High-performance fluoride-free and alkali-free liquid accelerator, preparation method and application thereof

Abstract

The present application relates to the technical field of building materials, and particularly relates to a high-performance fluoride-free and alkali-free liquid accelerator, a preparation method and application thereof, the high-performance fluoride-free and alkali-free liquid accelerator is prepared from the following components in percentage by weight: 35-50% of polycarboxylate aluminum dispersion liquid, 35-50% of aluminum sulfate, 1.0-3.5% of alkali liquid accelerator, 5.0-10% of pH regulator, and the rest is a suspended stabilizer aqueous solution; and the pH value is 2.0-3.5. The high-performance fluoride-free and alkali-free liquid accelerator has good storage stability, can be applied to cement, and can obtain the following properties of cement net paste: initial setting time of 1.5-2.5 min, final setting time of 3-10 min, 6h compressive strength of cement mortar of more than 1.0 MPa, 24h compressive strength of more than 13 MPa, and relative strength of more than 95% at 28 days, and can also be used to prepare high-performance sprayed concrete, and meet the requirement of concrete resilience rate of less than 10%.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a high-performance fluorine-free and alkali-free liquid quick-setting agent, its preparation method, and its application. Background Technology

[0002] Accelerators are indispensable admixtures for shotcrete. Their function is to promote cement setting and hardening, improve the early strength of shotcrete, and help speed up the construction period. With the acceleration of large-scale highway and railway network construction projects in my country, as well as mining and undersea tunnel excavation, the demand for accelerators for shotcrete is increasing. Traditional powdered accelerators suffer from slow dissolution and uneven dispersion, limiting their application to dry-spraying concrete. High-alkali liquid accelerators, used in wet-spraying concrete, suffer from significant strength loss and poor impermeability of hardened concrete. Their high alkali content also causes severe environmental pollution and poses significant health risks to construction workers. While fluorine-containing alkali-free liquid accelerators offer advantages such as good durability, superior mechanical properties, and lower rebound, meeting the requirements of GB / T35159-2017 "Alkali-free Liquid Accelerators for Shotcrete," they require large amounts of aluminum sulfate, leading to sedimentation and stratification, poor storage stability, and severe equipment corrosion due to the extensive use of hydrofluoric acid or fluorosilicic acid. These accelerators are also extremely harmful or carcinogenic, seriously impacting the health of personnel during production and use. Their unstable quality also poses safety hazards to shotcrete projects.

[0003] Existing Chinese application CN101423356A discloses a method for preparing an accelerator using aluminum sulfate, sodium fluorosilicate, and triethanolamine as main raw materials. This accelerator introduces sodium salts and fluoride ions, which may lead to alkali-aggregate reaction in the later stages, affecting the durability of concrete. Chinese application CN101475335A discloses an alkali-free accelerator with aluminum sulfate, metal fluorides, and amines as main components, with the addition of pH adjusters and thickeners. Its compatibility with cement is narrow, and the dosage is relatively large. A small amount of fluoride ions can play a reinforcing role, but fluoride, as the main accelerator component, although having a good accelerating effect, is not conducive to the rapid curing of concrete when the dosage is too large. It hinders cement hydration, resulting in low or even no initial hourly strength or early 1-day strength of concrete.

[0004] Currently, the development of alkali-free quick-setting agent technology still faces problems such as high aluminum sulfate content, poor storage stability, and poor adaptability in use. If excessive fluoride is introduced, the product will be harmful and the early strength effect will be poor.

[0005] The China Railway Corporation's enterprise standard Q / CR 807-2020, "Liquid Alkali-Free Accelerating Agent for Shotcrete in Tunnels," requires a fluoride ion content of less than 0.05% and specifies the corresponding 6-hour, 1-day, and 28-day mortar strengths. This indicates that in actual engineering projects, shotcrete needs to rapidly harden within several hours to form a structure with initial support capabilities on the surrounding rock surface. Therefore, there is a particular need to develop green, high-performance, fluoride-free, and alkali-free liquid accelerating agents to better formulate high-performance shotcrete. Summary of the Invention

[0006] In order to solve the above-mentioned technical problems of the present invention, the present invention provides a high-performance fluorine-free and alkali-free liquid quick-setting agent, its preparation method and application, so as to solve the above-mentioned technical problems existing in the prior art.

