A magnesium-based gelling material and preparation method thereof

Abstract

This application discloses a magnesium-based cementitious material and a preparation method thereof, relating to the field of magnesium-based cementitious materials. The material is made from the following components: 80-120 parts magnesium oxide cement, 0.1-0.6 parts hydrating agent, 0.6-1.2 parts carbonating agent, 120-180 parts aggregate, and 50-60 parts water; the carbonating agent comprises one or more of sodium bicarbonate, sodium sesquicarbonate dihydrate, and hydromagnesite seeds. The application utilizes the hydrating agent and the carbonating agent to synergistically form a continuous network structure of hydrated magnesium carbonate within the magnesium-based cementitious material, filling the voids, thereby fixing carbon and improving the density and compressive strength of the magnesium-based cementitious material.

Description

Technical Field

[0001] The present application relates to the field of magnesium-based gelling materials, and in particular to a magnesium-based gelling material and a preparation method thereof. Background Art

[0002] The preparation and production of widely used Portland cement (PC) is accompanied by the consumption of a large amount of calcium raw materials, mainly limestone, and at the same time generates a large amount of energy consumption and releases a large amount of carbon dioxide. In order to reduce carbon emissions, the use of technical paths that replace or partially replace Portland cement is conducive to reducing carbon emissions. At present, calcined magnesite is a new magnesium-based binder material. Its distribution area is less affected by regional factors and its reserves are huge. It is used as a preliminary alternative material for Portland cement. However, the cementitious material prepared by calcined magnesite as a magnesium-based binder material has the problems of poor early mechanical properties and poor carbon fixation effect. Summary of the Invention

[0003] In view of the shortcomings of the above-mentioned related technologies, the present application provides a magnesium-based cementitious material and a preparation method thereof. In the present application, a hydrating agent and a carbonating agent are used to form a continuous network structure of hydrated magnesium carbonate within the magnesium-based cementitious material to fill the voids, thereby fixing carbon and improving the density and compressive strength of the magnesium-based cementitious material.

[0004] In the first aspect, the present application provides a magnesium-based gelling material adopting the following technical solution:

[0005] A magnesium-based cementitious material is made of the following components: 80-120 parts of magnesium oxide cement, 0.1-0.6 parts of a hydrating agent, 0.6-1.2 parts of a carbonating aid, 120-180 parts of aggregate, and 50-60 parts of water;

[0006] The carbonation aid includes one or more of sodium bicarbonate, sodium sesquicarbonate dihydrate and hydrogen magnesite seeds.

[0007] Preferably, the carbonation aid comprises hydrogen magnesite seeds and sodium sesquicarbonate dihydrate in a weight ratio of 1:1-1.5.

[0008] Preferably, the carbonation aid comprises hydrogen magnesite seeds and sodium sesquicarbonate dihydrate in a weight ratio of 1:1.24.

[0009] Preferably, the hydrating agent includes one or both of sodium chloride and magnesium acetate.

[0010] Preferably, the hydrating agent is magnesium acetate.

[0011] Preferably, the weight ratio of the water to the magnesium oxide cement is 0.5-0.6:1.

[0012] Preferably, the weight ratio of the water to the magnesium oxide cement is 0.55:1.

[0013] Preferably, the magnesium oxide cement comprises magnesium oxide, silicon dioxide, calcium oxide and iron oxide.

[0014] Preferably, the weight ratio of the magnesium oxide to the silicon dioxide is 9:0.4-0.5.

[0015] Preferably, the weight ratio of the magnesium oxide to the silicon dioxide is 61:3.

