A slag-phosphogypsum-based solid waste cementitious material, its preparation method and application

Abstract

The present invention provides a slag-phosphogypsum-based solid waste cementitious material, its preparation method and application, belonging to the technical field of building materials. The slag-phosphogypsum-based solid waste cementitious material of the present invention, by mass percentage, comprises 45-55% of slag, 40-50% of phosphogypsum, 0.5-5% of carbide slag and 2-10% of silica fume, and the water-cement ratio is 0.35-0.50. After mixing slag, phosphogypsum, carbide slag and silica fume evenly, water is added and stirred to obtain a slurry, which is poured into a mold, left standing, demolded and then cured under standard conditions to obtain the slag-phosphogypsum-based solid waste cementitious material. The present invention uses two calcium-containing solid wastes, slag and phosphogypsum, as the main raw materials, uses carbide slag as an alkaline activator, and adds silica fume to further improve the performance of the solid waste cementitious material, having the characteristics of low carbon, low cost and high performance, and at the same time reducing the environmental and ecological problems caused by the large accumulation of solid waste materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a slag-phosphogypsum-based solid waste cementitious material, a preparation method thereof, and an application thereof. Background Art

[0002] Solid waste cementitious materials have become the focus in the industry in recent years due to their advantages of low resource consumption and low production energy consumption. Their raw materials mainly include blast furnace slag, fly ash, metakaolin, red mud, etc. Solid waste cementitious materials have received extensive attention because of their rich raw material sources, high strength, low production cost, environmental friendliness, good corrosion resistance, good fire resistance, good durability, and the ability to fix toxic heavy metal ions. Through the synergistic hydration of different solid wastes, cementitious materials with properties equivalent to those of traditional cement can be prepared, which can not only consume a large amount of stockpiled solid waste, but also reduce carbon dioxide emissions and energy consumption, and are considered the most potential green cementitious materials.

[0003] The patent with the publication number CN113149477A proposes a fully solid waste cementitious material, a preparation method thereof, and an application thereof. The fully solid waste cementitious material includes 22.5%-27.5% phosphogypsum, 22.5%-27.5% carbide slag, and 45%-55% slag powder by mass percentage. Although this patent realizes the utilization of solid waste, the highest 3d compressive strength of the prepared cementitious material after curing is 2.645 MPa, the highest 7d compressive strength is 3.621 MPa, and the highest 28d compressive strength is 4.96 MPa. The compressive strength still cannot meet the actual needs. The patent with the publication number CN113149477A proposes a composite industrial solid waste cementitious material, a preparation method thereof, and an application thereof. Its raw materials are 30-40 parts of lithium slag, 10-15 parts of blast furnace slag, 15-20 parts of steel slag powder, 5-10 parts of silica fume, 5-10 parts of phosphogypsum, 5-10 parts of Portland cement clinker, and 5-10 parts of quicklime. Although the raw materials involve industrial solid waste, components such as cement and quicklime are also used, which undoubtedly increases the production cost, and its compressive strength is also relatively low and cannot meet the actual production requirements.

[0004] Therefore, the present invention proposes a new type of slag-phosphogypsum-based solid waste cementitious material, a preparation method thereof, and an application thereof. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a new type of slag-phosphogypsum-based solid waste cementitious material, a preparation method thereof, and an application thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention:

[0008] A slag phosphogypsum-based solid waste cementitious material, wherein the raw materials include 45-55% slag, 40-50% phosphogypsum, 0.5-5% carbide slag and 2-10% silica fume in terms of mass percentage, and the water-cement ratio is 0.35-0.50.

[0009] Furthermore, the slag is S95 grade or above. Slag is divided into three grades according to the activity index: S75, S95 and S105. S95 grade slag is a kind of high-activity slag powder that meets the requirements of the national standard GB / T18046-2000. It is mainly processed by water-quenched blast furnace slag through drying, grinding and other processes. The activity index of S95 grade slag powder requires a 28d compressive strength ratio of ≥95% and a specific surface area of ​​≥350m 2 / kg, the slag used in the present invention is a by-product produced in the blast furnace ironmaking process.

