A low-carbon multi-component magnesium gelling material and preparation method thereof
By using composite excitation methods of calcined clay, magnesium oxide and auxiliary excitants in low-carbon multivariate magnesium gelling materials, the problem of poor mechanical properties of calcined clay-based gelling materials in the early stage was solved, and high-strength and low-carbon gelling materials were achieved, which were suitable for a wide range of application scenarios.
Patent Information
- Application Number
- CN202310474745.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-04-27
- Publication Date
- 2025-05-13
- Estimated Expiration
- 2043-04-27
AI Technical Summary
The existing cementitious materials based on calcined clay have poor early mechanical properties and are difficult to meet actual engineering needs.
Low-carbon polymagnesium gelling materials are used to improve the early mechanical properties of the gelling materials by using calcined clay and magnesium oxide as gelling components, and auxiliary exciters such as sodium sulfate, calcium chloride, sodium bicarbonate, and sodium carbonate, combined with multi-composite excitation methods.
The early and late strength of the gelled material is significantly improved, with 3d strength up to 18MPa and 7d strength up to 26MPa, meeting actual engineering needs and reducing unit carbon emissions and energy consumption.
Smart Images
Figure CN116444183B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of low-carbon cementitious materials, and in particular to a low-carbon multi-component magnesium cementitious material and a preparation method thereof. Background Art
[0002] The production of silicate cement is accompanied by the consumption of a large amount of calcium raw materials, mainly limestone, which results in huge energy consumption. At present, magnesium cementitious materials with magnesium silicate hydrate (MSH) as the main product have attracted wide attention, but there is currently a lack of large-scale application. The research and development of magnesium cementitious materials has become an important direction in the research of building materials.
[0003] At the same time, the production of Portland cement leads to huge CO2 emissions. According to statistics, CO2 emissions from the cement industry account for 8% of the world's total anthropogenic carbon emissions, and the use of supplementary cementitious materials (SCMs) to replace or partially replace Portland cement is considered to be the most effective technical approach to reduce carbon emissions. Commonly used SCMs mainly include industrial by-products such as iron and steel, power plants, etc., such as mineral powder and fly ash, but such materials are less in reserve in developing countries and underdeveloped industrial regions, making it difficult to meet actual building material needs. Calcined clay, as a relatively new potential supplementary cementitious material, is less affected by regional distribution and has huge reserves, so it has great potential application value.
[0004] However, the current cementitious materials based on calcined clay generally have the problem of poor early mechanical properties, which makes it difficult to meet actual engineering needs. Summary of the invention
[0005] The purpose of the present invention is to overcome the above technical deficiencies, propose a low-carbon multi-component magnesium cementitious material and a preparation method thereof, and solve the technical problem that cementitious materials based on calcined clay in the prior art generally have poor early mechanical properties and are difficult to meet actual needs.
[0006] In a first aspect, the present invention provides a low-carbon multi-element magnesium cementitious material, the raw materials of which include: a cementitious component and an auxiliary activator; wherein the cementitious component is composed of calcined clay and magnesium oxide; and the auxiliary activator is at least one of sodium sulfate, calcium chloride, sodium bicarbonate, and sodium carbonate.
[0007] In a second aspect, the present invention provides a method for preparing a low-carbon multi-component magnesium gelling material, comprising the following steps:
[0008] The gelling component, the auxiliary activator, the water reducing agent and water are uniformly mixed to obtain a slurry;
[0009] After the slurry is formed and cured, a low-carbon multi-component magnesium cementitious material is obtained.
[0010] Compared with the prior art, the beneficial effects of the present invention include:
[0011] The present invention innovatively proposes to use a multi-component composite excitation method, based on the ion dissolution process of the early system, combined with the hydration mechanism of calcined clay, and utilizing the organic coordination of multiple chemical auxiliary stimulants to effectively improve the early mechanical properties of cementitious materials; the present invention improves the early strength of the material and ensures the later strength of the material, and the mechanical properties are significantly developed. In response to the problem of low early strength of general calcined clay-based cementitious materials, the low-carbon multi-component magnesium cementitious material of the present invention has a 3d strength of up to 18MPa and a 7d strength of up to 26MPa. The low-carbon multi-component magnesium cementitious material provided by the present invention has a wide range of application scenarios, a simple process flow, and greatly reduced unit carbon emissions and energy consumption, and has great potential application value. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Picture 1 It is the 1d, 3d, 7d and 28d compressive strength of the cementitious materials obtained in Examples 1-3 of the present invention and Comparative Examples 1-2. DETAILED DESCRIPTION
[0013] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0014] In a first aspect, the present invention provides a low-carbon multi-element magnesium cementitious material, the raw materials of which include: a cementitious component and an auxiliary activator; wherein the cementitious component is composed of calcined clay and magnesium oxide; and the auxiliary activator is at least one of sodium sulfate, calcium chloride, sodium bicarbonate, and sodium carbonate.
