Cement-based material containing high-volume slag as well as preparation method and application of cement-based material

Abstract

The invention discloses a cement-based material containing high-volume slag as well as a preparation method and application of the cement-based material. The cement-based material comprises the following components in parts by mass: 17-38 parts of Portland cement, 1-3 parts of nano silicon dioxide, 60-80 parts of mineral powder and 0.89-1.58 parts of a water reducing agent. The high-activity nano silicon dioxide is used for promoting hydration of cement and mineral powder to generate more hydration products and optimizing the pore structure of the cement-based material, and the chloride ion resistance of the cement-based material is improved by enhancing the chloride ion binding capacity of the cement-based material and improving pores. The method has important significance for enhancing the durability of the marine concrete.

Description

Technical Field

[0001] The present invention relates to a cement-based material and a preparation method thereof, and in particular to a cement-based material containing a large amount of slag and a preparation method and application thereof, belonging to the technical field of building materials. Background Art

[0002] Concrete is widely used in harsh environments such as the ocean and western salt lakes. The high content of chlorides and sulfates in these environments can lead to a reduction in the durability of concrete and a shortening of its service life. In order to improve the durability of concrete in harsh environments, a large amount of slag is currently used to replace cement to improve the chloride ion resistance of concrete.

[0003] The main components of slag are CaO, SiO 2 and Al 2 O 3 Adding slag to cement-based materials is beneficial to enhancing the chloride ion resistance of cement-based materials. However, when the slag content is too high (80%), due to the insufficient early activity of slag, problems such as loose structure and decreased chloride ion binding ability will occur in cement-based materials containing a large amount of slag, which not only affects their durability but also severely limits the amount of slag used in cement-based materials, becoming a technical problem restricting the application of cement-based materials containing a large amount of slag.

[0004] In patent CN112279590A, a sulfate-resistant concrete is disclosed, which uses surface-modified nano-silica and metal-organic framework nano-sheet-silica composites to prepare anti-sulfate composite particles; however, the anti-sulfate composite particles in this patent cannot be used to resist chloride ions in the marine environment. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a cement-based material containing a large amount of slag with improved chloride ion resistance; another object of the present invention is to provide a preparation method of a cement-based material containing a large amount of slag; another object of the present invention is to provide an application of a cement-based material containing a large amount of slag.

[0006] Technical Solution: A cement-based material containing a large amount of slag according to the present invention has the following raw material proportion by weight: 17-38 parts by mass of portland cement, 1-3 parts by mass of nano-silica, 60-80 parts by mass of slag powder, and 0.89-1.58 parts by mass of water reducer.

[0007] In the above technical solution, nano-silica is added to the cement-based material containing a large amount of slag to improve the chloride ion resistance of the cement-based material containing a large amount of slag by optimizing the pore structure and enhancing chloride ion binding of nano-silica.

[0008] Further, the portland cement is PⅠ42.5 portland cement.

[0009] Further, the nano-silica is hydrophilic fumed nano-silica of the Hydrophilic-380 type.

[0010] Further, the particle size of the nano-silica is 7 - 40 nm.

[0011] Further, the blast furnace slag powder is of the V500 type.

[0012] Further, the water reducing agent is a polycarboxylate water reducing agent.

[0013] On the other hand, the present invention provides a method for preparing a cement-based material containing a large amount of blast furnace slag, comprising the following steps:

[0014] Step 1: Mix nano-silica, mixing water, and a water reducing agent, and then disperse them to obtain a uniformly dispersed nano-silica solution;

[0015] Step 2: Stir and mix cement and blast furnace slag powder to obtain a uniformly mixed powder material;

[0016] Step 3: Stir the uniformly dispersed nano-silica solution and the uniformly mixed powder material to obtain a cement-based material containing a large amount of blast furnace slag.

[0017] Further, in Step 1, after mixing nano-silica, mixing water, and a water reducing agent, ultrasonic dispersion is carried out.

[0018] Further, in Step 3, a mixer is used for stirring the powder material.

[0019] Further, in Step 3, the stirring speed of the mixer is 140 ± 5 r / min.

[0020] On the other hand, the present invention provides an application of the above-mentioned cement-based material containing a large amount of blast furnace slag in the preparation of marine concrete.

