阅读说明：本技术 一种Ca/Al层状双氢氧化物的碳酸基胶凝材料及其制备方法和应用 (Ca/Al layered double hydroxide carbonic acid-based cementing material and preparation method and application thereof ) 是由 龙广成 王凡 白敏� 王继林 曾晓辉 谢友均 于 2021-09-28 设计创作，主要内容包括：本发明公开了一种Ca/Al层状双氢氧化物的碳酸基胶凝材料及其制备和应用。本发明添加一定细度石灰石粉为唯一前体,混合偏铝酸钠为激发剂形成复合胶凝材料,在解决固体废弃物高值化、资源化利用的同时,生产出具有较高强度的碳酸基胶凝材料,偏铝酸钠促使碳酸钙的重构形成的层状双电层结构显著提高了形成的胶凝材料的力学性能,形成的胶凝材料同时兼备水泥材料的使用要求与固体废弃物的资源化利用。(The invention discloses a carbonic acid-based cementing material of Ca/Al layered double hydroxide, and a preparation method and application thereof. According to the invention, limestone powder with a certain fineness is added as a unique precursor, and mixed sodium metaaluminate is used as an activator to form the composite gelled material, so that the high-valued and resource utilization of solid wastes is solved, and simultaneously, the carbonic acid-based gelled material with higher strength is produced, the sodium metaaluminate promotes the reconstruction of calcium carbonate to form a layered double electric layer structure, the mechanical property of the formed gelled material is obviously improved, and the formed gelled material simultaneously has the use requirement of a cement material and the resource utilization of the solid wastes.)

1. The Ca/Al layered double hydroxide carbonic acid-based cementing material is characterized in that limestone is used as a precursor, mixed sodium metaaluminate is used as an exciting agent for reaction, and the Ca/Al layered double hydroxide carbonic acid-based cementing material is formed under the condition that the surface of the limestone, the contact surface of limestone particles and part of the limestone are dissolved and reshaped.

2. The method for preparing a Ca/Al layered double hydroxide carbonic acid based cementitious material as claimed in claim 1, wherein the method comprises the steps of uniformly mixing limestone powder and sodium metaaluminate by stirring to obtain a powdery prefabricated reaction matrix, adding water to the uniformly mixed matrix, and stirring to prepare the carbonic acid based cementitious material.

3. The carbonate-based cementitious material according to claim 2,

in the carbonic acid-based cementing material, the mass ratio of calcium carbonate to sodium metaaluminate is 10: 1-1: 1, preferably 5: 1-1: 1, more preferably 3: 1-2: 1, most preferably 2: 1.

4. the production method according to claim 2,

the input ratio of the total mass of the limestone powder and the sodium metaaluminate to the water is as follows: 1: 0.3-1: 0.6.

5. the production method according to claim 2,

the limestone powder is heavy limestone powder with 200-800 meshes, preferably 400-800 meshes, and further preferably 600-800 meshes; the sodium metaaluminate is 100-200 meshes, and preferably 200 meshes.

6. The production method according to claim 2,

the limestone powder and sodium metaaluminate are dried in an air drying oven at 75-105 ℃ for 12-24 hours before use; and stirring the limestone powder and sodium metaaluminate mixture for 4-12 h or carrying out ultrasonic-assisted mixing for 15-30 min by using 40-60Hz power to obtain a powdery prefabricated reaction matrix.

7. The production method according to claim 2,

the stirring speed of the matrix and water is 400 r/min-1000 r/min, the time is 2 min-5 min, and the temperature is 15-35 ℃.

8. The production method according to claim 2,

adding water, stirring and forming, and then placing the formed test piece in an indoor environment for curing to a test age to obtain the high-strength carbonic acid base cementing material.

9. Use of the Ca/Al layered double hydroxide carbonate based cement according to claim 1 or the Ca/Al layered double hydroxide carbonate based cement prepared by the method according to any of claims 2 to 8 as a cement replacement as a cement.

10. A process for the preparation of Ca/Al layered double hydroxides, characterized in that a process according to any one of claims 2 to 8 is used.

Technical Field

The invention belongs to the technical field of building materials, relates to an early high-strength carbonic acid-based cementing material, and a preparation method and application thereof, and particularly relates to an early high-strength carbonic acid-based cementing material taking limestone powder as a unique precursor and sodium metaaluminate as an activator, and a preparation method and application thereof.

