Composition for safely preparing high-strength geopolymer

Abstract

The invention provides a composition for safely preparing a high-strength geopolymer. The composition comprises fly ash, slag powder, an activating agent and water, wherein the activating agent is calcium hydroxide 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 activator they usually use is strongly alkaline sodium hydroxide, which seriously endangers personal safety when used on site. 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 produce 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 powder, an activator, and water, wherein the activator is calcium hydroxide and sodium fluoride.

[0005] In a specific embodiment, the mass ratio of the calcium hydroxide to the sodium fluoride is 1:(1.1 to 1.2).

[0006] In a specific embodiment, based on the total mass of the fly ash and the slag powder being 100%, the dosage of the activator is 15% to 30%.

[0007] In a specific embodiment, based on the total mass of the fly ash and the slag powder being 100%, the dosage of the activator is 19% to 26%.

[0008] In a specific embodiment, based on the total mass of the fly ash and the slag powder being 100%, the dosage of the activator is 24% to 25.6%.

[0009] In a specific embodiment, based on the total mass of the fly ash and the slag powder being 100%, the mass content of the fly ash is 80% to 90%, and the mass content of the slag powder is 10% to 20%.

[0010] In a specific embodiment, based on the total mass of the fly ash and slag powder being 100%, the amount of water used is 48% to 56%.

[0011] In a specific embodiment, in the fly ash, the mass content of silicon dioxide ≥ 40%.

[0012] In a specific embodiment, in the fly ash, the mass content of silicon dioxide ≥ 45%.

[0013] In a specific embodiment, the specific surface area of the fly ash ≥ 1500 m 2 / kg.

[0014] In a specific embodiment, the specific surface area of the fly ash ≥ 1800 m 2 / kg.

[0015] In a specific embodiment, the specific surface area of the fly ash ≥ 1820 m 2 / kg.

[0016] In a specific embodiment, the specific surface area of the slag powder is 400 to 450 m 2 / kg.

[0017] The second aspect of the present invention provides the application of geopolymers prepared from the compositions described in 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 and acidified wells, or in drilling plugging.

[0018] Advantages of the present invention:

[0019] The present invention not only solves the problem that the traditional activator sodium hydroxide of geopolymers is prone to endanger personal safety during use, but also solves the problem of the low strength of geopolymers prepared using alternative compositions such as sodium sulfate and calcium hydroxide as activators. Specific embodiments

[0020] The following further illustrates the present invention with reference to embodiments, but the embodiments of the present invention are only exemplary descriptions, and in no case do they limit the present invention.

[0021] Preparation of fly ash-based geopolymers

[0022] Example 1

[0023] Ultra-fine fly ash: specific surface area 1820 m 2 / kg, mass content of silicon dioxide 45%, 80 parts by mass.

[0024] S95 grade slag powder: 20 parts by mass.

[0025] Calcium hydroxide: 6 parts by mass.

[0026] Sodium fluoride: 6.82 parts by mass.

[0027] Water: 50 parts by mass.

[0028] Prepare on-site during use or when measuring performance indicators: Mix 80 parts by mass of ultra-fine fly ash (specific surface area 1820 m 2 / kg, mass content of silicon dioxide 45%), 20 parts by mass of S95-grade slag powder, 6 parts by mass of calcium hydroxide, 6.82 parts by mass of sodium fluoride and 50 parts by mass of water, and stir evenly to obtain Composition 1# for preparing fly ash-based geopolymers.

[0029] Example 2

[0030] Ultra-fine fly ash: specific surface area 1820 m 2 / kg, mass content of silicon dioxide 45%, 80 parts by mass.

[0031] S95-grade slag powder: 20 parts by mass.

[0032] Calcium hydroxide: 12 parts by mass.

[0033] Sodium fluoride: 13.6 parts by mass.

[0034] Water: 56 parts by mass.

[0035] Prepare on-site during use or when measuring performance indicators: Mix 80 parts by mass of ultra-fine fly ash (specific surface area 1820 m 2 / kg, mass content of silicon dioxide 45%), 20 parts by mass of S95-grade slag powder, 12 parts by mass of calcium hydroxide, 13.6 parts by mass of sodium fluoride and 56 parts by mass of water, and stir evenly to obtain Composition 2# for preparing fly ash-based geopolymers.

[0036] Example 3

[0037] Ultra-fine fly ash: specific surface area 1820 m 2 / kg, mass content of silicon dioxide 45%, 85 parts by mass.

[0038] S95-grade slag powder: 15 parts by mass.

[0039] Calcium hydroxide: 9 parts by mass.

[0040] Sodium fluoride: 10.23 parts by mass.

[0041] Water: 53 parts by mass.