[0007] According to a first aspect of the present invention, the present invention provides a high-performance fluorine-free and alkali-free liquid quick-setting agent, which is prepared by weight percentage from the following components: 35% to 50% aluminum polycarboxylate dispersion, 35% to 50% aluminum sulfate, 1.0% to 3.5% alkali-containing liquid quick-setting agent, 5.0% to 10% pH adjuster, and the balance being an aqueous suspension stabilizer; the pH value of the high-performance fluorine-free and alkali-free liquid quick-setting agent is 2.0 to 3.5.

[0008] In the above scheme, the high-performance fluorine-free and alkali-free liquid accelerator consists of an aqueous solution of aluminum polycarboxylate dispersion, aluminum sulfate, an alkaline liquid accelerator, a pH adjuster, and a suspension stabilizer. The aluminum polycarboxylate dispersion increases the aluminum ion content and dispersion stability of the liquid accelerator, thereby improving cement hydration efficiency and accelerator setting effect. Although aluminum sulfate can react with gypsum in cement to form a hardened product, thus accelerating the hardening speed of cement, its large dosage leads to unstable product storage performance. The pH adjuster can further promote the formation of stable complexes of aluminum salts, improving the stability of the entire accelerator product system. The suspension stabilizer aqueous solution has anti-stratification properties under both acidic and alkaline conditions. The alkaline liquid accelerator, provided that the percentage of Na2O alkali is less than 1.0%, can adjust the pH value of the liquid and the aluminate ions that contribute to the accelerator setting effect. This invention relates to a high-performance, fluorine-free, alkali-free liquid accelerator. By limiting the dosage of polycarboxylate aluminum dispersion, aluminum sulfate, alkaline liquid accelerator, pH adjuster, and suspension stabilizer aqueous solution within a reasonable range, the components achieve better synergistic effects. This results in a high-performance, fluorine-free, alkali-free liquid accelerator with a significant rapid-setting effect. It is non-toxic and harmless, and can be used to formulate high-performance shotcrete. It is suitable for shotcrete applications in tunnels, marine engineering, and subways, including support, repair, leak prevention, and water plugging. Concrete using this invention exhibits a rebound rate of less than 10%, a significant rapid-setting effect, an early 6-hour strength of not less than 1.0 MPa, and a later relative strength exceeding 95%. The raw materials used in this invention are all non-toxic and harmless, environmentally friendly, and pollution-free throughout the entire process of production, transportation, and use. Furthermore, the overall application cost is reduced by approximately 20%.

[0009] Further, the preparation method of the polycarboxylate aluminum dispersion is as follows: a polycarboxylate water-reducing agent mother liquor with a mass concentration of 40% to 50%, amorphous aluminum hydroxide, and water are mixed in a mass ratio of (30-35):(30-35):(30-35) and reacted for 2 hours to obtain a semi-transparent colloidal polycarboxylate aluminum dispersion.

[0010] In the above scheme, the polycarboxylate aluminum dispersion is composed of polycarboxylate superplasticizer mother liquor, amorphous aluminum hydroxide, and water. The synergistic complexation reaction between the polycarboxylate superplasticizer mother liquor and amorphous aluminum oxide can increase the aluminum ion content and dispersion stability of the liquid accelerator, thereby improving the cement hydration efficiency and accelerator effect.

[0011] Furthermore, the polycarboxylate superplasticizer mother liquor is selected from one or two of early-strength polycarboxylate superplasticizer mother liquor and standard polycarboxylate superplasticizer mother liquor; the amorphous aluminum hydroxide is one or two of boehmite and nano aluminum hydroxide powder.

[0012] In the above scheme, by further limiting the types of polycarboxylate superplasticizer mother liquor and amorphous aluminum hydroxide, and reducing the amount of aluminum sulfate quick-setting component, it is more conducive to maximizing the aluminum ion content and dispersion stability of liquid quick-setting agent, and more conducive to improving cement hydration efficiency and quick-setting effect.

