CN114394772A

CN114394772A - Ecological cementing material and preparation method thereof

Info

Publication number: CN114394772A
Application number: CN202210175861.8A
Authority: CN
Inventors: 杨晓滨; 李辉; 危鹏; 刘文欢; 姜宏健; 常宁
Original assignee: Shanghai Baiaoheng New Material Co ltd
Current assignee: Shanghai Baiaoheng New Material Co ltd
Priority date: 2022-02-25
Filing date: 2022-02-25
Publication date: 2022-04-26

Abstract

The invention discloses an ecological cementing material and a preparation method thereof, and relates to the technical field of building materials, wherein the raw materials of the ecological cementing material comprise the following components in parts by mass: 5-20 parts of red mud, 5-25 parts of gypsum, 30-50 parts of slag powder and 30-50 parts of fly ash. The raw materials of the invention comprise red mud, industrial by-product gypsum and other solid wastes (such as fly ash, slag and the like) in the silicon-aluminum industry, and the raw materials are ground to a certain fineness, then are uniformly mixed, are stirred by adding water, are molded and are maintained in a standard way, and the preparation of the ecological cementing material is finished. By fully playing the coupling excitation role of the red mud and the industrial byproduct gypsum, the gelling activity of the ecological cementing material is improved, and the hydration products are connected more tightly, so that the overall structure of the cementing material is compact. The 28-day compressive strength of the material can reach more than 50MPa, and the material has the characteristic of reasonable strength.

Description

Ecological cementing material and preparation method thereof

Technical Field

The technical field of building materials, in particular to an ecological cementing material and a preparation method thereof.

Background

Ordinary portland cement (cement for short) is the most widely used cementing material at present, and its production process can be summarized as "two-grinding one-burning", and in the course of production it needs to consume large quantity of mineral raw material and energy and produce CO₂And (4) discharging. CO of the cement industry at present₂Emission of CO occupying the whole country₂The total discharge amount is 18-22%, and the annual consumption amount of limestone minerals is about 31.05 hundred million tons. The heat energy consumption is 3200KJ/kg for producing 1 ton of cement clinker, the electric energy consumption is 80kWh for producing 1 ton of cement, and simultaneously, a large amount of dust and nitrogen oxides are discharged. Therefore, the cement industry has the conditions of high pollution, high energy consumption and high emission, and the low-carbon ecological cementing material which can replace cement and has no clinker or less clinker is urgently needed.

Meanwhile, in recent years, with the rapid growth and development of the production capacity of the alumina smelting industry, the problem of red mud treatment, which is a byproduct of the alumina industry, becomes increasingly severe. The red mud is extremely fine particle strongly alkaline solid waste generated in the process of producing alumina by taking bauxite as a raw material. The output quantity of the method varies according to ore grade, production method and technical level, and most manufacturers produce 0.8 t-1.5 t of red mud when producing 1t of alumina at present. In 2020, the comprehensive utilization amount of red mud is 849 ten thousand tons, and the comprehensive utilization rate is only 8%.

The industrial byproduct gypsum is waste residue which is generated by chemical reaction in industrial production and takes calcium sulfate (containing zero to two crystal waters) as a main component, and mainly comprises the following components: phosphogypsum discharged in the process of producing phosphoric acid or other phosphates by taking phosphate ore and sulfuric acid as raw materials; desulfurized gypsum produced in a limestone/lime-gypsum wet desulfurization process; titanium gypsum generated when titanic acid is produced by sulfuric acid acidolysis of ilmenite; citric acid gypsum generated in the process of preparing citric acid by a fermentation method; fluorgypsum generated in the process of preparing hydrofluoric acid by decomposing fluorite with sulfuric acid; and waste ceramic mold gypsum, etc. Wherein, the phosphogypsum, the desulfurized gypsum and the titanium gypsum are the most main industrial by-product gypsum, and the phosphogypsum, the desulfurized gypsum and the titanium gypsum account for more than 80 percent of the total output of the industrial by-product gypsum.

