CN114956626A

CN114956626A - Red mud and II-grade fly ash geopolymer and preparation method thereof

Info

Publication number: CN114956626A
Application number: CN202210719315.6A
Authority: CN
Inventors: 陈静; 白冰
Original assignee: Beijing Jiaotong University
Current assignee: Beijing Jiaotong University
Priority date: 2022-06-23
Filing date: 2022-06-23
Publication date: 2022-08-30

Abstract

The invention provides red mud and II-grade fly ash geopolymer and a preparation method thereof. The method comprises the following steps: the composite material comprises red mud, II-grade fly ash, alkaline solution and water glass which are formed according to certain mass, wherein the red mud and the II-grade fly ash are used as basic raw materials, and the mixed solution of the alkaline solution and the water glass is used as an alkaline activator. According to the invention, a large amount of red mud waste and II-grade fly ash are fully utilized as raw materials, and the optimized proportion of the geopolymer prepared under the action of an alkaline activator is realized under the excitation of a mixed solution of NaOH solution and water glass. The method of adding cement into the cured geopolymer raw material, coating finish paint on the surface and the like weakens the phenomenon of 'saltpetering' of the geopolymer, improves the compressive strength and can be widely used in building materials.

Description

Red mud and II-grade fly ash geopolymer and preparation method thereof

Technical Field

The invention relates to the technical field of building material preparation, in particular to a red mud and II-grade fly ash geopolymer and a preparation method thereof.

Background

The red mud is a solid waste with strong basicity generated in the industrial production process of alumina, and 1.0-2.0 t of red mud is produced when 1t of alumina is produced. As a large country for producing alumina, China produces thousands of tons of red mud every year, and the accumulated storage capacity reaches hundreds of millions of tons and is continuously increased. At present, most of red mud is treated by adopting an open dam-building and stacking mode, so that a large amount of land resources are occupied, more maintenance and management costs are consumed, and environmental pollution and potential safety hazards are easily caused. The harm of the red mud is reduced to the maximum extent, and the realization of multi-channel and large-scale resource utilization of the red mud is imperative.

Relating to red mudThe research of comprehensive utilization mainly focuses on the preparation of building materials, ceramic materials, adsorbing materials, novel functional materials, extraction and recovery of valuable metals and the like at present, wherein the method for producing building structural materials such as cement, concrete and the like or using the building structural materials as filling materials of roadbeds and dams is an effective method capable of absorbing red mud on a large scale at present. The red mud is rich in Al required by geopolymer reaction ₂ O ₃ 、SiO ₂ And Na ₂ O, etc., which have been proved to be useful for preparing high-performance polymer materials, have gradually become one of the effective ways for the comprehensive utilization of red mud in recent years. However, the red mud has high alkali content, is easy to generate the problem of 'saltpetering', not only destroys the color uniformity of the geopolymer surface, but also causes certain harm to the geopolymer surface for a long time. The addition amount of the red mud in the product is generally not high, and the application of the red mud in traditional inorganic silicate materials such as cement is greatly limited. Especially, the red mud produced by the Bayer process, which accounts for 90% of the total global alumina production, can hardly be directly applied to building materials because the alkali content is more than 10%.

At present, due to the limitation of the technical process in the prior art, most research works on red mud-based polymers are still in the laboratory stage, are limited to indoor experimental research on material preparation, material performance and the like, and are rarely applied to large-scale engineering practice.

Disclosure of Invention

The invention provides a red mud and II-grade fly ash geopolymer and a preparation method thereof, which aim to realize the optimized preparation of the high-strength geopolymer under the action of an alkaline activator.

According to one aspect of the present invention, there is provided a red mud and class ii fly ash geopolymer comprising: the composite material comprises red mud, II-grade fly ash, alkaline solution and water glass which are formed according to certain mass, wherein the red mud and the II-grade fly ash are used as basic raw materials, and the mixed solution of the alkaline solution and the water glass is used as an alkaline activator.