[0015] The system of the present invention is suitable for kaolinite clay, and magnesium oxide can react with metakaolinite generated by calcining kaolinite clay. Kaolinite clay usually contains minerals such as kaolinite, montmorillonite and illite, which have good volcanic ash activity after calcining at 600℃-800℃. Under the action of magnesium oxide, they can react with water to generate hydration products with gelling effect and water hardness. However, the calcined clay system activated by magnesium oxide alone has the disadvantage of low early strength; the auxiliary activators (sodium sulfate, calcium chloride, sodium carbonate, sodium bicarbonate) in the system of the present invention are synergistically activated with magnesium oxide to further improve the early performance of the system and ensure the later strength.
[0016] In this embodiment, the particle size of the calcined clay is 0.1-1000 μm, and the content of kaolinite in the calcined clay is between 40% and 80%. There is a good linear correlation between the reactivity of the calcined clay and the content of kaolinite in the calcined clay. The inventors found that the calcination degree of the calcined clay has a great influence on the performance of the cementitious material. Studies have shown that as the calcination temperature gradually increases, the reactivity of the calcined clay first increases and then decreases, and can be divided into three stages: when calcined to 500-600°C, the clay particles are broken, kaolinite is dehydroxylated to metakaolin, the degree of structural disorder increases, and the reactivity appears and gradually increases; when calcined to 700-800°C, the clay particles are flocculent, the degree of structural disorder further increases, and the reactivity reaches the highest in this temperature range; when calcined to 900°C, sintering, recrystallization and other phenomena will occur, the particle size increases, and the reactivity drops suddenly. After the heating and heat preservation process is completed, in order to further improve the reactivity of the calcined clay, rapid cooling by fan is better than natural cooling in the furnace. In some preferred embodiments of the present invention, the calcined clay is obtained by heating the clay from room temperature to 200-300°C at a heating rate of 5°C / min, then heating from 200-300°C to 700-800°C at a heating rate of 10°C / min, and keeping it at 700-800°C for 1-2h, followed by rapid cooling. Under this calcination system, the calcined clay obtained has the best activity, which is more conducive to making the cementitious material formed by the reaction with water under the action of magnesium oxide and auxiliary activator have higher early strength.
[0017] In this embodiment, the mass ratio of calcined clay to magnesium oxide is (1-8):1, and further is 4:1.
[0018] In this embodiment, the auxiliary stimulant accounts for 0.05%-10% of the mass of the gelling component, further 0.05%-2%, and further 1%. If the amount of the auxiliary stimulant is too high, the stimulating effect cannot be further improved, and the cost is greatly increased.
[0019] In this embodiment, the raw materials of the low-carbon multi-element magnesium gelling material further include: a water reducing agent, which accounts for 1%-3% of the mass of the gelling component.
[0020] In this embodiment, the raw materials of the low-carbon multi-element magnesium gelling material further include: water. Furthermore, the water accounts for 40%-60% of the mass of the gelling component.
[0021] In a second aspect, the present invention provides a method for preparing a low-carbon multi-component magnesium gelling material, comprising the following steps:
[0022] S1. Mix the gelling component, auxiliary activator, water reducing agent and water to obtain slurry;
[0023] S2. After the slurry is formed and cured, a low-carbon multi-element magnesium cementitious material is obtained.
[0024] In some specific embodiments of the present invention, the step of uniformly mixing the gelling component, the auxiliary activator, the water reducing agent and the water comprises:
[0025] Pour the gelling components into a mixer and stir, add auxiliary activator, water reducing agent and water and continue stirring until uniform.
[0026] In this embodiment, the curing process is carried out under standard curing conditions. Specifically, the standard curing conditions are as follows: relative humidity is greater than 95% and the temperature is 20±3°C.