[0010] Furthermore, the phosphogypsum is hemihydrate phosphogypsum. Hemihydrate phosphogypsum (HPG) is industrial waste residue produced by phosphorus chemical enterprises in the process of wet production of phosphoric acid. Its main component is calcium sulfate dihydrate (CaSO4·2H2O). Hemihydrate calcium sulfate (CaSO4·0.5H2O) is formed after dehydration treatment. It has self-gelling properties and is highly available.

[0011] Furthermore, the CaO content in the carbide slag is ≥65.0%. The carbide slag used in the present invention is waste slag with calcium hydroxide as the main component after acetylene gas is obtained by hydrolyzing calcium carbide.

[0012] Furthermore, the specific surface area of ​​the silica fume is ≥19.0m 2 / g, and the SiO2 content is ≥96.0%. The silicon ash used in the present invention is obtained by collecting and treating the smoke escaping with the exhaust gas during the high-temperature smelting of industrial silicon and ferrosilicon in an industrial electric furnace through a capture device.

[0013] Exemplarily, the slag phosphogypsum-based solid waste cementitious material comprises, by weight percentage, 50.84% ​​slag, 45.76% phosphogypsum, 1.40% carbide slag and 2.00% silica fume, with a water-cement ratio of 0.40.

[0014] Exemplarily, the slag phosphogypsum-based solid waste cementitious material comprises, by weight percentage, 49.81% raw materials, 44.82% phosphogypsum, 1.37% carbide slag and 4.00% silica fume, with a water-cement ratio of 0.40.

[0015] Exemplarily, the slag phosphogypsum-based solid waste cementitious material comprises, by weight percentage, 48.77% slag, 43.89% phosphogypsum, 1.34% carbide slag and 6.00% silica fume, with a water-cement ratio of 0.40.

[0016] The second technical solution of the present invention:

[0017] A preparation method of the slag-phosphogypsum-based solid waste cementitious material, comprising the following steps:

[0018] Weigh slag, phosphogypsum, carbide slag and silica fume according to mass percentage, mix them evenly and then add water and stir to obtain a slurry;

[0019] Pour the slurry into a mold, compact it, let it stand, and then demold it;

[0020] After standard curing of the demolded specimen, the slag-phosphogypsum-based solid waste cementitious material is obtained.

[0021] Further, after adding water, stir at 140 ± 5 r / min for 1 - 2 min, and then stir at 285 ± 10 r / min for 2 - 3 min.

[0022] Further, cure under the conditions of 20°C ± 1°C and a relative humidity of not less than 90%.

[0023] The third technical solution of the present invention:

[0024] Application of the slag-phosphogypsum-based solid waste cementitious material in the construction field.

[0025] When the slag, phosphogypsum, carbide slag and silica fume of the present invention are used to prepare the slag-phosphogypsum-based solid waste cementitious material, the compressive strength of the material is jointly improved through various synergistic effects. The principle is as follows:

[0026] 1. Alkali activation

[0027] The main component of carbide slag is calcium hydroxide (Ca(OH)2), which has strong alkalinity and can provide an alkaline environment for the system. Under alkaline conditions, active components such as silicate and aluminate in the slag are activated and undergo hydration reactions to generate hydration products such as calcium silicate hydrate (C-S-H) gel and calcium aluminosilicate hydrate (C-A-S-H). These hydration products fill the pores in the material, forming a stable skeleton structure, making the structure more dense, and thus improving the compressive strength.

[0028] 2. Sulfate activation

[0029] Phosphogypsum contains a large amount of sulfate ions (SO4 2- ), which can act as a sulfate activator. Sulfate ions react with calcium ions (Ca 2+ ) in the slag and carbide slag to generate hydration products such as ettringite (AFt). The interweaving of ettringite not only fills the pores of the material, but also forms a denser microstructure through the interaction with C(A)-S-H gel, further improving the strength of the material.