Background

Calcium carbonate is an indispensable mineral widely existing in nature and is abundant in reserves. It is not only an important component of rocks and minerals, but also a major component of animal bones or shells. Calcium carbonate also plays a key role in the global carbon cycle. In addition, calcium carbonate is often used as a model structure to study ionic solution crystallization and nucleation. In the construction field, calcium carbonate is widely used as a material for plastics, chemical building materials, adhesives and sealing materials. China is a super large country for producing and using calcium carbonate, and the annual yield of the calcium carbonate exceeds 3000 million tons in nearly 5 years; particularly in 2019, the yield reaches 3595 ten thousand tons, which accounts for 28.8 percent of the global yield. However, the mining of calcium carbonate inevitably produces a large amount of calcium carbonate-rich powder waste. Therefore, how to treat the massive solid wastes with high quality and high efficiency is always a great challenge for building a resource-saving and environment-friendly society; at the same time, the cement industry is under great pressure to reduce energy consumption and greenhouse gas emissions, and there is a pressing need to actively find alternatives to certain sustainable and reliable materials. The calcium carbonate is doped into the gel composite material, so that no obvious side effect is caused on the mechanical property of the gel composite material, and even positive synergistic effect is caused on the early strength, the hydration process, the durability and the microstructure of the gel composite material. Therefore, limestone powder, due to its significant advantages of low price, low environmental pressure, etc., has been able to partially or completely replace portland cement to participate in the formation of cementitious materials, and has attracted researchers' attention.

Calcium carbonate has been considered as an inert substance and is not highly active at room temperature. The calcium carbonate can improve the activity after high-temperature calcination and mechanical stirring, so that the calcium carbonate can be widely applied to cement composite materials. Specifically, the performance of the gelled composite material is influenced by physical effects and chemical effects such as microaggregate filling, microcrystalline dilution nucleation and the like. Meanwhile, limestone powder with certain activity accelerates C by virtue of unique microcrystalline nucleation effect of limestone powder₃The A is hydrated to generate hydrated calcium aluminate, thereby improving the mechanical property of the concrete. On the other hand, calcium carbonate can regulate the content of C-S-H gelCa/Si and C of₃S reacts to form hydrated calcium carbonate. It is reported that the use of limestone powder to partially replace cement not only improves the workability of concrete, but also improves the strength and impermeability of concrete. It is noteworthy that the limit of the substitution is always set at around 10-50% in order not to significantly affect the workability of the cement. Due to extremely complex construction, application requirements such as rapid repair, early strength support and the like are gradually increased. Meanwhile, the concrete is continuously subjected to large-scale degradation under complex conditions, which provides power for searching cement substitutes. In view of this need, the researchers are very interested in further expanding this limitation, creating adhesives made entirely or almost entirely of waste, achieving 100% replacement. In recent years, a preliminary result is obtained in the research of preparing alkali activated cement in a sodium silicate-alkali solution by taking limestone powder as a unique precursor. Since the structure of the limestone powder is dissolved in the alkaline medium, the formation of strength may be due to recrystallization of the limestone powder. Meanwhile, calcium ions are carbonated by carbon dioxide, so that a compact structure is formed on the matrix, and the development of strength is facilitated. The above studies have mainly focused on carbosilicate systems, but the development of the carboaluminate system also provides a new perspective for alkali active materials with calcium carbonate as the main precursor. The sodium metaaluminate aqueous solution is alkaline and is commonly used for the engineering plugging by mixing water glass. In addition, it can be used as a good filler in combination with aluminum sulfate. However, the reaction of low-doped sodium metaaluminate with limestone powder is not significant due to the rapid dissolution of sodium metaaluminate. At the same time, the less exothermic heat of dissolution of sodium metaaluminate is insufficient to promote the reaction with the limestone powder. Therefore, the method provided by the invention can provide a new thought for high-value utilization of calcium carbonate, is simple in strategy, and provides an important reference for research of calcium carbonate-based cementing materials.