[0013] Boehmite and nano-aluminum hydroxide powder are amorphous aluminum hydroxide ultrafine powders, and their dissolution rate is much higher than that of ordinary aluminum hydroxide ultrafine powders. Furthermore, the fineness of the amorphous aluminum hydroxide ultrafine powder is greater than 1500 mesh.

[0014] Further, the preparation method of the early-strength polycarboxylate superplasticizer mother liquor is as follows: methyl allyl polyethylene glycol with a molecular weight of 4000-6000 is polymerized with acrylic acid at a molar ratio of 1:(6.0-8.0); the preparation method of the standard polycarboxylate superplasticizer mother liquor is as follows: methyl allyl polyethylene glycol with a molecular weight of 2400-3000 is polymerized with acrylic acid at a molar ratio of 1:(3.5-5.0).

[0015] In the above scheme, by further specifying the preparation methods of early-strength polycarboxylate superplasticizer mother liquor and standard polycarboxylate superplasticizer mother liquor, it is possible to obtain polycarboxylate superplasticizer mother liquor with better performance, which is more conducive to increasing the aluminum ion content and dispersion stability of liquid accelerator, and more conducive to improving cement hydration efficiency and accelerator effect.

[0016] Furthermore, the amount of the alkaline liquid quick-setting agent is 2.5% to 3.0%; the alkaline liquid quick-setting agent is selected from sodium aluminate, or the product of sodium hydroxide and aluminum hydroxide reacting in water at 95°C to 100°C.

[0017] In the above scheme, by further limiting the dosage and type of alkaline liquid quick-setting agent, it is more conducive to improving the quick-setting effect of alkali-free liquid quick-setting agent.

[0018] Furthermore, the suspending stabilizer in the aqueous solution is one or both of lentinan gum and xanthan gum; the concentration of the aqueous solution is 0.2% to 0.5%.

[0019] In the above scheme, by further limiting the type and concentration of the suspension stabilizer in the aqueous solution, it is more conducive to forming a stable alkali-free liquid quick-setting agent.

[0020] Furthermore, the pH value of the alkali-free liquid quick-setting agent is 2.5 to 3.0, resulting in a better quick-setting effect.

[0021] The pH adjuster is a basic amino acid; preferably, the basic amino acid is selected from one or more of arginine, lysine, and histidine; more preferably, the basic amino acid is selected from arginine. The amount of the pH adjuster is 7.0% to 8.0%.

[0022] In the above scheme, by further limiting the type and amount of pH adjuster, the formation of stable complexes of aluminum salts can be further promoted, thereby improving the stability of the system.

[0023] According to a second aspect of the present invention, the present invention also provides a method for preparing the above-mentioned alkali-free liquid quick-setting agent, comprising the following steps: taking a polycarboxylate aluminum dispersion, heating it to 50-80°C, adding an aqueous suspension stabilizer, then adding aluminum sulfate, stirring for 10-40 minutes, adding an alkali-containing liquid quick-setting agent and a pH adjuster, continuing to stir for 10-40 minutes, and cooling to obtain the product.

[0024] According to a third aspect of the invention, the invention also provides the application of the above-described high-performance fluorine-free and alkali-free liquid quick-setting agent in shotcrete.

[0025] Furthermore, a high-performance, fluorine-free, alkali-free liquid accelerator is added to the cement at a mass percentage of 5-8%.

[0026] Preferably, the initial setting time of the obtained cement paste is 1.5 to 2.5 min, the final setting time is 5 to 10 min, the compressive strength of the cement mortar at 6 hours is above 1.0 MPa, the compressive strength at 24 hours is above 13.0 MPa, and the compressive strength ratio at 28 days is above 95%.

[0027] And / or, the high-performance fluorine-free and alkali-free liquid quick-setting agent is used to prepare C30-C50 shotcrete, meeting the requirements of concrete rebound rate less than 10% and dust reduction to 20 mg / m³. 3 the following.