Preferably, the red mud and class ii fly ash polymers according to formulation one comprise the following components: 70g of red mud, 70g of grade II fly ash, 20g of alkaline solution and 50g of water glass solution, wherein the temperature of the alkaline solution is 60 ℃, and the temperature of the water glass solution is 20 ℃.

Preferably, the red mud and class ii fly ash polymers according to formula two comprise the following components: 70g of red mud, 70g of grade II fly ash, 20g of alkaline solution and 50g of water glass solution, wherein the temperature of the alkaline solution is 40 ℃, and the temperature of the water glass solution is 20 ℃.

Preferably, the red mud and II-grade fly ash polymers according to the third formula comprise the following components: 62.5-67.5 g of red mud, 62.5-67.5 g of class II fly ash, 20g of alkaline solution and 50g of water glass solution, wherein the temperature of the alkaline solution is 25-35 ℃, and the temperature of the water glass solution is 20 ℃.

Preferably, the ratio of the mixture of the red mud and the fly ash to the mixed solution of the NaOH solution and the water glass is 2:1, the mass ratio of the NaOH solution to the water glass is 1:2.5, the modulus of the water glass is 3.3, and the service temperature of the NaOH solution is 60 ℃.

According to another aspect of the invention, there is provided a method for preparing the red mud and class II fly ash geopolymer, comprising:

the method comprises the steps of taking red mud and class II fly ash as basic raw materials, mixing and uniformly stirring the red mud and the class II fly ash to obtain a raw material mixture, taking a mixed solution of an alkaline solution and water glass as an excitant, pouring the excitant into the raw material mixture, uniformly stirring to obtain a mixture, pouring the mixture into a mold, placing the mold on a vibrating table for vibration, placing the mold in a constant-temperature constant-humidity curing box for curing for 12 hours, and demolding to obtain the red mud and the class II fly ash geopolymer.

Preferably, when the red mud and class ii fly ash geopolymer formulation one is used, the method comprises:

(1) drying the red mud for 24 hours at 105 ℃ in a drying oven, crushing the red mud by using a crusher, sieving the red mud by using a 300-mesh sieve, and drying the fly ash for 12 hours at 105 ℃ in the drying oven for later use after sieving the fly ash by using the 300-mesh sieve;

(2) placing a conical flask on a balance for peeling, weighing a certain amount of NaOH solid particles, placing the NaOH solid particles in the conical flask, adding a proper amount of distilled water into the conical flask, shaking in one direction, adding the distilled water to a position near a scale mark after the solid particles are fully dissolved, and finally sucking the distilled water by using a rubber head dropper for titration to obtain a prepared mixed solution of NaOH and water glass;

(3) weighing red mud and fly ash with fixed mass, and uniformly stirring to obtain a raw material mixture;

(4) pouring the mixed solution of NaOH and water glass into the raw material mixture, stirring for about 15 minutes until the slurry is uniformly mixed to obtain a mixture;

(5) using a 4cm multiplied by 4cm mould, coating a layer of engine oil or a release agent, pouring the mixture into the mould, placing the mould on a vibration table, vibrating for about 30s, scraping the surface with a scraper, wrapping the solidified mixture with a preservative film, placing the solidified mixture in a constant-temperature constant-humidity curing box at 60 ℃, and demoulding after 12 h;

(6) weighing the mass of the demolded test piece, marking, and putting the test piece into a constant-temperature constant-humidity curing box for curing at 60 ℃ for 14d, 21d and 28 d;

(7) and (3) carrying out compressive strength test on the samples cured at different ages by using a universal press machine to obtain the compressive strength of the prepared red mud and II-grade fly ash geopolymer.

