An environmentally friendly, early-strength, alkali-free quick-setting agent, its preparation method and application

Abstract

This invention discloses an environmentally friendly, early-strength, alkali-free accelerator, its preparation method, and its application, belonging to the field of concrete admixture technology. In preparing this environmentally friendly, early-strength, alkali-free accelerator, aluminum sulfate is not directly used in the reaction. Instead, it is obtained by reacting concentrated sulfuric acid and fluorosilicic acid with the alumina component in industrial by-product aluminum sludge. Utilizing the principle that concentrated sulfuric acid releases a large amount of heat upon contact with water and the exothermic reaction of acid and base, the solubility of aluminum ions is further enhanced, realizing the resource utilization of industrial by-product aluminum sludge. This invention also significantly improves the reactivity of industrial by-product fluorosilicone slag through mechanical activation and chemical stimulation, as well as the synergistic effect of grinding aids. This allows it to be used in the preparation of accelerators, achieving the effect of promoting early setting and strength, turning waste into treasure, and saving on the raw material cost of accelerators.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, specifically relating to an environmentally friendly, early-strength, alkali-free quick-setting agent, its preparation method, and its application. Background Technology

[0002] Accelerators, an essential admixture for shotcrete, promote rapid setting and hardening of cement concrete and are widely used in tunnel construction for railway and highway projects. Alkali-free accelerators, as a key material in modern shotcrete construction, represent an important direction for the development of high-performance and green building materials. These accelerators fundamentally solve three key problems by minimizing the use of traditional alkali metal components: first, eliminating the decline in concrete durability caused by alkali-aggregate reaction; second, reducing the corrosive hazards to workers' skin during construction; and third, reducing the later-stage strength loss of concrete. With the rapid growth of underground engineering projects such as tunnel construction, mine support, and slope reinforcement worldwide, the market demand for environmentally friendly alkali-free accelerators is showing a significant upward trend, driving continuous innovation in their preparation technology.

[0003] Currently, alkali-free liquid quick-setting agents on the market still have practical application problems such as high price, short stable storage period, and poor cement adaptability. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an environmentally friendly, early-strength, alkali-free accelerator, its preparation method, and its application. The provided environmentally friendly, early-strength, alkali-free accelerator is alkali-free and chlorine-free, has a low dosage, fast setting time, high early strength (1-day compressive strength ≥15MPa), no later-stage strength loss, 28-day compressive strength ratio ≥100%, good compatibility with cement, and low rebound rate. All indicators meet the requirements of GB / T35159-2017 "Accelerators for Shotcrete".

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One of the technical solutions of this invention is to provide an environmentally friendly, early-strength, alkali-free quick-setting agent, which, by mass percentage, includes, in addition to water, the following components:

[0007] 50%~65% accelerator, 5%~10% fluoride, 4%~8% modified fluorosilicone slag suspension, 2%~3% complexing agent, 1%~2% early strength agent, 0.5%~1% stabilizer, and 0.5%~1% viscosity modifier.

[0008] The preparation steps of the coagulant include: adding aluminum mud and aluminum hydroxide to water, adding concentrated sulfuric acid and fluorosilicic acid solution under stirring, heating to react, cooling, and filtering to obtain the liquid as the coagulant, wherein the fluorosilicic acid solution is a by-product of phosphorus chemical industry;

[0009] The fluoride is at least one of magnesium fluorosilicate, ammonium fluoroaluminate, sodium fluorosilicate, sodium fluoroaluminate, and sodium fluoride.

[0010] The preparation steps of the modified fluorosilicone slag suspension include: mixing fluorosilicone slag, nanocrystal seeds and diethanol monoisopropanolamine, wet grinding and filtering, and the resulting suspension is the modified fluorosilicone slag suspension.

[0011] The complexing agent is an organic alcohol amine.

[0012] Aluminum sludge is obtained from the alumina on the surface of metallic aluminum treated with acid (sulfuric acid) and alkali (sodium hydroxide). Analysis shows that its elements include aluminum, silicon, calcium, and magnesium, with alumina as the main compound. It is an ideal raw material for accelerators. Fluorosilicone slag is a byproduct of phosphate fertilizer production. Because it contains fluorine and a large amount of silica, using this waste fluorosilicone slag in alkali-free accelerators to provide fluorine and silica can not only reduce the production cost of accelerators but also enable the high-value utilization of silica slag and alleviate the environmental pollution caused by fluorosilicone slag to some extent.

