Powder accelerator master batch with high aluminum-sulfur ratio as well as preparation method and application of powder accelerator master batch

Abstract

The invention discloses a high-aluminum-sulfur-ratio powder accelerator master batch and a preparation method and application thereof.The preparation method comprises the steps that 1, an inorganic aluminum source and fluosilicic acid are blended and subjected to a closed reaction, meanwhile, concentrated sulfuric acid is dropwise added to promote the reaction to rapidly rise the temperature, and a reaction solution a is obtained while the molecular structure of the inorganic aluminum source is destroyed; 2, magnesium salt, a stabilizer and organic amine are added into the reaction liquid a prepared in the step 1, the reaction kettle is closed, a high-temperature pressure reaction is conducted, fluorine ions enter a product crystal phase under the high-temperature pressure condition, and a reaction liquid b is obtained; 3, the high-temperature reaction liquid b prepared in the step 2 is guided into a grinding and crushing device, natural cooling, drying, crushing and grinding are conducted, and a powder accelerator master batch with the high aluminum-sulfur ratio is prepared; the inorganic aluminum source comprises aluminum hydroxide and gamma-aluminum oxide. The accelerator is an organic-inorganic complex composite material, the aluminum-sulfur ratio is 1: 0.9-1: 1.3, and the accelerator has a strong fluorine ion curing effect, is high in product stability and has a remarkable effect of improving the strength of concrete.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixtures, and more specifically, this invention relates to a high aluminum-sulfur ratio powder accelerator masterbatch, its preparation method, and its application. Background Technology

[0002] In recent years, the field of alkali-free accelerators has developed rapidly, with a significant increase in the number of industry patents. However, due to transportation distance limitations, manufacturers have repeatedly compressed the performance of liquid alkali-free accelerators to control costs, leading to a decline in their overall performance, particularly in product stability and cement compatibility. In actual construction, to achieve the desired setting effect, construction sites often need to increase the dosage of liquid accelerators, resulting in a persistently high concrete rebound rate, increasing material waste and construction costs. Therefore, in comparison, powdered alkali-free accelerators show better application prospects. In-depth research on published patents and literature reveals that current powdered alkali-free accelerators, such as patents CN113264711A, CN117534362B, CN115677255B, and CN112142359B, all use compound formulations to prepare powdered accelerators, and no alkali-free powdered accelerator products prepared using a synthetic process have yet appeared. The compound formulations often contain soluble salts or organic phases, which result in a long dissolution time and poor product stability.

[0003] Currently, the main raw material for both liquid and powder alkali-free quick-setting agents is aluminum sulfate, and the aluminum sulfate content in these products is generally between 40% and 70%. With the continuous increase in aluminum sulfate content, excessive SO4²⁻ is introduced into the quick-setting agents. - This significantly increases the risk of secondary ettringite formation within the concrete. This problem not only leads to a loss of strength in the later stages of concrete development but may also trigger sulfate attack, severely impairing its long-term durability. Existing technologies to reduce sulfur content include patent CN113135689A, which uses a combination of multiple accelerators, including aluminum sulfate octadecylhydrate as the first accelerator component, aluminum dihydrogen phosphate as the second, and sodium aluminate as the third. This achieves a low-sulfur profile, but aluminum dihydrogen phosphate is prone to absorbing moisture and clumping, leading to unstable performance, and its high price limits its application. Patent CN111377649B uses aluminum nitrate instead of aluminum sulfate to achieve low sulfur content, but aluminum nitrate is a precursor to explosives, posing numerous production restrictions. Furthermore, the aforementioned low-sulfur accelerators are all in liquid form; if powder reprocessing is required, spray drying equipment is needed, and the homogeneity of the finished product cannot be guaranteed.

[0004] Therefore, the present invention aims to provide a novel high aluminum-to-sulfur ratio powder accelerator masterbatch to overcome the shortcomings of the prior art. Summary of the Invention