Preferably, when formulation two of said red mud and class ii fly ash polymers is employed, said method comprises:

(4) pouring the mixed solution of NaOH and water glass into the raw material mixture, and stirring for about 15 minutes until the slurry is uniformly mixed to obtain a mixture;

(6) weighing the mass of the demolded test piece, marking the test piece, putting the test piece into a constant-temperature constant-humidity curing box, curing the test piece for 28 days at the temperature of 60 ℃, then continuously curing the test piece for 3 days, 7 days and 14 days at the temperature of 80 ℃, soaking the test piece in deionized water for 72 hours after the test piece is exposed in the air for 7 days, and testing Na in the soaking solution by using ion chromatography ⁺ And CO ₃ ^2- Ion concentration, water content of the geopolymer tested;

Preferably, when the third formulation of red mud and class ii fly ash geopolymer is used, the method comprises:

(1) drying the red mud for 24 hours at 105 ℃ in a drying oven, then crushing the red mud by a crusher, sieving the red mud by a 300-mesh sieve, drying the fly ash for 12 hours at 105 ℃ in the drying oven for later use after sieving the fly ash by the 300-mesh sieve, and sieving and drying the cement;

(2) placing a conical flask on a balance for peeling, weighing a certain amount of NaOH solid particles, placing the NaOH solid particles in the conical flask, adding a proper amount of distilled water into the conical flask, shaking in one direction, adding distilled water to a position near a scale mark after the solid particles are fully dissolved, and finally sucking the distilled water by using a rubber-tipped dropper for titration to obtain a prepared mixed solution of NaOH and water glass;

(3) weighing red mud, fly ash and cement with fixed mass, and uniformly stirring;

(6) weighing the mass of the demolded test piece, marking, and then putting the test piece into a constant-temperature constant-humidity curing box for curing for 28 days at the temperature of 60 ℃;

(7) exposing the cured geopolymer in air, standing for 7 days, soaking in deionized water for 72h, and testing Na in the soaking solution by ion chromatography ⁺ And CO ₃ ^2- Ion concentration, and water content and compressive strength of the geopolymer were tested.

Preferably, the method further comprises: in order to prevent the polymer surface of the red mud and the class II fly ash from being saltpetering, at least one of the following three measures is adopted:

after the red mud and the II-level fly ash geopolymer are cured, coating finish paint on the surfaces of the red mud and the II-level fly ash geopolymer;

adding cement into the raw materials of the red mud and the II-grade fly ash geopolymer, forming slurry by utilizing the reaction of the cement and redundant water in the geopolymer, cementing the geopolymer raw materials, and reducing the porosity of the geopolymer and the precipitation of a saltpetering product;

after the red mud and II-level fly ash geopolymer are cured, the curing temperature is raised, curing is continued for a period of time, the whiskering phenomenon is weakened through water molecules in the evaporated geopolymer, and the whiskering degree is represented through testing the water content and the surface ion concentration of the geopolymer.

Preferably, the finishing paint comprises the following components in percentage by weight: 10% of methyl hydrogen-containing silicone oil emulsion, 10% of cationic hydroxyl silicone oil emulsion, 15% of acrylic emulsion, 5% of organic silicon defoamer, 2% of preservative, 2% of mildew preventive, 1% of water reducing agent and the balance of deionized water.

According to the technical scheme provided by the embodiment of the invention, a large amount of red mud waste and II-grade fly ash are fully utilized as raw materials, and the optimized proportion of the high-strength geopolymer prepared under the action of the alkaline activator is realized under the excitation of the mixed solution of NaOH solution and water glass. The 'saltpetering' phenomenon of the geopolymer is weakened by adding cement into the cured geopolymer raw material, coating finish on the surface and the like, the compressive strength is improved, and the method can be widely applied to building materials.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic diagram of XRD (X-ray diffraction) detection of a white substance on the surface of a geopolymer provided by an embodiment of the invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

For the convenience of understanding the embodiments of the present invention, the following description will be further explained by taking several specific embodiments as examples in conjunction with the drawings, and the embodiments are not to be construed as limiting the embodiments of the present invention.

Example one

The embodiment of the invention provides an optimized proportioning method for preparing a high-strength red mud-based polymer under the action of an alkaline activator, and also provides three methods for weakening the 'saltpetering' of the high-strength red mud and II-grade fly ash geopolymer.