[0030] 3. Pozzolanic reaction

[0031] Silica fume contains highly reactive silicon dioxide (SiO2), which can undergo a pozzolanic reaction with calcium hydroxide (Ca(OH)2) released from carbide slag to form more C-(A)-S-H gels. This reaction not only increases the amount of hydration products but also optimizes the pore structure of the material, making the material more dense.

[0032] 4. Microaggregate filling effect

[0033] Slag, phosphogypsum, carbide slag, and silica fume have good particle size distributions. In the cementitious material, these particles can be closely packed to fill the pores with each other, reducing the number of large pores and improving the microstructure of the material. This microaggregate filling effect can effectively improve the density of the material, thereby increasing the compressive strength.

[0034] 5. Synergistic mechanism

[0035] Chemical synergy: The alkali activation of carbide slag combined with the sulfate activation of phosphogypsum can more fully activate the activity of slag and silica fume. Slag releases calcium, aluminum and other ions in an alkaline environment and reacts with sulfate ions in phosphogypsum and silica provided by silica fume to form C-(A)-S-H gels and ettringite. These hydration products are intertwined to form a stable network structure.

[0036] Physical synergy: Slag and phosphogypsum have larger particles that can provide a skeleton support, while silica fume particles are fine and can fill the pores between large particles. This synergy of physical filling and chemical reaction makes the microstructure of the material more dense.

[0037] Compared with the prior art, the present invention has the following advantages and technical effects:

[0038] (1) The present invention uses two calcium-containing solid wastes, slag and phosphogypsum, as the main raw materials, uses carbide slag as an alkaline activator, and adds silica fume to further improve the performance of the solid waste cementitious material. Through the synergistic effects such as alkali activation, sulfate activation, pozzolanic reaction, and microaggregate filling, the hydration products and microstructure of the material are jointly optimized. The synergistic effect reduces the porosity of the material, increases the hydration products, and makes the structure more dense, thus significantly improving the compressive strength of the slag-phosphogypsum-based solid waste cementitious material.

[0039] (2) The slag-phosphogypsum-based solid waste cementitious material of the present invention does not use chemical activators such as NaOH and Na2SiO3, but uses solid waste materials as alkaline activators, reducing the introduction of external alkali and lowering the raw material cost. Compared with other solid waste cementitious materials using chemical activators, the present invention not only avoids the carbon emissions generated during the production process of chemical activators, but also has lower construction costs and safer construction.

[0040] (3) The slag-phosphogypsum-based solid waste cementitious material of the present invention does not require high-temperature curing. Compared with other solid waste cementitious materials that need high-temperature curing to form strength, it can not only further reduce carbon emissions, but also shorten the construction period and improve construction efficiency.

[0041] (4) As a widely used solid waste material, the raw material slag of the present invention has a relatively high price. A high dosage will increase the cost. The present invention uses phosphogypsum to replace part of the slag. On the one hand, it can alleviate the problem of a large amount of phosphogypsum accumulation. On the other hand, it can reduce the cost and increase the added value.

[0042] (5) All precursor materials used in the present invention are solid wastes, and no chemical activator and high-temperature curing are required, which further reduces the construction cost, carbon emissions and energy consumption. The slag-phosphogypsum-based solid waste cementitious material of the present invention has relatively high early strength, and its 28-day compressive strength can reach up to 57.7 MPa, fully meeting the actual engineering needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0044] Figure 1 is a flow chart of the preparation method of a slag-phosphogypsum-based solid waste cementitious material of the present invention;

[0045] Figure 2 are the test results of the compressive strength of the slag-phosphogypsum-based solid waste cementitious material in Examples 1-6;

[0046] Figure 3 are the test results of the compressive strength of the slag-phosphogypsum-based solid waste cementitious material in Comparative Examples 1-7;

[0047] Figure 4 is a scanning electron microscope (SEM) image of the slag-phosphogypsum-based solid waste cementitious material prepared in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The various exemplary embodiments of the present invention will now 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 embodiments of the present invention.

