A rapid-hardening and early-strength waste-based geopolymer grouting repair material and its preparation method

Abstract

The present invention relates to a rapid-hardening and early-strength waste-based geopolymer grouting repair material and a preparation method thereof. The grouting repair material comprises fly ash, slag, silica fume, cement, an alkali activator and water, and the mass parts of each component are respectively: 20-35 parts of fly ash, 65-75 parts of slag, 2-5 parts of silica fume, 2-5 parts of cement, 35-45 parts of alkali activator and 0-6 parts of water; the method specifically is: stirring fly ash, slag, silica fume and cement to obtain a precursor; stirring the alkali activator and water to obtain an activator solution; stirring the precursor and the activator solution to obtain the rapid-hardening and early-strength waste-based geopolymer grouting repair material. Compared with the prior art, the present invention gives full play to the performance advantages of geopolymer itself in the field of grouting materials, improves the repair performance of the grouting materials, and provides a feasible solution for the future development problems in industries such as road repair and grouting reinforcement; the fluidity meets the requirements of grouting construction, and the final product has excellent performance.

Description

Technical Field

[0001] The present invention belongs to the technical fields of road grouting and building crack repair, and relates to a rapid-hardening and early-strength waste-based geopolymer grouting repair material and a preparation method thereof. Background Art

[0002] Building grouting materials refer to fluid materials that are injected into the cracks, holes, etc. of structures under the action of pressure, etc., to achieve effects such as increasing bearing capacity, preventing leakage, and improving the overall performance of the structure. Grouting materials are widely used in road repair and building crack repair, playing a role of filling and consolidation in cracks and pores, and are the key to realizing the functions of leak stoppage and reinforcement. This requires that the grout of the grouting material has low viscosity, good fluidity, and strong injectability in the initial stage. At the same time, to meet the actual application requirements such as emergency repair and shorten the construction period, the grouting material should also have the performance characteristics of rapid hardening and early strength. Compared with the common cement-based grouting materials on the market, geopolymer materials can consume industrial solid waste while having a shorter setting time and higher early strength, and are ideal matrices for producing grouting materials.

[0003] Patent CN113666655A discloses a material for promoting the formation of geopolymer in a high-humidity environment and a preparation method thereof. The raw materials include solid waste, activator, additive, and water; the solid waste is industrial solid waste, including fly ash and phosphate tailings sand; the activator is an alkaline activator, which is one of sodium hydroxide activator, sodium hydroxide-silica fume composite activator, and water glass activator; the additive is xanthan gum, and the addition amount of the additive is 1% of the solid waste; the mass ratio of water to solid waste (water-solid ratio) is 0.5 - 0.75. However, this patent only focuses on and attempts to solve the formation of geopolymer under special conditions such as high-humidity environment, and does not use suitable solid waste as a precursor to improve the early strength of geopolymer. Specifically, the initial setting time of the geopolymer in the examples is relatively long, and it cannot develop high mechanical strength in a very short time.

[0004] Patent CN108516739A discloses a rapid-setting and early-strength geopolymer grouting material and a preparation method thereof, including a skeleton material, an external admixture skeleton material, an alkali activator, and a chemical auxiliary agent. The mass parts of the skeleton material, external admixture skeleton material, alkali activator, and chemical auxiliary agent are 40 - 100 parts, 0 - 20 parts, 5 - 10 parts, and 0.5 - 10 parts respectively. Although this patent uses industrial solid wastes such as fly ash and slag, it does not solve the problem of the strength development of the grouting material in a short time, and there is still a need to further improve the durability of the grouting material and shorten the curing time. Summary of the Invention

[0005] The object of the present invention is to overcome at least one defect of the above-mentioned existing technologies and provide a rapid-hardening and early-strength waste-based geopolymer grouting repair material and a preparation method thereof. The present invention uses fly ash, slag, silica fume and cement as precursors and sodium hydroxide and sodium silicate as alkali activators, giving full play to the performance advantages of geopolymers in the field of grouting materials, improving the repair performance of grouting materials, and providing a feasible solution for the future development of industries such as road repair and grouting reinforcement.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a rapid-hardening and early-strength waste-based geopolymer grouting repair material, which includes fly ash, slag, silica fume, cement, alkali activator and water. The mass parts of each component are 20-35 parts of fly ash, 65-75 parts of slag, 2-5 parts of silica fume, 2-5 parts of cement, 35-45 parts of alkali activator and 0-6 parts of water.