The red mud contains high-content aluminosilicate, when cheap II-grade fly ash is used for preparing geopolymer, the fineness of II-grade fly ash is 200-300 meshes, and the particle fineness determines the specific surface area of fly ash particles, the reaction rate of geopolymer and the reaction completion degree. Geopolymerization is a complex heterogeneous process involving a series of dissolution and polymerization reactions in which the Si-O-Al and Si-O-Si covalent bonds in the active aluminosilicate starting material are broken down in strongly basic solutions to form shared siloxatetrahedrons [ SiO ₄ ] ^4- Alo tetrahedron ₄ ] ^4- Further, a polycondensation reaction, i.e., an alkali metal cation Na, is caused under the action of an alkali activator ⁺ 、K ⁺ 、Ca ⁺ And the process of filling the silicon-oxygen tetrahedron and the aluminum-oxygen tetrahedron forms the inorganic high polymer with a net structure, namely the poly-aluminosilicate gel, and simultaneously discharges excessive water and rapidly hardens. The geopolymers are therefore also referred to as polyaluminosilicate compounds.

The geopolymer prepared by using the class II fly ash under the action of the alkaline activator has low fineness and small specific surface area of particles, and can not consume a large amount of the alkaline activator, so Na under the capillary action ⁺ With excess water as carrier, Na gradually evaporates as the water diffuses to the surface of the geopolymer ⁺ Will remain on the surface of the geopolymer and CO in the air ₂ The reaction forms white powdery crystals, a phenomenon known as "saltpetering". As shown in FIG. 1, by XRD analysis of white substance on the surface of geopolymer, the white substance is mainly Na ₂ CO ₃ And NaHCO ₃ Specific mineral components are shown in table 1.

The invention further adds cement into the raw materials, utilizes the reaction of the cement and the excess water in the geopolymer to form slurry, further agglutinates the geopolymer raw materials, reduces the porosity of the geopolymer and the precipitation of 'saltpetering' products, and simultaneously enhances the compressive strength of the geopolymer. Or after standard curing is finished, raising the curing temperature and continuing curing for a period of time, and weakening the phenomenon of efflorescence by evaporating water molecules in the geopolymer. The degree of "saltpetering" is characterized by the water content and surface ion concentration of the polymer under test.

The polymer "saltpetering" mineral constituents of Table 1

The invention provides a finishing paint for preventing the surface of geopolymer from being saltpetering, which is applied to the surface of geopolymer after the standard curing of geopolymer is finished, is nontoxic and tasteless, is close to transparent, belongs to an environment-friendly material, and is used for reducing the porosity of geopolymer and isolating the contact of geopolymer and air. Thereby achieving the purpose of weakening polymer 'saltpetering'.

Specifically, red mud and II-grade fly ash are used as basic raw materials, a mixed solution of an alkaline solution and water glass is used as an excitant, and the red mud and II-grade fly ash are prepared by the following four specific formulas:

formula 1:

and (2) formula:

and (3) formula:

and (4) formula: the finishing coat comprises the following components in percentage by mass (100%):

the four formulas for preparing the high-strength geopolymer adopt an alkaline solution as a NaOH solution, the concentration is 10mol/L, the baume degree of a water glass solution is 38 degrees, and the modulus is 3.3.

The invention relates to a method for preparing high-strength geopolymer by using red mud and II-grade fly ash as raw materials, which comprises the following steps:

the first step of the formula:

(2) preparing a mixed solution of an alkaline activator, NaOH and water glass. For the preparation of the NaOH solution, solid particles with a purity of 98% were used, after placing the erlenmeyer flask on a scale with an accuracy of 0.01g for "peeling", weighing a certain amount of solid NaOH, then adding a suitable amount of distilled water to the erlenmeyer flask and shaking it around one direction, taking care that the process is exothermic and keeping track of the scald. After the solid particles are fully dissolved, adding distilled water to the position near the scale mark, and finally sucking the distilled water by using a rubber head dropper for titration. The modulus of the water glass is 3.3, and in order to reduce test errors, the mixed solution is not prepared separately, but is directly added into a uniform mixture of the red mud and the fly ash according to the proportion. The prepared NaOH solution needs to be placed in a water bath tank with the regulated temperature for standby;