Titanium dioxide production mainly uses a sulfuric acid method production process, a large amount of titanium gypsum with calcium dihydrate as a main component is also generated in the process of producing titanium dioxide, and the amount of titanium gypsum generated in one ton of titanium dioxide produced by the sulfuric acid method is about 6-10 tons. The titanium gypsum comprises CaSO as main ingredient₄·2H₂And O. In recent years, with the rapid temperature rise of the titanium industry, the yield of titanium dioxide is rising year by year. At present, more than 90 percent of the domestic titanium dioxide is produced by adopting a sulfuric acid method production process. The current stockpiled phosphogypsum reaches more than 2 hundred million tons, and the actual utilization rate is less than 40 percent. Because the phosphogypsum slag generally contains harmful impurities such as phosphorus, fluorine, organic matters and the like, a large amount of phosphogypsum is not effectively utilized so far, and the phosphogypsum slag which is piled up and buried not only occupies a large amount of land, but also is easy to cause serious pollution to atmosphere and underground water. Meanwhile, sintering flue gas desulfurization is still in a development period, and a complete industrial chain is not formed by utilizing desulfurization byproducts. Therefore, the desulfurized gypsum is not effectively recycled at home, and most of the desulfurized gypsum is still treated by adopting a stacking mode except that part of the desulfurized gypsum is used for cement retarder or building gypsum, so that a large amount of land is occupied, resources are wasted, and secondary pollution to the surrounding environment is also caused.

Therefore, how to utilize wastes such as red mud and industrial byproduct gypsum in a large scale and high efficiency to realize environment reduction and enterprise synergy is a problem which needs to be solved urgently.

Disclosure of Invention

The invention aims to provide an ecological cementing material (PRM ecological cementing material prepared by synergistically exciting other solid wastes by using red mud-industrial byproduct gypsum) and a preparation method thereof, wherein the alkalinity of red mud and CaSO in gypsum are utilized₄·2H₂The O enhancement effect and the early strength effect are coupled and excited to activate the silicon-aluminum activity of the slag powder and the fly ash, the generated hydration products of ettringite, C-S-H and C-A-S-H gel are fully exerted, the characteristics of various solid waste materials are fully exerted, the full-solid waste cementing material product is prepared, and the problem that the ecological cementing material prepared by utilizing industrial solid waste and low carbon in the prior art is generally manufactured into the ecological cementing material is solvedThe method has the common key technical problems of high cost, complex manufacturing process, unsuitability for industrial production and low performance of the ecological cementing material.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides an ecological cementing material, which comprises the following raw materials in parts by mass: 5-20 parts of red mud, 5-25 parts of gypsum (industrial byproduct), 30-50 parts of slag powder and 30-50 parts of fly ash.

Further, the specific surface area of the red mud is more than 300m²Bayer process red mud or sintering process red mud per kg.

Further, the gypsum has a specific surface area of more than 300m²/kg phosphogypsum, titanium gypsum or desulfurized gypsum, the main mineral phase of which is CaSO₄·2H₂O。

Further, the specific surface area of the fly ash is more than 300m²Kg, strength activity index is more than or equal to 70 percent.

Further, the specific surface area of the slag powder is more than 300m²And/kg, the 7d strength activity index is more than or equal to 55 percent, the 28d strength activity index is more than or equal to 75 percent, and the vitreous body content is more than or equal to 85 percent.

The invention also provides a preparation method of the ecological cementing material, which comprises the following steps:

(1) grinding the red mud dried at 105-110 ℃ by using grinding equipment, and then sieving the ground material until the specific surface area of the particles is more than 300m²Up to/kg;

(2) grinding the industrial by-product gypsum dried at 75-80 ℃ by using grinding equipment, and then sieving the ground material until the specific surface area of the particles is more than 300m²Up to/kg;

(3) specific surface area > 300m²Drying/kg of fly ash and slag powder at 105-110 ℃ for later use in a mixing and stirring way;

(4) weighing the red mud, the slag powder, the fly ash and the gypsum according to the parts by weight of the raw materials, pouring the red mud, the slag powder and the fly ash into mixing equipment, stirring the mixture until the mixture is uniform, then adding the gypsum, and continuing to stir the mixture uniformly; adding water and uniformly stirring for one time;

(5) pouring the uniformly stirred slurry into a mold, fully compacting on a compaction table, trowelling the surface, and maintaining to obtain the ecological cementing material.

Further, standard curing is carried out for 48 hours at the curing temperature (20 +/-1) DEG C and the humidity of more than 95%, the mold is removed and then the sample is placed into a constant-temperature curing chamber to be cured for 3d, 7d and 28d, the curing air temperature (20 +/-1) DEG C, and at least 5mm of space is reserved between the test pieces during curing.

Further, the adding amount of the water is 30-33% of the total mass of the raw materials, and is preferably 32% of the total mass of the raw materials.

The red mud-industrial byproduct gypsum is used for synergistically exciting the fly ash-slag powder, the ecological cementing material is prepared by utilizing various solid wastes, the ecological cementing material is expected to become a low-carbon cementing material for replacing common portland cement, and the synergistic green sustainable development of the industries such as metallurgy, electric power, steel and the like is promoted while the industrial solid wastes are recycled.

