Alkali-free accelerator as well as preparation method and application thereof

Abstract

The invention discloses an alkali-free accelerator and a preparation method and application thereof in the technical field of concrete additives, and the alkali-free accelerator provided by the invention comprises the following components in percentage by mass: 40%-50% of aluminum sulfate, 10%-15% of magnesium sulfate, 0.2%-0.6% of diethanol amine, 0.5%-1% of catechol-4-ammonium sulfonate, 5%-10% of a stabilizer and the balance of water. The stabilizer comprises silicate dispersion liquid and silica sol. The alkali-free accelerator provided by the invention can be used for spraying concrete, the mixing amount of the alkali-free accelerator is generally 4-6% of the mass of cement, the alkali-free accelerator is good in rapid setting effect and has excellent early and later compressive strength, and meanwhile, the alkali-free accelerator has relatively excellent stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete additive, in particular to a non-alkali accelerator and a preparation method and application thereof. BACKGROUND

[0002] The concrete accelerator refers to an additive that can make the concrete quickly coagulate and harden, and is an indispensable additive in major projects such as tunnels, railways and bridges. According to the alkali content, the accelerator is divided into high-alkali accelerator (alkali content > 5.0%), low-alkali accelerator (alkali content > 1.0%, ≤5.0%) and non-alkali accelerator (alkali content ≤1.0%). The accelerator can make the cement generate a large amount of needle-shaped ettringite in a short time, and the needle-shaped ettringite randomly overlaps to form a network structure to cause the accelerator, and the filling effect of C-S-H gel makes the structure more compact and the strength higher. Compared with the alkali accelerator, the non-alkali accelerator has the advantages of low alkali content, high later strength, less corrosion damage to construction personnel during construction, and can greatly improve the later strength of the sprayed concrete, which is beneficial to the construction of the project.

[0003] The over-saturated aluminum sulfate in the existing liquid non-alkali accelerator can generate various aluminum hydroxyl polynuclear complex ions through the hydrolysis reaction of aluminum ions, and finally generate aluminum hydroxide precipitate, so there are problems such as poor stability and large compatibility difference. It has positive significance to solve the above problems and research high-performance non-alkali accelerator to improve the construction efficiency of the project. SUMMARY

[0004] The purpose of the present application is to provide a non-alkali accelerator and a preparation method and application thereof, which specifically solve the technical problems of poor stability and large compatibility difference of the existing non-alkali accelerator.

[0005] The present application achieves the above-mentioned purposes through the following technical solutions: As a first aspect of the present application, the present application provides a non-alkali accelerator, which comprises, in terms of mass percentage, 40%-50% of aluminum sulfate, 10%-15% of magnesium sulfate, 0.2%-0.6% of diethanolamine, 0.5%-1% of ammonium pyrocatechol-4-sulfonate, 5%-10% of a stabilizer, and the rest is water, wherein the stabilizer comprises a silicate dispersion liquid and a silica sol.

[0006] As a further optimized scheme of the present application, the silicate mineral raw material for preparing the silicate dispersion liquid is selected from any one of soapstone, vermiculite or bentonite, and the mass concentration of the silicate dispersion liquid is 20%-30%.

[0007] As a further optimized scheme of the present application, the concentration of the silica sol is 15g / L-20g / L.

[0008] As a further optimized scheme of the present application, the mixing mass ratio of the silicate dispersion liquid and the silica sol is 10-15:1.

[0009] As a second aspect of the present application, a preparation method of the alkali-free accelerator is also provided, which comprises the following steps: (1) a silicate dispersion liquid prepared by finely grinding a silicate mineral raw material into powder and then dispersing it in water, and a silica sol prepared by hydrolyzing tetraethyl orthosilicate under acidic conditions are mixed to obtain a stabilizer; (2) according to the formula amount, aluminum sulfate is added to water, and then magnesium sulfate, diethanolamine and ammonium pyrocatechol-4-sulfonate are sequentially added, stirred and heated to 50-60°C to obtain a mixture, and finally the stabilizer prepared in step (1) is added, stirred until uniform, and cooled to room temperature to obtain the alkali-free accelerator.

[0010] As a further optimized scheme of the present application, in step (1), the addition concentration of the tetraethyl orthosilicate is 0.3-0.4 mol / L, the hydrolysis temperature is 50-70°C, and the hydrolysis time is 20-40 min, and the acid addition amount is 2-6% of the mass of the tetraethyl orthosilicate.