(3) weighing red mud and fly ash with fixed mass, and uniformly stirring;

(4) pouring the mixed solution of the NaOH solution and the water glass into the uniformly stirred raw material mixture, and stirring for about 15 minutes until the slurry is uniformly mixed and no or few bubbles appear;

(5) a4 cm × 4cm × 4cm mold is used, and a layer of machine oil or mold release agent is coated to facilitate mold release. Pouring the uniformly stirred mixture into a mold, placing the mold on a vibration table, vibrating for about 30s, scraping the surface by using a scraper, wrapping the surface by using a preservative film after slight solidification, placing the wrapped surface in a constant-temperature constant-humidity curing box at 60 ℃ for 12h, and then demolding;

(7) and (5) carrying out compressive strength test on the samples cured at different ages by using a universal press.

The formula II comprises the following steps:

and (5) continuing curing the geopolymer cured for 28d at the temperature of 80 ℃ for 3d, 7d and 14d respectively after finishing curing in a standard curing box in the same formula steps (1) to (6). After the completion of the reaction, the reaction product is exposed to the air for 7 days and then soaked in deionized water for 72 hours, and Na in the soaking solution is tested by ion chromatography ⁺ And CO ₃ ^2- Ion concentration, water content and compressive strength of test geopolymer。

The formula comprises the following three steps:

(1) the step of the same formula is added, and the sieving and the drying of the cement are added;

(2) the same step one;

(4) - (6) a step of preparing the same;

The formula comprises the following four steps:

step (1) - (6) of the same formula

And cleaning the surface of the cured geopolymer with clear water, removing trace 'saltpetering' products, uniformly coating the surface of the cured geopolymer with the prepared finish, exposing the surface of the cured geopolymer in the air for 90 days, observing the surface color of the geopolymer, and testing the compressive strength.

Example two

The raw materials comprise red mud and class II fly ash, wherein the red mud is obtained from undisturbed red mud of Shandong Xin aluminum production factory, the chemical components of the red mud and the class II fly ash are shown in table 2.1, and the mixture ratio of the raw materials is shown in table 2.2.

TABLE 2.1 chemical composition of the raw materials

TABLE 2.2 raw material proportions

The raw materials required by the test are screened by a 300-mesh round-hole sieve and then are placed in a drying box at 105 ℃ for drying for 12 hours; preparing a NaOH solution with the concentration of 10mol/L, wherein the NaOH solution belongs to an unstable solution and needs to be prepared for use on site, and the prepared solution is placed in a water bath tank at 60 ℃ for standby after standing until the solution is colorless and transparent;

weighing the red mud and the II-grade fly ash according to the proportion of 1:1, and then uniformly stirring;

the liquid-solid ratio is 0.5, namely the ratio of the mixture of the red mud and the fly ash to the mixed solution of the NaOH solution and the water glass is 2:1, wherein the mass ratio of the NaOH solution to the water glass is 1: 2.5;

after the raw materials are uniformly stirred, pouring a mixed solution of NaOH solution and water glass, continuously stirring for 10-15 minutes until the slurry is nearly uniform, pouring the mixture into a mould coated with engine oil, vibrating on a vibrating table until the surface of the slurry is discharged, and then leveling by a scraper; standing for about 5-10 minutes, sealing a preservative film after the surface is micro-solidified, placing in a constant-temperature water bath box at 60 ℃ for 12 hours, and then demolding;

the test piece is marked and then wrapped by a preservative film, and is placed in a constant-temperature constant-humidity water bath box with the temperature of 60 ℃ and the humidity of 95 percent, and is taken out after being respectively maintained for 14d, 21d and 28 d;

exposing the test piece cured for 28d to the air for 7d, soaking the test piece in deionized water for 72h, and testing Na by using ion chromatography ⁺ And CO ₃ ^2- The concentration and the water content of the sample are tested, and the results are shown in Table 2.3;

TABLE 2.3 ion concentration and water content of cured 28d geopolymer

The compressive strength of the test pieces of different ages was tested using a universal press at a displacement rate of 0.2mm/min, and the results are shown in Table 2.4.