[0027] In some specific embodiments of the present invention, the step of obtaining a low-carbon multinary magnesium cementitious material after the slurry is formed and cured includes: casting the slurry into a mold, sealing to prevent water loss, demolding after placing it at a temperature of 20±3°C for 1 day, and then curing it under standard curing conditions to a specified age to obtain a low-carbon multinary magnesium cementitious material. The specified age can be 3 days, 7 days, or 28 days, and the present invention is not limited to this.
[0028] To avoid redundancy, in the following examples and comparative examples of the present invention, the chemical composition of the clay is obtained by X-ray fluorescence spectroscopy (XRF) analysis, and the specific chemical oxide composition is shown in Table 1.
[0029] Table 1 Chemical oxide composition of clay (wt%)
[0030] CaO SiO AlO FeO MgO NaO KO LOI 0.030 56.786 35.629 2.003 0.340 0.199 3.493 1.312
[0031] The calcined clay was obtained by the following method: the temperature of the clay with the above composition was raised from room temperature to 200°C at a rate of 5°C / min, then raised to 700°C at a rate of 10°C / min, and kept at 700°C for 1 hour, and then rapidly cooled.
[0032] Example 1
[0033] Weigh 40g of magnesium oxide and 160g of calcined clay in a plastic cup, and dry mix for 3 minutes to ensure the uniformity of the sample. Dissolve 2g of sodium sulfate in 120g of deionized water. Add deionized water containing sodium sulfate to a plastic cup, and add 5g of polycarboxylic acid water reducer to ensure the fluidity of the sample, mix for three minutes, and finally cast the slurry in a 20mm×20mm×20mm mold, and seal it with plastic wrap to prevent moisture loss. Demould after placing at a temperature of 20±3℃ for 1 day, record it as x4, and test the compressive strength. Place the remaining block samples in a curing room with a relative humidity greater than 98% and a temperature of 20±3℃, and cure them for 3 days, 7 days, and 28 days respectively, and test the compressive strength.
[0034] Example 2
[0035] Weigh 40g of magnesium oxide and 160g of calcined clay in a plastic cup, and dry mix for 3 minutes to ensure the uniformity of the sample. Dissolve 2g of calcium chloride in 120g of deionized water. Add deionized water containing calcium chloride to a plastic cup, and add 5g of polycarboxylic acid water reducer to ensure the fluidity of the sample, mix for three minutes, and finally cast the slurry in a mold of 20mm×20mm×20mm, and seal it with plastic wrap to prevent water loss. Demould after placing at a temperature of 20±3℃ for 1 day, record it as x5, and test the compressive strength. Place the remaining block samples in a curing room with a relative humidity greater than 98% and a temperature of 20±3℃, and cure them for 3 days, 7 days, and 28 days respectively, and test the compressive strength.
[0036] Example 3
[0037] Weigh 40g of magnesium oxide and 160g of calcined clay in a plastic cup, and dry mix for 3 minutes to ensure the uniformity of the sample. Dissolve 2g of sodium bicarbonate in 120g of deionized water. Add deionized water containing sodium bicarbonate to a plastic cup, and add 5g of polycarboxylic acid water reducer to ensure the fluidity of the sample, mix for three minutes, and finally cast the slurry in a mold of 20mm×20mm×20mm, and seal it with plastic wrap to prevent water loss. Demould after placing at a temperature of 20±3℃ for 1 day, record it as x6, and test the compressive strength. Place the remaining block samples in a curing room with a relative humidity greater than 98% and a temperature of 20±3℃, and cure them for 3 days, 7 days, and 28 days respectively, and test the compressive strength.
[0038] Comparative Example 1
[0039] Weigh 40g of magnesium oxide and 160g of calcined clay in a plastic cup, and dry mix for 3 minutes to ensure the uniformity of the sample. Weigh 120g of deionized water, add the deionized water to the plastic cup, and add 5g of polycarboxylic acid water reducer to ensure the fluidity of the sample, mix for three minutes, and finally cast the slurry in a 20mm×20mm×20mm mold, and seal it with plastic wrap to prevent moisture loss. Demould after placing at a temperature of 20±3℃ for 1 day, record it as x1, and test the compressive strength. Place the remaining block samples in a curing room with a relative humidity greater than 98% and a temperature of 20±3℃, and cure them for 3 days, 7 days, and 28 days respectively, and test the compressive strength.