[0042] Prepare on-site during use or when measuring performance indicators: Mix the ultra-fine fly ash (specific surface area 1820 m2 85 parts by mass of ultrafine fly ash (specific surface area 1820 m² / kg, silica mass content 45%), 15 parts by mass of S95 slag powder, 9 parts by mass of calcium hydroxide, 10.23 parts by mass of sodium fluoride and 53 parts by mass of water are mixed and stirred evenly to obtain Composition 3# for preparing fly ash-based geopolymers.

[0043] Example 4

[0044] Ultrafine fly ash: specific surface area 1820 m 2 ² / kg, silica mass content 45%, 90 parts by mass.

[0045] S95 slag powder: 10 parts by mass.

[0046] Calcium hydroxide: 11 parts by mass.

[0047] Sodium fluoride: 12.5 parts by mass.

[0048] Water: 54 parts by mass.

[0049] Prepare on-site during use or when measuring performance indicators: Mix 90 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 ² / kg, silica mass content 45%), 10 parts by mass of S95 slag powder, 11 parts by mass of calcium hydroxide, 12.5 parts by mass of sodium fluoride and 54 parts by mass of water, and stir evenly to obtain Composition 4# for preparing fly ash-based geopolymers.

[0050] Comparative Example 1

[0051] Ultrafine fly ash: specific surface area 1820 m 2 ² / kg, silica mass content 45%, 80 parts by mass.

[0052] S95 slag powder: 20 parts by mass.

[0053] Sodium hydroxide: 7 parts by mass.

[0054] Water: 47 parts by mass.

[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 ² / kg, silica mass content 45%), 20 parts by mass of S95 slag powder, 7 parts by mass of sodium hydroxide and 47 parts by mass of water, and stir evenly to obtain Composition D1# for preparing fly ash-based geopolymers.

[0056] Comparative Example 2

[0057] Ultrafine fly ash: specific surface area 1820 m 2 / kg, the mass content of silica is 45%, 85 parts by mass.

[0058] S95 slag powder: 15 parts by mass.

[0059] Sodium hydroxide: 11 parts by mass.

[0060] Water: 48.4 parts by mass.

[0061] Prepare on-site during use or when measuring performance indicators: Mix 85 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 / kg, the mass content of silica is 45%), 15 parts by mass of S95 slag powder, 11 parts by mass of sodium hydroxide, and 48.4 parts by mass of water, and stir evenly to obtain Composition D2# for preparing fly ash-based geopolymers.

[0062] Comparative Example 3

[0063] Ultrafine fly ash: specific surface area 1820 m 2 / kg, the mass content of silica is 45%, 90 parts by mass.

[0064] S95 slag powder: 10 parts by mass.

[0065] Sodium hydroxide: 14 parts by mass.

[0066] Water: 49 parts by mass.

[0067] Prepare on-site during use or when measuring performance indicators: Mix 90 parts by mass of ultrafine fly ash (specific surface area 1820 m 2 / kg, the mass content of silica is 45%), 10 parts by mass of S95 slag powder, 14 parts by mass of sodium hydroxide, and 49 parts by mass of water, and stir evenly to obtain Composition D3# for preparing fly ash-based geopolymers.

[0068] Comparative Example 4

[0069] Ultrafine fly ash: specific surface area 1820 m 2 / kg, the mass content of silica is 45%, 80 parts by mass.

[0070] S95 slag powder: 20 parts by mass.

[0071] Calcium hydroxide: 6 parts by mass.

[0072] Sodium sulfate: 11.54 parts by mass.

[0073] Water: 52 parts by mass.

[0074] Prepare on-site during use or when measuring performance indicators: Mix ultrafine fly ash (specific surface area 1820 m 280 parts by mass of ultrafine fly ash (specific surface area 1820 m² / kg, silica mass content 45%), 20 parts by mass of S95 slag powder, 6 parts by mass of calcium hydroxide, 11.54 parts by mass of sodium sulfate and 52 parts by mass of water are mixed and stirred evenly to obtain Composition D4 for preparing fly ash-based geopolymers.

[0075] Comparative Example 5

[0076] Ultrafine fly ash: specific surface area 1820 m² / kg, silica mass content 45%, 85 parts by mass. 2 / kg, silica mass content 45%, 85 parts by mass.

[0077] S95 slag powder: 15 parts by mass.

[0078] Calcium hydroxide: 9 parts by mass.

[0079] Sodium sulfate: 17.3 parts by mass.

[0080] Water: 55 parts by mass.

[0081] Prepare on-site during use or when measuring performance indicators: Mix 85 parts by mass of ultrafine fly ash (specific surface area 1820 m² / kg, silica mass content 45%), 15 parts by mass of S95 slag powder, 9 parts by mass of calcium hydroxide, 17.3 parts by mass of sodium sulfate and 55 parts by mass of water, and stir evenly to obtain Composition D5 for preparing fly ash-based geopolymers. 2 / kg, silica mass content 45%), 85 parts by mass, 15 parts by mass of S95 slag powder, 9 parts by mass of calcium hydroxide, 17.3 parts by mass of sodium sulfate and 55 parts by mass of water are mixed and stirred evenly to obtain Composition D5 for preparing fly ash-based geopolymers.