TABLE 2.4 compressive strengths of polymers of red mud-class II fly ash at different ages

EXAMPLE III

The raw materials are shown in the table 2.1, and the raw material ratio is shown in the table 2.2.

The geopolymer was cured for 28 days and then cured at 80 ℃ for 3d, 7d, and 14d, respectively, as in example 1.

After the completion of the reaction, the reaction product is exposed to the air for 7 days and then soaked in deionized water for 72 hours, and Na in the soaking solution is tested by ion chromatography ⁺ And CO ₃ ^2- The ion concentration and the water content of the geopolymer are shown in Table 3.1;

TABLE 3.180 deg.C maintenance of polymer ion concentration and water content in different ages

The compressive strength of the test pieces of different ages was tested using a universal press at a displacement rate of 0.2mm/min, and the results are shown in Table 3.2.

TABLE 3.2 compressive strengths of polymers of red mud-class II fly ash of different ages

Example four

The raw materials comprise red mud, class II fly ash and cement, wherein the red mud is obtained from undisturbed red mud of Shandong Xin aluminum production factory, the chemical components of the red mud and the class II fly ash are shown in table 4.1, and the mixture ratio of the raw materials is shown in table 4.2.

TABLE 4.1 chemical composition of the starting materials

TABLE 4.2 raw material proportions

The raw materials required by the test are screened by a 300-mesh round-hole sieve and then are placed in a drying box at 105 ℃ for drying for 12 hours; preparing a NaOH solution with the concentration of 10mol/L, standing the prepared solution until the solution is colorless and transparent, and placing the solution in a water bath box with a set temperature for later use;

weighing the red mud and the class II fly ash according to the proportion of 1:1 respectively, adding 3.5%, 7% and 10.5% of cement, and uniformly stirring;

the following optimal mixture ratio is obtained through a plurality of times of experiments: the liquid-solid ratio is 0.5, namely the mass ratio of the mixture of the red mud, the fly ash and the quicklime powder to the mixed solution of the NaOH solution and the water glass is 2:1, the mass ratio of the NaOH solution to the water glass is 1:2.5, the modulus of the water glass is 3.3, and the service temperature of the NaOH solution is 60 ℃. The optimal proportion is beneficial to changing the workability of the raw material gel structure and the final setting time.

After the raw materials are uniformly stirred, pouring a mixed solution of NaOH solution and water glass, continuously stirring for 10-15 minutes until the slurry is nearly uniform, pouring the mixture into a mould coated with engine oil, vibrating on a vibrating table until the surface of the slurry is discharged, and then leveling by a scraper; standing for about 5-10 minutes, sealing a preservative film after the surface is micro-solidified, placing in a constant-temperature water bath box at 60 ℃ for 6 hours, and then demolding;

marking the test piece, wrapping the test piece by using a preservative film, placing the test piece in a constant-temperature constant-humidity water bath box with the temperature of 60 ℃ and the humidity of 95%, and curing for 28 days and taking out the test piece;

exposing the test piece cured for 28d to the air for 7d, soaking the test piece in deionized water for 72h, and testing Na by using ion chromatography ⁺ And CO ₃ ^2- The concentration and the water content of the sample are measured, and the results are shown in Table 4.3;

TABLE 4.3 concentration and water content of polymer ions cured for 28 days by cement with different contents

The compressive strength of the test pieces of different ages was measured using a universal press at a displacement rate of 0.2mm/min, and the results are shown in Table 4.3.

