Slag-steel slag-circulating fluidized bed fly ash-based composite cementing material and preparation method thereof

Abstract

The invention discloses a preparation method of a slag-steel slag-circulating fluidized bed fly ash based composite cementing material. The preparation method comprises the following steps: grinding and stripping desulfurization wastes of a power plant, then mixing with slag powder, steel slag powder, circulating fluidized bed fly ash and water to obtain gel material slurry, and carrying out standard curing on the obtained gel material slurry to obtain the slag-steel slag-circulating fluidized bed fly ash-based composite gel material. The composite cementing material has relatively high compressive strength and good volume stability. By applying the technology, a large amount of solid waste can be consumed, the recycling target of adjusting measures to local conditions and treating waste with waste is achieved, and meanwhile the method has the value of circular economy and energy conservation and environmental protection.

Description

Technical Field

[0001] The present invention relates to the technical field of resource treatment of solid waste, and particularly relates to a slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material and a preparation method thereof. Background Art

[0002] With the continuous acceleration of the industrialization process, the discharge of industrial solid waste has increased rapidly. How to effectively dispose of and resourcefully utilize these solid wastes has become an important problem to be solved urgently. Among them, slag, steel slag, and circulating fluidized bed fly ash, as the main solid wastes generated in the industrial production process, have long caused serious problems such as occupation of land resources, environmental pollution, and ecological damage due to improper stacking treatment. Slag is a by - product in the iron and steel smelting process and has high potential activity. However, due to the limitations of traditional activation technologies, a large amount of slag cannot be effectively utilized. Steel slag is also an important solid waste in the iron and steel industry. Although it has certain cementitious potential, it is difficult to be directly and efficiently utilized due to problems such as poor volume stability and high free calcium oxide content, resulting in a large amount of stacking and environmental pollution. Circulating fluidized bed fly ash is a solid waste generated by new coal - burning technologies. Due to its complex mineral composition and low activity, it is difficult to be fully activated by traditional methods, resulting in an increasing stockpile of circulating fluidized bed fly ash.

[0003] The production of traditional cementitious materials mostly relies on natural resources and high - energy - consuming production processes, bringing great pressure to the environment.

[0004] Existing technologies have conducted more research on the activation of single solid waste, but there is insufficient research on the synergistic activation of slag, steel slag, and circulating fluidized bed fly ash.

[0005] In order to promote the efficient resource utilization of industrial solid waste, it is particularly urgent to develop a composite cementitious material that can simultaneously synergistically activate the activities of slag, steel slag, and circulating fluidized bed fly ash and its preparation technology. Summary of the Invention

[0006] In order to overcome the above - mentioned technical problems, the purpose of the present invention is to provide a slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material and a preparation method thereof. This composite cementitious material has high compressive strength and good volume stability. Applying this technology can dispose of a large amount of solid waste, achieving the resource utilization goal of "adapting measures to local conditions and treating waste with waste", and at the same time having the value of circular economy and energy conservation and environmental protection.

[0007] In order to achieve the above - mentioned purpose, the technical solution adopted by the present invention is:

[0008] A preparation method of a slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material, comprising the following steps;

[0009] The desulfurization waste of the power plant is ground and peeled, and then mixed with slag powder, steel slag powder, circulating fluidized bed fly ash and water to obtain a gel material slurry. The obtained gel material slurry is subjected to standard curing to obtain the slag-steel slag-circulating fluidized bed fly ash-based composite gel material.

[0010] The grinding and peeling is not only for a single raw material or activator, but includes grinding a certain raw material, grinding a composite activator and grinding a composite powder rich in active silicon and aluminum.

[0011] The D of the circulating fluidized bed fly ash 50 are respectively: (11.92 - 13.82) μm; the free calcium oxide content of the circulating fluidized bed fly ash is 0.14%.

[0012] The circulating fluidized bed fly ash is dried at 100 - 110 °C for 22 - 24 h before mixing. The purpose of this is to fully reduce the moisture content of the circulating fluidized bed fly ash, inhibit the adverse reaction of f-CaO with water, prevent the fly ash from caking and causing poor fluidity, and avoid the pre-hydration of the active silicon and aluminum components in the fly ash caused by a humid environment.

[0013] The mass ratio of the slag powder: steel slag powder: circulating fluidized bed fly ash: desulfurization solid waste of the power plant and water is (10 - 50):20:(25 - 65):5:50. Within this range, the mechanical strength of the circulating fluidized bed fly ash-slag-steel slag-based gel material is relatively high, and good flow and rheological properties can be obtained by adding components such as water reducers.

