Preparation method of steel slag-based cementing material based on carbide slag-ardealite composite excitation

Abstract

The invention belongs to the field of building materials, and particularly discloses a preparation method of a steel slag-based cementing material based on carbide slag-ardealite composite excitation, and the steel slag-based cementing material comprises the following components in parts by mass: 70-85 parts of steel slag powder, 10-20 parts of a pretreated ardealite compound, 5-12 parts of carbide slag powder, 0.3-1 part of basalt fiber, 0.3-0.8 part of a polycarboxylate superplasticizer, and 0.05-0.1 part of a citric acid retarder. The pretreated phosphogypsum compound is prepared from 60 to 80 weight percent of beta-type semi-hydrated gypsum powder and 20 to 40 weight percent of dihydrate gypsum whisker; according to the invention, carbide slag provides an alkaline environment to excite steel slag active minerals to release silicon and aluminum ions to generate C-S-H gel as a strength bearing phase, beta-type hemihydrate gypsum in a pretreated phosphogypsum compound reacts with aluminum ions to generate needle-like ettringite to fill pores, and dihydrate gypsum whiskers inhibit crack propagation; and high-doping-amount utilization of three industrial solid wastes of the steel slag, the carbide slag and the phosphogypsum is realized.

Description

Technical Field

[0001] The invention belongs to the field of building materials, and in particular relates to a method for preparing a steel slag-based gelling material based on carbide slag-phosphogypsum composite activation. Background Art

[0002] Steel slag, calcium carbide slag, and phosphogypsum are bulk industrial solid wastes produced by the steel, chemical, and phosphate fertilizer industries. Long-term storage not only occupies land resources, but may also cause soil and water pollution. Efficient resource utilization methods are urgently needed.

[0003] Steel slag: The main components are active minerals such as tricalcium silicate and dicalcium silicate. However, due to its dense glassy structure, it is difficult to fully activate its activity when used alone as a cementitious material, and it needs to rely on alkaline activators or composite activation systems.

[0004] Carbide slag: The main component is calcium hydroxide, which has strong alkalinity and can be used as an alkaline activator. However, direct use can easily lead to excessive alkalinity in the system, affecting the setting time and volume stability.

[0005] Phosphogypsum: Its main component is calcium sulfate dihydrate, which contains impurities such as phosphorus and fluorine. It needs to be pretreated to remove impurities and increase sulfate activity before it can effectively participate in the gelling reaction.

[0006] Traditional steel slag-based cementitious materials mostly use a single activator (such as sodium hydroxide, sodium carbonate, etc.), which has problems such as low activation efficiency, high cost, and poor environmental friendliness. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing steel slag-based cementitious materials based on carbide slag-phosphogypsum composite excitation, so as to solve the problems proposed in the above background technology that traditional steel slag-based cementitious materials mostly use a single activator, have low excitation efficiency, high cost and poor environmental friendliness.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] The steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation comprises, by mass fraction, 70-85 parts of steel slag powder, 10-20 parts of pretreated phosphogypsum composite, 5-12 parts of carbide slag powder, 0.3-1 part of basalt fiber, 0.3-0.8 part of polycarboxylic acid water reducer, and 0.05-0.1 part of citric acid retarder; the pretreated phosphogypsum composite comprises 60-80wt% of β-hemihydrate gypsum powder and 20-40wt% of dihydrate gypsum whiskers.

[0010] The method for preparing a steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation comprises:

[0011] S1. Dry-mix steel slag powder and carbide slag powder for 3-10 minutes to obtain an alkali-activated powder with a pH of ≥12.5-13;

[0012] S2. Add the pretreated phosphogypsum composite to the alkali-activated powder and wet-mix for 4-5 minutes to obtain a mixture;

[0013] S3. Add basalt fiber, polycarboxylate water reducer and citric acid retarder to the mixture in sequence and mix until the materials are homogenized to obtain a steel slag-based cementitious material.

[0014] Preferably, the specific surface area of ​​the steel slag powder is ≥450m 2 / kg, f-CaO≤2%; the calcium carbide slag powder Ca(OH)2≥75%, D50≤10μm.

[0015] Preferably, the preparation method of the pretreated phosphogypsum composite comprises:

[0016] Flash phosphogypsum at 180±5℃ for 10min to convert it into β-hemihydrate gypsum;

[0017] Wash the β-hemihydrate gypsum with 4.8% to 5.2% citric acid solution to remove impurities;

[0018] 0.5% by mass of Ca(OH)2 is added to the pickling solution to adjust the pH value of the system to 6-6.5, and dihydrate gypsum whiskers are precipitated, dried, ground and mixed to obtain a pretreated phosphogypsum composite.

