Low water-cement ratio, high fluidity early strength composite cement, its preparation method and use

Abstract

This invention provides a low water-cement ratio, high fluidity, early-strength composite cement, its preparation method, and its applications, belonging to the field of building materials. The cement is composed of the following raw materials by mass fraction: 100-1000 parts silicate cement, 80-130 parts sulfoaluminate cement, 0.5-5 parts water-reducing agent, 0.1-5 parts silicate, 1-5 parts nano-silica, and 1-50 parts water. This invention provides a low water-cement ratio, high fluidity, and early-strength composite cement. At a relatively low water-cement ratio, it exhibits good fluidity, high early-stage (24-hour) strength, and stable strength growth in later stages (3 days, 7 days), which is beneficial for rapid emergency repair work such as borehole wall protection and leak sealing, and has good application prospects.

Description

Technical Field

[0001] This invention belongs to the field of building materials, specifically relating to a low water-cement ratio, high fluidity, early-strength composite cement, its preparation method, and its uses. Background Technology

[0002] Cement is the most commonly used cementitious material in the engineering field today. Various engineering constructions and emergency rescue facilities rely heavily on cement. Until a new cementitious material can replace cement, its application prospects and applicable fields will remain at the forefront of the engineering industry.

[0003] Cement slurry sealing is an important technique in drilling. When encountering loose and fractured formations, various factors can cause downhole leakage, which is often addressed with cement slurry for sealing and plugging. The cementitious properties of cement slurry solidify the fractured formation, restoring its strength and sealing the leakage channels, allowing drilling to resume. To meet the needs of rapid sealing and emergency repairs, cement slurry typically requires good fluidity, a short setting time, and high early strength. In the presence of groundwater inflow, it may even need certain erosion resistance. Commonly used silicate cement and sulfoaluminate cement each have their advantages and disadvantages. Silicate cement is low in cost, widely applicable, and readily available, but its setting time is longer and its strength gain is slower. Sulfoaluminate cement has a short setting time, forms solid blocks, and has high strength, but it is a special type of cement with higher economic costs and is difficult to obtain in some areas.

[0004] Patent application (CN115925384A) discloses a cement-based self-leveling flooring material with a high fly ash content. This material is composed of the following raw materials in percentage by weight: ordinary silicate cement 2.5–27.5%, quick-dissolving sodium silicate powder 1.5–2%, lightly calcined dolomite powder 2–5%, calcium oxide 0.5–2.5%, calcium hydroxide 0.5–1%, sulfoaluminate cement 0–25%, expanding agent 0.5–1.5%, fly ash 60–71.5%, aluminum sulfate 0–0.6%, calcium formate 0–0.8%, dispersible latex powder 0–1%, water-reducing agent 0.3–0.4%, defoamer 0.02–0.12%, low-viscosity cellulose ether 0.03–0.05%, and retarder 0–0.1%. However, this material has poor fluidity and slurry strength.

[0005] Based on the above problems, there is an urgent need for a cement system that balances economic cost and performance to solve the difficulties in actual production. Summary of the Invention

[0006] The purpose of this invention is to provide a low water-cement ratio, high fluidity, early-strength composite cement, its preparation method, and its applications.

[0007] The present invention provides a composite cement, which is composed of the following raw materials in parts by weight: 100-1000 parts silicate cement, 80-130 parts sulfoaluminate cement, 0.5-5 parts water-reducing agent, 0.1-5 parts silicate, 1-5 parts nano silica, and 1-50 parts water.

[0008] Furthermore, the composite cement is composed of the following raw materials in parts by weight: 500-900 parts silicate cement, 80-120 parts sulfoaluminate cement, 0.5-3 parts water-reducing agent, 0.1-3 parts silicate, 1-3 parts nano silica, and 1-30 parts water.