[0016] Using the above technical solution, in this application, the hydration and carbonation reactions of magnesium oxide cement are shown as follows:

[0017] MgO+H2O→Mg(OH)2;

[0018] 2Mg(OH)2+CO2+2H2O→MgCO3·Mg(OH)2·3H2O;

[0019] Mg(OH)2+CO2+2H2O→MgCO3·3H2O;

[0020] 5Mg(OH)2+4CO2→4MgCO3·Mg(OH)2·4H2O;

[0021] 5Mg(OH)2+4CO2+H2O→4MgCO3·Mg(OH)2·5H2O;

[0022] On the one hand, it is beneficial to absorb and utilize carbon dioxide in the matrix of the magnesium-based gel material and the air to fix carbon and reduce carbon emissions. On the other hand, it is beneficial to the formation of hydrated magnesium carbonate and improves the compressive strength of the magnesium-based gel material.

[0023] In a second aspect, the present application provides a method for preparing a magnesium-based gelling material using the following technical solution:

[0024] A method for preparing a magnesium-based cementitious material comprises the following steps: mixing magnesium oxide cement and aggregate to obtain a solid mixture; mixing a hydrating agent, a carbonation aid and water to obtain a liquid mixture; mixing and stirring the solid mixture and the liquid mixture to obtain a solid-liquid mixture; and curing the solid-liquid mixture by controlling the carbon dioxide concentration and relative humidity to obtain the magnesium-based cementitious material.

[0025] Preferably, the curing includes pre-curing for 1-2 days at a temperature of 50-60°C.

[0026] Preferably, the carbon dioxide concentration during the curing is controlled at 5-20%.

[0027] Preferably, the carbon dioxide concentration condition for the maintenance is controlled at 10%.

[0028] Preferably, the relative humidity condition of the curing is controlled to be 70-85%.

[0029] Preferably, the relative humidity condition of the curing is controlled to be 78%.

[0030] In summary, this application includes at least one of the following beneficial technical effects:

[0031] 1. The present invention forms a continuous network structure of hydrated magnesium carbonate in the magnesium-based cementitious material by synergistically forming a hydrating agent and a carbonating aid to fill the voids, thereby fixing carbon and improving the density and compressive strength of the magnesium-based cementitious material.

[0032] 2. The present application reduces the formation of brucite on the surface of magnesium oxide by selecting a carbonation aid, thereby expanding the reaction surface area, carrying out continuous hydration and carbonation, and further improving the carbonation degree (carbonation level) and compressive strength.

[0033] 3. This application controls the carbon dioxide concentration and relative humidity conditions during curing to meet the optimal carbon dioxide concentration for the development of the strength of the solid-liquid mixture while providing the water consumption required for the carbonation reaction. The combined effect is beneficial to the hydration and carbonation reactions, thereby improving the compressive strength of the magnesium-based cementitious material. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a thermogravimetric analysis diagram of Example 2 of the present application;

[0035] Figure 2 This is a thermogravimetric analysis diagram of Example 6 of the present application;

[0036] Figure 3 This is a thermogravimetric analysis diagram of Example 7 of the present application;

[0037] Figure 4 This is a thermogravimetric analysis diagram of Comparative Example 1 of the present application;

[0038] Figure 5 This is a thermogravimetric analysis diagram of comparative example 3 of the present application. DETAILED DESCRIPTION

[0039] The present application is described in further detail below in conjunction with Examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. In the following examples, if specific conditions are not specified, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. The methods used are conventional methods well known in the art unless otherwise specified, and the consumables and reagents used are commercially available unless otherwise specified. Unless otherwise indicated, the professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content may also be applied to the present invention.

[0040] The raw materials used in the examples and comparative examples can be obtained from commercial sources. The contents of the components in the magnesium oxide cement are as follows: MgO content 91.5%, SiO2 content 4.5%, CaO content 2.5%, and Fe2O3 content 1%.

[0041] Examples 1-7

[0042] Examples 1-7 of the present application provide a magnesium-based gelling material, the preparation steps of which are as follows:

[0043] A solid mixture is obtained by mixing magnesium oxide cement and aggregate, a hydrating agent, a carbonating aid and water are mixed to obtain a liquid mixture, the solid mixture and the liquid mixture are mixed and stirred to obtain a solid-liquid mixture, the carbon dioxide concentration is controlled to be 10% and the relative humidity is controlled to be 78%, the solid-liquid mixture is pre-cured at a temperature of 50-60° C. for 1 day, and then cured at room temperature to obtain a magnesium-based cementitious material.