[0019] Preferably, the β-hemihydrate gypsum powder has SO3 ≥ 40%, soluble phosphorus ≤ 0.08%, and fluorine ≤ 0.05%, and the aspect ratio of the gypsum whiskers is 60-80.

[0020] Preferably, the surface of the basalt fiber in step S3 is coated with an alkali-resistant ZrO2 coating, and the coating thickness is ≤2 μm.

[0021] Preferably, the system temperature is maintained at ≤35° C. during the wet mixing process in step S2.

[0022] Preferably, the wet mixing water in step S2 is obtained by adjusting the citric acid solution.

[0023] Preferably, before adding basalt fiber to the mixture in step S2, nano calcium carbonate accounting for 1 to 3% of the mass of the steel slag powder is added.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention provides an alkaline environment by carbide slag to stimulate the active minerals in steel slag to release silicon and aluminum ions to generate CSH gel as the strength-bearing phase. The β-type hemihydrate gypsum in the pre-treated phosphogypsum composite reacts with aluminum ions to generate needle-shaped ettringite to fill the pores, dihydrate gypsum whiskers to inhibit crack expansion, and basalt fiber to improve toughness, thereby achieving high-dosage utilization of three industrial solid wastes: steel slag, carbide slag, and phosphogypsum. The prepared cementitious material has high compressive strength and low porosity, and has the advantages of optimized construction performance, low raw material cost, and low carbon and environmental protection, providing a new path for high-value utilization of industrial solid waste and performance upgrading of cementitious materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0027] Figure 1 It is a flowchart of the method of the present invention. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0031] As attached Figure 1 As shown:

[0032] Example 1: This example provides a steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation, which comprises, by mass fraction: 80 parts of steel slag powder, 18 parts of pretreated phosphogypsum composite, 10 parts of carbide slag powder, 0.6 parts of basalt fiber, 0.5 parts of polycarboxylate water reducer, and 0.08 parts of citric acid retarder;

[0033] The pretreated phosphogypsum composite comprises 70 wt% of beta-type hemihydrate gypsum powder and 30 wt% of dihydrate gypsum whiskers.

[0034] The method for preparing a steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation comprises:

[0035] Flash pyrolysis of phosphogypsum at 180°C for 10 min to convert it into β-hemihydrate gypsum. The β-hemihydrate gypsum powder contains 49.2% SO3, 0.07% soluble phosphorus, and 0.04% fluorine.

[0036] Wash the β-hemihydrate gypsum with 5% citric acid solution to remove impurities;

[0037] 0.5% by mass of Ca(OH)2 was added to the pickling solution to adjust the pH value of the system to 6-6.5, and dihydrate gypsum whiskers were precipitated, dried, ground and mixed to obtain a pretreated phosphogypsum composite, wherein the aspect ratio of the gypsum whiskers was 75.

[0038] S1, the specific surface area is 480m 2 / kg, f-CaO = 1.8% of steel slag powder and Ca (OH) 2 = 78%, D50 = 8μm of calcium carbide slag powder dry mixing for 5 minutes to obtain pH = 12.8 alkali activated powder;

[0039] S2. Add the pretreated phosphogypsum composite to the alkali-activated powder, maintain the system temperature at 32° C. and wet-mix for 4.5 minutes to obtain a mixture, and adjust the wet-mix water with a citric acid solution;

[0040] S3. First, add nano-calcium carbonate accounting for 1.5% of the mass of the steel slag powder to the mixture, and then add coated basalt fiber coated with a 1.2 μm thick alkali-resistant ZrO2 coating, a polycarboxylic acid water reducer, and a citric acid retarder in sequence, and mix until the materials are homogenized to obtain a steel slag-based cementitious material.

[0041] Steam pre-curing: 40℃ / 6h → room temperature curing: 20℃ / RH≥95% to 28 days.

[0042] Performance testing:

[0043]

[0044]

[0045] The working principle of gradient excitation is as follows: Ca(OH)2 in carbide slag provides an alkaline environment, destroying the active mineral components (such as tricalcium silicate and dicalcium silicate) in the glassy structure in the steel slag, releasing internal silicon ions, aluminum ions and other ions. The silicon ions combine with hydroxide ions to form calcium silicate hydrate gel (CSH), which is a three-dimensional network structure and is the main bearing phase of the strength of the cementitious material.