Disclosure of Invention

The invention aims to solve the problem of resource utilization of a large amount of waste limestone powder and reduce carbon dioxide emission of a cement-based material, and provides an early high-strength carbonic acid-based cementing material which is prepared by synthesizing a layered double electric layer carbonic acid-based cementing material base material by using waste limestone powder as a unique precursor and sodium metaaluminate as an activator, and a high-strength carbonic acid-based cementing material is formed under the condition of solving the problem of the prior solid waste accumulation.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

a carbonic acid-based cementing material of Ca/Al layered double hydroxide is prepared by using limestone as precursor and mixed sodium metaaluminate as activator to react, and dissolving and remolding the surface of limestone, contact surface of limestone particles and part of limestone to form the carbonic acid-based cementing material of Ca/Al layered double hydroxide.

According to the preparation method of the Ca/Al layered double hydroxide carbonic acid-based cementing material, limestone powder and sodium metaaluminate are stirred and mixed uniformly to obtain a powdery prefabricated reaction matrix, water is added into the uniformly mixed matrix, and the carbonic acid-based cementing material is prepared by stirring.

Further, the air conditioner is provided with a fan,

in the carbonic acid-based cementing material, the mass ratio of calcium carbonate to sodium metaaluminate is 10: 1-1: 1, preferably 5: 1-1: 1, more preferably 3: 1-2: 1, most preferably 2: 1.

further, the air conditioner is provided with a fan,

the input ratio of the total mass of the limestone powder and the sodium metaaluminate to the water is as follows: 1: 0.3-1: 0.6.

further, the air conditioner is provided with a fan,

the limestone powder is heavy limestone powder with 200-800 meshes, preferably 400-800 meshes, and further preferably 600-800 meshes; the sodium metaaluminate is 100-200 meshes, and preferably 200 meshes.

The sodium metaaluminate is of analytical grade.

Further, the air conditioner is provided with a fan,

the limestone powder and sodium metaaluminate are dried in an air drying oven at 75-105 ℃ for 12-24 hours before use; and stirring the limestone powder and sodium metaaluminate mixture for 4-12 h or carrying out ultrasonic-assisted mixing for 15-30 min by using 40-60Hz power to obtain a powdery prefabricated reaction matrix.

Further, the air conditioner is provided with a fan,

the stirring speed of the matrix and water is 400 r/min-1000 r/min, the time is 2 min-5 min, and the temperature is 15-35 ℃.

Further, the air conditioner is provided with a fan,

adding water, stirring and forming, and then placing the formed test piece in an indoor environment for curing to a test age to obtain the carbonic acid based cementing material.

Deionized water is preferred.

Preferably, the carbonate-based cement is formed under low humidity conditions (< 85% RH).

The application of the carbonic acid-based cementing material of Ca/Al layered double hydroxide prepared by the method replaces cement to be used as a cementing material.

The invention actually provides a method for preparing Ca/Al layered double hydroxide, namely a method for preparing the carbonic acid-based cementing material of the Ca/Al layered double hydroxide.

The invention prepares Ca/Al-containing layered double hydroxide cementing material by cheap limestone powder and sodium metaaluminate. Calcium carbonate is used as a matrix, layered double hydroxide is directly polymerized on the surface of the calcium carbonate in the air by a simple chemical method, and the mechanical property, especially the breaking strength, of the material is improved by using sodium metaaluminate to dissolve and cooperate with calcium carbonate to reconstruct into a layered double hydroxide layer structure.

Compared with the prior art, the invention has the advantages that:

(1) the method is environment-friendly and easy to operate, and is a green preparation method;

(2) the invention takes waste limestone powder as a precursor material, and synthesizes a carbonic acid-based gelled material containing a layered hydroxide structure by a simple chemical solvent thermal precipitation method;

(3) the carbonic acid base cementing material prepared by the invention has high compressive strength and high breaking strength, and in addition, the layered hydroxide also has other functional properties, such as adsorptivity and catalysis.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) photograph of CC/SMA ═ 10:1 in example 1 of the present invention;

FIG. 2 is a Scanning Electron Microscope (SEM) photograph of CC/SMA as 7.5:1 in example 2 of the present invention;

FIG. 3 is a Scanning Electron Microscope (SEM) photograph of CC/SMA ═ 5:1 in example 3 of the present invention;

FIG. 4 is a Scanning Electron Microscope (SEM) photograph of CC/SMA as 3:1 in example 4 of the present invention;

FIG. 5 is a Scanning Electron Microscope (SEM) photograph of CC/SMA ═ 2:1 in example 5 of the present invention;