[0082] Comparative Example 6

[0083] Ultrafine fly ash: specific surface area 1820 m² / kg, silica mass content 45%, 90 parts by mass. 2 / kg, silica mass content 45%, 90 parts by mass.

[0084] S95 slag powder: 10 parts by mass.

[0085] Calcium hydroxide: 11 parts by mass.

[0086] Sodium sulfate: 21.15 parts by mass.

[0087] Water: 58 parts by mass.

[0088] Prepare on-site during use or when measuring performance indicators: Mix 90 parts by mass of ultrafine fly ash (specific surface area 1820 m² / kg, silica mass content 45%), 10 parts by mass of S95 slag powder, 11 parts by mass of calcium hydroxide, 21.15 parts by mass of sodium sulfate and 58 parts by mass of water, and stir evenly to obtain Composition D6 for preparing fly ash-based geopolymers. 2 / kg, silica mass content 45%), 90 parts by mass, 10 parts by mass of S95 slag powder, 11 parts by mass of calcium hydroxide, 21.15 parts by mass of sodium sulfate and 58 parts by mass of water are mixed and stirred evenly to obtain Composition D6 for preparing fly ash-based geopolymers.

[0089] The dosages of the components in each example and comparative example are shown in Table 1.

[0090] Table 1

[0091]

[0092] Performance test

[0093] The compressive strength test of fly ash-based geopolymers was carried out according to the national standard GBT19139-2003 "Test Methods for Oil Well Cement". Among them, the temperature for the compressive strength test was cured at 70 °C for 24 h, and the results obtained are shown in Table 2.

[0094] Table 2

[0095] Fly ash-based geopolymers Compressive strength / MPa Fly ash-based geopolymer 1# 20 Fly ash-based geopolymer 2# 30 Fly ash-based geopolymer 3# 24 Fly ash-based geopolymer 4# 28 Fly ash-based geopolymer D1# 18 Fly ash-based geopolymer D2# 23 Fly ash-based geopolymer D3# 26 Fly ash-based geopolymer D4# 9 Fly ash-based geopolymer D5# 11 Fly ash-based geopolymer D6# 13

[0096] According to the results in Table 2, at 70 °C, the fly ash-based geopolymers prepared in the examples all had relatively high compressive strength at 24 h. Among them, Example 1 was comparable to Comparative Example 1 and slightly higher than Comparative Example 1; Example 3 was comparable to Comparative Example 2 and slightly higher than Comparative Example 2; Example 4 was comparable to Comparative Example 3 and slightly higher than Comparative Example 3. Therefore, the fly ash-based geopolymers of the present invention showed excellent compressive strength performance, indicating that the combination of sodium fluoride and calcium hydroxide had the ability to activate geopolymers comparable to that of sodium hydroxide, and the use of the combination of sodium fluoride and calcium hydroxide could avoid the serious problem of endangering personal safety caused by directly using sodium hydroxide on site. However, the compressive strengths of the geopolymers in Comparative Example 4, Comparative Example 5 and Comparative Example 6 were all small, indicating that the strength of the geopolymers formed by using the combination of sodium sulfate and calcium hydroxide to replace sodium hydroxide for activation was not high and the activation ability was insufficient.

[0097] 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 powder, an activator and water, wherein the activator is calcium hydroxide and sodium fluoride.

2. The composition according to claim 1, characterized in that, The mass ratio of the calcium hydroxide to the sodium fluoride is 1:(1.1 to 1.2).

3. The composition according to claim 1, characterized in that, Based on the total mass of the fly ash and the slag powder being 100%, the dosage of the activator is 15% to 30%.

4. The composition according to claim 1, wherein Based on the total mass of the fly ash and the slag powder being 100%, the dosage of the activator is 19% to 26%.

5. The composition according to claim 1, wherein Based on the total mass of the fly ash and the slag powder being 100%, the mass content of the fly ash is 80% to 90%, and the mass content of the slag powder is 10% to 20%.

6. The composition according to claim 1, characterized in that, Based on the total mass of the fly ash and the slag powder being 100%, the dosage of the water is 48% to 56%.

7. The composition according to claim 1, wherein In the fly ash, the mass content of silicon dioxide ≥ 40%; Preferably, in the fly ash, the mass content of silicon dioxide ≥ 45%.

8. The composition according to claim 1, wherein The specific surface area of the fly ash ≥ 1500 m 2 / kg; Preferably, the specific surface area of the fly ash ≥ 1800 m 2 / kg.

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

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

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