Composition for preparing geopolymer with adjustable thickening time

Abstract

The invention provides a composition for preparing a geopolymer with adjustable thickening time. The composition comprises fly ash, slag, an activating agent and water, wherein the activating agent is a calcium hydroxide compound and sodium fluoride.

Description

Technical Field

[0001] The present invention relates to a composition for preparing geopolymers. Background Art

[0002] Fly ash-based geopolymers are cementitious materials prepared by mixing fly ash with an activator alkali. They are named because their hydration products are aluminosilicate polymers with a three-dimensional network structure and their reaction process is similar to geochemical processes. The main hydration product of geopolymers is sodium aluminosilicate gel, which has good stability in acidic environments such as hydrochloric acid, nitric acid, and carbonic acid. Therefore, it is very suitable for operations in wells with stimulation measures such as acidification.

[0003] Although geopolymers have good acid corrosion resistance, the activators used in them are usually strongly alkaline sodium hydroxide, which seriously endangers personal safety during on-site use. Sodium hydroxide has strong corrosiveness and generates a large amount of heat when dissolved in water, corroding and burning the skin and mucous membranes. In addition, after skin contact with sodium hydroxide, it may mix with sweat to generate heat, burn the skin to form wounds, and endanger personal safety. Therefore, using an activator that is friendly to the environment and personal safety, easy to control, and can produce high-strength fly ash-based geopolymers is of great significance for promoting the on-site application of fly ash-based geopolymers. Summary of the Invention

[0004] One aspect of the present invention provides a composition for preparing geopolymers, which includes fly ash, slag, an activator, and water, wherein the activator is a calcium hydroxide complex and sodium fluoride.

[0005] In a specific embodiment, the calcium hydroxide complex is obtained by a chemical reaction between sodium silicate and calcium oxide.

[0006] In a specific embodiment, the calcium hydroxide complex is obtained by reacting sodium silicate and calcium oxide at 20 to 40 °C for 20 to 30 h.

[0007] In a specific embodiment, the calcium hydroxide complex is obtained by reacting sodium silicate and calcium oxide at 25 to 35 °C for 24 h.

[0008] In a specific embodiment, the mass ratio of the sodium silicate to the calcium oxide is 10:90 to 20:80.

[0009] In a specific embodiment, based on the total mass of the sodium silicate and the calcium oxide being 100%, when preparing the calcium hydroxide complex, 25% to 45% of water, such as 30% of water, is further included.

[0010] In a specific embodiment, the particle size of the calcium hydroxide complex is 100 mesh to 200 mesh.

[0011] In a specific embodiment, the mass ratio of the calcium hydroxide complex to the sodium fluoride is (1 to 1.1):1.

[0012] In a specific embodiment, in the fly ash, the mass content of silicon dioxide ≥ 40%.

[0013] In a specific embodiment, in the fly ash, the mass content of silicon dioxide ≥ 45%.

[0014] In a specific embodiment, the specific surface area of the fly ash is greater than 1500 m 2 / kg.

[0015] In a specific embodiment, the specific surface area of the fly ash ≥ 1800 m 2 / kg.

[0016] In a specific embodiment, the specific surface area of the fly ash ≥ 1820 m 2 / kg.

[0017] In a specific embodiment, the specific surface area of the slag is 400 to 450 m 2 / kg.

[0018] In a specific embodiment, based on the total mass of the fly ash and the slag being 100%, the dosage of the activator is 13% to 26%, and the dosage of water is 50% to 56%.

[0019] In a specific embodiment, the composition further includes a retarder.

[0020] In a specific embodiment, the retarder is sodium ethylene diamine tetra (methylene phosphonate).

[0021] In a specific embodiment, based on the total mass of the fly ash and the slag being 100%, the dosage of the retarder is 0.2% to 3%.

[0022] The second aspect of the present invention provides the application of the geopolymer prepared from the composition according to any one of the first aspect of the present invention in well cementing and / or plugging. For example, in well cementing operations in engineering wells such as CCUS wells, acidified wells, etc., or in drilling plugging.

[0023] Advantages of the present invention:

[0024] Using the composition of the present invention to prepare geopolymers, not only can the strength be comparable to that of geopolymers prepared with sodium hydroxide, but also the problem that the thickening time of geopolymers activated by sodium fluoride and calcium hydroxide is difficult to control due to the too fast reaction rate between sodium fluoride and calcium hydroxide can be solved, that is, the activator of the present invention can slow down the reaction rate between calcium hydroxide and sodium fluoride and extend the thickening time of geopolymers; further, in the case of using a retarder in combination, the thickening time can be better controlled. In addition, the activator of the present invention is safe and environmentally friendly. Detailed Embodiments

[0025] The present invention will be further described below in conjunction with embodiments, but the embodiments of the present invention are only illustrative explanations, and this implementation method does not constitute a limitation to the present invention under any circumstances.

[0026] Preparation of Calcium Hydroxide Complex

[0027] Example 1

[0028] Sodium silicate: 15 parts by mass.