[0044] The composition and proportion of the raw materials of Examples 1-7 are shown in Table 1 below:

[0045] Table 1:

[0046]

[0047] Example 8

[0048] Example 8 of the present application provides a magnesium-based cementitious material. The difference between Example 8 and Example 2 is that the carbon dioxide concentration condition for curing and controlling the magnesium-based cementitious material in Example 8 during the preparation process is 5%.

[0049] Example 9

[0050] Example 9 of the present application provides a magnesium-based cementitious material. The difference between Example 9 and Example 2 is that the carbon dioxide concentration condition for curing and controlling the magnesium-based cementitious material in Example 9 during the preparation process is 20%.

[0051] Example 10

[0052] Example 10 of the present application provides a magnesium-based cementitious material. The difference between Example 10 and Example 2 is that the relative humidity condition of the magnesium-based cementitious material in Example 10 during the preparation process is maintained at 70%.

[0053] Example 11

[0054] Example 11 of the present application provides a magnesium-based cementitious material. The difference between Example 11 and Example 2 is that the relative humidity condition of the magnesium-based cementitious material of Example 11 during the preparation process is maintained and controlled at 85%.

[0055] Comparative Example 1

[0056] Comparative Example 1 provides a magnesium-based gelling material. The difference between Comparative Example 1 and Example 2 is that Comparative Example 1 uses 0.29 g of sodium carbonate instead of sodium bicarbonate as a carbonation aid.

[0057] Comparative Example 2

[0058] Comparative Example 2 provides a magnesium-based gelling material. The difference between Comparative Example 2 and Example 2 is that during the preparation process of Comparative Example 2, 0.26 g of magnesium chloride is used instead of magnesium acetate as a hydrating agent.

[0059] Comparative Example 3

[0060] Comparative Example 3 provides a magnesium-based gelling material. The difference between Comparative Example 3 and Example 2 is that no hydrating agent is added during the preparation process of Comparative Example 3.

[0061] Test and Inspection

[0062] (1) Detecting the 14d compressive strength of the magnesium-based cementitious materials of Examples 1-11 and Comparative Examples 1-3,

[0063] The 28d compressive strength is shown in Table 2 below.

[0064] (2) The magnesium-based gelling materials of Examples 1-11 and Comparative Examples 1-3 were subjected to thermogravimetric analysis on a TGA-4000 device under the following conditions: temperature range 30-950°C, nitrogen atmosphere, heating rate 10°C / min. The CO2 solid storage ratio was calculated as shown in Table 2 below. The thermogravimetric analysis graphs of Example 2, Example 6, Example 7, Comparative Example 1 and Comparative Example 3 are shown in Table 2 below. Figure 1-5 shown.

[0065] CO2 sequestration ratio (S CO2 ) is calculated as shown in the formula: S CO2 =P CO2 / P RMC Where, P CO2 is the percentage of CO2 sequestered (i.e. the percentage of mass loss caused by the decarbonization part), PRMC is the percentage of MgO (i.e. the mass percentage of residual MgO after heating to 950°C).

[0066] Table 2:

[0067] Data Source <![CDATA[CO2 sequestration ratio (%)]]> 14d compressive strength (MPa) 28d compressive strength (MPa) Example 1 25.30 30 33 Example 2 28.84 35 38 Example 3 26.47 33 36 Example 4 23.63 24 28 Example 5 32.22 53 57 Example 6 36.11 47 49 Example 7 43.79 66 68 Example 8 27.13 30 37 Example 9 26.03 21 35 Example 10 25.31 30 34 Example 11 27.34 33 36 Comparative Example 1 17.89 15 21 Comparative Example 2 18.14 16 20 Comparative Example 3 15.12 11 15

[0068] Result Analysis

[0069] According to Table 1-2 and Figure 1-5 The data and graphs provided are used to further analyze this application.

