Environment-friendly red mud-based solid waste cementing material and preparation method thereof

Abstract

The invention discloses an environment-friendly red mud-based solid waste cementing material and a preparation method thereof, and belongs to the technical field of solid waste recycling. The environment-friendly red mud-based solid waste cementing material is prepared from the following raw materials: modified red mud, slag, gypsum, ceramic waste and an exciting agent. The red mud is synergistically modified by utilizing the rubber powder and the fly ash in a specific ratio, the curing effect of soluble sodium can be remarkably improved, meanwhile, the activity of aluminosilicate substances in the red mud can be effectively promoted, and the gelling activity of the red mud is improved. Various solid wastes (rubber powder obtained by grinding red mud and waste rubber, ceramic waste and slag) are added into the prepared cementing material, so that resource recycling of the various solid wastes can be realized. The prepared cementing material has high mechanical strength, the 28d breaking strength of the cementing material can reach 15.4 MPa to the maximum, the 28d compressive strength of the cementing material can reach 58.4 MPa to the maximum, and the preparation process is simple and suitable for large-scale application and popularization.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization, and more specifically relates to an environmentally friendly red mud-based solid waste gelling material and a preparation method thereof. Background Art

[0002] Red mud is a highly alkaline industrial solid waste generated during the production of alumina. Its large emission and long-term storage not only occupy a large amount of land resources, but also cause serious pollution to the surrounding environment, such as soil alkalinization and groundwater pollution. At present, the comprehensive utilization of red mud is an environmental and resource issue that needs to be solved urgently. Traditional cementitious materials such as cement consume a lot of energy and emit a lot of carbon dioxide during the production process, which puts great pressure on the environment. Therefore, cementitious materials that can effectively utilize solid waste resources such as red mud and are environmentally friendly have come into being.

[0003] However, since the aluminosilicate substances in red mud are not active, and the soluble sodium present in the liquid phase and the mineral phase surface in red mud easily migrates to the surface of red mud under the dissolution reaction and evaporation, resulting in the "frosting" phenomenon on the surface of red mud, affecting the mechanical strength of the final cementitious material. The existing methods to improve the above problems are usually to modify the red mud or add a large amount of stimulants when preparing cementitious materials. Adding a large amount of stimulants will not only cause waste of resources but also significantly affect the performance of cementitious materials. Commonly used modification methods include physical modification and chemical modification. Physical modification is usually carried out using fly ash, but the modification effect of this method is limited. The mechanical properties of the final cementitious material can only be improved to a small extent, and still cannot meet the requirements for the application of high-performance cementitious materials. Chemical modification involves a large amount of chemical reagents that will cause environmental pollution and other problems, and is not suitable for large-scale promotion and application. Summary of the invention

[0004] The purpose of the present invention is to provide an environmentally friendly red mud-based solid waste cementitious material and a preparation method thereof, so as to solve the problems existing in the above-mentioned prior art and realize the preparation of high-performance environmentally friendly red mud-based solid waste cementitious material.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is to provide an environmentally friendly red mud-based solid waste gelling material, comprising the following raw materials in parts by weight:

[0007] 30-50 parts of modified red mud, 15-25 parts of slag, 5-10 parts of gypsum, 6-8 parts of ceramic waste and 15-20 parts of activator;

[0008] The modified red mud is obtained by modifying red mud with rubber powder and fly ash.

[0009] Preferably, the preparation steps of the modified red mud include:

[0010] Mix red mud, rubber powder and fly ash and then perform heat treatment to obtain the modified red mud.

[0011] Preferably, the mass ratio of the rubber powder to the fly ash is 1-2:2; the ratio of the total mass of the rubber powder and the fly ash to the mass of the red mud is 6-8:5; the particle size of the rubber powder is 1-5 mm.

[0012] Furthermore, the rubber powder is obtained by drying, grinding and sieving waste rubber.

[0013] Preferably, the temperature of the heat treatment is 900-1000 °C, the heating rate is 5-10 °C / min, and the heat preservation time is 1-2 h.

[0014] Furthermore, after the heat treatment, there is also a step of grinding and then sieving through a 200-mesh sieve.