[0008] Fly ash is a solid waste generated in industries such as thermal power plants, metallurgy and chemical engineering, while slag is the residue after blast furnace ironmaking. Both industrial wastes can be used as precursors to undergo geopolymerization under the action of alkali activators. In the geopolymer system, fly ash has a certain viscosity-reducing effect on geopolymers, which can improve the fluidity of the slurry and facilitate the smooth progress of the grouting process; the incorporation of slag can shorten the setting time of geopolymers and accelerate the hardening of grouting materials. The incorporation of a small amount of silica fume can also shorten the setting time of geopolymers, and cement is the most common gelling material.

[0009] Further, the water-solid ratio of the grouting repair material is 0.23-0.27, where the water includes the water content in the alkali activator and the additional water, and the solid includes fly ash, slag, silica fume and cement.

[0010] Further, the calcium oxide content of the fly ash is 3-10% wt, and the specific surface area is 300-400 m 2 / kg.

[0011] Further, the calcium content of the slag is 58-60% wt, and the silicon content is 22-24% wt.

[0012] Further, the specific surface area of the silica fume is 15000-30000 m 2 / kg.

[0013] Further, the cement is ordinary Portland cement with a grade of P.O 42.5.

[0014] Further, the alkali activator is prepared by mixing sodium hydroxide and sodium silicate, and the modulus is 1.2-1.5.

[0015] One of the technical solutions of the present invention is to provide a preparation method of a rapid-hardening and early-strength waste-based geopolymer grouting repair material, and the method comprises the following steps:

[0016] (1) Stir fly ash, slag, silica fume and cement evenly to obtain a precursor;

[0017] (2) Stir an alkali activator and water evenly to obtain an activator solution;

[0018] (3) Stir the precursor obtained in step (1) and the activator solution obtained in step (2) evenly to obtain the rapid-hardening and early-strength waste-based geopolymer grouting repair material.

[0019] As a preferred technical solution, the stirring time in steps (1) and (2) is 120 - 180 s.

[0020] Further, the stirring method in step (3) is specifically as follows: Pour the precursor into a stirring pot, stir at a low speed, and slowly and evenly pour the activator solution along the wall of the pot after starting to stir (because the activator solution is relatively viscous and is not suitable to be poured all at once), let it stand, and then stir at a high speed until it is evenly mixed to obtain the rapid-hardening and early-strength waste-based geopolymer grouting repair material.

[0021] Further, the low-speed stirring time is 120 - 180 s, the activator solution is poured within 25 - 35 s after starting to stir, the standing time is 15 - 20 s, and the high-speed stirring time is 120 - 180 s.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The present invention uses fly ash, slag, silica fume and cement as the precursor, and uses sodium hydroxide and sodium silicate as the alkali activator, so that the geopolymer grouting material maintains good fluidity within 30 min after mixing, has a fast-developing compressive strength, meets the construction requirements of the grouting material, has the advantages of rapid hardening and early strength, improves the repair performance of the grouting material, gives play to the performance advantages of the geopolymer itself in the field of grouting materials, and provides a feasible solution for the future development problems of industries such as road repair and grouting reinforcement;

[0024] (2) The present invention provides a geopolymer ratio and a preparation method, and the prepared grouting material meets the requirements of grouting construction, and the final product has excellent performance. Specific embodiments

[0025] The present invention will be described in detail below in conjunction with specific embodiments. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0026] Unless otherwise specified, the equipment used in the following embodiments is all conventional equipment in the art; unless otherwise specified, the reagents used are all commercially available products or prepared by conventional methods in the art. Those not described in detail in the following embodiments can be achieved by conventional experimental means in the art.

[0027] The parts used in this embodiment are all based on mass as the basic unit.

