread) of concrete, achieving a good balance between water retention and fluidity. It can also improve the compressive strength and freeze-thaw resistance of concrete, making it durable. 2) The present invention obtains extract II by collecting the solid residue after extraction and treating it with sulfuric acid solution. When combined with the extract obtained by direct extraction in a specific ratio, the effect is optimal.

[0014] 3) The concrete viscosity modifier prepared by this invention has the effect of promoting cement hydration reaction and accelerating early strength development. This characteristic is suitable for engineering occasions that require rapid construction, early demolding, and winter construction, which have early strength requirements; 4) The agricultural waste-based water-reducing agent prepared by this invention using propanol and ethanol as extraction solvents and compounding extract one and extract two has the effect of significantly improving the freeze-thaw resistance of concrete, and the mass loss rate is small in the subsequent 200-500 freeze-thaw cycles, indicating that it has good durability. Detailed Implementation

[0015] The present application will now be described in further detail. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0016] I. Materials 1. Polycarboxylate superplasticizer: purchased from Wuhan Lingjiayi Chemical Co., Ltd., purity 99%; 2. Ultrafine limestone powder: particle size 5-10µm; 3. Sulfonating agent: at least one of sodium sulfite and sodium metabisulfite. Sodium sulfite is used in all the following experiments of this invention. 4. Pistachio shell: from pistachio nuts ( Pistacia vera L. The shell after removing the seeds; Unless otherwise specified, the methods used in this embodiment are conventional methods known to those skilled in the art, and the reagents and materials used are commercially available products.

[0017] II. Methods Example 1 In this embodiment, a raw material for preparing a concrete viscosity modifier is provided, which, by weight, includes 15 parts of agricultural waste-based water-reducing agent, 3 parts of polycarboxylate-based water-reducing agent, 8 parts of polyacrylamide, 7 parts of silica fume, 10 parts of fly ash, 12 parts of ultrafine limestone powder, 2 parts of calcium sulfate, and 43 parts of deionized water.

[0018] The specific steps for preparing this concrete viscosity modifier are as follows: Step 1: Soak the cleaned, dried, crushed and sieved pistachio shells in deionized water and extract them at 245℃ and 21.5MPa for 35 minutes to obtain an extract solution. Evaporate and concentrate the extract solution to 12% of its original volume, and then freeze-dry it under vacuum to obtain extract one. Step 2: Prepare a 56wt% lignin aqueous solution from the above extract, adjust the pH of the lignin aqueous solution to 13.2, add dihydroxyacetone, react at 85℃ for 1.5h, add sulfonating agent (sodium sulfite), react at 90℃ for 4h, adjust its pH to 7.6, and cool to room temperature to obtain agricultural waste-based water-reducing agent. Step 3: Mix agricultural waste-based water-reducing agent, polycarboxylate-based water-reducing agent, polyacrylamide, silica fume, fly ash, ultrafine limestone powder, calcium sulfate, and deionized water evenly, then spray granulate to obtain concrete viscosity modifier.

[0019] Example 2 In this embodiment, a raw material for preparing a concrete viscosity modifier is provided, which, by weight, includes 18 parts of agricultural waste-based water-reducing agent, 2 parts of polycarboxylate-based water-reducing agent, 6 parts of polyacrylamide, 5 parts of silica fume, 7 parts of fly ash, 16 parts of ultrafine limestone powder, 4 parts of calcium sulfate, and 42 parts of deionized water. The specific preparation methods are consistent with those in Example 1.

[0020] Example 3 In this embodiment, a raw material for preparing a concrete viscosity modifier is provided, which, by weight, includes 20 parts of agricultural waste-based water-reducing agent, 1 part of polycarboxylate-based water-reducing agent, 5 parts of polyacrylamide, 3 parts of silica fume, 5 parts of fly ash, 18 parts of ultrafine limestone powder, 8 parts of calcium sulfate, and 40 parts of deionized water. The specific preparation methods are consistent with those in Example 1.