[0015] Preferably, the particle size of the slag is ≤45 μm; the particle size of the ceramic waste is 5-10 mm.

[0016] Preferably, the activator includes one or more of sodium hydroxide, sodium carbonate and sodium silicate.

[0017] The second technical solution of the present invention: Provide a preparation method of the above-mentioned environmentally friendly red mud-based solid waste cementitious material, including the following steps:

[0018] Mix the modified red mud, slag, gypsum and ceramic waste according to the specified dosage to obtain a mixture, add an activator to the mixture, and then age to obtain the environmentally friendly red mud-based solid waste cementitious material.

[0019] Preferably, the activator is added in the form of an activator aqueous solution.

[0020] The present invention does not specifically limit the addition amount of water, as long as the hydration reaction can proceed during the preparation process of the cementitious material.

[0021] Preferably, the aging time is 24-48 h.

[0022] The third technical solution of the present invention: Provide the application of the above-mentioned environmentally friendly red mud-based solid waste cementitious material in the construction field.

[0023] The technical principle of the present invention is as follows:

[0024] The present invention first modifies red mud using rubber powder and fly ash. Rubber powder and fly ash synergistically modify red mud under a specific ratio, which can significantly improve the solidification effect of solidifying soluble sodium. At the same time, it can effectively promote the activity of silicate-aluminate substances in red mud and enhance the gelling activity of red mud. At high temperatures, chemical reactions such as the breaking of the polymer chains of rubber will occur, and the carbon element therein will be separated in the form of elemental carbon. The separated carbon will react with sodium compounds (such as NaOH, Na2O) in red mud to form stable sodium carbonate (Na2CO3), thereby solidifying sodium ions. The gas generated by the decomposition of rubber forms a microporous structure in the material, increasing the specific surface area and enhancing the reaction activity. At the same time, these micropores can adsorb and fix sodium ions to prevent their migration. The silicate-aluminate (such as SiO2, Al2O3) in fly ash reacts with sodium ions in red mud to form insoluble sodium aluminosilicate (such as nepheline, NaAlSiO4), further solidifying sodium ions. Fly ash melts at high temperatures to form a glass phase, which wraps sodium ions and prevents their migration. In addition, the carbon generated by the carbonization of rubber reacts with the silicate-aluminate in red mud at high temperatures, promoting the decomposition and recombination of silicate-aluminate to generate highly active silicate-aluminate. The amorphous silicate-aluminate in fly ash reacts with oxides in red mud at high temperatures to generate highly active silicate-aluminate. The quartz (SiO2) and mullite (Al6Si2O 13 ) in fly ash transform into a silicate-aluminate phase with higher activity at high temperatures.

[0025] The present invention selects rubber powder and fly ash with a specific mass ratio of 1-2:2 to efficiently modify red mud. When the dosage of rubber powder is too large, it will cause too many micropores in the modified red mud, affecting its mechanical strength and further reducing the mechanical properties of the resulting cementitious material. When the dosage of fly ash is too large, the glass phase formed by fly ash increases, which will not only wrap and fix sodium ions but also wrap the products after the carbonization of rubber, affecting the effect of fixing soluble sodium.

[0026] In the process of preparing the cementitious material, ceramic waste is used as the coarse aggregate and slag is used as the fine aggregate, which not only reduces the environmental pollution caused by the accumulation of solid waste but also significantly improves the compressive strength and durability of the cementitious material. The silicate and aluminate in slag generate C-S-H gel in the hydration reaction, improving the strength. The slag particles fill the pores and enhance the density. The ceramic particles, as high-hardness aggregates, enhance the compressive strength of the material. In addition, ceramic materials have excellent chemical stability, and their addition helps to improve the durability of the cementitious material.

[0027] The present invention discloses the following technical effects:

[0028] 1. The present invention uses rubber powder and fly ash to synergistically modify red mud under a specific ratio, which can significantly improve the solidification effect of solidifying soluble sodium. At the same time, it can effectively promote the activity of silicate-aluminate substances in red mud and enhance the gelling activity of red mud.