[0013] The environmentally friendly, early-strength, alkali-free quick-setting agent provided by this invention is composed of a variety of functional components in specific proportions. The quick-setting agent is a fluoroaluminate complex obtained by modifying aluminum mud. The aluminum mud and aluminum hydroxide, which are insoluble in water, are subjected to high-temperature acid leaching, which increases the concentration of aluminum ions in the liquid phase, accelerates the formation of ettringite, and improves the cement's setting effect.

[0014] The modified fluorosilicone slag suspension components are prepared by mechanically wet-milling and activating the fluorosilicone slag, while simultaneously chemically stimulating it with alkaline nanocrystals (destroying the lattice and morphology of the fluorosilicone slag to improve its activity). Diethanol monoisopropanolamine is used as a grinding aid (to improve the grindability and specific surface area of ​​the fluorosilicone slag). The resulting modified fluorosilicone slag suspension is more uniform and stable, with higher reactivity. The micron-sized silica particles and nanocrystals contained in the fluorosilicone slag suspension components have a synergistic effect, which can reduce the nucleation barrier of cement hydration, provide nucleation growth points for cement hydration products, accelerate the cement hydration process, and compensate for the adverse effects of fluoride components on early strength. This effectively improves the early compressive strength of mortar and concrete with accelerators, while ensuring a high guarantee rate of later strength and having no adverse effects on later strength.

[0015] The early strength agent component can promote the rapid hydration of silicate and aluminate minerals in cement, generating more dense CSH (calcium silicate hydrate) and AFt (calcium sulfoaluminate hydrate) hydration products in a short time, further improving early strength and reducing the rebound rate of shotcrete.

[0016] The synergistic effect of the accelerator, fluoride, and complexing agent components enables the alkali-free accelerator of this invention to achieve rapid setting requirements at a relatively low dosage, significantly shortening the cement setting time. The complexing agent component, an organic alcohol amine, can complex with aluminum ions in the accelerator component, promoting rapid dissolution of aluminum ions in the liquid phase, increasing the reaction rate between aluminum phase substances in the accelerator and cement minerals, and accelerating cement setting and hardening. The stabilizer and viscosity modifier components form a three-dimensional network structure in the liquid phase system, providing excellent suspension and dispersion effects for the various components of the accelerator system, avoiding crystallization, precipitation, and other phenomena, thus greatly improving stability.

[0017] Preferably, the mass ratio of concentrated sulfuric acid to the fluorosilicic acid solution is (3~5):1; the mass ratio of aluminum sludge to aluminum hydroxide is (1~2):1; the ratio of the total weight of water, concentrated sulfuric acid, and fluorosilicic acid solution to the total mass of aluminum sludge and aluminum hydroxide is (3~4):1; the concentration of the fluorosilicic acid solution is 30wt%~40wt%; and the heating reaction temperature is 70~90℃, and the time is 2~3h.

[0018] Preferably, the mass ratio of the fluorosilicone slag, nanocrystal seeds, and diethanol monoisopropanolamine is (4~5):(3~4):1.

[0019] Preferably, the nanocrystal seed is a suspension with a pH of 11-12 and containing 20wt%-25wt% hydrated calcium silicate with an average particle size of 100-200nm.

[0020] Preferably, the organic alcohol amine is at least one selected from monoethanolamine, diethanolamine, triethanolamine, and tetrahydroxypropylethylenediamine.

[0021] Preferably, the early strength agent is at least one selected from sodium formate, sodium aluminate, sodium bromide, and manganese sulfate.

[0022] Preferably, the stabilizer is at least one of boehmite, magnesium aluminum silicate, and hydrated magnesium silicate.

[0023] Preferably, the viscosity modifier is at least one of xanthan gum, guar gum, and hydroxyethyl cellulose.