[0009] Furthermore, the composite cement is composed of the following raw materials in parts by weight: 800 parts silicate cement, 100 parts sulfoaluminate cement, 2.7 parts water-reducing agent, 0.9 parts silicate, 0.9 to 2.7 parts nano silica, and 27 parts water.

[0010] Furthermore, the water-reducing agent is a melamine-type water-reducing agent.

[0011] Furthermore, the silicate is sodium silicate.

[0012] Furthermore, the sodium silicate is sodium silicate with a modulus of 2.8.

[0013] Furthermore, the nano-silica is fumed silica.

[0014] The present invention also provides a method for preparing the above-mentioned composite cement, the method comprising the following steps: mixing silicate cement, sulfoaluminate cement, water-reducing agent, silicate, nano-silica and water to obtain the composite cement.

[0015] The present invention also provides the use of the above-mentioned composite cement in the preparation of building cementitious materials.

[0016] Furthermore, the building cementitious material is a material used for drilling, wall protection, or leak sealing.

[0017] Furthermore, the building cementitious material is a material used for rapid emergency rescue.

[0018] The present invention has achieved the following beneficial effects:

[0019] This invention provides a low water-cement ratio, high fluidity, and early-strength composite cement. It exhibits good fluidity at a relatively low water-cement ratio, high early-stage (24-hour) strength, and stable strength growth in later stages (3 days and 7 days), which is beneficial for rapid emergency repairs such as borehole wall sealing and plugging, and has promising application prospects. Compared with patent application (CN115925384A), the composite cement of this invention has better fluidity and higher strength.

[0020] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0021] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following embodiments. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Detailed Implementation

[0022] The raw materials and equipment used in this invention are all known products, obtained by purchasing commercially available products.

[0023] The cement used in this invention is Esheng 425 ordinary Portland cement and Jiahua 425 sulfoaluminate cement.

[0024] The water-reducing agent is a melamine-type water-reducing agent. It is a white powder with a moisture content of 3.95% and a pH value of 8. The water-reducing rate for mortar is 14.2%, and the water-reducing rate for concrete is 26.2%.

[0025] Sodium silicate is a fast-dissolving sodium silicate with a modulus of 2.8.

[0026] Example 1

[0027] Table 1. Cement components in Example 1

[0028] raw material Quality Sulfoaluminate cement 10 Silicate cement 10 water 6 Water reducing agent 0.06

[0029] Preparation process: Mix the raw materials to obtain composite cement.

[0030] Example 2

[0031] Table 2. Cement components in Example 2

[0032] raw material Quality Sulfoaluminate cement 10 Silicate cement 20 water 9 Water reducing agent 0.09

[0033] Preparation process: as described in Example 1.

[0034] Example 3

[0035] Table 3. Cement components in Example 3

[0036] raw material Quality Sulfoaluminate cement 10 Silicate cement 40 water 15 Water reducing agent 0.15

[0037] Preparation process: as described in Example 1.

[0038] Example 4

[0039] Table 4. Cement components in Example 4

[0040] raw material Quality Sulfoaluminate cement 10 Silicate cement 60 water 21 Water reducing agent 0.21

[0041] Preparation process: as described in Example 1.

[0042] Example 5

[0043] Table 5. Cement components in Example 5

[0044] raw material Quality Sulfoaluminate cement 10 Silicate cement 80 water 27 Water reducing agent 0.27

[0045] Preparation process: as described in Example 1.

[0046] Example 6

[0047] Table 6. Cement components in Example 6

[0048] raw material Quality Sulfoaluminate cement 10 Silicate cement 80 Sodium silicate 0.09 water 27 Water reducing agent 0.27

[0049] Preparation process: as described in Example 1.

[0050] Example 7

[0051] Table 7. Cement components in Example 7

[0052] raw material Quality Sulfoaluminate cement 10 Silicate cement 80 Sodium silicate 0.45 water 27 Water reducing agent 0.27

[0053] Preparation process: as described in Example 1.