The invention discloses the following technical effects:

the invention prepares the ecological cementing material synergistically excited by red mud-industrial byproduct gypsum-fly ash-slag powder multi-solid waste, and in the synergistic effect of the multi-solid waste, the red mud belongs to alkaline solid waste and contains a large amount of NaOH and Na₂CO₃NaOH is a good alkali activator and is suitable for being used as an alkali excitation material; under the action of an alkaline activator, the aluminosilicate crystal structure and the glass phase structure in the solid waste are dissolved and damaged; the desulfurized gypsum belongs to the sulfuric acid solid waste, wherein Ca²⁺Preparing a calcareous foundation for the formation of C-S-H and C-A-S-H with three-dimensional network structures; in Ca²⁺Under the action of (3), SO₄ ^2-With gelled product and AlO^2-Reacting to generate ettringite; the alkaline and the sulfate have synergistic alteration effect on inert silicon-aluminum minerals, can accelerate the depolymerization of aluminosilicate minerals, synergistically and rapidly excite the mineral activity of alumino-silicate materials (blast furnace slag and fly ash) through alkaline solid waste (red mud) and sulfate solid waste (desulfurized gypsum), and generate hydration products of ettringite and C-S-H, C-A-S-H gel, thereby fully playing the characteristics of various industrial solid wastes and utilizing CaSO in gypsum₄·2H₂O enhancementThe effect and the early strength effect are used for preparing the novel ecological cementing material with high gelling property and high strength.

The invention can fully play the coupling synergistic action among all the components, improve the gelling activity of the ecological cementing material, and enable the hydration products in an excitation system to be connected more tightly, thereby enabling the cementing material to have a compact integral structure and generate certain strength. The compressive strength of the ecological cementing material prepared by the invention is more than 50MPa in 28 days.

The method utilizes the solid waste 100%, has the characteristics of easily obtained production raw materials, low cost and simple process, has wide application prospect, improves the comprehensive utilization efficiency and added value of resources of the solid waste such as red mud, industrial byproduct gypsum, fly ash and the like which are difficult to utilize, and effectively solves the ecological problems of land occupation, environmental pollution and the like caused by the large-scale stockpiling of the solid waste.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described 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 without creative efforts.

FIG. 1 is a 28-day hydration product XRD pattern for a sample of cementitious material prepared according to example 1 of the present invention;

FIG. 2 is a process flow diagram for the preparation of the ecological cement in example 1 of the present invention.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every intervening value, to the extent any stated value or intervening value in a stated range, and any other stated or intervening value in a stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all 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. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

In the embodiment of the invention, the specific surface area of the red mud is more than 300m²Per kg Bayer process red mud.

The gypsum has a specific surface area of more than 300m²Per kg of phosphogypsum, titanium gypsum or desulfurized gypsum.

The specific surface area of the fly ash is more than 300m²Kg, strength activity index is more than or equal to 70 percent.

The specific surface area of the slag powder is more than 300m²And/kg, the 7d strength activity index is more than or equal to 55 percent, the 28d strength activity index is more than or equal to 75 percent, and the vitreous body content is more than or equal to 85 percent.

The raw material amounts of examples 1 to 4 and comparative examples 1 to 2 are shown in Table 1:

TABLE 1 raw Material composition of cementitious Material

	Red mud content%	Coal ash%	Slag powder,%)	Industrial by-product gypsum%
					Example 1	20	35	35	10
Example 2	10	40	40	10
					Example 3	10	41	41	8
Example 4	15	37.5	37.5	10
					Comparative example 1	10	45	45	0
Comparative example 2	10	44	44	2

The preparation methods of the cementing materials of the examples 1 to 4 and the comparative examples 1 to 2 are as follows:

(1) grinding the Bayer process red mud dried at 110 ℃ by using a closed-circuit ball mill until the specific surface area of the particles is more than 300m²Up to/kg.

(2) Grinding the industrial byproduct phosphogypsum dried at 80 ℃ by a closed-circuit ball mill until the specific surface area of the particles is more than 300m²Up to/kg.

(3) Drying at 110 deg.C and having specific surface area of more than 300m²The/kg fly ash and slag powder are ready for mixing and stirring.

(4) Weighing Bayer process red mud, slag powder, fly ash and industrial byproduct gypsum according to the parts of raw materials, pouring the red mud, the slag powder and the fly ash into a stirring pot, mixing, stirring uniformly, adding the industrial byproduct gypsum, and continuously stirring uniformly; adding water accounting for 32 percent of the total mass of the raw materials, and uniformly stirring at one time.

(5) Pouring the uniformly stirred slurry into a mould, fully compacting on a compacting table, leveling the surface, curing (standard curing is carried out for 48 hours at the curing temperature of (20 +/-1) DEG C and the humidity of more than 95 percent, then putting the mixture into a constant-temperature curing chamber, curing for 3d, 7d and 28d, the curing air temperature is (20 +/-1) DEG C, and at least 5mm is left between test pieces during curing), and thus obtaining the ecological cementing material.