[0021] Example 4 In this embodiment, the preparation method of the concrete viscosity modifier was adjusted based on the raw materials used in Example 2. The specific steps after adjustment are as follows: Step 1: Soak the cleaned, dried, crushed and sieved pistachio shells in deionized water and extract them at 245℃ and 21.5MPa for 35 minutes to obtain an extract solution. Evaporate and concentrate the extract solution to 12% of its original volume, and then freeze-dry it under vacuum to obtain extract one. Step 2: Collect the solid residue after extraction, grind it evenly, add 0.15M sulfuric acid solution, the solid-liquid ratio is 1:15, keep it at 82°C for 2.5h with constant stirring. After the reaction is completed, vacuum filter to obtain filtrate, adjust the pH of the filtrate to 1.7, let it stand at 4°C for 20h, centrifuge, wash, and freeze dry under vacuum to obtain extract two. Step 3: Mix extract one and extract two at a mass ratio of 1:1 to prepare a 56wt% lignin aqueous solution. Adjust the pH of the lignin aqueous solution to 13.2, add dihydroxyacetone, react at 85℃ for 1.5h, add sulfonating agent (sodium sulfite), react at 90℃ for 4h, adjust the pH to 7.6, and cool to room temperature to obtain an agricultural waste-based water-reducing agent. Step 4: Mix agricultural waste-based water-reducing agent, polycarboxylate-based water-reducing agent, polyacrylamide, silica fume, fly ash, ultrafine limestone powder, calcium sulfate, and deionized water evenly, then spray granulate to obtain concrete viscosity modifier.

[0022] Example 5 In this embodiment, based on the raw materials for preparing the concrete viscosity modifier of Example 2, the preparation method of the concrete viscosity modifier has been adjusted. The specific steps after adjustment are as follows: Step 1: After cleaning, drying, crushing and sieving, pistachio shells are soaked in a propanol-ethanol mixed solvent (obtained by mixing propanol and ethanol in a volume ratio of 7:3) and extracted at 245℃ and 21.5MPa for 35 minutes to obtain an extract solution. The extract solution is evaporated and concentrated to 12% of its original volume, and then freeze-dried under vacuum to obtain extract one. Step 2: Prepare a 56wt% lignin aqueous solution from the above extract, adjust the pH of the lignin aqueous solution to 13.2, add dihydroxyacetone, react at 85℃ for 1.5h, add sulfonating agent (sodium sulfite), react at 90℃ for 4h, adjust the pH to 7.6, and cool to room temperature to obtain an agricultural waste-based water-reducing agent. Step 3: Mix agricultural waste-based water-reducing agent, polycarboxylate-based water-reducing agent, polyacrylamide, silica fume, fly ash, ultrafine limestone powder, calcium sulfate, and deionized water evenly, then spray granulate to obtain concrete viscosity modifier.

[0023] Example 6 In this embodiment, based on the raw materials for preparing the concrete viscosity modifier of Example 2, the preparation method of the concrete viscosity modifier has been adjusted. The specific steps after adjustment are as follows: Step 1: After cleaning, drying, crushing and sieving, pistachio shells are soaked in a propanol-ethanol mixed solvent (obtained by mixing propanol and ethanol in a volume ratio of 7:3) and extracted at 245℃ and 21.5MPa for 35 minutes to obtain an extract solution. The extract solution is evaporated and concentrated to 12% of its original volume, and then freeze-dried under vacuum to obtain extract one. Step 2: Collect the solid residue after extraction, grind it evenly, add 0.15M sulfuric acid solution, the solid-liquid ratio is 1:15, keep it at 82°C for 2.5h with constant stirring. After the reaction is completed, vacuum filter to obtain filtrate, adjust the pH of the filtrate to 1.7, let it stand at 4°C for 20h, centrifuge, wash, and freeze dry under vacuum to obtain extract two. Step 3: Mix extract one and extract two at a mass ratio of 1:1 to prepare a 56wt% lignin aqueous solution. Adjust the pH of the lignin aqueous solution to 13.2, add dihydroxyacetone, react at 85℃ for 1.5h, add sulfonating agent (sodium sulfite), react at 90℃ for 4h, adjust the pH to 7.6, and cool to room temperature to obtain an agricultural waste-based water-reducing agent. Step 4: Mix agricultural waste-based water-reducing agent, polycarboxylate-based water-reducing agent, polyacrylamide, silica fume, fly ash, ultrafine limestone powder, calcium sulfate, and deionized water evenly, then spray granulate to obtain concrete viscosity modifier.