[0049] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, 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. Each 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 may be independently included or excluded from the range.

[0050] Unless otherwise specified, 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 pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice 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 said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0051] Without departing from the scope or spirit of the present invention, various improvements and variations 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 examples of the present invention are merely exemplary.

[0052] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0053] An embodiment of the present invention provides a slag-phosphogypsum-based solid waste cementitious material. By mass percentage, the raw materials include 45 - 55% of slag, 40 - 50% of phosphogypsum, 0.5 - 5% of carbide slag, and 2 - 10% of silica fume, and the water-cement ratio is 0.35 - 0.50.

[0054] In a preferred embodiment of the present invention, the slag is slag of S95 grade or above. Slag powder is divided into three grades, S75, S95, and S105, according to the activity index. S95 grade slag powder is a high-activity slag powder that meets the requirements of national standard GB / T18046 - 2000. It is mainly processed from water-quenched blast furnace slag through processes such as drying and grinding. The activity index requirement for S95 grade slag powder is that the 28-day compressive strength ratio ≥ 95%, and the specific surface area ≥ 350m 2 / kg. The slag used in the present invention is a by-product in the process of blast furnace ironmaking. More specifically, the slag used in the embodiment of the present invention is S105 grade slag, and the activity index is 106.

[0055] In a preferred embodiment of the present invention, the phosphogypsum is hemihydrate phosphogypsum. Hemihydrate phosphogypsum (HPG) is industrial waste residue produced by phosphorus chemical enterprises in the process of wet production of phosphoric acid. Its main component is calcium sulfate dihydrate (CaSO4·2H2O). Hemihydrate calcium sulfate (CaSO4·0.5H2O) is formed after dehydration treatment. It has self-gelling properties and is highly available.

[0056] In a preferred embodiment of the present invention, the CaO content in the carbide slag is ≥ 65.0%, and the carbide slag used in the present invention is waste slag with calcium hydroxide as the main component after acetylene gas is obtained by hydrolyzing carbide. More specifically, the CaO content in the carbide slag used in the embodiment of the present invention is 92.88%.

[0057] In a preferred embodiment of the present invention, the specific surface area of ​​the silica fume is ≥19.0m 2 / g, and the SiO2 content is ≥96.0%. The silica ash used in the present invention is obtained by collecting and treating the smoke and dust emitted from the exhaust gas during the high-temperature smelting of industrial silicon and ferrosilicon in an industrial electric furnace through a special capture device. More specifically, the specific surface area of ​​the silica ash used in the embodiment of the present invention is 19.1m 2 / g, and the SiO2 content is 96.74%.

[0058] Exemplarily, the slag phosphogypsum-based solid waste cementitious material comprises, by weight percentage, 50.84% ​​slag, 45.76% phosphogypsum, 1.40% carbide slag and 2.00% silica fume, with a water-cement ratio of 0.40.

[0059] Exemplarily, the slag phosphogypsum-based solid waste cementitious material comprises, by weight percentage, 49.81% raw materials, 44.82% phosphogypsum, 1.37% carbide slag and 4.00% silica fume, with a water-cement ratio of 0.40.

[0060] Exemplarily, the slag phosphogypsum-based solid waste cementitious material comprises, by weight percentage, 48.77% slag, 43.89% phosphogypsum, 1.34% carbide slag and 6.00% silica fume, with a water-cement ratio of 0.40.

[0061] In a preferred embodiment of the present invention, a method for preparing the slag phosphogypsum-based solid waste cementitious material comprises the following steps:

[0062] Weigh slag, phosphogypsum, carbide slag and silica fume according to mass percentage, mix them evenly, add deionized water and stir to obtain a slurry;

[0063] Pour the slurry into a mold, vibrate it, let it stand, and then demould it;

[0064] The demoulding specimen is subjected to standard curing to obtain the slag phosphogypsum-based solid waste cementitious material.

