Preparation method of early-strength, fast-hardening, carbonization-resistant cement-based repair mortar

Abstract

The present invention relates to the technical field of cement-based repair mortars, and specifically discloses a method for preparing an early-strength, fast-hardening, carbonation-resistant cement-based repair mortar, comprising: (1) mixing wollastonite or pseudowollastonite and saturated lime water, adding basalt fibers, and heating the mixture; after the mixture is completed, mixing the fibers with sodium silicate powder, calcining the mixture in a protective atmosphere; mixing the obtained fibers with saturated lime water, and drying the mixture to obtain carbonation-resistant modified fibers; (2) mixing red mud, silica fume, sodium silicate powder, and water, and curing the mixture; after the mixture is completed, grinding the mixture, and calcining the powder to obtain an carbonation-resistant admixture; (3) mixing sulphoaluminate cement, fine aggregate, solid waste-based filler, the carbonation-resistant modified fibers, the carbonation-resistant admixture, a water reducer, and a defoaming agent, adding mixing water, and stirring the mixture evenly to obtain a cement-based repair mortar. The present invention effectively improves the carbonation resistance of sulphoaluminate cement-based repair mortar, improves its durability, and prevents the problem of strength shrinkage that may occur later.

Description

Technical Field

[0001] The invention relates to the technical field of cement-based repair mortars, and in particular to a method for preparing an early-strengthening, fast-hardening, carbonization-resistant cement-based repair mortar. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Concrete or cement-based structures are prone to defects such as potholes, spalling, cracks, and breakage during their service life, especially structures such as roads and bridges that are subject to frequent impacts, and dams that are subject to long-term water impacts. Timely repair of these defects can help prevent further damage and even structural safety issues. Structures such as roads and bridges often face the need for rapid repairs in order to open them to traffic as soon as possible and minimize the impact on traffic. Therefore, repair mortars usually need to have the characteristics of fast hardening and early strength. Cement materials are widely used to make repair mortars due to their high strength, simple construction, and low cost. However, the commonly used silicate cement has insufficient hardening speed and early strength, making it difficult to meet the needs of rapid repair projects.

[0004] Sulphoaluminate cement boasts rapid hardening and early strength (the time from adding water and stirring to completely losing plasticity and starting to develop strength generally takes no more than 1 hour), making it ideal for emergency repairs and winter construction, where rapid attainment of service strength and restoration of traffic are crucial. However, due to its low alkalinity, sulphoaluminate cement exhibits poor carbonation resistance. During service, the ettringite in its hydration products is susceptible to erosion and decomposition by carbon dioxide or other substances in the water, leading to strength loss and surface spalling. This results in insufficient durability for repair mortars prepared with this cement. Summary of the Invention

[0005] To address the above-mentioned issues, the present invention provides a method for preparing an early-strengthening, fast-hardening, carbonation-resistant cement-based repair mortar. This method effectively improves the carbonation resistance of sulphoaluminate cement-based repair mortar, enhancing its durability and alleviating the problem of strength shrinkage that may occur later in the process. Specifically, the technical solution of the present invention is as follows.

[0006] A method for preparing an early-strength, fast-hardening, carbonation-resistant cement-based repair mortar comprises the following steps:

[0007] (1) Wollastonite or pseudowollastonite powder and saturated lime water are mixed to form a slurry. Then, basalt fiber is added and heated to react. After the reaction is completed, the fiber is separated and calcined. After cooling to room temperature, the obtained fiber is mixed with saturated lime water and dried to remove moisture, thereby obtaining carbon-resistant modified fiber.

[0008] (2) Red mud powder, silica fume, sodium silicate powder and triethanolamine are mixed and ground to obtain an anti-carbonization admixture.

[0009] (3) Take the following raw materials: sulphoaluminate cement, fine aggregate, solid waste-based filler, the anti-carbon modified fiber, the anti-carbonization admixture, a water reducer, and a defoamer. Mix the above raw materials, add mixing water, and stir evenly to obtain a cement-based repair mortar.

[0010] Furthermore, in step (1), the ratio of the wollastonite or pseudo-wollastonite powder to saturated lime water is 1g: 5-8ml. Optionally, the fineness of the wollastonite or pseudo-wollastonite powder is not less than 400 mesh.

[0011] Furthermore, in step (1), the ratio of the basalt fiber to the slurry is 1 g: 10-30 ml. Optionally, the length of the fiber is 2-20 mm.