[0014] The grinding method is ball milling or vertical milling;

[0015] The slag is granulated blast furnace slag, and the D of the slag powder after grinding 50 is (9.73 - 11.52) μm;

[0016] The steel slag powder is steel slag fine powder, and the D of the steel slag fine powder 50 is (7.76 - 9.63) μm, and the free calcium oxide content of the steel slag fine powder is 0.49%.

[0017] The desulfurization waste of the power plant is desulfurized gypsum, and the D after grinding 50 is (5.07 - 8.50) μm.

[0018] The conditions for the standard curing are 20 ± 2 °C, 95 ± 2%.

[0019] The microstructure of the composite cementitious material is mainly a three-dimensional network structure, which is jointly bridged and overlapped by an amorphous gel phase and crystal phases such as ettringite. This structure has a highly dense structure mainly composed of harmless pores. Therefore, the above composite cementitious material has high mechanical strength, can effectively disperse external stresses and block the penetration of erosive ions, and macroscopically exhibits good durability and volume stability.

[0020] Advantages of the present invention:

[0021] After grinding, the particle sizes of the desulfurization waste from power plants, composite powder, etc. in the present invention are reduced. This is beneficial for the rapid dissolution and activation of the activation components and active silica-aluminum components during the hydration process. The SO4 in the activation components 2- reacts with OH- and the active silica-aluminum in circulating fluidized bed fly ash and slag to form hydration products such as amorphous gel and ettringite, improving the performance of the circulating fluidized bed fly ash-based cementitious material. In addition, tricalcium silicate in steel slag can also hydrate to form gel-like hydration products beneficial to strength development. During the hydration process of the circulating fluidized bed fly ash-based cementitious material, continuously generated gel-like products form a three-dimensional network structure, and at the same time coat and cement crystal phases such as quartz that have not participated in the reaction, making the microstructure of the cementitious material more dense and the porosity smaller, enhancing the compressive strength of the cementitious material.

[0022] Through the synergistic activation among slag, steel slag, circulating fluidized bed fly ash and desulfurized gypsum, the present invention enhances the compressive strength of the slag-steel slag-circulating fluidized bed fly ash-based composite cementitious material, can realize the large-scale resource utilization of slag, steel slag and circulating fluidized bed fly ash, effectively solves the environmental pollution problems caused by slag, steel slag and circulating fluidized bed fly ash, and has good environmental and economic benefits.

[0023] The 28-day compressive strength of the slag-steel slag-circulating fluidized bed fly ash-based composite cementitious material prepared by the present invention can reach more than 50 MPa, and can be used in fields such as house construction, coal mine backfilling, and road construction. It can significantly reduce the cement consumption, reduce the cost of the cementitious material, and at the same time promote the resource utilization of solid waste, with good economic and environmental benefits and is convenient for large-scale promotion. Description of the drawings

[0024] Figure 1 It is the particle size diagram of the raw materials prepared in Example 1, Example 3 and Example 5.

[0025] Figure 2 It is the MIP diagram of the slag-steel slag-circulating fluidized bed fly ash-based composite cementitious material prepared in Example 1, Example 3 and Example 5. Detailed implementation manners

[0026] The present invention will be further described in detail below with reference to the embodiments.

[0027] Unless otherwise specified, the "parts" described in the present invention are based on mass parts.

[0028] In the following embodiments, the circulating fluidized bed fly ash used is the ash produced after combustion in a circulating fluidized bed boiler, and its main chemical components and mass percentages are: SiO2-46.96%, Al2O3-23.68%, CaO-8.16%, Fe2O3-4.64%, and SO3-4.02%.

[0029] The D of desulfurized gypsum and steel slag powder used 50 The mineral powder used is S95 grade, D 50 The particle size is 9.73 μm; the water is tap water.

[0030] The free calcium oxide contents of the steel slag powder and circulating fluidized bed fly ash used are 0.49% and 0.14% respectively.

[0031] The description will not be repeated below.

[0032] Example 1

[0033] The preparation method of slag-steel slag-circulating fluidized bed fly ash-based composite cementitious material comprises the following steps:

[0034] (1) Weigh 10-50 parts of slag powder, 20 parts of steel slag powder, 25-65 parts of circulating fluidized bed fly ash, 5 parts of desulfurized gypsum and 50 parts of water by weight; dry the slag, steel slag, circulating fluidized bed fly ash and desulfurized gypsum at 110°C for 24 hours, and then grind the slag, steel slag and desulfurized gypsum in a ball mill to obtain the median particle size D of the slag powder, steel slag powder and desulfurized gypsum. 50 9.73μm, 7.76μm and 5.07μm respectively;