[0065] The flow chart of the preparation method of a slag-phosphogypsum-based solid waste cementitious material of the present invention is shown in Figure 1 .

[0066] In a preferred embodiment of the present invention, after adding water, it is stirred at 140 ± 5 r / min for 1 - 2 min, and then stirred at 285 ± 10 r / min for 2 - 3 min.

[0067] In a preferred embodiment of the present invention, curing is carried out under the conditions of 20°C ± 1°C and a relative humidity of not less than 90%.

[0068] The chemical compositions of the slag, phosphogypsum, carbide slag, and silica fume used in the embodiments of the present invention are shown in Table 1.

[0069] Table 1 Chemical compositions of each raw material

[0070]

[0071] The technical solutions of the present invention are further described below through examples.

[0072] Example 1

[0073] For a slag-phosphogypsum-based solid waste cementitious material by mass percentage, the raw materials include 50.84% slag, 45.76% phosphogypsum, 1.40% carbide slag, and 2.00% silica fume, and the water-cement ratio is 0.40. The preparation method includes the following steps:

[0074] (1) Weigh the slag, phosphogypsum, carbide slag, and silica fume according to the above mass percentages, and fully mix the four precursor raw materials;

[0075] (2) Add deionized water to the mixed precursor powder. First, add water and stir at 140 r / min for 2 min to fully mix the powder and water without agglomeration, and then stir at 285 r / min for 3 min to obtain a uniformly textured slurry;

[0076] (3) Pour the stirred slurry into a mold and vibrate it on a vibrating table until no obvious bubbles emerge;

[0077] (4) Let it stand for 1 d and then demold. During the demolding process, damage to the specimen should be avoided;

[0078] (5) Place the demolded specimen in a standard curing box at 20°C ± 1°C and a relative humidity of not less than 90% for curing. After curing, a slag-phosphogypsum-based solid waste cementitious material is obtained.

[0079] Example 2

[0080] A slag-phosphogypsum-based solid waste cementitious material, by mass percentage, the raw materials include 49.81% slag, 44.82% phosphogypsum, 1.37% carbide slag, and 4.00% silica fume, and the water-cement ratio is 0.40;

[0081] The preparation method of the slag-phosphogypsum-based solid waste cementitious material is the same as that in Example 1.

[0082] Example 3

[0083] A slag-phosphogypsum-based solid waste cementitious material, by mass percentage, the raw materials include 48.77% slag, 43.89% phosphogypsum, 1.34% carbide slag, and 6.00% silica fume, and the water-cement ratio is 0.40;

[0084] The preparation method of the slag-phosphogypsum-based solid waste cementitious material is the same as that in Example 1.

[0085] Example 4

[0086] A slag-phosphogypsum-based solid waste cementitious material, by mass percentage, the raw materials include 55% slag, 40% phosphogypsum, 0.5% carbide slag, and 9.5% silica fume, the water-cement ratio is 0.50, and the preparation method is the same as that in Example 1.

[0087] Example 5

[0088] A slag-phosphogypsum-based solid waste cementitious material, by mass percentage, the raw materials include 45% slag, 50% phosphogypsum, 3% carbide slag, and 2% silica fume, the water-cement ratio is 0.35, and the preparation method is the same as that in Example 1.

[0089] Example 6

[0090] A slag-phosphogypsum-based solid waste cementitious material, by mass percentage, the raw materials include 45% slag, 40% phosphogypsum, 5% carbide slag, and 10% silica fume, the water-cement ratio is 0.40, and the preparation method is the same as that in Example 1.

[0091] Comparative Example 1

[0092] Same as Example 1, the only difference is that the addition of phosphogypsum is omitted. A solid waste cementitious material, by mass percentage, the raw materials include 96.6% slag, 1.40% carbide slag, and 2.00% silica fume, and the water-cement ratio is 0.40;

[0093] The preparation method is the same as that in Example 1.