[0005] The core objective of this invention is to provide a high aluminum-to-sulfur ratio powdered accelerator masterbatch, its preparation method, and its application. Through a chemical synthesis process, an organic-inorganic complex composite material is obtained, with an aluminum-to-sulfur ratio between 1:0.9 and 1:1.3. Simultaneously, this product exhibits strong fluoride ion curing properties, significantly improving the strength of concrete.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a high aluminum-to-sulfur ratio powder accelerator masterbatch includes the following steps: Step 1: Inorganic aluminum source is mixed with fluorosilicic acid and reacted in a closed system. At the same time, concentrated sulfuric acid is added dropwise to promote rapid heating of the reaction, thereby destroying the molecular structure of the inorganic aluminum source and obtaining reaction solution a. Step 2: Add magnesium salt, stabilizer and organic amine to the reaction solution a obtained in step 1, seal the reaction vessel and react at high temperature and pressure. By allowing fluoride ions to enter the product crystal phase under high temperature and pressure, reaction solution b is obtained. Step 3: The high-temperature reaction liquid b obtained in Step 2 is introduced into a grinding and crushing device, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch. The inorganic aluminum source includes aluminum hydroxide and γ-alumina.

[0007] γ-alumina increases the aluminum content in the system, thereby improving the solidification and hardening effect of the product. Furthermore, compared to α-alumina, which is structurally stable and difficult to react, γ-alumina has a larger spatial structure, making it easier to introduce fluoride ions through Al-F bond formation, thus increasing the Al content. 3+ and F - With SO4 2- The proportion.

[0008] Preferably, the ratio of inorganic aluminum source to concentrated sulfuric acid is (50~78):(82~128); preferably, the mass ratio of inorganic aluminum source to fluorosilicic acid, magnesium salt, stabilizer and organic amine (by mass percentage) is (50~78):(58~230):(2~12):(3~26):(7~50).

[0009] Preferably, the reaction pressure in step 2 is between 0.1 and 0.6 MPa.

[0010] Preferably, the organic amine is an alcohol amine or a catecholamine, and more preferably one or more of diethanolamine, triethanolamine, triisopropanolamine, dopamine, and adrenaline.

[0011] Preferably, the stabilizer is any one or more of fumed silica, sepiolite, attapulgite, and hydrated magnesium silicate.

[0012] Preferably, the reaction temperature in step 2 is between 90 and 130°C.

[0013] Preferably, the reaction time in step 2 is 30~120 min.

[0014] Application of a high alumina-sulfur ratio powder accelerator masterbatch, wherein the high alumina-sulfur ratio powder accelerator masterbatch is added at an amount of 4-6% of the total mass of the cementitious material; Preferably, the high aluminum-sulfur ratio powder accelerator masterbatch is prepared as a liquid accelerator and added at a rate of 6-9% of the total mass of the cementitious material.

[0015] The dosage of high aluminum-sulfur ratio powder accelerator masterbatch and the liquid accelerator prepared therefrom shall refer to GB / T-35159.

[0016] Compared with the prior art, the solution of this invention has the following advantages: 1. The high aluminum-sulfur ratio powder quick-setting agent masterbatch prepared by the present invention has a particle size distribution of approximately 5~50 μm. It is an organic-inorganic complex composite material with the characteristics of low water solubility, high dispersibility, fast setting, early high strength, low sulfate corrosion hazard, and easy to use.

[0017] 2. The high aluminum-sulfur ratio powder quick-setting agent masterbatch prepared by the present invention has a strong fluoride ion curing effect, which reduces the adverse effects of free fluoride ions. While ensuring the fluoride ion's role in promoting coagulation, it can significantly improve strength and reduce the overall sulfate content, thus greatly reducing the risk of sulfate corrosion. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments.

[0019] Table 1: Proportions of each component in Examples 1-8 and Comparative Examples 1-7 Example 1: Step 1: Inorganic aluminum source is blended with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a1; Step 2: Add magnesium hydroxide, sepiolite and attapulgite in a mass ratio of 1:1, and diethanolamine and dopamine in a mass ratio of 1:1 to the reaction solution a1 obtained in step 1. Seal the reaction vessel and react for 90 min at a temperature of 110°C and a pressure of 0.3 MPa to obtain reaction solution b1. Step 3: The reaction liquid b1 obtained in step 2 is introduced into a grinding and crushing device, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 1.

[0020] Example 2: Step 1: Inorganic aluminum source is mixed with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a2; Step 2: Add magnesium hydroxide, magnesium oxide, sepiolite, and triethanolamine to the reaction solution a2 obtained in Step 1, seal the reaction vessel, and react for 120 min at a temperature of 95°C and a pressure of 0.1 MPa to obtain reaction solution b2. Step 3: The reaction liquid b2 obtained in step 2 is introduced into a grinding and crushing device, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 2.