[0012] Furthermore, in step (1), the heating temperature is 40-60° C., and the reaction time is 18-22 hours.

[0013] Furthermore, in step (1), the calcination treatment temperature is 570-650° C., and the calcination time is 1-1.5 hours.

[0014] Furthermore, in step (1), the ratio of the fiber to saturated lime water is 1 g: 30-40 ml. Optionally, the drying temperature is 70-100°C.

[0015] Furthermore, in step (2), the mass ratio of the red mud powder, silica fume, sodium silicate powder and triethanolamine is 1~2:2.3~3.7:0.35~0.52:0.15~0.24.

[0016] Furthermore, in step (2), the anti-carbonization admixture has a fineness of 300-600 mesh.

[0017] Furthermore, in step (3), the proportions of the raw materials are: 230-248 parts by weight of sulphoaluminate cement, 575-740 parts by weight of fine aggregate, 25-35 parts by weight of solid waste-based filler, 20-25 parts by weight of anti-carbon modified fiber, 45-70 parts by weight of anti-carbonization admixture, 3.5-5 parts by weight of water reducer, and 0.6-1.1 parts by weight of defoamer, and the mixing water is added according to a water-cement ratio of 0.25-0.32.

[0018] Furthermore, in step (3), the solid waste-based filler includes at least one of calcium carbonate, quartz powder, mica powder, shell powder, etc. Optionally, the specific surface area of ​​the solid waste-based filler is 350~450m 2 / kg.

[0019] Furthermore, in step (3), the water reducer includes any one of: polycarboxylic acid water reducer, naphthalene water reducer, melamine water reducer, lignin sulfonate water reducer, etc.

[0020] Furthermore, in step (3), the defoaming agent includes any one of: an organosilicon defoaming agent, a polyether defoaming agent, a fatty alcohol defoaming agent, etc.

[0021] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0022] (1) The sulphoaluminate cement-based repair mortar of the present invention is added with an anti-carbonation agent prepared from red mud, silica fume, sodium silicate powder, and triethanolamine, which can not only improve the mechanical strength of the mortar, but also improve the anti-carbonation ability of the mortar. The reason is that the red mud and silica fume undergo a gelling reaction under the action of the alkaline components in sodium silicate and red mud to form a cement, and the triethanolamine promotes the gelling reaction, thereby further improving the strength of the mortar. In addition, since the cement is highly alkaline, coupled with the action of the triethanolamine, the anti-carbonation system constructed in the mortar can effectively capture and solidify the carbonate ions formed by carbon dioxide and water, thereby making the sulphoaluminate cement-based repair mortar of the present invention have good anti-carbonation ability and durability.

[0023] (2) The carbon-resistant modified fiber in the repair mortar of the present invention can not only further enhance the carbonization resistance of the repair mortar, but also significantly improve the mechanical strength of the repair mortar. To this end, the present invention first adds basalt fiber to a slurry formed by calcium silicate or pseudo wollastonite powder and saturated lime water for modification. In this process, the silicon oxide tetrahedron and aluminum oxide tetrahedron structures on the surface of the basalt fiber depolymerize in an alkaline environment to form an active surface, which further reacts with calcium ions to form hydrated calcium silicate and hydrated calcium aluminate doped with calcium silicate or pseudo wollastonite particles loaded on the fiber surface. This surface-roughened fiber can form a stronger bonding force with the matrix after being added to the repair mortar, thereby improving the mechanical strength and crack resistance of the repair mortar. Furthermore, the calcium silicate hydrate and calcium aluminate hydrate form a porous structure after calcination and dehydration. The present invention utilizes this feature to store calcium hydroxide within the porous structure to form carbon-resistant modified fibers. This helps prevent the cement product bound to the fibers from carbonizing and decomposing, which would reduce the bonding strength between the fibers and the fibers and weaken the fibers' effect on improving the mechanical properties of the repair mortar. Furthermore, the wollastonite or pseudowollastonite cured on the fiber surface also exhibits excellent carbonization resistance, further enhancing the carbonization resistance of the sulfoaluminate cement-based repair mortar. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which constitute a part of the present invention, are used to provide further understanding of the present invention and are not intended to constitute an improper limitation of the present invention.

[0025] Figure 1 This is a sample picture of the carbon-resistant modified fiber prepared in Example 1 below.

[0026] Figure 2 The following are samples of the anti-carbonization admixtures prepared in Examples 1 and 2.