[0040] Comparative Example 2
[0041] Weigh 40g of magnesium oxide and 160g of fly ash in a plastic cup, and dry mix for 3 minutes to ensure the uniformity of the sample. Weigh 120g of deionized water, add the deionized water to the plastic cup, and add 5g of polycarboxylic acid water reducer to ensure the fluidity of the sample, mix for three minutes, and finally cast the slurry in a 20mm×20mm×20mm mold, and seal it with plastic wrap to prevent water loss. Demould after placing at a temperature of 20±3℃ for 1 day, record it as x2, and test the compressive strength. Place the remaining block samples in a curing room with a relative humidity greater than 98% and a temperature of 20±3℃, and cure them for 3 days, 7 days, and 28 days respectively, and test the compressive strength.
[0042] Comparative Example 3
[0043] Weigh 40g of magnesium oxide and 160g of fly ash in a plastic cup, and dry mix for 3 minutes to ensure the uniformity of the sample. Dissolve 2g of sodium bicarbonate in 120g of deionized water. Add deionized water containing sodium bicarbonate to a plastic cup, and add 5g of polycarboxylic acid water reducer to ensure the fluidity of the sample, mix for three minutes, and finally cast the slurry in a mold of 20mm×20mm×20mm, and seal it with plastic wrap to prevent water loss. Demould after placing at a temperature of 20±3℃ for 1 day, record it as x3, and test the compressive strength. Place the remaining block samples in a curing room with a relative humidity greater than 98% and a temperature of 20±3℃, and cure them for 3 days, 7 days, and 28 days respectively, and test the compressive strength.
[0044] See also Picture 1 By comparing Comparative Example 1 with Examples 1-3, it can be seen that the addition of different auxiliary stimulants (sodium bicarbonate, sodium sulfate, calcium chloride) can significantly improve the early strength and late strength of the system; among them, the 3d strength of Example 3 can reach 18MPa, and the 7d strength can reach 26MPa, indicating that the use of sodium bicarbonate as an auxiliary stimulant in combination with magnesium oxide has the best stimulating effect. In addition, it can be seen from Example 3 and Comparative Examples 1 to 3 that although sodium bicarbonate significantly improves the early strength in the magnesium oxide-activated calcined clay system, the addition of sodium bicarbonate has no obvious effect in the magnesium oxide-activated fly ash system (Comparative Examples 1 to 2), indicating that the present invention synergistically improves the early strength of low-carbon multi-component magnesium cementitious materials by compounding calcined clay with magnesium oxide and auxiliary stimulants.
[0045] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.
Claims
1. A low-carbon multi-component magnesium gelling material, characterized in that: The raw materials include: a gelling component and an auxiliary activator; wherein the gelling component is composed of calcined clay and magnesium oxide; the auxiliary activator is sodium bicarbonate; The mass ratio of the calcined clay to magnesium oxide is 4:1; The auxiliary activator accounts for 0.05%-10% of the mass of the gelling component; The raw materials of the low-carbon multi-element magnesium cementitious material also include: a water reducer, and the water reducer accounts for 1%-3% of the mass of the cementitious component; The raw materials of the low-carbon multi-element magnesium gelling material also include: water, and the water accounts for 40%-60% of the mass of the gelling component; The particle size of the calcined clay is 0.1-1000 μm, and the content of metakaolin in the calcined clay is between 40% and 80%; The calcined clay is obtained by heating the clay from room temperature to 200-300°C at a heating rate of 5°C / min, then heating the clay from 200-300°C to 700-800°C at a heating rate of 10°C / min, and keeping the temperature at 700-800°C for 1-2h, followed by rapid cooling.
2. A method for preparing the low-carbon multi-element magnesium gelling material as claimed in claim 1, characterized in that: The following steps are involved: The gelling component, the auxiliary activator, the water reducing agent and water are uniformly mixed to obtain a slurry; After the slurry is formed and cured, a low-carbon multi-component magnesium cementitious material is obtained.
3. The method for preparing the low-carbon multi-component magnesium gelling material according to claim 2, characterized in that: The curing process is carried out under standard curing conditions; wherein the standard curing conditions are as follows: relative humidity is greater than 95% and temperature is 20±3°C.
4. The method for preparing the low-carbon multi-element magnesium gelling material according to claim 2, characterized in that: The steps of obtaining a low-carbon multinary magnesium cementitious material after the slurry is formed and cured include: casting the slurry into a mold, sealing to prevent moisture loss, demoulding after placing it at a temperature of 20±3°C for 1 day, and then curing it under standard curing conditions to a specified age to obtain a low-carbon multinary magnesium cementitious material.