TABLE 4.3 Geopolymer 28d compressive strengths of different contents of cement

Example five:

taking acrylic emulsion, methyl hydrogen-containing silicone oil emulsion and cationic hydroxyl silicone oil emulsion according to the mass percentage, adding a proper amount of deionized water, putting the mixture into a colloid mill, uniformly mixing, slowly adding an organic defoaming agent, fully stirring, and sequentially adding a preservative, a mildew preventive, a water reducing agent and the balance of deionized water after uniform mixing. Stirring again at low speed, mixing thoroughly and filtering. And putting the filtered colloidal solution into a box, sealing and placing the box in a shade place for later use.

The cured geopolymer of 28d in example 1 was rinsed with clear water to remove traces of "saltpetering" products, and the finish was applied evenly to the surface, left exposed to air, and turned over every 10d to ensure adequate contact with air on each side. The surface color of the polymer was observed after 90d and the compressive strength test was carried out at a displacement rate of 0.2mm/min using a universal press, the results being shown in Table 5.1.

Table 5.190 d Geopolymer strength of the after-applied topcoat

According to the alkaline ion content, the water content and the compressive strength data of the geopolymer shown in tables 2.3 and 2.4, when Bayer process red mud and II-grade fly ash are used as raw materials and a mixed solution of NaOH solution and water glass is used as an alkali activator to prepare the geopolymer, the mass ratio of the red mud to the II-grade fly ash is 1:1, the concentration of the NaOH solution is 10mol/L, the modulus of the water glass is 3.3, the solid-liquid ratio is 0.5, the compressive strength of standard curing for 28d can reach about 40MPa, but the phenomenon of "saltpetering" can occur when the geopolymer is placed in the air.

The curing temperature is further increased after the standard curing is finished to evaporate water molecules in the geopolymer, so that the formation of a 'saltpetering' product is weakened, the compressive strength of the geopolymer is improved, and the compressive strength can reach about 45 MPa;

by adding cement accounting for 3.5-10.5% of the total mass into the raw materials for preparing the geopolymer, the cement and the excess water in the geopolymer are reacted to form slurry, the geopolymer raw materials are further cemented, the porosity of the geopolymer and the precipitation of a 'saltpetering' product are reduced, and the compressive strength of the geopolymer is enhanced to about 80 MPa;

by preparing the finishing coat and coating the finishing coat on the surface of the geopolymer after standard curing is finished, the porosity of the geopolymer is reduced, meanwhile, the isolated geopolymer surface is in direct contact with air, the formation of a 'saltpetering' product is reduced, and the strength of the geopolymer is kept at about 40 MPa. The three methods can weaken the occurrence of the phenomenon of 'saltpetering', the cost is the lowest when the temperature is raised, higher compressive strength can be obtained by adding cement, and the uniformity of the surface color of the geopolymer can be better maintained by smearing finish paint.

In conclusion, the invention has the following beneficial effects: the method fully utilizes a large amount of red mud waste and II-grade fly ash as raw materials, and under the excitation of a mixed solution of NaOH solution and water glass and under the curing condition of 60 ℃, the strength of different ages can reach 35-40 MPa; the compressive strength of the geopolymer can reach 40-45 MPa by further increasing the curing temperature; by adding 3-10% of cement in the raw materials, the strength of the geopolymer can reach 60-80 MPa; the surface of the cured geopolymer is coated with finish paint, so that the compressive strength can be kept at 35-40 MPa; the three methods effectively weaken the phenomenon of 'saltpetering' of the geopolymer, improve the compressive strength and can be widely used in building materials.

Those of ordinary skill in the art will understand that: the figures are merely schematic representations of one embodiment, and the blocks or flow diagrams in the figures are not necessarily required to practice the present invention.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, they are described in relative terms, as long as they are described in partial descriptions of method embodiments. The above-described embodiments of the apparatus and system are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A red mud and class II fly ash geopolymer, comprising: the composite material comprises red mud, II-grade fly ash, alkaline solution and water glass which are formed according to certain mass, wherein the red mud and the II-grade fly ash are used as basic raw materials, and the mixed solution of the alkaline solution and the water glass is used as an alkaline activator.