[0027] Figure 3 This is a compressive strength test diagram of the following Example 1.

[0028] Figure 4 The graphs are for testing the anti-carbonization performance of the following Examples 1 to 8.

[0029] Figure 5 This is a sample picture of the carbon-resistant modified fiber prepared in the following Example 2.

[0030] Figure 6 This is a compressive strength test diagram of the following Example 2.

[0031] Figure 7 This is a sample picture of the carbon-resistant modified fiber prepared in Example 3 below.

[0032] Figure 8 This is a sample of the anti-carbonization admixture prepared in Example 3 below.

[0033] Figure 9 This is a compressive strength test diagram of the following Example 3.

[0034] Figure 10 This is a sample of the anti-carbonization admixture prepared in Example 6 below.

[0035] Figure 11 The following are samples of the anti-carbonization admixtures prepared in Examples 7 and 8. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. Unless otherwise defined, all professional and scientific terms used in the present invention have the same meanings as those familiar to those skilled in the art. The preferred implementation methods and materials described in the present invention are for exemplary purposes only. The technical solutions of the present invention will now be further described with reference to specific embodiments.

[0037] Example 1:

[0038] A method for preparing an early-strength, fast-hardening, carbonation-resistant cement-based repair mortar comprises the following steps:

[0039] (1) Mix 400-mesh calcium silicate powder and saturated lime water in a ratio of 1g:7ml and stir evenly to form a slurry. Then add basalt fibers with a length distribution between 5 and 12mm and stir evenly. The ratio of the two is 1g:25ml. Then heat the system to 60℃ and keep it warm for 18 hours. During this period, add water in time to ensure that the system remains in a fluid state. After completion, filter out the fiber through a filter, place it in a heating furnace and heat it to 620℃ at a rate of 10℃ / min and keep it warm for 1.5 hours. Then cool it to room temperature, mix the obtained fiber with saturated lime water in a ratio of 1g:40ml and stir evenly, then heat it to 80℃ to dry and remove moisture, and obtain carbon-resistant modified fiber (such as Figure 1 as shown), and keep it as a standby.

[0040] (2) Red mud powder, silica fume, sodium silicate powder and triethanolamine were mixed in a mass ratio of 1.7:3.2:0.45:0.2 and then ground. After completion, the mixture was sieved through a 500-mesh sieve to obtain an anti-carbonization admixture (such as Figure 2 as shown in the middle left picture) and keep it ready for use.

[0041] (3) Weigh the raw materials according to the following proportions: 235 parts by weight of sulphoaluminate cement, 630 parts by weight of river sand with a particle size of 0.2-0.35 mm, and shell powder (specific surface area 408.7 m 2 The following ingredients are mixed thoroughly: 30 parts by weight of a mortar (100g / kg), 22 parts by weight of the carbon-resistant modified fiber of this embodiment, 65 parts by weight of the anti-carbonization admixture of this embodiment, 4.2 parts by weight of a polycarboxylate water-reducing agent, and 0.85 parts by weight of a silicone defoamer. After thoroughly mixing these ingredients, mixing water is added at a water-cement ratio of 0.28, and the mixture is stirred evenly to obtain a cement-based repair mortar.

[0042] Performance test: The cement-based repair mortar prepared in this embodiment was poured into a mold, demoulded after hardening, and then naturally cured to an age of 28 days to obtain a test piece. The compressive strength a of the test piece was tested according to the "Test method for strength of cement mortar (ISO method)" (GBT17671-2021). Figure 3 Then, the test piece was placed in a carbonization box (CO2 concentration was maintained at 20±0.5%, relative humidity in the box was controlled at 70±5%, and temperature was controlled at 20±2°C) for carbonization treatment for 14 days (as shown). Figure 4 After completion, the test piece was taken out and its compressive strength b was tested. The compressive strength retention rate was then calculated as compressive strength b / compressive strength a, which was 93.16%.

[0043] Example 2:

[0044] A method for preparing an early-strength, fast-hardening, carbonation-resistant cement-based repair mortar comprises the following steps:

[0045] (1) Mix 450-mesh calcium silicate powder and saturated lime water in a ratio of 1g:8ml and stir evenly to form a slurry. Then add basalt fibers with a length distribution between 10 and 20mm and stir evenly. The ratio of the two is 1g:30ml. Then heat the system to 50℃ and keep it warm for 20 hours. During this period, add water in time to ensure that the system remains in a fluid state. After completion, filter out the fiber through a filter, place it in a heating furnace and heat it to 570℃ at a rate of 10℃ / min and keep it warm for 1.5 hours. Then cool it to room temperature, mix the obtained fiber with saturated lime water in a ratio of 1g:35ml and stir evenly, then heat it to 100℃ to dry and remove moisture, and obtain carbon-resistant modified fiber (such as Figure 5 as shown), and keep it as a standby.