[0054] Example 8

[0055] Table 8. Cement components in Example 8

[0056] raw material Quality Sulfoaluminate cement 10 Silicate cement 80 Sodium silicate 0.9 water 27 Water reducing agent 0.27

[0057] Preparation process: as described in Example 1.

[0058] Example 9

[0059] Table 9. Cement components in Example 9

[0060] raw material Quality Sulfoaluminate cement 10 Silicate cement 80 Sodium silicate 0.09 water 27 Water reducing agent 0.27 Nano silica 0.09

[0061] Preparation process: as described in Example 1.

[0062] Example 10

[0063] Table 10 Cement components of Example 10

[0064] raw material Quality Sulfoaluminate cement 10 Silicate cement 80 Sodium silicate 0.09 water 27 Water reducing agent 0.27 Nano silica 0.18

[0065] Preparation process: as described in Example 1.

[0066] Example 11

[0067] Table 11 Cement components of Example 11

[0068] raw material Quality Sulfoaluminate cement 10 Silicate cement 80 Sodium silicate 0.09 water 27 Water reducing agent 0.27 Nano silica 0.27

[0069] Preparation process: as described in Example 1.

[0070] The following section describes the preparation of comparative samples.

[0071] Comparative Example 1

[0072] Table 12 Cement components of Comparative Example 1

[0073] raw material Quality Sulfoaluminate cement 90 Silicate cement 0 water 27 Water reducing agent 0.27

[0074] Preparation process: as described in Example 1.

[0075] Comparative Example 2

[0076] Table 13 Cement components of Comparative Example 2

[0077] raw material Quality Sulfoaluminate cement 0 Silicate cement 90 water 27 Water reducing agent 0.27

[0078] Preparation process: as described in Example 1.

[0079] The following experimental examples demonstrate the beneficial effects of the present invention.

[0080] Experiment Example 1: Testing the properties of cement grout

[0081] The fluidity and strength (24h, 3d, 7d) of the cement slurries prepared in Comparative Examples 1-11 and Comparative Examples 1-2 were compared. The test methods for the fluidity and strength (24h, 3d, 7d) of the cement slurries are as follows: Cement slurry fluidity test:

[0082] 1. Place the glass plate horizontally, moisten it with a damp cloth, and place the round mold in the center of the glass plate for later use.

[0083] 2. Weigh each component of the cement according to the proportions in Tables 1 to 13. First, add the cement (300g in total) to the mixing pot, then add the other components and stir immediately (stir slowly for 120s, stop for 15s, stir quickly for 120s).

[0084] 3. Quickly pour the mixed cement paste into the truncated cone mold, smooth it with a scraper, lift it vertically, and start timing. Let the cement paste flow on the glass plate for 30 seconds, and use a steel ruler to measure the maximum diameter in two mutually perpendicular directions. The average value is the flowability of the cement paste.

[0085] Compressive strength:

[0086] Sample preparation: Apply a layer of release agent evenly to the inner wall of the mold. Quickly pour the mixed cement paste into the 40x40x40mm compression mold and shake for 30 seconds to eliminate air bubbles. Use a scraper to remove excess cement paste from the mold, making the cement paste flush with the mold.

[0087] Sample curing: Place the mold into the curing chamber for standard curing. After curing for 12 hours, remove the mold and mark each sample. Then place the sample in the curing chamber to cure for the required age for the test and perform compressive strength test.

[0088] Compressive strength test: Place the cured specimen in the center of the pressure testing machine to ensure uniform stress on the specimen. After the test is completed, remove the damaged specimen and clean the residue on the placement platform to ensure the accuracy of the test results.

[0089] The specific performance is shown in Table 14.