[0035] (2) Add the circulating fluidized bed fly ash, steel slag powder, desulfurized gypsum, slag, standard sand and water into a mortar mixing pot, stir them thoroughly to mix them evenly, and obtain a cementitious material mortar;

[0036] (3) Pour the cementitious material mortar prepared in step (2) into the mold three times, tamp it thoroughly, vibrate it on a vibration table for 60 seconds, smooth the surface, and then place it in a standard curing room at a curing temperature of 20±2°C and a humidity of 90±5%. After curing for 24 hours, take it out of the curing box, remove the mold, and continue to use the standard curing system for curing for 28 days. Take out the test block to complete the preparation of the circulating fluidized bed fly ash-based cementitious material.

[0037] Examples 2 to 5.

[0038] Examples 2 to 5 are the same as Example 1, except that the dosages of slag powder and circulating fluidized bed fly ash in step (1) are different, as specifically shown in Table 1:

[0039] Table 1

[0040]

[0041] The 3d, 7d, and 28d compressive strengths of the cementitious materials prepared in Examples 1 to 5 were tested, and the results are shown in Table 2;

[0042] Table 2

[0043]

[0044] Furthermore, the effect of the compressive strength of the slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material was analyzed from the microscopic structure:

[0045] The mercury intrusion porosimetry (MIP) was used to further analyze the properties of the slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material, and to analyze the mechanism of the synergistic activation of circulating fluidized bed fly ash and slag by steel slag powder and desulfurized gypsum to enhance the compressive strength of the cementitious material.

[0046] Specimens in Examples 1, 3, and 5 were selected for relevant test analysis:

[0047] (1) Particle size distribution diagram of raw materials

[0048] The particle size distribution diagrams of circulating fluidized bed fly ash, steel slag, slag, and desulfurized gypsum are as Figure 1 shown.

[0049] (2) MIP analysis of composite cementitious materials with different dosages of circulating fluidized bed fly ash

[0050] The pore size distribution of the slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material at 28d age is as Figure 2 shown, and the cumulative pore volume is shown in Table 3. In the hardened paste, the pore sizes can be divided into harmless pores (<20nm), less harmful pores (20 - 50nm), more harmful pores (50 - 200nm), and harmful pores (>200nm).

[0051] Table 3

[0052]

[0053] From Figure 2As can be seen from Table 3, with increasing circulating fluidized bed fly ash content, the pore structure gradually shifts toward larger pores, indicating a decrease in the pore size of the block. In Examples 1, 3, and 5, pores with diameters <20 nm account for 57.26%, 68.39%, and 16.89%, respectively. This is because Example 3 has the highest proportion of harmless pores, indicating that Example 3 produces more hydration products, followed by Example 1, and Example 5 produces the least. This conclusion is corroborated by the compressive strength of each example.

[0054] In summary, the method of preparing cementitious materials by synergistically stimulating circulating fluidized bed fly ash and slag with steel slag micropowder and gypsum can not only greatly improve the utilization rate of circulating fluidized bed fly ash, but also effectively improve the compressive properties of circulating fluidized bed fly ash-based cementitious materials, so that their compressive strength can reach above 50 MPa. It can be used in engineering fields with high compressive strength requirements such as house construction, mine filling, and road construction, and has good environmental and economic benefits. The present invention creatively proposes a method for synergistically stimulating circulating fluidized bed fly ash, steel slag micropowder, and desulfurized gypsum to prepare circulating fluidized bed fly ash-based cementitious materials of different strength grades. This discovery can make it better applicable to multiple fields with different compressive strength requirements.

[0055] Example 6 and Example 7

[0056] The preparation method of slag-steel slag-circulating fluidized bed fly ash-based composite cementitious material comprises the following steps:

[0057] (1) Weigh 30 parts of slag powder, 20 parts of steel slag powder, 45 parts of circulating fluidized bed fly ash, 5 parts of desulfurized gypsum and 225 parts of water by weight; dry the slag powder, steel slag powder, circulating fluidized bed fly ash and desulfurized gypsum at 110°C for 24 hours; place the circulating fluidized bed fly ash-slag powder composite powder (based on the ratio of circulating fluidized bed fly ash and slag powder in Example 3) in a ball mill and grind for 60 minutes and 90 minutes respectively. The median particle size D of the composite powder obtained is 0.0447 ... 50 7.52μm and 5.38μm;

[0058] (2) Add the circulating fluidized bed fly ash-slag composite powder, steel slag powder, desulfurized gypsum, standard sand and water into a mortar mixing pot, stir them thoroughly to mix them evenly, and obtain a cementitious material slurry;

[0059] (3) Pour the cementitious material slurry prepared in step (2) into the mold three times, tamp it thoroughly, and vibrate it on a vibrating table for 60 seconds. After smoothing the surface, place it in a standard curing room and set the curing temperature to 20±5°C. After curing for 24 hours, remove it from the curing room and remove the mold. After standard curing for 28 days, remove the test block, and complete the preparation of the slag-steel slag-circulating fluidized bed fly ash-based composite cementitious material.