[0021] There are various ions in the marine environment, and the action mechanisms of enhancing sulfate erosion resistance and chloride ion resistance are not the same. The use of nano-silica in the cement-based material of the present invention can effectively enhance the chloride ion resistance, but it is not suitable for enhancing the sulfate erosion resistance of the cement-based material. The reason is that the present invention enhances the chloride ion resistance of the cement-based material from two aspects: densifying pores and increasing the chloride ion binding ability of the cement-based material. However, when the pores are too dense, erosion products (such as gypsum and ettringite) formed by sulfate erosion will cause greater stress expansion, resulting in the generation of microcracks in the cement-based material and affecting the durability of the cement-based material.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: The nano-silica described in the present invention can exert the pozzolanic effect and nucleation effect, promote the hydration of high-volume slag cement, improve its pore structure, enhance its chloride ion binding ability, and ultimately further improve the chloride ion resistance of cement-based materials containing high-volume slag. It is of great significance for further increasing the slag content in cement and enhancing the durability of marine concrete. Description of the Drawings

[0023] Figure 1 Chloride ion diffusion coefficients of the comparative example and the examples;

[0024] Figure 2 and Figure 3 Chloride ion distribution maps of chloride ions in the cement-based materials after soaking in 5 wt.% NaCl solution for 180 days for the comparative example and the examples;

[0025] Figure 4 Total porosity of the comparative example and the examples;

[0026] Figure 5 Pore distribution of the comparative example and the examples;

[0027] Figure 6 Chloride ion binding rate of the comparative example and the examples. Detailed Embodiments

[0028] The technical solutions of the present invention will be further described below in conjunction with the detailed embodiments. The following comparative examples and examples are carried out according to the technical solutions of the present invention, and the detailed implementation processes and specific operation methods are given, but the protection scope of the present invention is not limited to the following examples.

[0029] In the examples of the present invention, the following raw materials are used: The nano-silica is hydrophilic fumed nano-silica of the Hydrophilic-380 type, produced by Shanghai Macklin Biochemical Co., Ltd., with a particle size of 7-40 nm and a specific surface area of 380 m 2 / g. The Portland cement is PⅠ42.5 Portland cement produced by Fushun Cement Co., Ltd. The slag powder is V500 type slag powder produced by Wuhan Huashen Intelligent Technology Co., Ltd., meeting the requirements of the current standard GB / T18046. The solid content of the polycarboxylate water reducer is 20%

[0030] Comparative Example 1

[0031] The specific implementation process is as follows: Weigh 100 parts by mass of cement and 45 parts by mass of water. Mix the water and cement in a blender at a stirring speed of 140 ± 5 r / min for 6 minutes until evenly mixed. After mixing, pour the slurry into a mold for forming and vibrating, and then cover it with plastic wrap for standard curing (20 ± 2°C, ≥ 95% RH). Demold after 1 day of standard curing, and then continue standard curing until the age of the specimen and conduct tests. According to the national standard, the chloride diffusion coefficient of the specimen is measured by the RCM method to be 27.07×10 -12 m 2 / s.

[0032] Comparative Example 2

[0033] The specific implementation process is as follows: Weigh 40 parts by mass of cement, 60 parts by mass of mineral powder, and 45 parts by mass of water. First, mix the mineral powder and cement evenly, and then mix the water and the powder in a blender at a stirring speed of 140 ± 5 r / min for 6 minutes until evenly mixed. After mixing, pour the slurry into a mold for forming and vibrating, and then cover it with plastic wrap for standard curing (20 ± 2°C, ≥ 95% RH). Demold after 1 day of standard curing, and then continue standard curing until the age of the specimen and conduct tests. According to the national standard, the chloride diffusion coefficient of the specimen is measured by the RCM method to be 20.11×10 -12 m 2 / s.

[0034] Comparative Example 3

[0035] The specific implementation process is as follows: Weigh 20 parts by mass of cement, 80 parts by mass of mineral powder, and 45 parts by mass of water. First, mix the mineral powder and cement evenly, and then mix the water and the powder in a blender at a stirring speed of 140 ± 5 r / min for 6 minutes until evenly mixed. After mixing, pour the slurry into a mold for forming and vibrating, and then cover it with plastic wrap for standard curing (20 ± 2°C, ≥ 95% RH). Demold after 1 day of standard curing, and then continue standard curing until the age of the specimen and conduct tests. According to the national standard, the chloride diffusion coefficient of the specimen is measured by the RCM method to be 25.71×10 -12 m 2 / s.