[0028] The high-performance fluorine-free and alkali-free liquid quick-setting agent of this invention can reduce the overall application cost by about 20% compared with existing products when applied to shotcrete. It is suitable for tunnel, marine engineering, subway support, repair, leak prevention, water plugging and other projects.

[0029] The technical solution provided by this invention has the following beneficial effects:

[0030] This invention discloses a high-performance, fluorine-free, alkali-free liquid accelerator for formulating high-performance shotcrete, suitable for shotcrete applications in tunnels, marine engineering, and subways, including support, repair, leak prevention, and water plugging. Concrete using this high-performance, fluorine-free, alkali-free liquid accelerator exhibits a rebound rate of less than 10%, a significant rapid-setting effect, and an early 6-hour compressive strength exceeding 1.0 MPa with virtually no loss of relative strength in the later stages. Furthermore, this alkali-free liquid accelerator is non-toxic and harmless, reducing dust concentration to 20 mg / m³.3 The relative strength of high-performance shotcrete with accelerator added after 28 days is more than 95% that of high-performance concrete without accelerator added, the overall application cost is reduced by about 20%, and there is no pollution throughout the entire production, transportation and use process. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] The polycarboxylate superplasticizer mother liquor used in the following examples was prepared according to the following method.

[0033] Preparation of early-strength polycarboxylate superplasticizer mother liquor: synthesized under general redox aqueous solution system production process conditions with a molar ratio of methyl allyl polyethylene glycol 5000: acrylic acid = 1:6.5 to obtain an unneutralized 50% early-strength polycarboxylate superplasticizer mother liquor.

[0034] Preparation of standard polycarboxylate superplasticizer mother liquor: synthesized under general redox aqueous solution system production process conditions with a molar ratio of methyl allyl polyethylene glycol 3000: acrylic acid = 1:4 to obtain 50% unneutralized standard polycarboxylate superplasticizer mother liquor.

[0035] Example 1

[0036] A fluorine-free and alkali-free liquid quick-setting agent is prepared from the following components by mass percentage: 45% aluminum polycarboxylate dispersion, 40% aluminum sulfate, 2.0% alkali-based liquid quick-setting agent, 6.5% pH adjuster, and the remainder being 6.5% of a 0.3% aqueous suspension stabilizer solution. The aluminum polycarboxylate dispersion is prepared from an early-strength polycarboxylate superplasticizer mother liquor, amorphous aluminum hydroxide, and water; the amorphous aluminum hydroxide is specifically nano-aluminum hydroxide. The alkali-based liquid quick-setting agent is specifically 40% sodium aluminate. The suspension stabilizer in the aqueous suspension stabilizer solution is vinyl ether.

[0037] The preparation method of the above-mentioned alkali-free liquid quick-setting agent includes the following steps:

[0038] Take 15 kg of unneutralized 50% early-strength polycarboxylate superplasticizer mother liquor, add 15 kg of amorphous aluminum hydroxide, heat to 60℃, stir for 30 minutes, add 15 kg of water to fully react and dissolve the aluminum hydroxide; then add 40 kg of aluminum sulfate octadecahydrate, stir for 20-30 minutes, add 2.0 kg of alkaline liquid quick-setting agent, 6.5 kg of arginine, and 6.5 kg of 0.3% Wenlun glue aqueous solution, stir at 60℃ for 20 minutes, and cool to room temperature to obtain the transparent emulsion-like high-performance fluorine-free and alkali-free liquid quick-setting agent product HPCA-1.

[0039] The concentration of HPCA-1 was found to be 50.7%, and the pH was 2.5.

[0040] Example 2

[0041] An alkali-free liquid quick-setting agent is prepared from the following components by mass percentage: 45% aluminum polycarboxylate dispersion, 40% aluminum sulfate, 2.0% alkali-based liquid quick-setting agent, 6.5% pH adjuster, and the remainder is 6.5% a 0.3% aqueous suspension stabilizer solution; the pH of the finished alkali-free liquid quick-setting agent is 2.3. The aluminum polycarboxylate dispersion is prepared from a standard polycarboxylate superplasticizer mother liquor, amorphous aluminum hydroxide, and water; the amorphous aluminum hydroxide is specifically nano-aluminum hydroxide; the alkali-based liquid quick-setting agent is sodium aluminate; and the suspension stabilizer in the aqueous suspension stabilizer solution is succinate.