[0024] The second technical solution of this invention provides a method for preparing the above-mentioned environmentally friendly early-strength alkali-free quick-setting agent, comprising the following steps:

[0025] Prepare the raw materials according to the raw material ratio, add water, stabilizer and viscosity modifier to the reaction vessel, and shear and disperse to obtain a dispersion suspension; add coagulant and fluoride to the dispersion suspension in sequence, stir and then add modified fluorosilicone slag suspension and complexing agent, continue stirring to obtain a turbid liquid, and finally add early strength agent, and after stirring, obtain environmentally friendly early strength alkali-free quick-setting agent.

[0026] Preferably, the shearing rate of the shear dispersion is 2000~3000 rpm, and the time is 30~60 min.

[0027] Preferably, the stirring time after adding the fluoride is 30 min; the stirring time after adding the complexing agent is 1-2 h; and the stirring time after adding the early strength agent is 30-60 min.

[0028] The third technical solution of the present invention provides an application of the above-mentioned environmentally friendly early-strength alkali-free quick-setting agent in the preparation of shotcrete.

[0029] Preferably, the dosage of the environmentally friendly early-strength alkali-free quick-setting agent is 5% to 7% of the mass of the cementitious material.

[0030] The beneficial technical effects of the present invention are as follows:

[0031] In preparing the environmentally friendly, early-strength, alkali-free quick-setting agent, this invention does not directly use aluminum sulfate in the reaction. Instead, it obtains the agent by reacting concentrated sulfuric acid and fluorosilicic acid with the alumina component in industrial by-product aluminum sludge. By utilizing the principle that concentrated sulfuric acid releases a large amount of heat when it comes into contact with water and that acid-base reactions are exothermic, the solubility of aluminum ions is further improved, thereby realizing the resource utilization of industrial by-product aluminum sludge.

[0032] This invention utilizes mechanical activation and chemical stimulation of industrial byproduct fluorosilicone slag, along with the synergistic effect of grinding aids, to greatly enhance the reactivity of fluorosilicone slag. This slag is then used in the preparation of accelerators, achieving the effect of promoting early setting and strength, turning waste into treasure, and saving on the cost of accelerator raw materials.

[0033] The environmentally friendly, early-strength, alkali-free quick-setting agent of this invention has a simple preparation process, is green and environmentally friendly, and is suitable for large-scale promotion and application. Detailed Implementation

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0035] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0036] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0039] The aluminum sludge used in this invention has an alumina content of 63.5%.

[0040] The main components of the fluorosilicone slag used in this invention are silicon dioxide (47.3%) and fluorine (12.2%).

[0041] Unless otherwise specified, "%" in the embodiments of this invention refers to "mass percentage".

[0042] Example 1

[0043] Preparation of environmentally friendly, early-strength, alkali-free quick-setting agent:

[0044] Raw material dosage: 50% coagulant, 5% fluoride (magnesium fluorosilicate), 4% modified fluorosilicone slag suspension, 2% complexing agent (monoethanolamine), 1% early strength agent (sodium formate), 0.5% stabilizer (boehmite), 0.5% viscosity modifier (xanthan gum), water to make up to 100%.

[0045] S1: Preparation of the coagulant: Aluminum sludge and aluminum hydroxide are added to water, and concentrated sulfuric acid and fluorosilicic acid are added while stirring. The mixture is heated to 70°C and stirred for 2 hours. After cooling, the homogeneous liquid obtained by filtration is the coagulant. The mass ratio of concentrated sulfuric acid to fluorosilicic acid solution is 3:1; the mass ratio of aluminum sludge to aluminum hydroxide is 2:1; the ratio of the total weight of water, concentrated sulfuric acid, and fluorosilicic acid solution to the total weight of aluminum sludge and aluminum hydroxide is 3:1; the fluorosilicic acid solution is a by-product of phosphorus chemical industry, and its concentration is 30%.

[0046] S2: Preparation of modified fluorosilicone slag suspension: Fluorosilicone slag, nanocrystals, and diethanol monoisopropanolamine are mixed, wet-milled, and filtered to obtain the modified fluorosilicone slag suspension. The nanocrystals are a suspension with a pH of 11.2 and a calcium silicate hydrate concentration of 20wt% (GK-3Z, produced by Shijiazhuang Chang'an Yucai Building Materials Co., Ltd.); the mass ratio of fluorosilicone slag, nanocrystals, and diethanol monoisopropanol is 5:4:1.