[0094] Comparative Example 2

[0095] Same as Example 1, the only difference is that the addition of carbide slag is omitted. A solid waste cementitious material, by mass percentage, the raw materials include 50.84% slag, 45.76% phosphogypsum, and 3.40% silica fume, and the water-cement ratio is 0.40;

[0096] The preparation method is the same as that of Example 1.

[0097] Comparative Example 3

[0098] Same as Example 1, except that the addition of silica fume is omitted. A solid waste cementitious material, by mass percentage, includes 50.84% of slag, 45.76% of phosphogypsum, and 3.40% of carbide slag, and the water-cement ratio is 0.40;

[0099] The preparation method is the same as that of Example 1.

[0100] Comparative Example 4

[0101] Same as Example 1, except that a slag-phosphogypsum-based solid waste cementitious material, by mass percentage, includes 65% of slag, 20% of phosphogypsum, 10% of carbide slag, and 5% of silica fume, and the water-cement ratio is 0.40;

[0102] The preparation method is the same as that of Example 1.

[0103] Comparative Example 5

[0104] Same as Example 1, except that the water-cement ratio of the slag-phosphogypsum-based solid waste cementitious material is 0.60.

[0105] Comparative Example 6

[0106] Same as Example 1, except that the water-cement ratio of the slag-phosphogypsum-based solid waste cementitious material is 0.20.

[0107] Comparative Example 7

[0108] Same as Example 1, except that the carbide slag is replaced with calcium hydroxide in equal mass.

[0109] The raw material compositions of the precursor materials of the slag-phosphogypsum-based solid waste cementitious materials in the examples and comparative examples are shown in Table 2.

[0110] Table 2 Compositions of the precursor materials of the slag-phosphogypsum-based solid waste cementitious materials in the examples and comparative examples (mass percentage, %)

[0111]

[0112] Performance test

[0113] Referring to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)", the compressive strengths of the slag-phosphogypsum-based solid waste cementitious materials in Examples 1-6 and Comparative Examples 1-7 were respectively tested at 3d, 7d, 14d, and 28d. The test results of the compressive strengths of the slag-phosphogypsum-based solid waste cementitious materials in Examples 1-6 are shown in Figure 2 , and the test results of the compressive strengths of the slag-phosphogypsum-based solid waste cementitious materials in Comparative Examples 1-7 are shown inFigure 3 It can be seen that the slag-phosphogypsum-based solid waste cementitious material has excellent mechanical properties. This is because several raw materials can undergo hydration reactions under alkaline conditions to generate hydration products such as calcium silicate hydrate (C-S-H), calcium aluminate hydrate (C-A-H), calcium silicoaluminate hydrate (C-A-S-H), and ettringite, which improve the strength of the material. The 28-day compressive strength reaches 57.7 MPa.

[0114] Compared with Example 1, in Comparative Example 1, the addition of phosphogypsum was omitted, resulting in the lack of sulfate ions necessary for the formation of ettringite in the system. Moreover, due to the loss of the sulfate activation effect provided by phosphogypsum by slag, the strength of the solidified paste decreased significantly.

[0115] Compared with Example 1, in Comparative Example 2, the addition of carbide slag was omitted, resulting in the inability to form an alkaline environment in the system, and the structure of slag particles could not be destroyed to release active components, so the hydration reaction could not proceed. And the self-activation efficiency of slag itself is limited, which further causes a significant decrease in the strength of the solidified paste.

[0116] Compared with Example 1, in Comparative Example 3, the addition of silica fume was omitted, resulting in the inability to consume the excess hydroxide ions in the later stage of the system, and the deterioration of the hydration product gel. The continuous hydration process will also cause the deterioration of the crystal structure of calcium hydroxide. In addition, the micro-filling effect and nucleation effect of silica fume will be lost. All these will lead to a decrease in the later compressive strength of the solidified paste.