[0042] The preparation method of the above-mentioned alkali-free liquid quick-setting agent includes the following steps:

[0043] Take 15.0 kg of unneutralized 50% standard polycarboxylate superplasticizer mother liquor, add 15 kg of amorphous aluminum hydroxide, heat to 60℃, stir for 30 minutes, add 15 kg of water to allow the aluminum hydroxide to fully react and dissolve; then add 40 kg of aluminum sulfate octadecahydrate, stir for 20-30 minutes, add 2.0 kg of alkaline liquid quick-setting agent, 6.5 kg of arginine, and 6.5 kg of 0.3% Wenlun glue aqueous solution, stir at 60℃ for 20 minutes, and cool to room temperature to obtain the transparent emulsion-like high-performance fluorine-free and alkali-free liquid quick-setting agent product HPCA-2.

[0044] The concentration of HPCA-2 was found to be 51.0%, and the pH was 2.3.

[0045] Example 3

[0046] A high-performance, fluorine-free, alkali-free liquid quick-setting agent is prepared from the following components by mass percentage: 40% aluminum polycarboxylate dispersion, 45% aluminum sulfate, 3.0% alkali-based liquid quick-setting agent, 7.0% pH adjuster, and the remainder being 5% of a 0.5% aqueous suspension stabilizer solution. The aluminum polycarboxylate dispersion is prepared from an early-strength polycarboxylate superplasticizer mother liquor, amorphous aluminum hydroxide, and water; the amorphous aluminum hydroxide is specifically nano-aluminum hydroxide; the alkali-based liquid quick-setting agent is sodium aluminate; and the suspension stabilizer in the aqueous suspension stabilizer solution is xanthan gum.

[0047] The preparation method of the above-mentioned alkali-free liquid quick-setting agent includes the following steps:

[0048] Take 13.5 kg of unneutralized 50% early-strength polycarboxylate superplasticizer mother liquor, add 13.5 kg of amorphous aluminum hydroxide, heat to 60℃, stir for 30 minutes, add 13.5 kg of water to allow the aluminum hydroxide to fully react and dissolve; then add 45 kg of aluminum sulfate octadecahydrate, stir for 20-30 minutes, add 3.0 kg of alkaline liquid quick-setting agent, 7.0 kg of lysine, and 5.0 kg of 0.5% xanthan gum aqueous solution, stir at 60℃ for 20 minutes, and cool to room temperature to obtain the transparent emulsion-like high-performance fluorine-free and alkali-free liquid quick-setting agent product HPCA-3.

[0049] The concentration of HPCA-3 was found to be 48.6%, and the pH was 2.4.

[0050] Example 4

[0051] An alkali-free liquid quick-setting agent is prepared from the following components by mass percentage: 40% aluminum polycarboxylate dispersion, 45% aluminum sulfate, 3.0% alkali-based liquid quick-setting agent, 7.0% pH adjuster, and the remainder is 5% a 0.5% aqueous solution of a suspension stabilizer; the pH of the finished alkali-free liquid quick-setting agent is 2.4. The aluminum polycarboxylate dispersion is prepared from a standard polycarboxylate superplasticizer mother liquor, amorphous aluminum hydroxide, and water; the amorphous aluminum hydroxide is specifically nano-aluminum hydroxide; the alkali-based liquid quick-setting agent is sodium aluminate; and the suspension stabilizer in the aqueous solution is xanthan gum.

[0052] The preparation method of the above-mentioned alkali-free liquid quick-setting agent includes the following steps:

[0053] Take 13.5 kg of unneutralized 50% standard polycarboxylate superplasticizer mother liquor, add 13.5 kg of amorphous aluminum hydroxide, heat to 60℃, stir for 30 minutes, add 13.5 kg of water to fully react and dissolve the aluminum hydroxide; then add 40 kg of aluminum sulfate octadecahydrate, stir for 20-30 minutes, add 3.0 kg of alkaline liquid quick-setting agent, 7.0 kg of lysine, and 5.0 kg of 0.5% xanthan gum aqueous solution, stir at 60℃ for 20 minutes, and cool to room temperature to obtain the transparent emulsion-like high-performance fluorine-free and alkali-free liquid quick-setting agent product HPCA-4.