[0046] (2) Red mud powder, silica fume, sodium silicate powder and triethanolamine are mixed in a mass ratio of 1:2.3:0.35:0.15 and then ground. After completion, the mixture is passed through a 600-mesh sieve to obtain an anti-carbonization admixture (such as Figure 2 as shown in the middle right picture) and keep it ready for use.

[0047] (3) Weigh the raw materials in the following proportions: 248 parts by weight of sulphoaluminate cement, 740 parts by weight of river sand with a particle size of 0.2-0.35 mm, and mica powder (specific surface area 350.3 m 2 The following ingredients are mixed thoroughly: 35 parts by weight of a mortar (100g / kg), 25 parts by weight of the carbon-resistant modified fiber of this example, 45 parts by weight of the anti-carbonization admixture of this example, 5 parts by weight of a polycarboxylate water-reducing agent, and 1.1 parts by weight of a silicone defoamer. After thoroughly mixing these ingredients, add mixing water at a water-cement ratio of 0.32 and stir evenly to obtain a cement-based repair mortar.

[0048] Performance test: The cement-based repair mortar prepared in this embodiment is poured into a mold, demoulded after hardening, and then naturally cured to an age of 28 days to obtain a test piece. First, the compressive strength a of the test piece is tested according to the "Test method for strength of cement mortar (ISO method)" (GBT 17671-2021) (such as Figure 6 Then, the test piece was placed in a carbonization box (CO2 concentration was maintained at 20±0.5%, relative humidity in the box was controlled at 70±5%, and temperature was controlled at 20±2°C) for carbonization treatment for 14 days (as shown). Figure 4 After completion, the test piece was taken out and its compressive strength b was tested. The compressive strength retention rate was then calculated as compressive strength b / compressive strength a, which was 90.84%.

[0049] Example 3:

[0050] A method for preparing an early-strength, fast-hardening, carbonation-resistant cement-based repair mortar comprises the following steps:

[0051] (1) Mix 500-mesh calcium silicate powder and saturated lime water in a ratio of 1g:5ml and stir evenly to form a slurry. Then add basalt fibers with a length distribution between 2 and 10mm and stir evenly. The ratio of the two is 1g:10ml. Then heat the system to 40℃ and keep it warm for 22 hours. During this period, add water in time to ensure that the system remains in a fluid state. After completion, filter out the fiber through a filter, place it in a heating furnace and heat it to 650℃ at a rate of 10℃ / min and keep it warm for 1 hour. Then cool it to room temperature, mix the obtained fiber with saturated lime water in a ratio of 1g:30ml and stir evenly, then heat it to 70℃ to dry and remove moisture, and obtain carbon-resistant modified fiber (such as Figure 7 as shown), and keep it as a standby.

[0052] (2) Red mud powder, silica fume, sodium silicate powder and triethanolamine were mixed in a mass ratio of 2:3.7:0.52:0.24 and then ground. After the mixture was finished, it was passed through a 300 mesh sieve to obtain an anti-carbonization admixture (such as Figure 8 as shown), and keep it as a standby.

[0053] (3) Weigh the raw materials in the following proportions: 230 parts by weight of sulphoaluminate cement, 575 parts by weight of river sand with a particle size of 0.2-0.35 mm, and calcium carbonate powder (specific surface area 449.6 m 2 The following ingredients are mixed thoroughly: 25 parts by weight of a mortar (100g / kg), 20 parts by weight of the carbon-resistant modified fiber of this example, 70 parts by weight of the anti-carbonization admixture of this example, 3.5 parts by weight of a calcium lignin sulfonate water reducer, and 0.6 parts by weight of a polyether defoamer. After thoroughly mixing these ingredients, mixing water is added at a water-cement ratio of 0.25, and the mixture is stirred evenly to obtain a cement-based repair mortar.