FIG. 6 is a Scanning Electron Microscope (SEM) photograph of CC/SMA ═ 1:1 in example 6 of the present invention;

fig. 7 is a phase diffraction (XRD) photograph of CC/SMA 10:1 in example 1 of the present invention;

fig. 8 is a phase diffraction (XRD) photograph of CC/SMA ═ 7.5:1 in example 2 of the present invention;

fig. 9 is a phase diffraction (XRD) photograph of CC/SMA 5:1 in example 3 of the present invention;

fig. 10 is a phase diffraction (XRD) photograph of CC/SMA 3:1 in example 4 of the present invention;

fig. 11 is a phase diffraction (XRD) photograph of CC/SMA ═ 2:1 in example 5 of the present invention;

fig. 12 is a phase diffraction (XRD) photograph of CC/SMA ═ 1:1 in example 6 of the present invention.

Detailed Description

In order to better explain the invention, the following examples are given to further illustrate the invention, but the invention is not limited to the following examples, which should not be construed as a limitation of the invention.

Example 1 preparation of a calcium carbonate-based Cement with CC/SMA ═ 10:1

Drying (75 ℃, 12h) mesh waste limestone powder (800 meshes) and sodium metaaluminate (150 meshes) according to the ratio of 10:1, mixing and stirring uniformly (4 h). Then, mixing the following components in a water-cement ratio of 3: 10 measured amounts of water were added and stirred at 800rpm (3min,20 ℃) with a stirrer and placed in a 40 x 160mm cube mould. And (3) carrying out water retention sealing treatment on the surface of the sample by adopting a plastic film (1 d). The treated sample was maintained at 20 ℃ and 75% RH for the test period. As can be seen from fig. 1 and 7, Ca/Al layered double electric layer hydroxide was formed and the diffraction intensity of calcium carbonate was reduced. The microstructure of the formed carbonic acid-based cementing material is loose, and the structure of the Ca/Al layered double-layer hydroxide is not compact enough. The mechanical properties are shown in Table 1.

Example 2 preparation of calcium carbonate-based cements with CC/SMA ═ 7.5:1

Drying (75 ℃, 12h) mesh waste limestone powder (800 meshes) and sodium metaaluminate (150 meshes) according to the ratio of 7.5:1, mixing and stirring uniformly (4 h). Then, mixing the following components in a water-cement ratio of 3: 10 measured amounts of water were added and stirred at 800rpm (3min,20 ℃) with a stirrer and placed in a 40 x 160mm cube mould. And (3) carrying out water retention sealing treatment on the surface of the sample by adopting a plastic film (1 d). The treated sample was maintained at 20 ℃ and 75% RH for the test period. As can be seen from FIGS. 2 and 8, the diffraction intensity of the formed Ca/Al layered double electric layer hydroxide was increased. The microstructure of the carbonate-based gelled material formed under this condition was compact compared to example 1, and the Ca/Al layered double electric layer hydroxide structure was clearly clearer. The mechanical properties are shown in Table 1.

Example 3 preparation of a calcium carbonate-based Cement with CC/SMA ═ 5:1

Drying (75 ℃, 12h) mesh waste limestone powder (800 meshes) and sodium metaaluminate (150 meshes) according to the ratio of 5:1, mixing and stirring uniformly (4 h). Then, mixing the following components in a water-cement ratio of 3: 10 measured amounts of water were added and stirred at 800rpm (3min,20 ℃) with a stirrer and placed in a 40 x 160mm cube mould. And (3) carrying out water retention sealing treatment on the surface of the sample by adopting a plastic film (1 d). The treated sample was maintained at 20 ℃ and 75% RH for the test period. As can be seen from fig. 3 and 9, the diffraction intensity of the formed Ca/Al layered double electric layer hydroxide further increased, while the diffraction intensity of calcium carbonate continued to decrease. The microstructure of the carbonic acid-based cementing material formed under the condition is gradually clear, and the Ca/Al layered double-electric-layer hydroxide structure is obviously formed. The mechanical properties are shown in Table 1.