[0054] The concentration of HPCA-4 was found to be 47.8%, and the pH was 2.2.

[0055] Example 5

[0056] HPCA-5, a high-performance fluorine-free and alkali-free liquid quick-setting agent, differs from Example 1 in that the amorphous aluminum hydroxide synthesized from the polycarboxylate aluminum dispersion is specifically boehmite; it is prepared from the following components by mass percentage: 35% polycarboxylate aluminum dispersion, 50% aluminum sulfate, 2.0% alkali liquid quick-setting agent, 7.5% pH adjuster, and the remainder is 5.5% aqueous suspension stabilizer solution with a concentration of 0.3%.

[0057] The concentration of HPCA-5 was found to be 48.8%, and the pH was 2.1.

[0058] Example 6

[0059] HPCA-6, a high-performance fluorine-free and alkali-free liquid quick-setting agent, differs from Example 2 in that the amorphous aluminum hydroxide synthesized from the polycarboxylate aluminum dispersion is specifically boehmite; it is prepared from the following components by mass percentage: 50% polycarboxylate aluminum dispersion, 35% aluminum sulfate, 2.0% alkali liquid quick-setting agent, 6.5% pH adjuster, and the remainder is 6.5% aqueous suspension stabilizer solution with a concentration of 0.3%.

[0060] The concentration of HPCA-6 was found to be 50.8%, and the pH was 3.2.

[0061] Example 7

[0062] HPCA-7, a high-performance fluorine-free and alkali-free liquid quick-setting agent, differs from Example 3 in that the amorphous aluminum hydroxide synthesized from the polycarboxylate aluminum dispersion is specifically boehmite; it is prepared from the following components by mass percentage: 45% polycarboxylate aluminum dispersion, 40% aluminum sulfate, 1.0% alkali liquid quick-setting agent, 6.5% pH adjuster, and the remainder is 7.5% aqueous suspension stabilizer solution with a concentration of 0.3%.

[0063] The concentration of HPCA-6 was found to be 46.8%, and the pH was 3.0.

[0064] Example 8

[0065] HPCA-8, a high-performance fluorine-free and alkali-free liquid quick-setting agent, differs from Example 4 in that the amorphous aluminum hydroxide synthesized from the polycarboxylate aluminum dispersion is specifically boehmite; it is prepared from the following components by mass percentage: 45% polycarboxylate aluminum dispersion, 40% aluminum sulfate, 5.0% alkali liquid quick-setting agent, 6.5% pH adjuster, and the remainder is 3.5% aqueous suspension stabilizer solution with a concentration of 0.3%.

[0066] The concentration of HPCA-8 was found to be 46.8%, and the pH was 2.5.

[0067] Comparative Example 1

[0068] A non-alkali liquid quick-setting agent PCA-1 differs from Example 1 in that the alkali liquid quick-setting agent is composed of half the mass of powdered sodium fluoride; it is prepared from the following mass percentage components: 45% aluminum polycarboxylate dispersion, 40% aluminum sulfate, 1.0% sodium fluoride, 6.5% pH adjuster, and the remainder is 4.5% aqueous suspension stabilizer solution with a concentration of 0.3%.

[0069] The concentration of PCA-1 was found to be 50.8%, and the pH was 2.3.

[0070] Comparative Example 2

[0071] A non-alkali liquid quick-setting agent, PCA-2, differs from Example 2 in that its alkali-containing quick-setting agent component is fluorinated cryolite. It is prepared from the following mass percentage components: 45% aluminum polycarboxylate dispersion, 40% aluminum sulfate, 2.0% cryolite, 6.5% pH adjuster, and the remainder is 6.5% aqueous suspension stabilizer solution with a concentration of 0.3%.