[0090] Table 14. Cement slurry properties of Comparative Examples 1-2 and Examples 1-11

[0091] Flowability (cm) 24-hour strength (MPa) 3D strength (MPa) 7-day strength (MPa) Comparative Example 1 22 31.3 53.1 - Comparative Example 2 26 9.7 44.1 - Example 1 10 12.5 16.7 - Example 2 13 8.9 26.5 - Example 3 19 9 28 - Example 4 20 12.4 34 - Example 5 22 15.1 48.6 - Example 6 23 22.7 44.6 - Example 7 22 25.1 42.4 - Example 8 21 21.6 43.9 - Example 9 23 23.7 43.6 50.0 Example 10 21 24.6 45.9 52.5 Example 11 19 26.7 46.5 60.2

[0092] In the table, "-" indicates that it has not been tested.

[0093] Compared with Comparative Example 1, Examples 1-5 reduced the amount of sulfoaluminate cement used, saving costs and making the raw materials more readily available.

[0094] Comparative Examples 2 and Examples 1-5 show that, compared to the early (24h) strength of ordinary silicate cement, the composite cement obtained by mixing silicate cement and sulfoaluminate cement at a mass ratio of 1:8 in this invention exhibits significantly improved early strength. Examples 6-8 demonstrate that the addition of sodium silicate further enhances the early strength of the cement slurry, and the composite cement prepared with low sodium silicate content shows higher strength at 3 days compared to high sodium silicate content. Examples 9-11 show that the addition of nano-silica further improves the early strength of the cement slurry, and the strength of the cement slurry steadily increases at 7 days.

[0095] The composite cement prepared by this invention can achieve good fluidity under low water-cement ratio conditions, and has lower economic cost and wider applicability. It also has good engineering applicability while taking into account economic value.

[0096] In summary, this invention provides a low water-cement ratio, high fluidity, early-strength composite cement, its preparation method, and its applications. This cement is composed of the following raw materials in the indicated mass fractions: 100–1000 parts silicate cement, 80–130 parts sulfoaluminate cement, 0.5–5 parts water-reducing agent, 0.1–5 parts silicate, 1–5 parts nano-silica, and 1–50 parts water. This invention provides a low water-cement ratio, high fluidity, and early-strength composite cement that exhibits good fluidity at a relatively low water-cement ratio, high early-age (24-hour) strength, and stable strength growth in later stages (3 days, 7 days). This is beneficial for rapid emergency repair work such as borehole wall protection and leak sealing, and has promising application prospects.

Claims

1. A composite cement, characterized in that, The composite cement is composed of the following raw materials in parts by weight: 100-1000 parts silicate cement, 80-130 parts sulfoaluminate cement, 0.5-5 parts water-reducing agent, 0.1-5 parts silicate, 1-5 parts nano silica, and 1-50 parts water.

2. The composite cement according to claim 1, characterized in that, The composite cement is composed of the following raw materials in parts by weight: 500-900 parts silicate cement, 80-120 parts sulfoaluminate cement, 0.5-3 parts water-reducing agent, 0.1-3 parts silicate, 1-3 parts nano silica, and 1-30 parts water.

3. The composite cement according to claim 1, characterized in that, The composite cement is composed of the following raw materials in parts by weight: 800 parts silicate cement, 100 parts sulfoaluminate cement, 2.7 parts water-reducing agent, 0.9 parts silicate, 0.9 to 2.7 parts nano silica, and 27 parts water.

4. The composite cement according to claim 1, characterized in that, The water-reducing agent is a melamine-type water-reducing agent.

5. The composite cement according to claim 1, characterized in that, The silicate is sodium silicate.

6. The composite cement according to claim 1, characterized in that, The nano-silica is fumed silica.

7. A method for preparing the composite cement according to any one of claims 1-6, characterized in that, The method includes the following steps: mixing silicate cement, sulfoaluminate cement, water-reducing agent, silicate, nano silica and water to obtain the final product.

8. Use of the composite cement according to any one of claims 1-6 in the preparation of building cementitious materials.

9. The use according to claim 8, characterized in that, The building cementitious material is used for drilling, wall protection, or leak sealing.

10. The use according to claim 8, characterized in that, The building cementitious material is used for rapid emergency rescue.