[0028] The main raw materials in this embodiment are as follows:

[0029] The fly ash is Class F fly ash from a certain power plant, Grade II ash, with a specific surface area of 350 m 2 / kg, and its main chemical composition is shown in Table 1; the slag is S95 grade, with a calcium content of 58.8% wt and a silicon content of 23.1% wt; the silica fume is a by-product of the smelting of ferrosilicon and industrial silicon in steel alloys, with a specific surface area of 23000 m 2 / kg; the cement is ordinary Portland cement with a grade of P.O42.5; the modulus of the alkali activator is 1.2, and it is prepared from sodium hydroxide and sodium silicate. The calculation method is as follows:

[0030] G1 = (80G2N(M1 - M2)) / (62M2P)

[0031] In the formula, G2 is the mass of sodium silicate, N is the content of sodium oxide in sodium silicate, which is selected as 27.2% in this embodiment, M1 is the initial modulus of sodium silicate, which is selected as 1.5 in this embodiment, M2 is the preparation modulus of the alkali activator required in the embodiment, which is selected as 1.2 in this embodiment, and P is the purity of sodium hydroxide, which is selected as 95% in this embodiment. The mass of sodium hydroxide G1 to be added is calculated. In this embodiment, the mass ratio of sodium hydroxide to sodium silicate G1 / G2 is 0.0924.

[0032] Table 1 Main chemical composition of fly ash

[0033]

[0034] Example:

[0035] A rapid hardening and early strength waste-based geopolymer grouting repair material, and the specific proportions of each raw material are as follows:

[0036] Fly ash 2 parts, slag 7 parts, silica fume 0.5 part, cement 0.5 part, alkali activator 3.8 parts, water 0.54 part;

[0037] The water content of the alkali activator is 51.5%, and the ratio of water to solid precursor (water-solid ratio) is 0.25. The water includes the water content in the alkali activator and the additional water.

[0038] A preparation method of a rapid-hardening and early-strength waste-based geopolymer grouting repair material is as follows:

[0039] Mix 2 parts by mass of fly ash, 7 parts by mass of slag, 0.5 part by mass of silica fume and 0.5 part by mass of cement, and stir the raw materials for 120 s until evenly mixed to form a precursor.

[0040] Pour 3.8 parts by mass of the alkali activator into a beaker, add 0.54 part by mass of water, and stir for 120 s to obtain an activator solution.

[0041] Pour the precursor into a stirring pot and stir at a low speed for 120 s. Slowly and evenly pour the activator solution along the inner wall of the pot within 30 s after starting the stirring, let it stand for 15 s, and then stir at a high speed for 120 s until evenly mixed to obtain a geopolymer grouting repair material.

[0042] Comparative Example 1:

[0043] A fly ash-slag geopolymer and its preparation method are basically the same as those in the example, except that silica fume and cement are removed and replaced with fly ash.

[0044] The specific proportions of each raw material are as follows:

[0045] Fly ash 3 parts, slag 7 parts, alkali activator 3.8 parts, water 0.54 part;

[0046] The water-solid ratio is 0.25.

[0047] Comparative Example 2:

[0048] A geopolymer with a low slag content and its preparation method are basically the same as those in Comparative Example 1, except that the amount of slag is reduced and an excessive amount of fly ash is added.

[0049] The specific proportions of each raw material are as follows:

[0050] Fly ash 5 parts, slag 5 parts, alkali activator 3.8 parts, water 0.54 part;

[0051] The water-solid ratio is 0.25.

[0052] Comparative Example 3:

[0053] A geopolymer with a high water-solid ratio and its preparation method are basically the same as those in Comparative Example 1, except that an excessive amount of water is added.

[0054] The specific proportions of each raw material are as follows:

[0055] 3 parts of fly ash, 7 parts of slag, 3.8 parts of alkali activator, and 1.04 parts of water;

[0056] The water-solid ratio is 0.3.

[0057] Table 2 Mix ratios of the examples and comparative examples

[0058]

[0059] The compressive strength test, fluidity test, and setting time test were carried out on the above examples and comparative examples 1 to 3. The results are shown in Table 3. The compressive strength test method refers to the national standard "Test Method for the Strength of Cement Mortar" (GB / T 17671-1999) to test the 4h compressive strength of the formed neat cement mortar specimens. The fluidity test refers to the cement paste fluidity test method in the national standard "Test Methods for the Homogeneity of Concrete Admixtures" (GB / T 8077-2012) to test the fluidity of the fresh mortar and the fluidity of the mortar after mixing for 30 min. The setting time test method refers to the national standard "Test Methods for the Standard Consistency Water Requirement, Setting Time and Soundness of Cement" (GB / T 1346-2011) to test the initial setting time and final setting time.