The XRD pattern of the 28-day hydration product for the cement sample prepared in example 1 is shown in FIG. 1. from FIG. 1, it can be seen that the 28-day hydration product for the cement sample prepared in example 1 is mainly calcium silicate hydrate gel and ettringite, and also un-reacted dihydrate gypsum, quartz and mullite. This illustrates the alkalinity of the red mud and the CaSO in the gypsum during the co-excitation of the multi-solid wastes of example 1₄·2H₂The O enhancement effect and the early strength effect stimulate the silicon-aluminum activity of the slag powder and the fly ash to generate hydration products of ettringite and C-S-H gel. The red mud, the gypsum, the slag and the fly ash are utilized to realize the most compact filling of micron-nanometer particles and the synergistic optimization of the chemical activity of the material, fully exert the characteristics of various solid waste materials and better realize the improvement of the mechanical property of the prepared cementing material. The process flow diagram for the preparation of the ecological cement material in this example is shown in FIG. 2.

The compression strength of the test blocks of examples 1-4 and comparative examples 1-2 were then tested according to the standard (GB/T17671-1999 "Cement mortar Strength test method (ISO method)), and the results are shown in Table 2.

TABLE 2 Properties of the Binders

The data in table 2 show that the activity of the slag powder glass body and the fly ash is more completely excited with the increase of the red mud content, but if the content of the red mud is too high, residue is generated, and meanwhile, a certain plate-shaped structure is generated in the process of forming crystals by the cementing material, so that the overall strength of the cementing material is influenced. Under the combined action of the two types of excitants, the gelling activity of the slag and the fly ash is fully excited, so that the compression resistance of the cementing material taking the slag and the fly ash as main materials is greatly improved. However, when an activator is selected, the mechanical properties of the cement produced are significantly reduced.

The cement prepared in example 1 was subjected to compositional examination, as shown in Table 3.

TABLE 3 cementitious Material chemistry

As can be seen from Table 3, the ecological cement contains a wide variety of elements, mainly including SiO₂、CaO、Al₂O₃、Fe₂O₃、MgO、TiO₂、Na₂O, and the like. M₂O/SiO₂0.041(0.2 to 0.48) (M is an alkali metal ion); SiO 2₂/Al₂O₃＝1.28(3.3～4.5)。

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims

1. The ecological cementing material is characterized in that raw materials comprise the following components in parts by mass: 5-20 parts of red mud, 5-25 parts of gypsum, 30-50 parts of slag powder and 30-50 parts of fly ash.

2. The ecological cementing material of claim 1, wherein the red mud has a specific surface area of more than 300m²Bayer process red mud or sintering process red mud per kg.

3. The ecological cementing material of claim 1, wherein the gypsum has a specific surface area of more than 300m²/kg of phosphogypsum, titanium gypsum or desulfurized gypsum.

4. The ecological cementing material of claim 1, wherein the specific surface area of the fly ash is more than 300m²The activity index of the steel is more than or equal to 70 percent in terms of strength per kg and 28 days.

5. An ecological method according to claim 1Cementitious material, characterised in that the slag powder specific surface area is greater than 300m²And/kg, the 7d strength activity index is more than or equal to 55 percent, the 28d strength activity index is more than or equal to 75 percent, and the vitreous body content is more than or equal to 85 percent.

6. A preparation method of the ecological cementing material of any one of the claims 1 to 5, which is characterized by comprising the following steps:

(1) drying red mud at 105-110 deg.C, grinding, sieving until the specific surface area of granules is greater than 300m²Up to/kg;

(2) drying gypsum at 75-80 deg.C, grinding, sieving until the specific surface area of granules is greater than 300m²Up to/kg;

(3) specific surface area > 300m²Drying/kg of fly ash and slag powder at 105-110 ℃ for later use;

(4) weighing the red mud, the slag powder, the fly ash and the gypsum according to the parts by weight of the raw materials, mixing the red mud, the slag powder and the fly ash, stirring uniformly, then adding the gypsum, and continuing to stir uniformly; adding water and uniformly stirring for one time;

(5) and pouring the uniformly stirred slurry into a mould, and maintaining to obtain the ecological cementing material.

7. The preparation method according to claim 6, wherein the standard curing is carried out for 48 hours at a curing temperature (20 + 1) DEG C and a humidity of more than 95%, and then the mixture is placed into a constant-temperature curing chamber for curing to a fixed age at a curing air temperature (20 + 1) DEG C.

8. The preparation method according to claim 6, wherein the amount of the added water is 30-33% of the total mass of the raw materials.