[0046] The β-hemihydrate gypsum and dihydrate gypsum whiskers in the pretreated phosphogypsum composite provide sulfate ions. After flash calcination and pickling to remove impurities, the sulfate activity is significantly increased. These react with the aluminum ions in the steel slag to form needle-shaped ettringite. These needle-shaped crystals can penetrate and fill the pores in the cementitious material. At the same time, the acicular ettringite has its own expansion properties, further squeezing the voids and improving the density and impermeability of the cementitious material.

[0047] Ultimately, the CSH gel forms a continuous three-dimensional skeleton, providing compressive strength; the needle-shaped ettringite fills the gaps in the skeleton, strengthening the interface transition zone while inhibiting crack propagation (improving flexural strength / toughness); the two work together to reduce the internal porosity of the cementitious material to below 15%, achieving high density, thereby improving strength (28d compressive strength ≥49.7MPa), impermeability (P8~P12) and frost resistance (F100~F200) properties.

[0048] Specific surface area of ​​steel slag powder ≥450m 2 / kg is used to increase the reaction area with alkali solution and accelerate the dissolution of vitreous;

[0049] Carbide slag D50≤10μm is used to refine particles and improve the dissolution efficiency of Ca(OH)2;

[0050] Pre-treated phosphogypsum soluble phosphorus ≤ 0.08%, fluorine ≤ 0.05%: avoid impurities interfering with the reaction between sulfate ions and aluminum ions.

[0051] The wet mixing temperature is ≤35℃ to prevent premature hydration of phosphogypsum and ensure the continuous release of sulfate ions;

[0052] Nano-calcium carbonate further fills nano-scale pores, improves the density of the cementitious material, and strengthens the "skeleton-filling" effect. At the same time, nano-calcium carbonate can act as a crystal nucleus to promote the growth and crystallization of hydration products and improve the strength of the cementitious material.

[0053] The basalt fiber is coated with an alkali-resistant ZrO2 coating, which has good stability in alkaline environments. The addition of basalt fiber can improve the toughness and crack resistance of the cementitious material and prevent cracks in the cementitious material during the hardening process.

[0054] The aspect ratio of gypsum whiskers is 60 to 80, and they have high strength and modulus. The addition of gypsum whiskers can increase the strength and toughness of cementitious materials, while improving the microstructure of cementitious materials.

[0055] Through the chain reaction of "alkali breaking of vitreous body → ion release → generation of gel + needle-shaped crystals → construction of dense structure", the transformation of steel slag from "inert waste slag" to "highly active cementitious material" is achieved, while carbide slag and phosphogypsum are consumed, achieving the dual goals of "solid waste resource utilization + high-performance materials".

[0056] Example 2: This example provides a steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation, which includes, by mass fraction: 75 parts of steel slag powder, 15 parts of pretreated phosphogypsum composite, 8 parts of carbide slag powder, 0.4 parts of basalt fiber, 0.7 parts of polycarboxylate water reducer, and 0.06 parts of citric acid retarder;

[0057] The pretreated phosphogypsum composite comprises 65 wt% of beta-type hemihydrate gypsum powder and 35 wt% of dihydrate gypsum whiskers.

[0058] The method for preparing a steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation comprises:

[0059] Flash phosphogypsum at 180°C for 10 minutes to convert it into β-hemihydrate gypsum. The β-hemihydrate gypsum powder contains 48.5% SO3, 0.06% soluble phosphorus, and 0.03% fluorine.

[0060] Wash the β-hemihydrate gypsum with 5% citric acid solution to remove impurities;

[0061] 0.5% by mass of Ca(OH)2 was added to the pickling solution to adjust the pH value of the system to 6-6.5, and dihydrate gypsum whiskers were precipitated, dried, ground and mixed to obtain a pretreated phosphogypsum composite, wherein the aspect ratio of the gypsum whiskers was 70.