[0054] Performance test: The cement-based repair mortar prepared in this embodiment is poured into a mold, demoulded after hardening, and then naturally cured to an age of 28 days to obtain a test piece. First, the compressive strength a of the test piece is tested according to the "Test method for strength of cement mortar (ISO method)" (GBT 17671-2021) (such as Figure 9 Then, the test piece was placed in a carbonization box (CO2 concentration was maintained at 20±0.5%, relative humidity in the box was controlled at 70±5%, and temperature was controlled at 20±2°C) for carbonization treatment for 14 days (as shown). Figure 4 After completion, the test piece was taken out and its compressive strength b was tested. The compressive strength retention rate was then calculated as compressive strength b / compressive strength a, which was 95.31%.

[0055] Example 4:

[0056] A method for preparing an early-strength, fast-hardening, carbonation-resistant cement-based repair mortar comprises the following steps: weighing the following raw materials in the following proportions: 235 parts by weight of sulphoaluminate cement, 630 parts by weight of river sand with a particle size of 0.2 to 0.35 mm, and shell powder (specific surface area 408.7 m 2 / kg), 30 parts by weight of carbon-resistant modified fiber (the same as in Example 1), 22 parts by weight of polycarboxylate superplasticizer, 4.2 parts by weight of polycarboxylate water-reducing agent, and 0.85 parts by weight of silicone defoamer. These ingredients were mixed thoroughly, and then mixing water was added at a water-cement ratio of 0.28. The mixture was then stirred evenly to obtain a cement-based repair mortar.

[0057] Performance test: The cement-based repair mortar prepared in this embodiment is poured into a mold, demoulded after hardening, and then naturally cured to an age of 28 days to obtain a test piece. First, the compressive strength a of the test piece is tested according to the "Test Method for Cement Mortar Strength (ISO Method)" (GBT 17671-2021). Then, the test piece is placed in a carbonization box (CO2 concentration is maintained at 20±0.5%, relative humidity in the box is controlled at 70±5%, and temperature is controlled at 20±2°C) for carbonization treatment for 14 days (such as Figure 4 After completion, the test piece was taken out and its compressive strength b was tested. The compressive strength retention rate was then calculated as compressive strength b / compressive strength a, which was 67.02%.

[0058] Example 5:

[0059] A method for preparing an early-strength, fast-hardening, carbonation-resistant cement-based repair mortar comprises the following steps: weighing the following raw materials in the following proportions: 235 parts by weight of sulphoaluminate cement, 630 parts by weight of river sand with a particle size of 0.2 to 0.35 mm, and shell powder (specific surface area 408.7 m 2 The following ingredients were mixed thoroughly: 30 parts by weight of alumina (1000 t / kg), 22 parts by weight of basalt fibers with a length distribution between 5 and 12 mm, 65 parts by weight of an anti-carbonation admixture (the same as in Example 1), 4.2 parts by weight of a polycarboxylate water-reducing agent, and 0.85 parts by weight of a silicone defoamer. After thoroughly mixing these ingredients, mixing water was added at a water-cement ratio of 0.28, and the mixture was stirred evenly to obtain a cement-based repair mortar.

[0060] Performance test: The cement-based repair mortar prepared in this embodiment is poured into a mold, demoulded after hardening, and then naturally cured to an age of 28 days to obtain a test piece. First, the compressive strength a of the test piece is tested according to the "Test Method for Cement Mortar Strength (ISO Method)" (GBT 17671-2021). Then, the test piece is placed in a carbonization box (CO2 concentration is maintained at 20±0.5%, relative humidity in the box is controlled at 70±5%, and temperature is controlled at 20±2°C) for carbonization treatment for 14 days (such as Figure 4After completion, the test piece was taken out and its compressive strength b was tested. The compressive strength retention rate was then calculated as compressive strength b / compressive strength a, which was 85.49%.

[0061] Example 6:

[0062] A method for preparing an early-strength, fast-hardening, carbonation-resistant cement-based repair mortar comprises the following steps:

[0063] (1) Silica fume, sodium silicate powder and triethanolamine are mixed in a mass ratio of 3.3:0.35:0.15 and then ground. After completion, the mixture is passed through a 600-mesh sieve to obtain an anti-carbonization admixture (such as Figure 10 as shown), and keep it as a standby.