[0047] S3: Add water, stabilizer and viscosity modifier sequentially to the reaction vessel, and stir at high speed for 60 minutes using a high-speed shear disperser at 2000 rpm to obtain a well dispersed suspension.

[0048] S4: Under stirring, the coagulant and fluoride prepared in S1 are added sequentially to the dispersed suspension prepared in S3, and stirred for 30 min. Then, the modified fluorosilicone slag suspension and complexing agent prepared in S2 are added, and stirred for 2 h to obtain a turbid liquid.

[0049] S5: Finally, add the early strength agent and stir for 60 minutes to obtain the environmentally friendly early strength alkali-free quick-setting agent.

[0050] Example 2

[0051] Preparation of environmentally friendly, early-strength, alkali-free quick-setting agent:

[0052] Raw material dosage: 55% coagulant, 7% fluoride (sodium fluoroaluminate), 5% modified fluorosilicone slag suspension, 2% complexing agent (diethanolamine), 1% early strength agent (sodium aluminate), 0.5% stabilizer (magnesium aluminum silicate), 1% viscosity modifier (xanthan gum), water to make up to 100%.

[0053] S1: Preparation of the coagulant: Aluminum sludge and aluminum hydroxide are added to water, and concentrated sulfuric acid and fluorosilicic acid are added while stirring. The mixture is heated to 80°C and stirred for 2 hours. After cooling, the homogeneous liquid obtained by filtration is the coagulant. The mass ratio of concentrated sulfuric acid to fluorosilicic acid solution is 3:1; the mass ratio of aluminum sludge to aluminum hydroxide is 1.5:1; the ratio of the total weight of water, concentrated sulfuric acid, and fluorosilicic acid solution to the total weight of aluminum sludge and aluminum hydroxide is 3:1; the fluorosilicic acid solution is a by-product of phosphorus chemical industry, and its concentration is 35%.

[0054] S2: Preparation of modified fluorosilicone slag suspension: Fluorosilicone slag, nanocrystals, and diethanol monoisopropanolamine are mixed, wet-milled, and filtered to obtain the modified fluorosilicone slag suspension. The nanocrystals are a suspension with a pH of 11.8 and a calcium silicate hydrate concentration of 25wt% (GK-3Z, produced by Shijiazhuang Chang'an Yucai Building Materials Co., Ltd.); the mass ratio of fluorosilicone slag, nanocrystals, and diethanol monoisopropanol is 4:4:1.

[0055] S3: Add water, stabilizer and viscosity modifier sequentially to the reaction vessel, and stir at high speed for 60 minutes using a high-speed shear disperser at 3000 rpm to obtain a well dispersed suspension.

[0056] S4: Under stirring, the coagulant and fluoride prepared in S1 are added sequentially to the dispersed suspension prepared in S3, and stirred for 30 min. Then, the modified fluorosilicone slag suspension and complexing agent prepared in S2 are added, and stirred for 2 h to obtain a turbid liquid.

[0057] S5: Finally, add the early strength agent and stir for 30 minutes to obtain the environmentally friendly early strength alkali-free quick-setting agent.

[0058] Example 3

[0059] Preparation of environmentally friendly, early-strength, alkali-free quick-setting agent:

[0060] Raw material dosage: 65% coagulant, 8% fluoride (sodium fluorosilicate), 8% modified fluorosilicone slag suspension, 3% complexing agent (triethanolamine), 2% early strength agent (sodium bromide), 1% stabilizer (boehmite), 0.5% viscosity modifier (hydroxyethyl cellulose), water to make up to 100%.

[0061] S1: Preparation of the coagulant: Aluminum sludge and aluminum hydroxide are added to water, and concentrated sulfuric acid and fluorosilicic acid are added while stirring. The mixture is heated to 90°C and stirred for 3 hours. After cooling, the homogeneous liquid obtained by filtration is the coagulant. The mass ratio of concentrated sulfuric acid to fluorosilicic acid solution is 5:1; the mass ratio of aluminum sludge to aluminum hydroxide is 1:1; the ratio of the total weight of water, concentrated sulfuric acid, and fluorosilicic acid solution to the total weight of aluminum sludge and aluminum hydroxide is 4:1; the fluorosilicic acid solution is a by-product of phosphorus chemical industry, and its concentration is 40%.