[0072] The concentration of PCA-2 was found to be 50.8%, and the pH was 2.2.

[0073] Comparative Example 3

[0074] A non-alkali liquid quick-setting agent PCA-3 differs from Example 3 in that the pH adjuster component is diethanolamine instead of basic lysine; it is prepared from the following mass percentage components: 40% aluminum polycarboxylate dispersion, 45% aluminum sulfate, 2.0% alkali liquid quick-setting agent, 7.0% diethanolamine with a mass concentration of 85% as the pH adjuster, and the remainder is 5% aqueous suspension stabilizer solution with a concentration of 0.5%.

[0075] The concentration of PCA-3 was found to be 50.2%, and the pH was 2.4.

[0076] Comparative Example 4

[0077] A comparative alkali-free liquid quick-setting agent PCA-4 differs from Example 4 in that the suspension stabilizer component is magnesium aluminum silicate instead of xanthan gum; the composition is 40% aluminum polycarboxylate dispersion, 45% aluminum sulfate, 3.0% alkali liquid quick-setting agent, 7.0% pH adjuster, and the remainder is 5% magnesium aluminum silicate aqueous solution with a concentration of 0.5%.

[0078] The test results showed that the concentration of PCA-4 was 53.8% and the pH was 2.5.

[0079] The liquid accelerators of the above embodiments and comparative examples were used at a dosage of 6% of the cement mass percentage. The test results were shown in Table 1 below, referring to the test methods related to the setting time and strength of cement mortar with liquid accelerators in GB / T 35159-2017.

[0080] Table 1

[0081]

[0082] As can be seen from the experimental data in Table 1, the high-performance fluorinated alkali-free liquid accelerator of the present invention (Examples 1-8) achieves better synergistic effects by selecting specific proportions of polycarboxylate aluminum dispersion, aluminum sulfate, alkali-containing liquid accelerator, pH adjuster, and suspension stabilizer aqueous solution. This results in cement paste with an initial setting time of approximately 2 minutes, a final setting time within the range of 3-10 minutes, a compressive strength of cement mortar above 1.0 MPa after 6 hours, a compressive strength of cement mortar above 15.0 MPa after 1 day, and a compressive strength ratio of over 98% after 28 days. In contrast, while the fluorinated components in Comparative Examples 1 and 2 shorten the initial and final setting times of cement, the hourly strength within one day is significantly affected. Comparative Examples 3 and 4 show similar performance indicators, but all exhibit a certain degree of decline, potentially indicating a decreasing storage performance or potential quality instability issues.

[0083] Indoor tests were conducted on shotcrete using a method of first preparing C40 pumped concrete and then adding a liquid accelerator. Generally, it takes about 30 minutes for the concrete to be transported from the mixing plant to the tunnel construction site. After arriving at the construction site, the concrete has good workability, and the slump is controlled between 100 and 120 mm.

[0084] Therefore, the actual single-unit concrete mix proportion is: cement: fine aggregate (0.3-2.5mm): coarse aggregate (3.0-8.0mm): water: polycarboxylate pumping agent: mineral powder = 460kg: 910kg: 880kg: 190kg: 4.6kg: 46kg. The cement used is PO42.5 Esheng cement, and the liquid accelerator is added at 7% of the total cementitious material, i.e., 35kg. Samples from Examples 1-8 and Comparative Examples 1-4 were prepared using the post-addition method. Concrete specimens were wet-sprayed and molded under laboratory conditions, and the rebound rate was measured using the wire mesh top spraying method. The test results are shown in Table 2 below.