[0064] (2) Weigh the raw materials in the following proportions: 248 parts by weight of sulphoaluminate cement, 740 parts by weight of river sand with a particle size of 0.2-0.35 mm, and mica powder (specific surface area 350.3 m 2 The following ingredients were mixed thoroughly: 35 parts by weight of a mortar (100g / kg), 25 parts by weight of carbon-resistant modified fiber (the same as in Example 2), 45 parts by weight of the anti-carbonization admixture of this example, 5 parts by weight of a polycarboxylate water-reducing agent, and 1.1 parts by weight of a silicone defoamer. After thoroughly mixing these ingredients, mixing water was added at a water-cement ratio of 0.32, and the mixture was stirred evenly to obtain a cement-based repair mortar.

[0065] Performance test: The cement-based repair mortar prepared in this embodiment is poured into a mold, demoulded after hardening, and then naturally cured to an age of 28 days to obtain a test piece. First, the compressive strength a of the test piece is tested according to the "Test Method for Cement Mortar Strength (ISO Method)" (GBT 17671-2021). Then, the test piece is placed in a carbonization box (CO2 concentration is maintained at 20±0.5%, relative humidity in the box is controlled at 70±5%, and temperature is controlled at 20±2°C) for carbonization treatment for 14 days (such as Figure 4 After completion, the test piece was taken out and its compressive strength b was tested. The compressive strength retention rate was then calculated as compressive strength b / compressive strength a, which was 80.17%.

[0066] Example 7:

[0067] A method for preparing an early-strength, fast-hardening, carbonation-resistant cement-based repair mortar comprises the following steps:

[0068] (1) Red mud powder, silica fume and sodium silicate powder are mixed in a mass ratio of 2:3.7:0.52 and then ground. After the mixture is finished, it is passed through a 300-mesh sieve to obtain an anti-carbonization admixture (such as Figure 11 as shown in the middle left picture) and keep it ready for use.

[0069] (2) Weigh the raw materials in the following proportions: 230 parts by weight of sulphoaluminate cement, 575 parts by weight of river sand with a particle size of 0.2-0.35 mm, and calcium carbonate powder (specific surface area 449.6 m 2 The following ingredients were mixed thoroughly: 25 parts by weight of a 100% slurry (100g / kg), 20 parts by weight of carbon-resistant modified fiber (the same as in Example 3), 70 parts by weight of the anti-carbonization admixture of this example, 3.5 parts by weight of a calcium lignin sulfonate water reducer, and 0.6 parts by weight of a polyether defoamer. After thoroughly mixing these ingredients, mixing water was added at a water-cement ratio of 0.25, and the mixture was stirred evenly to obtain a cement-based repair mortar.

[0070] Performance test: The cement-based repair mortar prepared in this embodiment is poured into a mold, demoulded after hardening, and then naturally cured to an age of 28 days to obtain a test piece. First, the compressive strength a of the test piece is tested according to the "Test Method for Cement Mortar Strength (ISO Method)" (GBT 17671-2021). Then, the test piece is placed in a carbonization box (CO2 concentration is maintained at 20±0.5%, relative humidity in the box is controlled at 70±5%, and temperature is controlled at 20±2°C) for carbonization treatment for 14 days (such as Figure 4 After completion, the test piece was taken out and its compressive strength b was tested. The compressive strength retention rate was then calculated as compressive strength b / compressive strength a, which was 82.57%.

[0071] Example 8:

[0072] A method for preparing an early-strength, fast-hardening, carbonation-resistant cement-based repair mortar comprises the following steps:

[0073] (1) Red mud powder, silica fume and triethanolamine were mixed in a mass ratio of 1:2.3:0.15 and then ground. After the mixture was finished, it was passed through a 600-mesh sieve to obtain an anti-carbonization admixture (such as Figure 11 as shown in the middle right picture) and keep it ready for use.

[0074] (2) Weigh the raw materials in the following proportions: 248 parts by weight of sulphoaluminate cement, 740 parts by weight of river sand with a particle size of 0.2-0.35 mm, and mica powder (specific surface area 350.3 m 2 The following ingredients were mixed thoroughly: 35 parts by weight of a mortar (100g / kg), 25 parts by weight of carbon-resistant modified fiber (the same as in Example 2), 45 parts by weight of the anti-carbonization admixture of this example, 5 parts by weight of a polycarboxylate water-reducing agent, and 1.1 parts by weight of a silicone defoamer. After thoroughly mixing these ingredients, mixing water was added at a water-cement ratio of 0.32, and the mixture was stirred evenly to obtain a cement-based repair mortar.