[0029] 2. In the process of preparing the cementitious material of the present invention, a variety of solid wastes (red mud, rubber powder obtained by grinding waste rubber, ceramic waste, slag) are added, which can realize the resource reuse of a variety of solid wastes and avoid the environmental pollution caused by the accumulation of the above solid wastes.

[0030] 3. The cementitious material prepared by the present invention has high mechanical strength. Its 28-day flexural strength can reach up to 15.4 MPa at most, and its 28-day compressive strength can reach up to 58.4 MPa at most. Moreover, the preparation process of the present invention is simple and suitable for large-scale popularization and application. Detailed Embodiments

[0031] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0032] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0033] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0034] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of the present invention are only exemplary.

[0035] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, that is, they are meant to include but not limited to.

[0036] It should be noted that the parts not described in detail in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0037] The descriptions of the raw materials used in the following examples and comparative examples of the present invention are as follows:

[0038] The red mud is taken from a certain alumina plant in Nanning. After testing, the density is 2.6 g / cm 3 , the specific surface area is 457 m 2 / kg, and the water content is 4.8%;

[0039] The treatment of waste rubber is as follows: The waste rubber is placed in an oven for drying, and then ground and sieved to obtain rubber powder with a particle size of 1-5 mm;

[0040] The treatment of ceramic waste is as follows: The ceramic waste is placed in an oven for drying, and then ground and sieved to obtain ceramic waste powder with a particle size of 5-10 mm;

[0041] The slag is taken from a certain iron and steel smelting plant in Nanning. After testing, the density is 2.6 g / cm 3 , the specific surface area is 457 m 2 / kg, and the water content is 4.8%; The treatment of the slag is as follows: The slag is placed in an oven for drying, and then ground and sieved to obtain slag powder with a particle size ≤ 45 μm;

[0042] It should be noted that the accurate description of the sources and properties of the red mud and slag used in the following examples and comparative examples is only for the purpose of full disclosure. Red mud and slag from other sources can also achieve corresponding technical effects by adopting the technical solution of the present invention.

[0043] Other raw materials used are all commercially available products without special instructions.

[0044] The commercially available ordinary Portland P.O42.5 cement used in the performance tests of the present invention below is purchased from Guangxi China Resources Cement Co., Ltd.

[0045] The room temperature involved in the present invention is calculated as 25 ± 5 °C without special instructions.

[0046] Examples 1-3 and Comparative Examples 1-7 provide the preparation of modified red mud.

[0047] Example 1

[0048] Take 50 g of rubber powder, 100 g of fly ash and 180 g of red mud. After mixing the three, place them in a reaction kettle and heat them to 950 °C at a heating rate of 8 °C / min and hold for 1.5 h. Take out the product, grind it and sieve it through a 200-mesh sieve to obtain modified red mud.

[0049] Example 2

[0050] Take 80 g of rubber powder, 100 g of fly ash, and 252 g of red mud. After mixing the three, place them in a reaction kettle and heat them to 900 °C at a heating rate of 5 °C / min and hold for 2 h. Take out the product, grind it, and pass it through a 200-mesh sieve to obtain modified red mud.

[0051] Example 3

[0052] Take 100 g of rubber powder, 100 g of fly ash, and 240 g of red mud. After mixing the three, place them in a reaction kettle and heat them to 980 °C at a heating rate of 9 °C / min and hold for 1.5 h. Take out the product, grind it, and pass it through a 200-mesh sieve to obtain modified red mud.

[0053] Comparative Example 1

[0054] The difference from Example 1 is: adjust the rubber powder to 150 g, and at the same time adjust the red mud to 300 g, and the others are the same as Example 1.

[0055] Comparative Example 2

[0056] The difference from Example 1 is: adjust the rubber powder to 20 g, and at the same time adjust the red mud to 144 g, and the others are the same as Example 1.

[0057] Comparative Example 3

[0058] The difference from Example 1 is: adjust the fly ash to 300 g, and at the same time adjust the red mud to 480 g, and the others are the same as Example 1.