Example 4 preparation of a calcium carbonate-based Cement with CC/SMA ═ 3:1

Drying (75 ℃, 12h) mesh waste limestone powder (800 meshes) and sodium metaaluminate (150 meshes) according to the ratio of 3:1, mixing and stirring uniformly (4 h). Then, mixing the following components in a water-cement ratio of 3: 10 measured amounts of water were added and stirred at 800rpm (3min,20 ℃) with a stirrer and placed in a 40 x 160mm cube mould. And (3) carrying out water retention sealing treatment on the surface of the sample by adopting a plastic film (1 d). The treated sample was maintained at 20 ℃ and 75% RH for the test period. As can be seen from fig. 4 and 10, the diffraction intensity of the formed Ca/Al layered double electric layer hydroxide further increased, while the diffraction intensity of calcium carbonate continued to decrease. The microstructure of the carbonic acid-based cementing material formed under the condition is clearer, and the Ca/Al layered double-layer hydroxide structure is compact. The mechanical properties are shown in Table 1.

Example 5 preparation of calcium carbonate-based cements with CC/SMA ═ 2:1

Drying (75 ℃, 12h) mesh waste limestone powder (800 meshes) and sodium metaaluminate (150 meshes) according to the ratio of 2:1, mixing and stirring uniformly (4 h). Then, mixing the following components in a water-cement ratio of 3: 10 measured amounts of water were added and stirred at 800rpm (3min,20 ℃) with a stirrer and placed in a 40 x 160mm cube mould. And (3) carrying out water retention sealing treatment on the surface of the sample by adopting a plastic film (1 d). The treated sample was maintained at 20 ℃ and 75% RH for the test period. As can be seen from fig. 5 and 11, the diffraction intensity of the formed Ca/Al layered double electric layer hydroxide further increased, while the diffraction intensity of calcium carbonate continued to decrease. The carbonic acid group gelled material formed under the condition has a compact microstructure, the Ca/Al layered double electric layer hydroxide structure is closely distributed, and the layered superposition is obvious. The mechanical properties are shown in Table 1.

Example 6 preparation of calcium carbonate-based cements with CC/SMA ═ 1:1

Drying (75 ℃, 12h) mesh waste limestone powder (800 meshes) and sodium metaaluminate (150 meshes) according to the ratio of 1:1, mixing and stirring uniformly (4 h). Then, mixing the following components in a water-cement ratio of 3: 10 measured amounts of water were added and stirred at 800rpm (3min,20 ℃) with a stirrer and placed in a 40 x 160mm cube mould. And (3) carrying out water retention sealing treatment on the surface of the sample by adopting a plastic film (1 d). The treated sample was maintained at 20 ℃ and 75% RH for the test period. As can be seen from fig. 6 and 12, the diffraction intensity of the formed Ca/Al layered double electric layer hydroxide decreased, and the diffraction intensity of calcium carbonate decreased again. The carbonic acid-based cementing material formed under the condition has a loose microstructure, and the double electric layers of Ca/Al layered double electric layer hydroxide structures are not compact in adhesion. The mechanical properties are shown in Table 1.

TABLE 1 flexural and compressive strengths of 1d and 28d of samples 1 to 6

As can be seen from Table 1, the content ratio of the waste limestone powder to sodium metaaluminate has a significant effect on the flexural strength of the resulting carbonate-based cementitious material. The flexural strength of samples 2 to 6 was increased, as compared to sample 1, with the 3d flexural strength of sample 5 being increased by 1220% and the 28d flexural strength being increased by 4533%. The compressive strength of samples 2 to 6 was also increased compared to sample 1, with the 3d compressive strength of sample 5 being increased by 787.5% at the maximum growth rate and by 3550% at the 28d compressive strength. However, sample 6 has reduced compressive and flexural strength compared to sample 5. Because poor adhesion of the Ca/Al layered double electric layer hydroxide product to the poor layered double electric layer interface results in higher porosity and poor micro-bridging effect, which affects the mechanical properties of the formed carbonate-based cementitious material.

Drying waste limestone powder of 200 meshes (sample 7-A), 400 meshes (sample 7-B) or 600 meshes (sample 7-C) and sodium metaaluminate (150 meshes) according to the ratio of 2:1, mixing and stirring uniformly (4 h). Then, mixing the following components in a water-cement ratio of 3: 10 measured amounts of water were added and stirred at 800rpm (3min,20 ℃) with a stirrer and placed in a 40 x 160mm cube mould. And (3) carrying out water retention sealing treatment on the surface of the sample by adopting a plastic film (1 d). The treated sample was maintained at 20 ℃ and 75% RH for the test period. The mechanical properties are shown in Table 2.

TABLE 2 flexural and compressive strengths of 1d and 28d of sample 7