[0070] Reference Figure 1-5 The thermal decomposition process of magnesium-based cementitious materials is divided into three stages. The first stage is the dehydration of bound water in the magnesium-based cementitious materials below 300°C, the second stage is the decomposition of uncarbonized brucite at 300-460°C, and the third stage is the dehydroxylation and decarbonization of the magnesium-based cementitious materials at 460-900°C. The different decomposition stages are distinguished by deconvolution of the weight loss curve, and the area corresponding to the decomposition of each phase is obtained to calculate the CO2 sequestration ratio. The higher the CO2 sequestration ratio, the higher the carbonization degree (carbonation degree) of the magnesium-based cementitious materials. It can be seen from Table 2 that the CO2 sequestration ratio of the magnesium-based cementitious materials of Examples 1-11 of the present application is higher than that of Comparative Examples 1-3, indicating that the degree of carbonation of the magnesium-based cementitious materials of Examples 1-11 of the present application is higher than that of Comparative Examples 1-3, and the 14d compressive strength and 28d compressive strength of the magnesium-based cementitious materials of Examples 1-11 of the present application are much higher than the 14d compressive strength and 28d compressive strength of Comparative Examples 1-3.

[0071] Taking Example 2 as a reference, Examples 1 and 3 demonstrate the effect of the ratio of water to magnesium oxide cement on the carbonation degree and compressive strength of magnesium-based cementitious materials. The CO2 sequestration ratio, 14d compressive strength and 28d compressive strength of the magnesium-based cementitious materials in Example 2 are all higher than those in Example 1 and Example 3, indicating that controlling the water-cement ratio to 0.55 is beneficial to improving the CO2 sequestration ratio, 14d compressive strength and 28d compressive strength of magnesium-based cementitious materials.

[0072] Taking Example 2 as a reference, Example 4 shows the effect of the type of hydrating agent on the carbonation degree and compressive strength of magnesium-based cementitious materials. The CO2 solidification ratio, 14d compressive strength and 28d compressive strength of the magnesium-based cementitious materials in Example 2 are all higher than those in Example 2, indicating that the use of magnesium acetate as a hydrating agent is beneficial to improving the CO2 solidification ratio, 14d compressive strength and 28d compressive strength of magnesium-based cementitious materials.

[0073] Taking Example 2 as a reference, Examples 5-7 show the effects of the type and ratio of carbonation reagents on the carbonation degree and compressive strength of magnesium-based cementitious materials. The CO2 solid storage ratio, 14d compressive strength and 28d compressive strength of the magnesium-based cementitious materials of Examples 5-7 are all higher than those of the magnesium-based cementitious materials of Example 2. On the one hand, it shows that the use of sodium sesquicarbonate dihydrate as a carbonation reagent is more conducive to improving the CO2 solid storage ratio, 14d compressive strength and 28d compressive strength of magnesium-based cementitious materials than the use of sodium bicarbonate as a carbonation reagent. On the other hand, it can be seen from Examples 6 and 7 that after adding hydrogen magnesite seeds, the improvement in CO2 solidification ratio, 14d compressive strength and 28d compressive strength of Example 7 compared with those of Example 2 is much higher than the improvement in CO2 solidification ratio, 14d compressive strength and 28d compressive strength of Example 6 compared with those of Example 5, indicating that the use of sodium sesquicarbonate dihydrate and hydrogen magnesite seeds as carbonating agents has a synergistic effect in improving the CO2 solidification ratio, 14d compressive strength and 28d compressive strength of magnesium-based cementitious materials.