[0060] Table 3 Compressive strength, fluidity, and setting time of the examples and comparative examples

[0061]

[0062] For the grouting material, the 4h compressive strength reflects the mechanical properties of the material after construction. At the same time, the rapid increase in strength in a short time also reflects the setting and hardening speed of the material, which can better evaluate whether the grouting material has excellent performance. As shown in Table 3, compared with the fly ash slag geopolymer without silica fume and cement (comparative example 1), the low slag content geopolymer (comparative example 2), and the high water-solid ratio geopolymer (comparative example 3), the 4h compressive strength of this example reaches 30.1 MPa, showing a significant increase compared with comparative examples 1 to 3 and a relatively high strength value, meeting the requirements of rapid hardening and early strength of the grouting material.

[0063] The fresh fluidity and the fluidity after mixing for 30 minutes reflect the working performance of the grouting material. A larger fluidity is beneficial to the progress of grouting construction. The initial setting time and the final setting time reflect the constructible window time of the grouting material. The initial setting time refers to the time when the paste starts to lose plasticity after adding water, and the final setting time refers to the time when the paste completely loses plasticity after adding water. Generally, it is required that the initial setting time is not less than 30 minutes to meet the construction needs. As shown in Table 3, compared with the fly ash slag geopolymer without silica fume and cement (Comparative Example 1) and the geopolymer with a low slag content (Comparative Example 2), the fresh fluidity of this example is better, and the initial setting time is 33 minutes. At this time, Comparative Examples 1 and 2 have completely lost plasticity. Compared with the geopolymer with a high water-solid ratio (Comparative Example 3), the fluidity after 30 minutes in this example is greater than that in Comparative Example 3, which is convenient for grouting construction.

[0064] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A rapid-hardening and early-strength waste-based geopolymer grouting repair material, characterized in that, The grouting repair material comprises fly ash, slag, silica fume, cement, an alkali activator and water. The mass parts of each component are respectively: 20 - 35 parts of fly ash, 65 - 75 parts of slag, 2 - 5 parts of silica fume, 2 - 5 parts of cement, 35 - 45 parts of alkali activator and 0 - 6 parts of water; The water - solid ratio of the grouting repair material is 0.23 - 0.

27. The water therein includes two parts, namely the water content in the alkali activator and the additional water amount, and the solid includes fly ash, slag, silica fume and cement; The calcium oxide content of the fly ash is 3-10%wt, and the specific surface area is 300-400 m 2 / kg; The slag has a calcium content of 58 - 60%wt and a silicon content of 22 - 24%wt; The specific surface area of the silica fume is 15,000 - 30,000 m 2 / kg; The cement is ordinary Portland cement with a grade of P.O 42.5; The alkali activator is prepared by mixing sodium hydroxide and sodium silicate with a modulus of 1.2 - 1.5; The preparation method of the rapid - hardening and early - strength waste - based geopolymer grouting repair material, which comprises the following steps: (1) Stir fly ash, slag, silica fume and cement to obtain a precursor; (2) Stir the alkali activator and water to obtain an activator solution; (3) Stir the precursor obtained in step (1) and the activator solution obtained in step (2) to obtain the rapid - hardening and early - strength waste - based geopolymer grouting repair material; The stirring time in steps (1) and (2) is 120 - 180 s; The specific stirring method in step (3) is: pour the precursor into a stirring pot, stir at a low speed, and slowly and evenly pour the activator solution along the pot wall after starting to stir, let it stand, and then stir at a high speed until it is evenly mixed to obtain the rapid - hardening and early - strength waste - based geopolymer grouting repair material; The low - speed stirring time is 120 - 180 s, the activator solution is poured in within 25 - 35 s after starting to stir, the standing time is 15 - 20 s, and the high - speed stirring time is 120 - 180 s.

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