[0062] S2: Preparation of modified fluorosilicone slag suspension:

[0063] The modified fluorosilicone slag suspension is obtained by mixing fluorosilicone slag, nanocrystals, and diethanol monoisopropanolamine, followed by wet grinding and filtration. The nanocrystals are a suspension with a pH of 11.2 and a calcium silicate hydrate concentration of 20 wt% (GK-3Z, produced by Shijiazhuang Chang'an Yucai Building Materials Co., Ltd.). The mass ratio of fluorosilicone slag, nanocrystals, and diethanol monoisopropanolamine is 5:3:1.

[0064] S3: Add water, stabilizer and viscosity modifier sequentially to the reaction vessel, and stir at high speed for 30 minutes using a high-speed shear disperser at 3000 rpm to obtain a well dispersed suspension.

[0065] S4: Under stirring, the coagulant and fluoride prepared in S1 are added sequentially to the dispersed suspension prepared in S3, and stirred for 30 min. Then, the modified fluorosilicone slag suspension and complexing agent prepared in S2 are added, and stirred for 1 h to obtain a turbid liquid.

[0066] S5: Finally, add the early strength agent and stir for 30 minutes to obtain the environmentally friendly early strength alkali-free quick-setting agent.

[0067] Example 4

[0068] Preparation of environmentally friendly, early-strength, alkali-free quick-setting agent:

[0069] Raw material dosage: 60% coagulant, 7% fluoride (sodium fluoride), 7% modified fluorosilicone slag suspension, 2% complexing agent (tetrahydroxypropyl ethylenediamine), 1.5% early strength agent (manganese sulfate), 0.5% stabilizer (hydrated magnesium silicate), 1% viscosity modifier (guar gum), water to make up to 100%.

[0070] S1: Preparation of the coagulant: Aluminum sludge and aluminum hydroxide are added to water, and concentrated sulfuric acid and fluorosilicic acid are added while stirring. The mixture is heated to 80°C and stirred for 3 hours. After cooling, the homogeneous liquid obtained by filtration is the coagulant. The mass ratio of concentrated sulfuric acid to fluorosilicic acid solution is 5:1; the mass ratio of aluminum sludge to aluminum hydroxide is 1:1; the ratio of the total weight of water, concentrated sulfuric acid, and fluorosilicic acid solution to the total weight of aluminum sludge and aluminum hydroxide is 3:1; the fluorosilicic acid solution is a by-product of phosphorus chemical industry, and its concentration is 35%.

[0071] S2: Preparation of modified fluorosilicone slag suspension: Fluorosilicone slag, nanocrystals, and diethanol monoisopropanolamine are mixed, wet-milled, and filtered to obtain the modified fluorosilicone slag suspension. The nanocrystals are a suspension with a pH of 11.8 and a calcium silicate hydrate concentration of 25 wt% (GK-3Z, produced by Shijiazhuang Chang'an Yucai Building Materials Co., Ltd.); the mass ratio of fluorosilicone slag, nanocrystals, and diethanol monoisopropanol is 4:3:1.

[0072] S3: Add water, stabilizer and viscosity modifier sequentially to the reaction vessel, and stir at high speed for 60 minutes using a high-speed shear disperser at 2500 rpm to obtain a well dispersed suspension.

[0073] S4: Under stirring, the coagulant and fluoride prepared in S1 are added sequentially to the dispersed suspension prepared in S3, and stirred for 30 min. Then, the modified fluorosilicone slag suspension and complexing agent prepared in S2 are added, and stirred for 1 h to obtain a turbid liquid.

[0074] S5: Finally, add the early strength agent and stir for 60 minutes to obtain the environmentally friendly early strength alkali-free quick-setting agent.

[0075] Comparative Example 1

[0076] Preparation of alkali-free quick-setting agent:

[0077] The only difference from Example 1 is that the fluorosilicic acid solution is replaced with an equal mass of concentrated sulfuric acid in the preparation process of the coagulant component.

[0078] Comparative Example 2

[0079] Preparation of alkali-free quick-setting agent:

[0080] The only difference from Example 1 is that the modified fluorosilicone slag suspension component is not added.