[0029] Calcium oxide: 85 parts by mass.

[0030] Mix 15 parts by mass of sodium silicate with 85 parts by mass of calcium oxide, add water, react at 30 °C for 24 h, dry, and pulverize to 100 to 200 mesh to obtain calcium hydroxide complex 1#.

[0031] Example 2

[0032] Sodium silicate: 10 parts by mass.

[0033] Calcium oxide: 90 parts by mass.

[0034] Mix 10 parts by mass of sodium silicate with 90 parts by mass of calcium oxide, add water, react at 30 °C for 24 h, dry, and pulverize to 100 to 200 mesh to obtain calcium hydroxide complex 2#.

[0035] Example 3

[0036] Sodium silicate: 20 parts by mass.

[0037] Calcium oxide: 80 parts by mass.

[0038] Mix 20 parts by mass of sodium silicate with 80 parts by mass of calcium oxide, add water, react at 30 °C for 24 h, dry, and pulverize to 100 to 200 mesh to obtain calcium hydroxide complex 3#.

[0039] Preparation of Fly Ash-Based Geopolymer

[0040] Example 4

[0041] Prepare on-site during use or when measuring performance indicators: Mix 80 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 / kg, mass content of silicon dioxide 45%), 20 parts by mass of S95 slag powder, 6.5 parts by mass of calcium hydroxide complex 1#, 6.5 parts of sodium fluoride, 1.5 parts by mass of ethylenediaminetetramethylenephosphonic acid sodium and 50 parts by mass of water, and stir evenly to obtain Composition 1# for preparing fly ash-based geopolymers.

[0042] Example 5

[0043] Prepare on-site during use or when measuring performance indicators: Mix 80 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 / kg, mass content of silicon dioxide 45%), 20 parts by mass of S95 slag powder, 10 parts by mass of calcium hydroxide complex 1#, 10 parts of sodium fluoride, 1.5 parts by mass of ethylenediaminetetramethylenephosphonic acid sodium and 53 parts by mass of water, and stir evenly to obtain Composition 2# for preparing fly ash-based geopolymers.

[0044] Example 6

[0045] Prepare on-site during use or when measuring performance indicators: Mix 80 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 / kg, mass content of silicon dioxide 45%), 20 parts by mass of S95 slag powder, 13.6 parts by mass of calcium hydroxide complex 1#, 12.4 parts of sodium fluoride, 1.5 parts by mass of ethylenediaminetetramethylenephosphonic acid sodium and 56 parts by mass of water, and stir evenly to obtain Composition 3# for preparing fly ash-based geopolymers.

[0046] Example 7

[0047] Prepare on-site during use or when measuring performance indicators: Mix 80 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 / kg, mass content of silicon dioxide 45%), 20 parts by mass of S95 slag powder, 6.5 parts by mass of calcium hydroxide complex 2#, 6.5 parts of sodium fluoride, 1.5 parts by mass of ethylenediaminetetramethylenephosphonic acid sodium and 50 parts by mass of water, and stir evenly to obtain Composition 4# for preparing fly ash-based geopolymers.

[0048] Example 8

[0049] Prepare on-site during use or when measuring performance indicators: Mix 80 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 / kg, with a silica mass content of 45%) 80 parts by mass, 20 parts by mass of S95 slag powder, 10 parts by mass of calcium hydroxide complex 2#, 10 parts of sodium fluoride, 1.5 parts by mass of ethylenediaminetetramethylenephosphonic acid sodium salt, and 53 parts by mass of water are mixed and stirred evenly to obtain Composition 5# for preparing fly ash-based geopolymers.

[0050] Example 9

[0051] Prepare on-site during use or when measuring performance indicators: Mix 80 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 / kg, with a silica mass content of 45%), 20 parts by mass of S95 slag powder, 13.6 parts by mass of calcium hydroxide complex 2#, 12.4 parts of sodium fluoride, 1.5 parts by mass of ethylenediaminetetramethylenephosphonic acid sodium salt, and 56 parts by mass of water, and stir evenly to obtain Composition 6# for preparing fly ash-based geopolymers.

[0052] Example 11

[0053] Prepare on-site during use or when measuring performance indicators: Mix 80 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 / kg, with a silica mass content of 45%), 20 parts by mass of S95 slag powder, 6.5 parts by mass of calcium hydroxide complex 3#, 6.5 parts of sodium fluoride, 1.5 parts by mass of ethylenediaminetetramethylenephosphonic acid sodium salt, and 50 parts by mass of water, and stir evenly to obtain Composition 7# for preparing fly ash-based geopolymers.

[0054] Example 11

[0055] Prepare on-site during use or when measuring performance indicators: Mix 80 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 / kg, with a silica mass content of 45%), 20 parts by mass of S95 slag powder, 10 parts by mass of calcium hydroxide complex 3#, 10 parts of sodium fluoride, 1.5 parts by mass of ethylenediaminetetramethylenephosphonic acid sodium salt, and 53 parts by mass of water, and stir evenly to obtain Composition 8# for preparing fly ash-based geopolymers.