[0011] As a further optimized scheme of the present application, the acid is a 10% H2SO4 solution.

[0012] As a further optimized scheme of the present application, in step (2), the stirring rate is 200-300 r / min, and the stirring time is 2-4 h.

[0013] As a third aspect of the present application, the alkali-free accelerator is also applied as an admixture for shotcrete.

[0014] As a further optimized scheme of the present application, the addition amount of the alkali-free accelerator is 4-6% of the mass of the cement, and the accelerator has good setting effect and excellent early strength.

[0015] The present application has the following advantages: The present application introduces ammonium pyrocatechol-4-sulfonate into the alkali-free accelerator. On the one hand, the two hydroxyl groups in the structure of ammonium pyrocatechol-4-sulfonate can form a strong chelate (ring) complex with the central cation as a bidentate ligand, and combine with aluminum ions in the cement paste to form a chelated catechol complex, thereby significantly improving the initial setting and final setting time of the accelerator. On the other hand, the sulfonic acid group in its structure can significantly improve the adsorption rate and binding capacity of the cement particle surface, promote the rapid progress of the cement hydration reaction, and help the rapid setting, hardening and early strength development of the cement paste or concrete.

[0016] The present application adds a composite stabilizer prepared by mixing a silicate dispersion liquid and a silica sol into components of an alkali-free accelerator, and the stability time of the accelerator can be greatly improved by the cooperation of the silicate dispersion liquid and the silica sol, the stability effect of the accelerator is improved, and the coagulation efficiency is improved. DETAILED DESCRIPTION

[0017] It is necessary to point out here that the following detailed description is only used to further illustrate the present application, and cannot be understood as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above application content.

[0018] I. Materials and Methods The method used in the present application is a conventional method known to those skilled in the art, and the reagents and materials used are commercially available products, unless otherwise specified.

[0019] Aluminum sulfate, industrial grade tablet, iron-free aluminum sulfate, alumina content ≥ 16%; Magnesium sulfate, industrial grade, purity 99%, diethanolamine, industrial grade, purity 99%, o-phenylenediamine-4-ammonium sulfonate, analytical pure, purity 98%.

[0020] Example 1 The present application provides an alkali-free accelerator, which comprises, in terms of mass percentage, aluminum sulfate 50%, magnesium sulfate 10%, diethanolamine 0.4%, o-phenylenediamine-4-ammonium sulfonate 1%, stabilizer 5%, and the rest is water, the stabilizer comprises soapstone dispersion liquid and silica sol, and the mass ratio of the silicate dispersion liquid to the silica sol is 10:1.

[0021] The preparation method of the alkali-free accelerator comprises the following steps: (1) According to the formula amount, the soapstone required for preparing a soapstone dispersion liquid with a mass concentration of 20% is weighed and finely ground into powder and added into water, and the water bath is heated at 60°C and 300r / min for 30min, then the water bath heating is turned off, and the stirring is maintained at the same speed for at least 10h, and it is ready for use; (2) According to the mass ratio of 2:1, water and ethanol are prepared as solvents, then the formula amount of tetraethyl orthosilicate with a concentration of 0.36mol / L is added into a beaker and stirred to dissolve, then 4% of the mass of the tetraethyl orthosilicate is slowly added into the beaker as a mass concentration of 10% H2SO4 solution, and the stirring speed is 300r / min, and the temperature is kept at 70°C for 20min, and the silica sol is obtained after cooling; (3) The silicate dispersion liquid prepared in step (1) and the silica sol prepared in step (2) are mixed according to the above mass ratio to prepare the stabilizer. (4) Add aluminum sulfate to water according to the formula amount, then add magnesium sulfate, diethanolamine and catechol-4-sulfonate in sequence, stir at 300 r / min and heat to 60°C to obtain a mixture, finally add stabilizer, stir at 300 r / min for 2 h until uniform, and cool to room temperature to obtain alkali-free quick-setting agent.

[0022] Example 2 This embodiment provides an alkali-free quick-setting agent, which, by mass percentage, comprises 40% aluminum sulfate, 15% magnesium sulfate, 0.6% diethanolamine, 0.5% catechol-4-sulfonate ammonium, 10% stabilizer, and the remainder being water. The stabilizer includes a silicate dispersion and a silica sol, with the silicate dispersion and silica sol mixed in a mass ratio of 15:1.