[0062] S1, the specific surface area is 460m 2 / kg, f-CaO = 1.5% of steel slag powder and Ca (OH) 2 = 80%, D50 = 9 μm of calcium carbide slag powder dry mixing for 5 minutes to obtain an alkali-activated powder with a pH = 12.9;

[0063] S2. Add the pretreated phosphogypsum composite to the alkali-activated powder, maintain the system temperature at 30° C. and wet-mix for 4 minutes to obtain a mixture, and adjust the wet-mix water with a citric acid solution;

[0064] S3. First, add nano-calcium carbonate accounting for 1.5% of the mass of the steel slag powder to the mixture, and then add coated basalt fiber coated with a 0.8 μm thick alkali-resistant ZrO2 coating, a polycarboxylic acid water reducer, and a citric acid retarder in sequence, and mix until the materials are homogenized to obtain a steel slag-based cementitious material.

[0065] Steam-hot air dual acceleration: 60℃ steam curing for 4h → 80℃ hot air curing for 12h → natural curing.

[0066] Performance testing:

[0067] index Measured value Highway repair standards 4h compressive strength 28.5MPa ≥20MPa 24h compressive strength 46.3MPa ≥35MPa 28d compressive strength 61.7MPa ≥50MPa Bond strength 4.2MPa ≥3.0MPa

[0068] Result description:

[0069] By providing heterogeneous nucleation sites for ettringite, the generation rate of needle-shaped ettringite is increased by 3 times (XRD quantitative analysis). Steam at 60°C promotes the rapid hydration of aluminum ions in steel slag, generating high-density CSH gel within 4 hours. Phosphorus impurities generate hydroxyapatite, filling the interface transition zone, improving the density and meeting construction requirements.

[0070] It will be appreciated that in the development of any actual embodiment, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will, for those of ordinary skill having the benefit of this disclosure, be a routine undertaking of design, fabrication, and production without undue experimentation.

[0071] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. Steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation, characterized in that: The components include, by mass fraction: 70-85 parts of steel slag powder, 10-20 parts of pretreated phosphogypsum composite, 5-12 parts of carbide slag powder, 0.3-1 parts of basalt fiber, 0.3-0.8 parts of polycarboxylate water reducer, and 0.05-0.1 parts of citric acid retarder; The pretreated phosphogypsum composite comprises 60-80 wt% of beta-type hemihydrate gypsum powder and 20-40 wt% of dihydrate gypsum whiskers.

2. The method for preparing steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation according to claim 1, characterized in that: include: S1. Dry-mix steel slag powder and carbide slag powder for 3-10 minutes to obtain an alkali-activated powder with a pH of ≥12.5-13; S2. Add the pretreated phosphogypsum composite to the alkali-activated powder and wet-mix for 4-5 minutes to obtain a mixture; S3. Add basalt fiber, polycarboxylate water reducer and citric acid retarder to the mixture in sequence and mix until the materials are homogenized to obtain a steel slag-based cementitious material.

3. The method for preparing steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation according to claim 2, characterized in that: The specific surface area of ​​the steel slag powder is ≥450m 2 / kg, f-CaO≤2%; the calcium carbide slag powder Ca(OH)2≥75%, D50≤10μm.

4. The method for preparing steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation according to claim 2, characterized in that: The preparation method of the pretreated phosphogypsum composite comprises: Flash phosphogypsum at 180±5℃ for 10min to convert it into β-hemihydrate gypsum; Wash the β-hemihydrate gypsum with 4.8% to 5.2% citric acid solution to remove impurities; 0.5% by mass of Ca(OH)2 is added to the pickling solution to adjust the pH value of the system to 6-6.5, and dihydrate gypsum whiskers are precipitated, dried, ground and mixed to obtain a pretreated phosphogypsum composite.

5. The method for preparing steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation according to claim 4, characterized in that: The beta-type hemihydrate gypsum powder contains SO3≥40%, soluble phosphorus≤0.08%, and fluorine≤0.05%. The aspect ratio of the gypsum whiskers is 60-80.

6. The method for preparing steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation according to claim 2, characterized in that: In step S3, the surface of the basalt fiber is coated with an alkali-resistant ZrO2 coating, and the coating thickness is ≤2 μm.

7. The method for preparing steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation according to claim 2, characterized in that: During the wet mixing process in step S2, the system temperature is maintained at ≤35°C.

8. The method for preparing steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation according to claim 4, characterized in that: The wet mixing water in step S2 is obtained by adjusting the citric acid solution.

9. The method for preparing steel slag-based cementitious material based on carbide slag-phosphogypsum composite activation according to claim 2, characterized in that: In step S2, before adding basalt fiber to the mixture, nano calcium carbonate accounting for 1 to 3% of the mass of the steel slag powder is first added.

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