[0117] Compared with Example 1, in Comparative Example 4, the dosage ratio of each raw material was changed, resulting in a weakened synergistic effect between the precursor materials. For example, when the dosage of carbide slag is too high, calcium hydroxide crystals will precipitate, forming a large number of pores and stress concentration areas inside the solidified paste, which has an adverse effect on the strength; when the dosage of silica fume is too high, the alkalinity of the system will be reduced, which will affect the dissolution of precursor substances and the hydration reaction, thus reducing the strength.

[0118] Compared with Example 1, in Comparative Examples 5 and 6, the water-cement ratio was changed. First, too low a water-cement ratio will make the paste lose workability and cannot carry out effective hydration. Second, too high a water-cement ratio will lead to too high a water content in the paste, and the pores formed after the internal water evaporates will cause a decrease in compressive strength.

[0119] Compared with Example 1, in Comparative Example 7, traditional calcium hydroxide alkali activator was used to replace carbide slag, resulting in an increase in cost and carbon emissions. In addition, using strong alkaline chemical activators will have safety risks and will lead to problems such as reduced durability, poor volume stability, and easy carbonization of the paste.

[0120] The scanning electron microscope (SEM) image of the slag-phosphogypsum-based solid waste cementitious material prepared in Example 1 of the present invention is shown in Figure 4, it can be seen that at this time, ettringite and C-(A)-S-H gel are interconnected to form a whole, and the number of pores and microcracks inside the solidified paste is small.

[0121] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A slag-phosphogypsum-based solid waste cementitious material, characterized in that, By mass percentage, it consists of the following raw materials: 45 - 55% of slag, 40 - 50% of phosphogypsum, 0.5 - 5% of carbide slag, and 2 - 10% of silica fume, and the water - cement ratio is 0.35 - 0.50; The slag is S95 grade or above slag; the phosphogypsum is hemihydrate phosphogypsum; the mass content of CaO in the carbide slag is ≥65.0%; the specific surface area of the silica fume is ≥19.0m 2 / g, and the mass content of SiO2 is ≥96.0%.

2. The slag-phosphogypsum-based solid waste cementitious material according to claim 1, wherein By mass percentage, the raw materials include 50.84% of slag, 45.76% of phosphogypsum, 1.40% of carbide slag, and 2% of silica fume, and the water - cement ratio is 0.

40.

3. The slag-phosphogypsum-based solid waste cementitious material according to claim 1, characterized in that, By mass percentage, the raw materials include 49.81% of slag, 44.82% of phosphogypsum, 1.37% of carbide slag, and 4% of silica fume, and the water - cement ratio is 0.

40.

4. The slag-phosphogypsum-based solid waste cementitious material according to claim 1, wherein By mass percentage, the raw materials include 48.77% of slag, 43.89% of phosphogypsum, 1.34% of carbide slag, and 6% of silica fume, and the water - cement ratio is 0.

40.

5. A preparation method of the slag-phosphogypsum-based solid waste cementitious material according to any one of claims 1-4, characterized in that, It includes the following steps: Weigh slag, phosphogypsum, carbide slag, and silica fume according to mass percentage, mix them evenly, and then add water and stir to obtain a slurry; Pour the slurry into a mold, compact it, let it stand, and then demold it; After standard curing of the demolded specimen, the slag - phosphogypsum - based solid waste cementitious material is obtained.

6. The preparation method of the slag-phosphogypsum-based solid waste cementitious material according to claim 5, wherein After adding water, stir at 140 ± 5 r / min for 1 - 2 min, and then stir at 285 ± 10 r / min for 2 - 3 min.

7. The preparation method of the slag-phosphogypsum-based solid waste cementitious material according to claim 5, characterized in that, Carry out curing under the conditions of 20℃ ± 1℃ and a relative humidity of not less than 90%.

8. The application of the slag - phosphogypsum - based solid waste cementitious material according to any one of claims 1 - 4 in the construction field.

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