[0059] Comparative Example 4

[0060] The difference from Example 1 is: adjust the fly ash to 50 g, and at the same time adjust the red mud to 180 g, and the others are the same as Example 1.

[0061] Comparative Example 5

[0062] The difference from Example 1 is: adjust the heat treatment temperature to 750 °C, and the others are the same as Example 1.

[0063] Comparative Example 6

[0064] The difference from Example 1 is: adjust the heat treatment temperature to 1200 °C, and the others are the same as Example 1.

[0065] Comparative Example 7

[0066] The difference from Example 1 is: omit the addition of rubber powder, and at the same time adjust the red mud to 120 g, and the others are the same as Example 1.

[0067] Use inductively coupled plasma atomic emission spectrometry to detect the leaching concentration of soluble sodium in the modified red mud obtained in Examples 1 to 3 and Comparative Examples 1 to 7, and obtain the percentage (R, %) of insoluble sodium in the total sodium after normalization. The results are shown in Table 1.

[0068] Table 1 Test Results

[0069] Sample 1 2 3 4 5 6 7 8 9 10 R(％) 98.26 97.91 98.01 90.32 72.53 70.54 89.31 69.38 83.52 65.41

[0070] In Table 1, Samples 1 - 10 respectively correspond to the modified red mud obtained from Examples 1 - 3 and Comparative Examples 1 - 7 in sequence.

[0071] As can be seen from Table 1, the present invention uses rubber powder and fly ash with specific ratios to modify red mud at a specific heat treatment temperature, which can significantly improve the consolidation effect of soluble sodium and ensure that the proportion of insoluble sodium reaches more than 97.91%. It also shows that the heat treatment temperature has a significant impact on the consolidation effect of soluble sodium. This is because at a higher heat treatment temperature, the structure of the carbonized product of rubber powder changes, affecting its adsorption and consolidation effect on soluble sodium, resulting in a worse consolidation effect of soluble sodium; while at a lower heat treatment temperature, rubber powder and fly ash cannot achieve a higher carbonization effect, which also causes a worse consolidation effect of soluble sodium.

[0072] Examples 4 - 6 and Comparative Examples 8 - 14 provide the preparation of the cementitious material.

[0073] Example 4

[0074] Raw material preparation: 40 parts of the modified red mud obtained in Example 1, 20 parts of slag powder, 8 parts of gypsum, 7 parts of ceramic waste powder, 15 parts of sodium silicate, and 45 parts of water.

[0075] Preparation method: According to the specified dosage, mix the modified red mud, slag powder, gypsum, and ceramic waste powder to obtain a mixture; dissolve sodium silicate in water to obtain an activator solution; add the activator solution to the mixture, mix evenly, and then place it in a mold and age at room temperature for 48h to obtain the cementitious material.

[0076] Example 5

[0077] The difference from Example 4 is: Replace "the modified red mud obtained in Example 1" with "the modified red mud obtained in Example 2", and the others are the same as Example 4.

[0078] Example 6

[0079] The difference from Example 4 is: Replace "the modified red mud obtained in Example 1" with "the modified red mud obtained in Example 3", and the others are the same as Example 4.

[0080] Comparative Example 8

[0081] The difference from Example 4 is: Replace "the modified red mud obtained in Example 1" with "the modified red mud obtained in Comparative Example 1", and the others are the same as Example 4.

[0082] Comparative Example 9

[0083] The difference from Example 4 is that "the modified red mud obtained in Example 1" is replaced with "the modified red mud obtained in Comparative Example 4", and the others are the same as in Example 4.

[0084] Comparative Example 10

[0085] The difference from Example 4 is that "ceramic waste powder" is replaced with "stones" of the same amount and particle size, and the others are the same as in Example 4.

[0086] Comparative Example 11

[0087] The difference from Example 4 is that "slag powder" is replaced with "sand" of the same amount and particle size, and the others are the same as in Example 4.

[0088] Comparative Example 12

[0089] The difference from Example 4 is that the dosage of the modified red mud is adjusted to 80 parts, and the others are the same as in Example 4.