[0081] Comparative Example 3

[0082] Preparation of alkali-free quick-setting agent:

[0083] The only difference from Example 1 is that no nanocrystal seeds were added in the preparation process of the modified fluorosilicone slag suspension components.

[0084] The following is the experimental section (test examples) of this invention:

[0085] The recommended dosage of the environmentally friendly, early-strength, alkali-free quick-setting agent described in this invention in shotcrete is 5% to 7% of the total cementitious material (the dosage in this context has the same meaning). Table 1 shows the performance requirements for neat cement paste and mortar containing liquid alkali-free quick-setting agents as specified in GB / T 35159-2017 "Quick-setting Agents for Shotcrete".

[0086] Table 1 Performance requirements for neat cement paste and mortar with alkali-free quick-setting agent (GB / T 35159-2017)

[0087]

[0088] Test Item 1

[0089] The environmentally friendly, early-strength, alkali-free accelerators prepared in Examples 1-4, as well as the alkali-free accelerators in each comparative example, were tested for setting time, compressive strength, and other indicators according to the testing methods specified in GB / T 35159-2017 "Accelerators for Shotcrete". The cement used for testing was Esheng Cement PO 42.5R. The test results are shown in Table 2.

[0090] Table 2 Performance of the Accelerating Agent of the Present Invention

[0091]

[0092] As can be seen from the data in Table 2, the environmentally friendly, early-strength, alkali-free quick-setting agent of this invention exhibits excellent performance and requires a low dosage. At a dosage of 6% to 7%, all performance indicators, as tested by Esheng Cement, meet the requirements of GB / T 35159-2017 standard. It demonstrates high early strength, with a 1-day compressive strength greater than 15.0 MPa, ensuring construction safety and progress. Furthermore, the later-stage strength does not decline and may even improve, with a 28-day compressive strength ratio greater than 100%.

[0093] Test Item Two

[0094] The alkali-free quick-setting agent of Example 3 was used to conduct compatibility tests with Huaxin Cement PO 42.5, Gaozheng Cement PO 42.5, Yaobai Cement PO 42.5, Conch Cement PO 42.5 and Qilianshan Cement PO 42.5 to test the quick-setting agent and cement (test method is the same as test item 1). The test results are shown in Table 3.

[0095] Table 3 Performance of the environmentally friendly early-strength alkali-free quick-setting agent of the present invention (cement for engineering projects)

[0096]

[0097] As can be seen from the data in Table 3, when the environmentally friendly early-strength alkali-free quick-setting agent of the present invention is combined with cement for various engineering projects, all performance indicators meet the performance requirements of GB / T 35159-2017 for alkali-free quick-setting agents in Table 1. This indicates that the quick-setting agent of the present invention has good compatibility with various cements and can well meet the usage needs of various engineering projects.

[0098] Test Item 3

[0099] The environmentally friendly, early-strength, alkali-free quick-setting agents prepared in Examples 1-4, as well as the alkali-free quick-setting agents in each comparative example, were subjected to shotcrete rebound rate tests at a dosage of 6%-7%, according to the method mentioned in Appendix G of JGJ / T372-2016 "Technical Specification for Application of Shotcrete". The test results are shown in Table 4. The cement used in the test was Lafarge PO 42.5R cement, and the water-reducing agent was GK-3000 polycarboxylate high-performance water-reducing agent produced by Shijiazhuang Chang'an Yucai Building Materials Co., Ltd.

[0100] Table 4 Rebound rate of shotcrete

[0101]

[0102] As shown in Table 4, under the same shotcrete mix proportion, the liquid accelerator prepared using the alkali-free accelerator of this invention, at a dosage of 6%~7%, resulted in a low rebound rate (<6%) in the shotcrete, indicating good application performance. The alkali-free accelerator of Comparative Example 2, compared to Example 1, did not contain modified silica slag suspension components, resulting in a significantly higher rebound rate in the shotcrete even at a higher dosage than Example 1, exceeding 12%. The alkali-free accelerators of Comparative Examples 1~3, compared to the alkali-free accelerator of Example 4, also showed significantly higher rebound rates in the shotcrete at the same dosage (7%).