[0024] Example 7 In this embodiment, based on the raw materials for preparing the concrete viscosity modifier of Example 6, the mass ratio of extract one and extract two in step 3 of the concrete viscosity modifier preparation method is adjusted to 2:1. The remaining preparation methods are consistent with those in Example 6.

[0025] Example 8 In this embodiment, based on the raw materials for preparing the concrete viscosity modifier of Example 6, the mass ratio of extract one and extract two in step 3 of the concrete viscosity modifier preparation method is adjusted to 1:2. The remaining preparation methods are consistent with those in Example 6.

[0026] Comparative Example 1 In this comparative example, based on the raw materials for preparing the concrete viscosity modifier of Example 6, the pistachio shells and other materials in step 1 of the concrete viscosity modifier preparation method were adjusted to sugarcane bagasse. The remaining preparation methods are consistent with those in Example 6.

[0027] Comparative Example 2 In this comparative example, based on the raw materials for preparing the concrete viscosity modifier of Example 6, the pistachio shells and other materials in step 1 of the concrete viscosity modifier preparation method were adjusted to wheat straw. The remaining preparation methods are consistent with those in Example 6.

[0028] Blank group In this comparative example, a raw material for preparing a concrete viscosity modifier is provided, which, by weight, includes 18 parts of polycarboxylate superplasticizer, 8 parts of polyacrylamide, 7 parts of silica fume, 10 parts of fly ash, 12 parts of ultrafine limestone powder, 2 parts of calcium sulfate, and 43 parts of deionized water. The concrete viscosity modifier is prepared by mixing polycarboxylate superplasticizer, polyacrylamide, silica fume, fly ash, ultrafine limestone powder, calcium sulfate, and deionized water evenly, followed by spray granulation to obtain the concrete viscosity modifier.

[0029] III. Experimental Testing The concrete viscosity modifier was added to the following concrete systems at a dosage of 0.3-6% of the cement weight. With the other component proportions remaining unchanged, the concrete viscosity modifier in Examples 1-8, Comparative Examples 1-2, and the blank group was added at 1.5% of the cement weight (i.e., a dosage of 3.3 kg / m³). 3 The concrete mix composition used in this experiment is shown in Table 1 (unit: kg / m³). 3 Table 1. Concrete System Batching Table ; Note: The particle size of the pebbles is 5-25mm; (1) Tests on bleeding rate, slump, and spread The experiment was conducted according to the test methods in GB / T 50080-2016 Standard for Test Methods of Performance of Ordinary Concrete Mixtures. The bleeding rate (pressure bleeding test), slump, and spread of the concrete samples from Examples 1-8, Comparative Examples 1-2, and the blank group were tested. The test results are shown in Table 2: Table 2: Experimental Data Recording Table for Bleeding Rate, Slump, and Spread ; Experimental conclusion: This invention, by adding an agricultural waste-based water-reducing agent obtained from pistachio shells through extraction with a propanol-ethanol mixed solvent and sulfonation modification to a concrete viscosity modifier system, can effectively improve the workability (slump and spread) of concrete while reducing bleeding rate, achieving a good balance between water retention and fluidity. The optimal effect is achieved when the second extract obtained by collecting the solid residue after extraction and treating it with sulfuric acid solution is combined with the extract obtained from direct extraction in a specific ratio.

[0030] (2) Compressive strength test The 7-day and 28-day compressive strengths of concrete samples from Examples 1-8, Comparative Examples 1-2, and the blank group were tested using a GHT450 rebound hammer. The test results are shown in Table 3: Table 3 Compressive Strength Test Data Recording Table ; Experimental conclusions: Based on the data analysis in Table 3, it can be seen that the compound concrete viscosity modifier prepared by this invention can significantly improve the compressive strength of concrete. In Examples 5-6, the difference between the 7-day compressive strength and the 28-day compressive strength is small, indicating that the concrete strength development rate is fast and the early strength is high. This shows that the compound concrete viscosity modifier in Examples 5-6 has the effect of promoting cement hydration reaction and accelerating early strength development. This characteristic is suitable for engineering occasions that require rapid construction, early demolding, winter construction, etc., which have early strength requirements.