[0090] Comparative Example 13

[0091] The difference from Example 4 is that the dosage of the modified red mud is adjusted to 20 parts, and the others are the same as in Example 4.

[0092] Comparative Example 14

[0093] The difference from Example 4 is that "the modified red mud obtained in Example 1" is replaced with "the modified red mud obtained in Comparative Example 7", and the others are the same as in Example 4.

[0094] Refer to GB / T 17671-1999 "Test Method for Strength of Cement Mortar" to test the performance of the cementitious materials obtained in Examples 4-6 and Comparative Examples 8-14.

[0095] First, prepare the mortar, and use commercially available ordinary Portland P.O42.5 cement as the blank control; when preparing the mortar, the mass ratio of the cementitious material or commercially available ordinary Portland P.O42.5 cement to the standard sand is 1:2.5, and the water-cement ratio is 0.5. Then measure the flexural strength and compressive strength of the obtained mortar samples, and the results are shown in Table 2.

[0096] Table 2 Performance test results of mortar samples

[0097]

[0098]

[0099] In Table 2, mortar samples 1-11 correspond to the cementitious materials obtained in Examples 4-6, Comparative Examples 8-14, and commercially available ordinary Portland P.O42.5 cement in sequence.

[0100] As can be seen from Table 2, the cementitious material prepared by the technical solution of the present invention has excellent mechanical strength. The dosages of modified red mud, slag and ceramic waste in the cementitious material will significantly affect the mechanical strength of the cementitious material. Compared with the cementitious material prepared by using only fly ash-modified red mud in Comparative Example 14, the mechanical strength of the cementitious material prepared by the technical solution of the present application is significantly improved.

[0101] In addition, by comparing the mechanical strength data obtained from Comparative Examples 8-9 with the mechanical strength data of Example 4, it can be seen that when the dosage of rubber powder is too large, it will cause too many micropores in the modified red mud, affecting its mechanical strength, and thus reducing the mechanical properties of the obtained cementitious material.

[0102] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0103] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An environmentally friendly red mud-based solid waste cementitious material, characterized in that: Including the following raw materials by mass: 30-50 parts of modified red mud, 15-25 parts of slag, 5-10 parts of gypsum, 6-8 parts of ceramic waste and 15-20 parts of activator; The modified red mud is obtained by modifying red mud with rubber powder and fly ash.

2. The environmentally friendly red mud-based solid waste cementitious material according to claim 1, characterized in that: The preparation steps of the modified red mud include: The modified red mud is obtained by mixing red mud, rubber powder and fly ash and then subjecting them to heat treatment.

3. The environmentally friendly red mud-based solid waste cementitious material according to claim 2, characterized in that: The mass ratio of the rubber powder to fly ash is 1-2:2; the mass ratio of the total mass of the rubber powder and fly ash to the mass of red mud is 6-8:5; and / or the particle size of the rubber powder is 1-5 mm.

4. The environmentally friendly red mud-based solid waste cementitious material according to claim 2, characterized in that: The heat treatment temperature is 900-1000° C., the heating rate is 5-10° C. / min, and the heat preservation time is 1-2h.

5. The environmentally friendly red mud-based solid waste cementitious material according to claim 1, characterized in that: The particle size of the slag is ≤45 μm; and / or the particle size of the ceramic waste is 5 to 10 mm.

6. The environmentally friendly red mud-based solid waste cementitious material according to claim 1, characterized in that: The activator includes one or more of sodium hydroxide, sodium carbonate and sodium silicate.

7. The method for preparing the environmentally friendly red mud-based solid waste gelling material according to any one of claims 1 to 6, characterized in that: The steps include: The modified red mud, slag, gypsum and ceramic waste are mixed in prescribed amounts to obtain a mixture, an activator is added to the mixture, and then aged to obtain the environmentally friendly red mud-based solid waste cementitious material.

8. The preparation method according to claim 7, characterized in that: The activator is added in the form of an activator aqueous solution.

9. The preparation method according to claim 7, characterized in that: The aging time is 24 to 48 hours.

10. Use of the environmentally friendly red mud-based solid waste cementitious material according to any one of claims 1 to 6 in the field of construction.

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