[0103] In summary, the environmentally friendly, early-strength, alkali-free quick-setting agent prepared by this invention exhibits excellent comprehensive performance, a simple and environmentally friendly preparation process, low material cost, good compatibility with cement, low dosage, high early strength (1-day compressive strength ≥15MPa), no loss of later strength, 28-day compressive strength ratio ≥100%, and low rebound rate of shotcrete (<6%). All indicators meet the requirements of GB / T35159-2017 "Quick-setting Agents for Shotcrete", making it highly suitable for widespread application.

[0104] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An environment-friendly early-strength non-alkali accelerator, characterized in that, In addition to water, the components also include, by mass percentage: 50%~65% of a coagulant, 5%~10% of a fluoride, 4%~8% of a modified fluorosilicon slag suspension, 2%~3% of a complexing agent, 1%~2% of an early strength agent, 0.5%~1% of a stabilizer, and 0.5%~1% of a viscosity modifier; The preparation steps of the coagulant include: adding aluminum mud and aluminum hydroxide into water, adding concentrated sulfuric acid and fluorosilicic acid solution under stirring, heating reaction, and filtering the obtained liquid after cooling to obtain the coagulant, wherein the fluorosilicic acid solution is a by-product of phosphating industry; The fluoride is at least one of magnesium fluorosilicate, ammonium fluoroaluminate, sodium fluorosilicate, sodium fluoroaluminate, and sodium fluoride; The preparation steps of the modified fluorosilicon slag suspension include: mixing fluorosilicon slag, nanocrystalline seeds, and diethanol mono-isopropanol amine, wet grinding, and filtering to obtain the modified fluorosilicon slag suspension; The complexing agent is an organic alcohol amine; The mass ratio of the concentrated sulfuric acid to the fluorosilicic acid solution is (3~5):1; the mass ratio of the aluminum mud to the aluminum hydroxide is (1~2):1; the total weight ratio of the water, the concentrated sulfuric acid, and the fluorosilicic acid solution to the total mass of the aluminum mud and the aluminum hydroxide is (3~4):1; the concentration of the fluorosilicic acid solution is 30%~40%; the heating reaction temperature is 70~90℃, and the heating reaction time is 2~3h; The mass ratio of the fluorosilicon slag, the nanocrystalline seeds, and the diethanol mono-isopropanol amine is (4~5):(3~4):1; The nanocrystalline seeds are a suspension with a pH value of 11~12, a calcium silicate hydrate concentration of 20wt%~25wt%, and an average particle size of 100~200nm.

2. The environment-friendly early-strength non-alkali accelerator according to claim 1, characterized in that, The organic alcohol amine is at least one of monoethanolamine, diethanolamine, triethanolamine, and tetrahydroxypropyl ethylenediamine; and / or the early strength agent is at least one of sodium formate, sodium metaaluminate, sodium bromide, and manganese sulfate; and / or the stabilizer is at least one of pseudo-boehmite, magnesium aluminum silicate, and hydrated magnesium silicate.

3. The environment-friendly early-strength non-alkali accelerator according to claim 1, characterized in that, The viscosity modifier is at least one of xanthan gum, guar gum, and hydroxyethyl cellulose.

4. The method for preparing the environment-friendly early-strength non-alkali accelerator according to any one of claims 1-3, characterized in that, The method includes the following steps: Prepare raw materials according to the raw material ratio, add water, a stabilizer, and a viscosity modifier into a reaction container, shear and disperse to obtain a dispersion suspension; Add a coagulant and a fluoride into the dispersion suspension in sequence, add a modified fluorosilicon slag suspension and a complexing agent after stirring, continue to stir to obtain a turbid liquid, and finally add an early strength agent, stir, and obtain an environmentally friendly early strength type alkali-free accelerator.

5. The method for preparing the environment-friendly early-strength non-alkali accelerator according to claim 4, characterized in that, The shear speed of the shear dispersion is 2000~3000rpm, and the time is 30~60min; and / or the stirring time after adding the fluoride is 30min; the stirring time after adding the complexing agent is 1~2h; and the stirring time after adding the early strength agent is 30~60min.

6. Use of the environmentally friendly early strength type alkali-free accelerator according to any one of claims 1~3 in the preparation of shotcrete.

7. Use according to claim 6, characterized in that, The mixing amount of the environmentally friendly early strength type alkali-free accelerator is 5%~7% of the mass of cementitious materials.

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