[0085] Table 2

[0086]

[0087]

[0088] As can be seen from the test results in Table 2, the rebound rate of the shotcrete in Examples 1 to 8 using the high-performance fluorine-free and alkali-free liquid quick-setting agent of the present invention is more than half of the <10%, the 8-hour compressive strength of the concrete is 7.0 to 12.5 MPa, which can ensure the rapid formation and strength of the surrounding rock retaining concrete structure; the 3-day compressive strength is greater than 30.0 MPa, basically reaching 75 to 80% of the design strength, ensuring the early structural strength of the retaining concrete; the 28-day compressive strength is 46.0 to 52.0 MPa, exceeding the design strength by more than 115%.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-performance, fluorine-free, alkali-free liquid quick-setting agent, characterized in that, The product is prepared by weight percentage from the following components: 35%–50% aluminum polycarboxylate dispersion, 35%–50% aluminum sulfate, 1.0%–3.5% alkaline liquid quick-setting agent, 5.0%–10% pH adjuster, and the balance being an aqueous suspension stabilizer solution; the pH value of the high-performance fluorine-free and alkali-free liquid quick-setting agent is 2.0–3.5; the high-performance fluorine-free and alkali-free liquid quick-setting agent does not contain fluorides. The suspension stabilizer in the aqueous suspension stabilizer solution is one or both of Werlen gum and Xanthan gum. The concentration of the aqueous suspension stabilizer is 0.2% to 0.5%; The preparation method of the polycarboxylate aluminum dispersion is as follows: a polycarboxylate water-reducing agent mother liquor with a mass concentration of 40% to 50%, amorphous aluminum hydroxide, and water are mixed in a mass ratio of (30-35):(30-35):(30-35) to obtain the polycarboxylate aluminum dispersion; The polycarboxylate superplasticizer mother liquor is selected from one or two of the early-strength polycarboxylate superplasticizer mother liquor and standard polycarboxylate superplasticizer mother liquor; the amorphous aluminum hydroxide is one or two of the pseudoboehmite and nano aluminum hydroxide powder; the fineness of the amorphous aluminum hydroxide ultrafine powder is greater than 1500 mesh. The preparation method of the early-strength polycarboxylate superplasticizer mother liquor is as follows: methyl allyl polyethylene glycol with a molecular weight of 4000-6000 is polymerized with acrylic acid at a molar ratio of 1:(6.0-8.0); the preparation method of the standard polycarboxylate superplasticizer mother liquor is as follows: methyl allyl polyethylene glycol with a molecular weight of 2400-3000 is polymerized with acrylic acid at a molar ratio of 1:(3.5-5). The pH adjuster is a basic amino acid.

2. The high-performance fluorine-free and alkali-free liquid quick-setting agent according to claim 1, characterized in that, The alkaline liquid quick-setting agent is used at a mass percentage of 2.0% to 3.0%; the alkaline liquid quick-setting agent is selected from sodium aluminate, or the product of sodium hydroxide and aluminum hydroxide reacted in water at 95℃ to 100℃; the mass concentration of the alkaline liquid quick-setting agent is 35.0% to 45.0%.

3. The high-performance fluorine-free and alkali-free liquid quick-setting agent according to claim 1, characterized in that, The basic amino acid is selected from one or more of arginine, lysine, and histidine; the pH adjuster is used in a mass percentage of 7.0% to 8.0%.

4. The method for preparing the high-performance fluorine-free and alkali-free liquid quick-setting agent according to any one of claims 1-3, characterized in that, The process includes the following steps: Take a polycarboxylate aluminum dispersion, add an aqueous suspension stabilizer solution, heat to 50-80℃, then add aluminum sulfate, stir for 10-40 minutes, add an alkaline liquid quick-setting agent and a pH adjuster, continue stirring for 10-40 minutes, and cool to obtain a translucent emulsion.

5. The application of the high-performance fluorine-free and alkali-free liquid quick-setting agent according to any one of claims 1-3 in shotcrete.

6. The application according to claim 5, characterized in that, High-performance, fluorine-free, alkali-free liquid quick-setting agent is added to cement at a mass percentage of 5-8%. The initial setting time of the cement paste is 1.5~2.5min, the final setting time is 3~10min, the compressive strength of the cement mortar is above 1.0MPa after 6 hours, the compressive strength is above 13.0MPa after 24 hours, and the compressive strength ratio after 28 days is above 95%. And / or, the high-performance fluorine-free and alkali-free liquid quick-setting agent is used to prepare C30~C50 shotcrete, meeting the requirements of concrete rebound rate of less than 10% and dust reduction to 20mg / m³. 3 the following.

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