[0074] Taking Example 2 as a reference, Examples 8-11 demonstrate the effects of carbon dioxide concentration and relative humidity on the carbonation degree and compressive strength of magnesium-based cementitious materials during the curing process. The CO2 sequestration ratio, 14d compressive strength and 28d compressive strength of the magnesium-based cementitious materials in Example 2 are all higher than those of the magnesium-based cementitious materials in Examples 8-11, indicating that controlling the carbon dioxide concentration condition to 10% is beneficial to improving the CO2 sequestration ratio, 14d compressive strength and 28d compressive strength of the magnesium-based cementitious materials, and controlling the relative humidity condition to 78% is beneficial to improving the CO2 sequestration ratio, 14d compressive strength and 28d compressive strength of the magnesium-based cementitious materials.

[0075] Taking Example 2 as a reference, the CO2 solid storage ratio, 14d compressive strength and 28d compressive strength of the magnesium-based cementitious material obtained by using sodium carbonate as the carbonating agent instead of sodium bicarbonate in Comparative Example 1 are much lower than the CO2 solid storage ratio, 14d compressive strength and 28d compressive strength of the magnesium-based cementitious material in Example 2, indicating that the use of sodium bicarbonate and sodium sesquicarbonate dihydrate as carbonating agents is beneficial to significantly improve the carbonation degree and compressive strength of the magnesium-based cementitious material. Comparative Examples 2 and 3 show the influence of whether a hydrating agent is added and the type of hydrating agent on the carbonation degree and compressive strength of the magnesium-based cementitious material. In Comparative Example 2, the CO2 solidification ratio, 14d compressive strength and 28d compressive strength of the magnesium-based cementitious material obtained by using magnesium chloride as a hydrating agent instead of magnesium acetate are much lower than the CO2 solidification ratio, 14d compressive strength and 28d compressive strength of the magnesium-based cementitious material in Example 2. In Comparative Example 3, the CO2 solidification ratio, 14d compressive strength and 28d compressive strength of the magnesium-based cementitious material obtained without using a hydrating agent are further reduced on the basis of Comparative Example 2, indicating that the use of magnesium acetate and sodium chloride as hydrating agents is beneficial to significantly improve the carbonation degree and compressive strength of the magnesium-based cementitious material.

[0076] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A magnesium-based gelling material, characterized by: It is made of the following components: 80-120g of magnesium oxide cement, 0.1-0.6g of hydrating agent, 0.6-1.2g of carbonating aid, 120-180g of aggregate, and 50-60g of water; The carbonation aid comprises hydrogen magnesite seeds and sodium sesquicarbonate dihydrate in a weight ratio of 1:1-1.

5.

2. A magnesium-based gelling material according to claim 1, characterized in that: The hydrating agent includes one or both of sodium chloride and magnesium acetate.

3. The magnesium-based gelling material according to claim 1, characterized in that: The weight ratio of the water to the magnesium oxide cement is 0.5-0.6:

1.

4. The magnesium-based gelling material according to claim 1, characterized in that: The magnesium oxide cement comprises magnesium oxide, silicon dioxide, calcium oxide and iron oxide.

5. The magnesium-based gelling material according to claim 4, characterized in that: The weight ratio of the magnesium oxide to the silicon dioxide is 9:4-5.

6. A method for preparing a magnesium-based gelling material according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: mixing magnesium oxide cement and aggregate to obtain a solid mixture; mixing a hydrating agent, a carbonation aid and water to obtain a liquid mixture; mixing and stirring the solid mixture and the liquid mixture to obtain a solid-liquid mixture; and curing the solid-liquid mixture by controlling the carbon dioxide concentration and relative humidity to obtain the magnesium-based cementitious material.

7. The method for preparing a magnesium-based gelling material according to claim 6, characterized in that: The curing includes pre-curing for 1-2 days at a temperature of 50-60°C.

8. The method for preparing a magnesium-based gelling material according to claim 7, characterized in that: The carbon dioxide concentration condition for the maintenance is controlled at 5-20%.

9. The method for preparing a magnesium-based gelling material according to claim 6, characterized in that: The relative humidity condition of the curing is controlled to be 70-85%.

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