[0021] Example 3: Step 1: Inorganic aluminum source is mixed with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a3; Step 2: Add magnesium hydroxide, sepiolite, fumed silica and dopamine to the reaction solution a3 obtained in step 1, seal the reaction vessel, and react for 120 min at a temperature of 90°C and a pressure of 0.2 MPa to obtain reaction solution b3. Step 3: The reaction liquid b3 obtained in step 2 is introduced into a grinding and crushing device, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 3.

[0022] Example 4: Step 1: Inorganic aluminum source is mixed with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a4; Step 2: Add magnesium oxide, sepiolite and diethanolamine to the reaction solution a4 obtained in step 1, seal the reaction vessel, and react for 0.5 hours at a temperature of 130°C and a pressure of 0.6 MPa to obtain reaction solution b4. Step 3: The reaction liquid b4 obtained in step 2 is introduced into a grinding and crushing device, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 4.

[0023] Example 5: Step 1: Inorganic aluminum source is mixed with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a5; Step 2: Add magnesium hydroxide, sepiolite, triethanolamine and adrenaline in a mass ratio of 2:1 to the reaction solution a5 obtained in Step 1. Seal the reaction vessel and react for 90 min at a temperature of 120°C and a pressure of 0.4 MPa to obtain reaction solution b5. Step 3: The reaction liquid b5 obtained in step 2 is introduced into a grinding and crushing device, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 5.

[0024] Example 6: Step 1: Inorganic aluminum source is mixed with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a6; Step 2: Add magnesium hydroxide, sepiolite, and diethanolamine and dopamine in a mass ratio of 2:1 to the reaction solution a6 obtained in step 1. Seal the reaction vessel and react for 90 min at a temperature of 120°C and a pressure of 0.5 MPa to obtain reaction solution b6. Step 3: The reaction liquid b6 obtained in step 2 is introduced into a grinding and crushing device, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 6.

[0025] Example 7: Step 1: Inorganic aluminum source is mixed with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a7; Step 2: Add magnesium hydroxide, sepiolite and hydrated magnesium silicate in a mass ratio of 1:1 and diethanolamine and triethanolamine in a mass ratio of 2:1 to the reaction solution a7 obtained in step 1. Seal the reaction vessel and react for 120 min at a temperature of 120°C and a pressure of 0.5 MPa to obtain reaction solution b7. Step 3: The reaction liquid b7 obtained in step 2 is introduced into a grinding and crushing device, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 7.

[0026] Example 8: Step 1: Inorganic aluminum source is blended with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a8; Step 2: Add the reaction solution a8 obtained in Step 1 to magnesium hydroxide and magnesium oxide in a mass ratio of 2:1, sepiolite and triisopropanolamine and dopamine in a mass ratio of 2:1, seal the reaction vessel, and react for 60 min at a temperature of 120°C and a pressure of 0.5 MPa to obtain reaction solution b8. Step 3: The reaction liquid b8 obtained in step 2 is introduced into a grinding and crushing device, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 8.

[0027] Comparative Example 1: Referring to CN117534362B, a traditional alkali-free powder accelerator compounding scheme is adopted, using aluminum sulfate, magnesium sulfate, etc. as core accelerator components, compounded in a certain proportion, without undergoing a synthesis process. The compounding ratio is approximately (55% aluminum sulfate octadechydrate, 2.5% magnesium sulfate, 5% diethanolamine, 4% CSH nuclei, 1% boehmite, and the balance water), and the powder is obtained after rotary evaporation at 120°C.

[0028] Comparative Example 2: Using a compounding scheme from some published patents, fluorosilicate (magnesium fluorosilicate) was added as a fluoride ion donor for compounding. The compounding ratio was approximately (55% aluminum sulfate octadechydrate, 10% magnesium fluorosilicate, 2.5% magnesium sulfate, 5% diethanolamine, 4% CSH nuclei, 1% boehmite, and the balance water). The powder was obtained by rotary evaporation at 120°C.

[0029] Comparative Example 3: CN113135689A, "A Low-Sulfur, Low-Gel-Reducing Alkali-Free Liquid Accelerator and Its Preparation Method," describes an alkali-containing, fluorine-free product. It contains 35% aluminum sulfate octadechydrate, 12% aluminum dihydrogen phosphate, 2% sodium aluminate, 3% phosphoric acid, 3% diethanolamine, and 0.5% polyacrylamide. Specifically, aluminum sulfate and aluminum dihydrogen phosphate are dissolved in water, sodium aluminate is slowly added, followed by the addition of phosphoric acid, diethanolamine, and polyacrylamide. The resulting solution is the liquid accelerator.