[0075] Performance test: The cement-based repair mortar prepared in this embodiment is poured into a mold, demoulded after hardening, and then naturally cured to an age of 28 days to obtain a test piece. First, the compressive strength a of the test piece is tested according to the "Test Method for Cement Mortar Strength (ISO Method)" (GBT 17671-2021). Then, the test piece is placed in a carbonization box (CO2 concentration is maintained at 20±0.5%, relative humidity in the box is controlled at 70±5%, and temperature is controlled at 20±2°C) for carbonization treatment for 14 days (such as Figure 4 After completion, the test piece was taken out and its compressive strength b was tested. The compressive strength retention rate was then calculated as compressive strength b / compressive strength a, which was 76.23%.

[0076] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that they may modify the technical solutions described in the foregoing embodiments or substitute equivalents for some of the technical features. Any such modifications, equivalent substitutions, and improvements shall be within the scope of protection of the present invention.

Claims

1. A method for preparing an early-strength, fast-hardening, carbonation-resistant cement-based repair mortar, characterized in that: The steps include: (1) Wollastonite or pseudowollastonite powder and saturated lime water are mixed to form a slurry; then basalt fiber is added and heated to react. After the reaction is completed, the fiber is separated and calcined. After cooling to room temperature, the obtained fiber is mixed with saturated lime water and dried to remove moisture, thereby obtaining carbon-resistant modified fiber; (2) Red mud powder, silica fume, sodium silicate powder, and triethanolamine are mixed and ground to obtain an anti-carbonization admixture; (3) Take the following raw materials: sulphoaluminate cement, fine aggregate, solid waste-based filler, the anti-carbon modified fiber, the anti-carbonization admixture, water reducer, and defoamer; mix the above raw materials, add mixing water, and stir evenly to obtain a cement-based repair mortar.

2. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to claim 1, characterized in that: In step (1), the ratio of the wollastonite or pseudowollastonite powder to saturated lime water is 1 g: 5-8 ml.

3. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to claim 1, characterized in that: In step (1), the fineness of the wollastonite or pseudowollastonite powder is not less than 400 mesh.

4. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to claim 1, characterized in that: In step (1), the ratio of the basalt fiber to the slurry is 1 g: 10-30 ml.

5. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to claim 1, characterized in that: In step (1), the length of the fiber is 2 to 20 mm.

6. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to claim 1, characterized in that: In step (1), the heating temperature is 40-60° C., and the reaction time is 18-22 hours.

7. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to claim 1, characterized in that: In step (1), the calcination temperature is 570-650° C. and the calcination time is 1-1.5 hours.

8. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to claim 1, characterized in that: In step (1), the ratio of the fiber to saturated lime water is 1 g: 30-40 ml.

9. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to claim 1, characterized in that: In step (1), the drying temperature is 70-100°C.

10. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to claim 1, characterized in that: In step (2), the mass ratio of the red mud powder, silica fume, sodium silicate powder and triethanolamine is 1~2:2.3~3.7:0.35~0.52:0.15~0.

24.

11. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to claim 1, characterized in that: In step (2), the anti-carbonization admixture has a fineness of 300-600 mesh.

12. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to any one of claims 1 to 11, characterized in that: In step (3), the proportions of the raw materials are: 230-248 parts by weight of sulphoaluminate cement, 575-740 parts by weight of fine aggregate, 25-35 parts by weight of solid waste-based filler, 20-25 parts by weight of anti-carbon modified fiber, 45-70 parts by weight of anti-carbonization admixture, 3.5-5 parts by weight of water reducer, and 0.6-1.1 parts by weight of defoamer, and the mixing water is added according to a water-cement ratio of 0.25-0.

32.

13. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to any one of claims 1 to 11, characterized in that: In step (3), the solid waste-based filler includes at least one of calcium carbonate, quartz powder, mica powder, and shell powder.

14. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to any one of claims 1 to 11, characterized in that: In step (3), the specific surface area of ​​the solid waste-based filler is 350~450m 2 / kg.

15. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to any one of claims 1 to 11, characterized in that: In step (3), the water reducer includes any one of: polycarboxylic acid water reducer, naphthalene water reducer, melamine water reducer, and lignin sulfonate water reducer.

16. The method for preparing the early-strength, fast-hardening, carbonation-resistant cement-based repair mortar according to any one of claims 1 to 11, characterized in that: In step (3), the defoaming agent includes any one of: an organosilicon defoaming agent, a polyether defoaming agent, and a fatty alcohol defoaming agent.

Images