[0036] Example 1

[0037] The specific implementation process is as follows: Weigh 38 parts by mass of cement, 60 parts by mass of mineral powder, 2 parts by mass of nano-silica, 44.16 parts by mass of water, and 1.05 parts by mass of water reducer. Mix nano-silica, mixing water, and water reducer, and then perform ultrasonic dispersion to obtain a uniformly dispersed nano-silica solution. The total ultrasonic time is 5 min, the ultrasonic power is 800 W, and the ultrasonic mode is to work for 2 s and then pause for 2 s; then mix the mineral powder and cement evenly; finally, stir the uniformly dispersed nano-silica solution and the powder in a mixer at a stirring speed of 140 ± 5 r / min for 6 minutes until evenly stirred. After stirring, pour the slurry into a mold for molding and vibration compaction, and then cover it with a plastic wrap for standard curing (20 ± 2 °C, ≥ 95% RH). Demold after 1 day of standard curing, and then continue standard curing until the age of the specimen and then conduct tests. According to the national standard, the chloride ion diffusion coefficient of the specimen is measured by the RCM method to be 3.85×10 -12 m 2 / s.

[0038] Example 2

[0039] The specific implementation process is as follows: Weigh 19 parts by mass of cement, 80 parts by mass of mineral powder, 1 part by mass of nano-silica, 44.29 parts by mass of water, and 0.89 parts by mass of water reducer. Mix nano-silica, mixing water, and water reducer, and then perform ultrasonic dispersion to obtain a uniformly dispersed nano-silica solution. The total ultrasonic time is 5 min, the ultrasonic power is 800 W, and the ultrasonic mode is to work for 2 s and then pause for 2 s; then mix the mineral powder and cement evenly; finally, stir the uniformly dispersed nano-silica solution and the powder in a mixer at a stirring speed of 140 ± 5 r / min for 6 minutes until evenly stirred. After stirring, pour the slurry into a mold for molding and vibration compaction, and then cover it with a plastic wrap for standard curing (20 ± 2 °C, ≥ 95% RH). Demold after 1 day of standard curing, and then continue standard curing until the age of the specimen and then conduct tests. According to the national standard, the chloride ion diffusion coefficient of the specimen is measured by the RCM method to be 5.49×10 -12 m 2 / s.

[0040] Example 3

[0041] Specific implementation process: Weigh 18 parts by mass of cement, 80 parts by mass of slag powder, 2 parts by mass of nano-silica, 44.16 parts by mass of water, and 1.05 parts by mass of water reducer. Mix nano-silica, mixing water, and water reducer, and then perform ultrasonic dispersion to obtain a uniformly dispersed nano-silica solution. The total ultrasonic time is 5 min, the ultrasonic power is 800 W, and the ultrasonic mode is to work for 2 s and then pause for 2 s. Then mix the slag powder and cement evenly. Finally, stir the uniformly dispersed nano-silica solution and the powder in a mixer at a stirring speed of 140 ± 5 r / min for 6 minutes until evenly mixed. After stirring, pour the slurry into a mold for molding and vibration compaction, and then cover it with a plastic wrap for standard curing (20 ± 2 °C, ≥ 95% RH). Demold after 1 day of standard curing, and then continue standard curing until the age of the specimen for testing. According to the national standard, the chloride ion diffusion coefficient of the specimen is measured by the RCM method to be 1.75×10 -12 m 2 / s.

[0042] Example 4

[0043] Specific implementation process: Weigh 17 parts by mass of cement, 80 parts by mass of slag powder, 3 parts by mass of nano-silica, 43.74 parts by mass of water, and 1.58 parts by mass of water reducer. Mix nano-silica, mixing water, and water reducer, and then perform ultrasonic dispersion to obtain a uniformly dispersed nano-silica solution. The total ultrasonic time is 5 min, the ultrasonic power is 800 W, and the ultrasonic mode is to work for 2 s and then pause for 2 s. Then mix the slag powder and cement evenly. Finally, stir the uniformly dispersed nano-silica solution and the powder in a mixer at a stirring speed of 140 ± 5 r / min for 6 minutes until evenly mixed. After stirring, pour the slurry into a mold for molding and vibration compaction, and then cover it with a plastic wrap for standard curing (20 ± 2 °C, ≥ 95% RH). Demold after 1 day of standard curing, and then continue standard curing until the age of the specimen for testing. According to the national standard, the chloride ion diffusion coefficient of the specimen is measured by the RCM method to be 0.98×10 -12 m 2 / s.