[0060] Table 4

[0061]

[0062] Example 8

[0063] The preparation method of the early-strength slag-steel slag-circulating fluidized bed fly ash-based composite cementitious material comprises the following steps:

[0064] (1) Weigh 30 parts by weight of slag powder, 20 parts by weight of steel slag powder, 45 parts by weight of circulating fluidized bed fly ash, 5 parts by weight of desulfurized gypsum, and 225 parts by weight of water;

[0065] (2) adding the slag powder, steel slag powder, circulating fluidized bed fly ash, desulfurized gypsum and water into a slurry mixing pot, stirring thoroughly to mix them evenly, and obtaining a cementitious material slurry;

[0066] (3) Pour the cementitious material slurry prepared in step (2) into the mold, tamp it thoroughly, vibrate it on a vibration table for 60 seconds, smooth the surface, and then place it in a standard curing box. Set the curing temperature to 60±5°C. After curing for 12 hours, take it out of the curing box, remove the mold, and cure it at room temperature for 28 days. Take out the test block to complete the preparation of the circulating fluidized bed fly ash-based cementitious material.

[0067] The 3d, 7d and 28d compressive strengths of the circulating fluidized bed fly ash-based cementitious material prepared in this example were tested, and the results were 33.68 MPa, 49.96 MPa and 53.65 MPa, respectively.

[0068] It can be seen that thermal curing can improve the early compressive strength of slag-steel slag-circulating fluidized bed fly ash based composite cementitious materials.

[0069] Table 5

[0070]

[0071] The above description is only a preferred specific embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention within the technical scope disclosed in the present invention, and these changes should be covered by the scope of protection of the present invention.

Claims

1. A preparation method of a slag-steel slag-circulating fluidized bed fly ash-based composite cementitious material, characterized in that, It includes the following steps; The desulfurized waste of the power plant is ground and peeled, and then mixed with slag powder, steel slag powder, circulating fluidized bed fly ash and water to obtain a gel material slurry. The obtained gel material slurry is subjected to standard curing to obtain the slag-steel slag-circulating fluidized bed fly ash-based composite gel material.

2. The preparation method of a slag-steel slag-circulating fluidized bed fly ash-based composite cementitious material according to claim 1, characterized in that, The D of the circulating fluidized bed fly ash 50 are respectively: (11.92 - 13.82) μm; the free calcium oxide content of the circulating fluidized bed fly ash is 0.14%.

3. The preparation method of a slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material according to claim 2, characterized in that, The circulating fluidized bed fly ash is dried at 100-110°C for 22-24 h before mixing.

4. The preparation method of a slag-steel slag-circulating fluidized bed fly ash-based composite cementitious material according to claim 1, characterized in that, The mass ratio of the slag powder: steel slag powder: circulating fluidized bed fly ash: desulfurized solid waste of the power plant and water is (10-50): 20: (25-65): 5:

50.

5. The preparation method of a slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material according to claim 1, characterized in that, The grinding method is ball milling or vertical milling.

6. The preparation method of a slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material according to claim 1, characterized in that, The slag is granulated blast furnace slag, and the D of the slag powder after grinding is 50 (9.73 - 11.52) μm.

7. The preparation method of a slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material according to claim 1, characterized in that The steel slag powder is steel slag fine powder, and the steel slag fine powder D 50 is (7.76 to 9.63) μm, and the free calcium oxide content of the steel slag fine powder is 0.49%.

8. The preparation method of a slag-steel slag-circulating fluidized bed fly ash-based composite cementitious material according to claim 1, characterized in that, The desulfurization waste of the power plant is desulfurized gypsum, and D after grinding 50 is (5.07 - 8.50) μm.

9. The preparation method of a slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material according to claim 1, characterized in that The conditions for the standard curing are 20±2°C and 95±2%.

10. A slag - steel slag - circulating fluidized bed fly ash - based composite cementitious material prepared by the method according to any one of claims 1 - 9, characterized in that, The microstructure of the composite gel material is mainly a three-dimensional network structure, which is jointly bridged and overlapped by an amorphous gel phase and crystal phases such as ettringite; a highly dense structure mainly composed of harmless pores.

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