[0030] Comparative Example 4: Step 1: Inorganic aluminum source is mixed with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a9; Step 2: Add magnesium hydroxide and sepiolite to the reaction solution a9 obtained in Step 1, seal the reaction vessel, and react for 90 min at a temperature of 120°C and a pressure of 0.5 MPa to obtain reaction solution b9. Step 3: The reaction liquid b9 obtained in step 2 is introduced into a grinding and crushing device, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 9.

[0031] Comparative Example 5 Step 1: Inorganic aluminum source is mixed with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a10; Step 2: Add magnesium hydroxide and organic amine to the reaction solution a10 obtained in Step 1, seal the reaction vessel, and react for 90 min at a temperature of 120°C and a pressure of 0.5 MPa to obtain reaction solution b10. Step 3: The reaction liquid b10 obtained in step 2 is introduced into a specific container, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 10.

[0032] Comparative Example 6 Step 1: Inorganic aluminum source is mixed with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a11; Step 2: Add magnesium hydroxide, sepiolite and diethanolamine to the reaction solution a11 obtained in step 1, seal the reaction vessel, and react for 90 min at a temperature of 130°C and a pressure of 0 MPa to obtain reaction solution b11. Step 3: The reaction liquid b11 obtained in step 2 is introduced into a specific container, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 11.

[0033] Comparative Example 7 Step 1: Inorganic aluminum source is mixed with fluorosilicic acid to slow down the reaction, while concentrated sulfuric acid is added dropwise to promote a rapid increase in temperature and obtain reaction solution a12; Step 2: Add magnesium hydroxide, sepiolite, and diethanolamine and dopamine in a 1:1 mass ratio to the reaction solution a12 obtained in Step 1. Seal the reaction vessel and react for 90 min at a temperature of 85℃ and a pressure of 0.3MPa to obtain reaction solution b12. Step 3: The reaction liquid b12 obtained in step 2 is introduced into a specific container, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch 12.

[0034] Performance testing: The performance of the accelerators prepared in the examples and comparative examples was tested. The test items included sulfate content, product stability, and effect on improving the early strength of concrete.

[0035] I. Sulfate content test: Table 2: Al to sulfate ratio in the quick-setting agents of Examples 1-8 and Comparative Examples 1-7 II. Product Stability Testing Table 3: Performance test results of accelerators in Examples 1-8 and Comparative Examples 1-7 Note: The raw materials in Comparative Examples 7 and 8 did not react completely and could not be used in the next step.

[0036] In summary, high Al / SO4 2- Compared to other methods, it results in better solidification and hardening effects. Under the same Al phase introduction conditions, there can be fewer sulfate ions, which has a certain advantage in terms of subsequent sulfate corrosion.

[0037] Each accelerator was stored under certain conditions for a period of time, and its performance changes were observed. The accelerators in the examples maintained relatively stable performance after 3 months of storage, while the accelerators in Comparative Examples 1 and 2 exhibited varying degrees of agglomeration and performance degradation after the same storage time. For example, the agglomeration rate of the accelerator in Comparative Example 1 reached approximately 10%, and that of Comparative Example 2 was approximately 8%, while the agglomeration rates of the accelerators in the examples were all below 5%. Although the method described in this invention did indeed produce a relatively acceptable powder agglomeration rate for some raw materials, the stability of the products configured as liquid accelerators significantly declined due to the lack of materials for fixing or stabilizing / complexing fluoride ions.

[0038] III. Test on the effect of early strength enhancement of concrete The results of the settling and concrete strength tests were compared after incorporating the above-prepared powdered accelerator at 4% of the cementitious material mass (either as a liquid accelerator or directly as a powdered accelerator). The standard mix proportion of C30 shotcrete used in the examples and comparative examples was: 390 kg of PO42.5 Conch cement, 160 kg of water, 800 kg of manufactured sand, and 1050 kg of aggregate.