[0023] The preparation method of the alkali-free quick-setting agent includes the following steps: (1) According to the formula, weigh the silicate mineral raw material - soapstone required to prepare silicate dispersion with a mass concentration of 30%, grind it into powder and add it to water. Disperse it in a water bath at 50℃ and 300r / min for 30min. Then turn off the water bath heating and stir at the same stirring speed for at least 10h for later use. (2) Prepare water and ethanol as solvents in a mass ratio of 2:1. Then add 0.36 mol / L tetraethyl orthosilicate to a beaker and stir to make it mixed. In a water bath at 50°C, slowly add 6% of the mass of tetraethyl orthosilicate and 10% of the mass of H2SO4 solution and stir at a stirring speed of 300 r / min. Keep warm for 40 min and cool to obtain silica sol. (3) The silicate dispersion prepared in step (1) and the silica sol prepared in step (2) are mixed in the above mass ratio to prepare a stabilizer; (4) Add aluminum sulfate to water according to the formula amount, then add magnesium sulfate, diethanolamine and catechol-4-sulfonate in sequence, stir at 200 r / min and heat to 50°C to obtain a mixture, finally add stabilizer, stir at 200 r / min for 4 h until uniform, and cool to room temperature to obtain alkali-free quick-setting agent.

[0024] Example 3 This embodiment provides an alkali-free quick-setting agent, which, by mass percentage, comprises 45% aluminum sulfate, 12% magnesium sulfate, 0.2% diethanolamine, 0.7% catechol-4-sulfonate ammonium, 12% stabilizer, and the remainder being water. The stabilizer includes a silicate dispersion and a silica sol, with the silicate dispersion and silica sol mixed in a mass ratio of 15:1.

[0025] The method for preparing the alkali-free quick-setting agent in this embodiment is the same as in Example 1.

[0026] II. Verification Experiment 1. To investigate the effect of the composition of alkali-free quick-setting agent on its performance, the composition of alkali-free quick-setting agent was adjusted according to Table 1, and samples A-1 to A-4 of alkali-free quick-setting agent were prepared according to the preparation method given in Example 1.

[0027] Table 1. Composition of Alkali-Free Accelerating Agents ; The following performance tests were conducted on alkali-free quick-setting agent samples A-1 to A-4: (1) Determination of setting time of cement paste: Take 900g of standard cement (commercially available), with a water-cement ratio of 0.4 (the actual water consumption is the total water consumption minus the water content in the alkali-free quick-setting agent), add 36g of alkali-free quick-setting agent and stir evenly to obtain cement paste, and then determine it according to the evaluation standard in the national standard "GB / T 35159 2017 Quick-setting agent for shotcrete"; (2) Determination of mortar compressive strength: Take 900g of reference cement (commercially available), with a water-cement ratio of 0.4 (the actual water consumption is the total water consumption minus the water content in the alkali-free quick-setting agent), add 1350g of standard sand to the cement and stir until uniform, quickly add 36g of alkali-free quick-setting agent and stir until uniform, then add it to the mold (40 mm × 40 mm × 160 mm) for mortar compressive strength testing and shake it thoroughly. Place the mold containing cement in a heat preservation box at 20±2℃ for curing for 24 hours and then remove the mold. Subsequently, the performance of mortar compressive strength at a specific age is determined according to the evaluation standard in the national standard "GB / T 35159 2017 Quick-setting Agent for Shotcrete".

[0028] (3) Stability test of alkali-free quick-setting agent: According to the evaluation standard in GB / T 35159 2017 Quick-setting agent for shotcrete, a certain amount of alkali-free quick-setting agent sample is placed in a stoppered measuring cylinder and left to stand at a certain temperature for a period of time. The volume of the sediment at the top and bottom is tested. A volume ≤ 5 mL is considered stable and effective.

[0029] In addition, a blank control was used without the addition of alkali-free quick-setting agent, and the results are shown in Table 2.

[0030] Table 2. Performance Test Results ; As can be seen from Table 2, compared with sample A-2, the alkali-free quick-setting agent component of sample A-1 contains ammonium catechol-4-sulfonate. Due to the effect of the catechol-4-sulfonate group itself, it can play a strong role in the solidification of cement. In the early stage of hydration, aluminum sulfate and ammonium catechol-4-sulfonate can stimulate or accelerate the formation of ettringite, which has a positive effect on shortening the initial and final setting time of the cement paste. Moreover, because the cement generates a large number of needle-like ettringite in a short time and randomly overlaps to form a network structure, coupled with the filling effect of CSH gel, the mortar structure becomes denser and the compressive strength is also improved.