2. The red mud and class ii fly ash geopolymer of claim 1, wherein the red mud and class ii fly ash geopolymer comprises the following components according to formula one: 70g of red mud, 70g of grade II fly ash, 20g of alkaline solution and 50g of water glass solution, wherein the temperature of the alkaline solution is 60 ℃, and the temperature of the water glass solution is 20 ℃.

3. The red mud and class ii fly ash geopolymer of claim 1, wherein the red mud and class ii fly ash geopolymer comprises the following components according to formula ii: 70g of red mud, 70g of grade II fly ash, 20g of alkaline solution and 50g of water glass solution, wherein the temperature of the alkaline solution is 40 ℃, and the temperature of the water glass solution is 20 ℃.

4. The red mud and class II fly ash geopolymer of claim 1, wherein the red mud and class II fly ash geopolymer comprises the following components according to formula III: 62.5-67.5 g of red mud, 62.5-67.5 g of class II fly ash, 20g of alkaline solution and 50g of water glass solution, wherein the temperature of the alkaline solution is 25-35 ℃, and the temperature of the water glass solution is 20 ℃.

5. The red mud and class II fly ash geopolymer of claim 1, wherein the ratio of the mixture of the red mud and the fly ash to the mixed solution of the NaOH solution and the water glass is 2:1, the mass ratio of the NaOH solution to the water glass is 1:2.5, the modulus of the water glass is 3.3, and the service temperature of the NaOH solution is 60 ℃.

6. A method for preparing the red mud and grade II fly ash geopolymer according to any one of claims 1 to 5, which comprises:

7. The method according to claim 6, wherein when the formulation of red mud and class II fly ash geopolymer is used, the method comprises:

(1) drying the red mud for 24 hours at 105 ℃ in a drying oven, then crushing the red mud by a crusher, sieving the red mud by a 300-mesh sieve, and drying the fly ash for 12 hours at 105 ℃ in the drying oven for later use after sieving the fly ash by the 300-mesh sieve;

8. The method according to claim 6, wherein when using formulation two of said red mud and class ii fly ash geopolymer, said method comprises:

9. The method according to claim 6, characterized in that when the third formulation of red mud and class II fly ash geopolymer is used, the method comprises:

(1) drying the red mud for 24 hours at 105 ℃ in a drying oven, crushing the red mud by using a crusher, sieving the red mud by using a 300-mesh sieve, drying the fly ash for 12 hours at 105 ℃ in the drying oven for later use after sieving the fly ash by using a 300-mesh sieve, and sieving and drying the cement;

(6) weighing the mass of the demoulded test piece, marking, and then putting the test piece into a constant-temperature constant-humidity curing box for curing for 28 days at 60 ℃;

(7) exposing the cured geopolymer in the air, standing for 7d, soaking in deionized water for 72h, and testing Na in the soaking solution by ion chromatography ⁺ And CO ₃ ^2- Ion concentration, and water content and compressive strength of the geopolymer were tested.

10. The method of claim 6, further comprising: in order to prevent the polymer surface of the red mud and the class II fly ash from being saltpetering, at least one of the following three measures is adopted:

after the red mud and the II-grade fly ash geopolymer are cured, the curing temperature is raised, the curing is continued for a period of time, the whiskering phenomenon is weakened through water molecules in the evaporative geopolymer, and the whiskering degree is represented through testing the water content and the surface ion concentration of the geopolymer.

11. The method as claimed in claim 10, wherein the top coat comprises the following components in percentage by weight: 10% of methyl hydrogen-containing silicone oil emulsion, 10% of cationic hydroxyl silicone oil emulsion, 15% of acrylic emulsion, 5% of organic silicon defoamer, 2% of preservative, 2% of mildew preventive, 1% of water reducing agent and the balance of deionized water.