[0056] Example 12

[0057] Prepare on-site during use or when measuring performance indicators: Mix 80 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 / kg, with a silica mass content of 45%), 20 parts by mass of S95 slag powder, 13.6 parts by mass of calcium hydroxide complex 3#, 12.4 parts of sodium fluoride, 1.5 parts by mass of ethylenediaminetetramethylenephosphonic acid sodium salt, and 56 parts by mass of water, and stir evenly to obtain Composition 9# for preparing fly ash-based geopolymers.

[0058] Comparative Example 1

[0059] Replace the calcium hydroxide complex 1# in Example 4 with calcium hydroxide having the same amount of calcium hydroxide as that in the calcium hydroxide complex 1#.

[0060] Other conditions are the same as those in Example 5.

[0061] Obtain the composition D1# for preparing fly ash-based geopolymers.

[0062] Comparative Example 2

[0063] Replace the calcium hydroxide complex 1# in Example 6 with calcium hydroxide having the same amount of calcium hydroxide as that in the calcium hydroxide complex 1#.

[0064] Other conditions are the same as those in Example 6.

[0065] Obtain the composition D2# for preparing fly ash-based geopolymers.

[0066] Comparative Example 3

[0067] Replace the calcium hydroxide complex 1# in Example 8 with calcium hydroxide having the same amount of calcium hydroxide as that in the calcium hydroxide complex 1#.

[0068] Other conditions are the same as those in Example 8.

[0069] Obtain the composition D3# for preparing fly ash-based geopolymers.

[0070] Table 1

[0071]

[0072] Performance Test

[0073] Prepare the fly ash-based geopolymers, test the thickening time and compressive strength according to the national standard GBT19139 - 2003 "Test Methods for Oil Well Cement". Among them, the test of the thickening time is completed at 70°C; the test of the compressive strength is completed under the condition of curing at 70°C for 24 h, and the obtained results are shown in Table 2.

[0074] According to the results in Table 2, at 70 °C, the preparation of fly ash-based geopolymers using the technical solution of the present invention can control the thickening time. However, the technical solution of the comparative example cannot control the thickening time. Moreover, the fly ash-based geopolymers prepared based on the technical solution of Example 1 have comparable compressive strength performance to those prepared in the comparative example. Therefore, using the technical solution of the present invention can not only avoid the serious problem of endangering personal safety caused by directly using sodium hydroxide on-site, but also achieve the ability to activate geopolymers comparable to that of sodium hydroxide, and solve the problem of low compressive strength of the combination of sodium sulfate and calcium hydroxide; more importantly, using the technical solution of the present invention can control the thickening time.

[0075] Table 2

[0076]

[0077] Although the present invention has been described with reference to specific embodiments, those skilled in the art should understand that various changes can be made without departing from the true spirit and scope of the present invention. In addition, various changes can be made to the subject matter, spirit, and scope of the present invention to adapt to specific situations, materials, material compositions, and methods. All such changes are included within the scope of the claims of the present invention.

Claims

1. A composition for preparing geopolymers, comprising fly ash, slag, an activator and water, wherein the activator is a calcium hydroxide complex and sodium fluoride.

2. The composition according to claim 1, wherein The calcium hydroxide complex is obtained by a chemical reaction of sodium silicate and calcium oxide; Preferably, the calcium hydroxide complex is obtained by reacting sodium silicate and calcium oxide at 20 to 40 °C for 20 to 30 h.

3. The composition according to claim 2, characterized in that, The mass ratio of the sodium silicate to the calcium oxide is 10:90 to 20:80; Preferably, based on the total mass of the sodium silicate and the calcium oxide being 100%, 25% to 45% of water is further included when preparing the calcium hydroxide complex.

4. The composition according to claim 1, characterized in that, The particle size of the calcium hydroxide complex is 100 mesh to 200 mesh.

5. The composition according to claim 1, wherein The mass ratio of the calcium hydroxide complex to the sodium fluoride is (1 to 1.1):

1.

6. The composition according to claim 1, wherein In the fly ash, the mass content of silicon dioxide ≥ 40%; and / or The specific surface area of the fly ash is greater than 1500 m 2 / kg.

7. The composition according to claim 1, wherein The specific surface area of the slag is 400 to 450 m 2 / kg.

8. The composition according to claim 1, characterized in that, Based on the total mass of the fly ash and the slag being 100%, the dosage of the activator is 13% to 26%, and the dosage of the water is 50% to 56%.

9. The composition according to claim 1, wherein A retarder is further included in the composition; Preferably, the retarder is sodium ethylene diamine tetra (methylene phosphonate); Preferably, based on the total mass of the fly ash and the slag being 100%, the dosage of the retarder is 0.2% to 3%.

10. Use of the geopolymer prepared from the composition according to any one of claims 1 to 9 in well cementing and / or plugging leaks.

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