[0031] For sample A-3, catechol was added to its alkali-free quick-setting agent component. Compared with the blank sample, it can be seen that the addition of catechol to the alkali-free quick-setting agent can also shorten the initial and final setting time of the cement paste and improve the compressive strength of the mortar, but the overall effect is not as good as that of catechol-4-sulfonate ammonium.

[0032] For sample A-4, no stabilizer was added to its alkali-free quick-setting agent component, and its stabilization period of the alkali-free quick-setting agent was significantly shorter than that of other samples. The setting time of the mortar was also longer than that of other samples, and the compressive strength of the mortar also decreased accordingly.

[0033] To investigate the effect of stabilizer composition on the performance of alkali-free quick-setting agent, the stabilizer composition was adjusted according to Table 3, and alkali-free quick-setting agent samples B-1 to B-7 were prepared according to the preparation method described in Example 1.

[0034] Table 3. Composition of Stabilizers ; Note: The mass ratio of silicate dispersion to silica sol is 10:1.

[0035] The same performance tests as described above were performed on the alkali-free quick-setting agent samples B-1 to B-7, and the results are shown in Table 4.

[0036] Table 4. Performance Test Results ; The results are shown in Table 4. Different components of the stabilizer have different effects on its performance. The combined use of silicate dispersion and silica sol has a better effect on improving the performance of alkali-free quick-setting agent than using silicate dispersion or silica sol alone. It helps cement paste or concrete to set quickly, harden and generate early strength. In addition, a comparison of samples B-1 to B-3 shows that the type of silicate in the silicate dispersion affects the setting time of the cement paste and the compressive strength of the mortar. The soapstone dispersion was selected to achieve the best performance.

[0037] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An alkali-free quick-setting agent, characterized in that, The composition, by mass percentage, includes 40%-50% aluminum sulfate, 10%-15% magnesium sulfate, 0.2%-0.6% diethanolamine, 0.5%-1% catechol-4-sulfonate ammonium, 5%-10% stabilizer, and the remainder being water. The stabilizer includes silicate dispersion and silica sol.

2. The alkali-free quick-setting agent according to claim 1, characterized in that, The silicate mineral raw material used to prepare the silicate dispersion is selected from any one of soapstone, vermiculite, or bentonite.

3. The alkali-free quick-setting agent according to claim 1, characterized in that, The mass concentration of the silicate dispersion is 20%-30%.

4. The alkali-free quick-setting agent according to claim 1, characterized in that, The mass ratio of the silicate dispersion to the silica sol is 10-15:

1.

5. A method for preparing an alkali-free quick-setting agent as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) The silicate mineral raw material is first finely ground into powder, then added to water to disperse to prepare a silicate dispersion, then tetraethyl orthosilicate is hydrolyzed under acidic conditions to prepare a silica sol, and finally the silicate dispersion and silica sol are mixed to prepare a stabilizer. (2) Add aluminum sulfate to water according to the formula amount, then add magnesium sulfate, diethanolamine and catechol-4-sulfonate in sequence, stir and heat to 50℃-60℃ to obtain a mixture, and finally add the stabilizer prepared in step (1), stir until uniform, and cool to room temperature to obtain the alkali-free quick-setting agent.

6. The method for preparing an alkali-free quick-setting agent according to claim 1, characterized in that, In step (1), the concentration of added tetraethyl orthosilicate is 0.3 mol / L or 0.4 mol / L, the hydrolysis temperature is 50℃ or 70℃, the hydrolysis time is 20 min or 40 min, and the amount of acid added accounts for 2% or 6% of the mass of tetraethyl orthosilicate.

7. The method for preparing an alkali-free quick-setting agent according to claim 6, characterized in that, The acid is a 10% (w / w) H2SO4 solution.

8. The method for preparing an alkali-free quick-setting agent according to claim 5, characterized in that, In step (2), the stirring rate is 200r / min-300r / min and the stirring time is 2h-4h.

9. The use of an alkali-free quick-setting agent as described in any one of claims 1-4 as an admixture in shotcrete.

10. The application according to claim 9, characterized in that, The amount of the alkali-free quick-setting agent added is 4%-6% of the cement mass.