[0039] Table 4: Compressive strength of concrete in Examples 1-8 and Comparative Examples 1-7 According to GB35159 standard, performance test results show that the accelerator in the examples is slightly better than the comparative example in terms of accelerating setting effect. This is due to the effect of the high Al / S ratio and more F ion fixation. Furthermore, compared to the product in Comparative Example 2, which directly introduced fluorosilicate, this type of product has better setting due to the free release and flow of fluoride ions, but the 1-day strength is significantly weakened. The product can significantly improve the early strength of concrete. Compared with the comparative example, the use of γ-alumina effectively improves the setting and hardening performance while ensuring setting performance, and also slightly increases the strength.

[0040] In summary, the high aluminum-sulfur ratio powder accelerator masterbatch prepared by this invention, compared with traditional inorganic salt and organic compound blending schemes, innovates in preparation process and material system. It introduces γ-alumina into the accelerator synthesis system, introduces a high-temperature and pressurized environment to change the crystal structure, and controls the raw material ratio to achieve a higher aluminum-sulfur ratio at the molecular level. This ensures the product's setting and hardening performance. While belonging to a fluorinated accelerator system, it has minimal impact on strength and exhibits extremely high product stability. Based on the rapid setting and early strength mechanism, it can effectively improve setting and strength performance. Furthermore, its application in concrete engineering shows that this accelerator can be used as a powder accelerator and a liquid accelerator prepared by adding water, both with good stability. In addition, while improving the early strength of concrete, it reduces the risk of sulfate attack compared to traditional accelerators, demonstrating promising application prospects.

Claims

1. A method for preparing a high-alumina-sulfur ratio powder accelerator masterbatch, characterized in that, Includes the following steps: Step 1: Inorganic aluminum source is mixed with fluorosilicic acid and reacted in a closed system. At the same time, concentrated sulfuric acid is added dropwise to promote rapid heating of the reaction, thereby destroying the molecular structure of the inorganic aluminum source and obtaining reaction solution a. Step 2: Add magnesium salt, stabilizer and organic amine to the reaction solution a obtained in step 1, seal the reaction vessel and react at high temperature and pressure. By allowing fluoride ions to enter the product crystal phase under high temperature and pressure, reaction solution b is obtained. Step 3: The high-temperature reaction liquid b obtained in Step 2 is introduced into a grinding and crushing device, naturally cooled, dried, crushed, and ground to obtain a high aluminum-sulfur ratio powder quick-setting agent masterbatch. The inorganic aluminum source includes aluminum hydroxide and γ-alumina.

2. The method for preparing a high alumina-to-sulfur ratio powder accelerator masterbatch according to claim 1, characterized in that, The ratio of inorganic aluminum source to concentrated sulfuric acid is (50~78):(82~128); preferably, the mass ratio of inorganic aluminum source to fluorosilicic acid, magnesium salt, stabilizer and organic amine is (50~78):(58~230):(2~12):(3~26):(7~50).

3. The method for preparing a high alumina-to-sulfur ratio powder accelerator masterbatch according to claim 1, characterized in that, The reaction pressure in step 2 is between 0.1 and 0.6 MPa.

4. The method for preparing a high alumina-to-sulfur ratio powder accelerator masterbatch according to claim 1, characterized in that, The organic amine is an alcohol amine or a catechol amine, preferably any one or more of diethanolamine, triethanolamine, triisopropanolamine, dopamine, and adrenaline.

5. The method for preparing a high alumina-to-sulfur ratio powder accelerator masterbatch according to claim 1, characterized in that, The stabilizer is any one or more of fumed silica, sepiolite, attapulgite, and hydrated magnesium silicate.

6. The method for preparing a high alumina-to-sulfur ratio powder accelerator masterbatch according to claim 1, characterized in that, The reaction temperature range for step 2 is between 90 and 130°C.

7. The method for preparing a high alumina-to-sulfur ratio powder accelerator masterbatch according to claim 1, characterized in that, The reaction time for step 2 is 30~120 min.

8. A high-alumina-sulfur ratio powder accelerator masterbatch, characterized in that, The high aluminum-to-sulfur ratio powder accelerator masterbatch is prepared by the preparation method described in any one of claims 1 to 7.

9. The application of the high alumina-to-sulfur ratio powder accelerator masterbatch according to claim 1, characterized in that, The amount of the high alumina-sulfur ratio powder accelerator masterbatch added is 4-6% of the total mass of the cementitious material.

10. The application of a high alumina-to-sulfur ratio powder accelerator masterbatch according to claim 9, characterized in that, The high aluminum-sulfur ratio powder accelerator masterbatch is prepared as a liquid accelerator and added at a rate of 6-9% of the total mass of the cementitious material.

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