[0031] (3) Freeze-thaw resistance test The experiment was conducted according to the test method (rapid freezing method) of GB / T 50082-2024 Standard for Test Methods of Long-Term Performance and Durability of Concrete. Concrete samples from Examples 1-8, Comparative Examples 1-2, and the blank group were tested. The test results are shown in Table 4, as detailed below: Table 4: Record of Experimental Data on Freeze-Thaw Resistance ; Experimental Conclusion: Based on the data analysis in Table 4, the compound concrete viscosity modifier prepared in this invention is more effective in improving the freeze-thaw resistance of concrete compared to a single polycarboxylate superplasticizer. Example 6 shows the best effect, indicating that the agricultural waste-based superplasticizer prepared by combining extract one and extract two using propanol and ethanol as extraction solvents significantly improves the freeze-thaw resistance of concrete, and exhibits low mass loss during subsequent 200-500 freeze-thaw cycles, indicating good durability. The above examples only illustrate several implementation methods of this invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this invention, and these all fall within the scope of protection of this invention.

Claims

1. A concrete viscosity modifier, characterized in that: The raw materials for preparing the concrete viscosity modifier, by weight, include 15-20 parts of agricultural waste-based water-reducing agent, 1-3 parts of polycarboxylate-based water-reducing agent, 5-8 parts of polyacrylamide, 3-7 parts of silica fume, 5-10 parts of fly ash, 12-18 parts of ultrafine limestone powder, 2-8 parts of calcium sulfate, and 40-50 parts of deionized water. The agricultural waste-based water-reducing agent is obtained by solvent extraction of pistachio shells, followed by sulfonation modification of the extract.

2. The concrete viscosity modifier according to claim 1, characterized in that: The method for obtaining the agricultural waste-based water-reducing agent includes soaking the cleaned, dried, crushed, and sieved pistachio shells in a propanol-ethanol mixed solvent or deionized water, extracting them at 200-260℃ and 10-25MPa for 30-60 minutes to obtain an extract solution, evaporating and concentrating the extract solution to 10-20% of its original volume, and then freeze-drying it under vacuum to obtain extract one. The propanol-ethanol mixed solvent is obtained by mixing propanol and ethanol in a volume ratio of 7:

3.

3. The concrete viscosity modifier according to claim 1, characterized in that: The method for obtaining the agricultural waste-based water-reducing agent further includes collecting the solid residue after extraction, grinding it evenly, adding 0.1-0.3M sulfuric acid solution at a solid-liquid ratio of 1:10-20, keeping it at 80-90°C for 2-4 hours with continuous stirring, and after the reaction is completed, obtaining the filtrate by vacuum filtration, adjusting the pH of the filtrate to 1.5-2.0, letting it stand at 2-6°C for 18-24 hours, centrifuging, washing, and vacuum freeze-drying to obtain extract two.

4. The concrete viscosity modifier according to claim 1, characterized in that: The sulfonation modification process specifically involves preparing a 50-60 wt% lignin aqueous solution by mixing the above-mentioned extract one / extract one and extract two at a mass ratio of (1-2):(1-2), adjusting the pH of the lignin aqueous solution to 12-14, adding dihydroxyacetone, reacting at 70-95℃ for 1-2 hours, adding a sulfonating agent, reacting at 80-100℃ for 3-5 hours, adjusting the pH to 7-8, and cooling to room temperature to obtain an agricultural waste-based water-reducing agent.

5. The concrete viscosity modifier according to claim 4, characterized in that: The mass ratio of lignin to dihydroxyketone is 1:3-5, and the mass ratio of lignin to sulfonating agent is 1:0.5-2.

6. The concrete viscosity modifier according to claim 5, characterized in that: The sulfonating agent is at least one of sodium sulfite and sodium metabisulfite.

7. The concrete viscosity modifier according to claim 1, characterized in that: The particle size of the ultrafine limestone powder is 5-10µm.

8. A method for preparing a concrete viscosity modifier as described in any one of claims 1-7, characterized in that: A concrete viscosity modifier is obtained by uniformly mixing agricultural waste-based water-reducing agent, polycarboxylate-based water-reducing agent, polyacrylamide, silica fume, fly ash, ultrafine limestone powder, calcium sulfate, and deionized water, followed by spray granulation.

9. The application of a concrete viscosity modifier as described in any one of claims 1-7 in concrete, characterized in that: The concrete viscosity modifier is added to the concrete system at a rate of 0.3-6% of the cement content.