[0044] The chloride ion transport coefficient of the cement-based material with a high content of slag is as Figure 1As shown, from the experimental results of Comparative Examples 1-3, it can be seen that adding a large amount of slag can enhance the chloride ion transport resistance of cement-based materials. However, when the slag content increases from 60% to 80%, the chloride ion diffusion coefficient shows an upward trend, indicating that when the slag content is too high, the effectiveness of enhancing the chloride ion resistance of cement-based materials will be weakened. From the experimental results of Examples 1-4, it can be seen that adding nano-silica can significantly enhance the chloride ion resistance of cement-based materials containing a large amount of slag. This is mainly because, on the one hand, nano-silica promotes the hydration of cement with a large amount of slag, densifies the pores, optimizes the pore structure, and hinders the transport of chloride ions. As Figure 2 、 Figure 3 Figure is the distribution diagram of chloride ions with depth inside the specimen after the specimen is immersed in 5wt% NaCl solution for 6 months. It can be seen from the figure that after adding nano-SiO 2 , the chloride ion content in the deep part of the specimen decreases, indicating that nano-SiO 2 has the effect of hindering the transport of chloride ions and enhancing the chloride ion resistance of the specimen. As Figure 4 、 Figure 5 shows the cumulative porosity and pore distribution diagrams of Comparative Example 1, Comparative Example 3, and Example 3. It can be seen from the figure that the addition of nano-silica can reduce the cumulative porosity of cement-based materials containing a large amount of slag, optimize the pore structure, reduce the large pore volume, and increase the small pore volume. On the other hand, it can be seen from Figure 6 that nano-silica can enhance the chloride ion binding ability of cement-based materials containing a large amount of slag. This is mainly because nano-silica has the effect of promoting cement hydration, increasing the content of hydration product C-S-H gel and its Al / Si ratio, and thus enhancing the physical chloride ion binding ability of a large amount of slag. The enhancement of the chloride ion binding ability of the system helps to enhance the chloride ion resistance of the specimen.

Claims

1. A cement-based material containing a large amount of slag, characterized in that: The raw materials are proportioned as follows in parts by weight: 17-38 parts by weight of silicate cement, 1-3 parts by weight of nano silicon dioxide, 60-80 parts by weight of mineral powder, and 0.89-1.58 parts by weight of water reducing agent.

2. The cement-based material containing a large amount of slag according to claim 1, characterized in that: The silicate cement is PI42.5 silicate cement.

3. The cement-based material containing a large amount of slag according to claim 1, characterized in that: The nano silicon dioxide is hydrophilic gas phase nano silicon dioxide Hydrophilic-380 type.

4. The cement-based material containing a large amount of slag according to claim 1, characterized in that: The particle size of the nano silicon dioxide is 7-40nm.

5. The cement-based material containing a large amount of slag according to claim 1, characterized in that: The mineral powder is V500 type slag powder.

6. The cement-based material containing a large amount of slag according to claim 1, characterized in that: The water reducer is a polycarboxylate water reducer.

7. A method for preparing a cement-based material containing a large amount of slag, characterized in that: The following steps are involved: Step 1: Mix nano-silicon dioxide, mixing water and water reducing agent and disperse them to obtain a uniformly dispersed nano-silicon dioxide solution; Step 2: Stir and mix the cement and mineral powder to obtain a uniformly mixed powder; Step 3: Stir the uniformly dispersed nano-silicon dioxide solution and the uniformly mixed powder to obtain a cement-based material containing a large amount of slag.

8. The method for preparing a cement-based material containing a large amount of slag according to claim 7, characterized in that: In the step 1, nano silicon dioxide, mixing water and a water reducing agent are mixed and then ultrasonically dispersed.

9. The method for preparing a cement-based material containing a large amount of slag according to claim 7, characterized in that: In the step 3, a mixer is used to stir the powder.

10. Use of the cement-based material containing a large amount of slag according to any one of claims 1 to 6 in preparing marine concrete.

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