A method for preparing concrete using metallurgical solid waste

Abstract

The application discloses a method for preparing concrete by using metallurgical solid wastes, and belongs to the technical field of resource utilization of metallurgical solid wastes. The method uses iron mine waste rocks as coarse and fine aggregates for concrete, and uses self-produced iron tailings sand of a metallurgical enterprise as fine aggregate. Since the iron tailings sand is very fine sand, the iron mine waste rock artificial sand and the iron tailings sand are used as fine aggregate and are subjected to continuous grading treatment. Finally, the iron mine waste rocks and the iron tailings can replace all natural sand and stones in the concrete, so that the exploitation of natural resources is saved, the production cost of the concrete is reduced, the resource utilization rate of the iron mine waste rocks, the iron tailings and the sintering flue gas desulfurization ash in the concrete field is improved, and the application performance requirements such as the strength index of the concrete are met.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical solid waste resource utilization technology, specifically relating to a method for preparing concrete using metallurgical solid waste. Background Technology

[0002] The price of commercial concrete mixing aggregates (limestone or basalt as coarse aggregate and river sand as fine aggregate) has soared, and there is no longer a place to mine them, making the production cost of concrete increasingly higher.

[0003] Metallurgical enterprises possess a large amount of metallurgical solid waste resources, but their utilization rate is low. Metallurgical enterprises have a large amount of iron ore waste rock, which consists of stripped rock discharged during the iron ore mining process and unusable stones after iron ore processing. It is mainly quartz sandstone, with a hardness comparable to limestone or basalt, and can be mechanically crushed as coarse and fine aggregates.

[0004] Iron tailings are tailings obtained from magnetite ore through magnetic separation. They are metallurgical solid waste with TFe < 10%, and their stockpiles are huge, facing the problem of dam closure. They need to be monitored at all times to prevent dam failure. However, the particle size of iron tailings is too fine, and technical measures need to be taken to process them in order to give full play to the advantages of iron tailings.

[0005] Metallurgical enterprises emit over 100,000 tons of desulfurization ash from sintering flue gas annually, which is unusable, occupies land when stockpiled, pollutes groundwater, and impacts the surrounding environment. The concrete industry has a demand for sand, gravel, and admixtures, and there is also a large amount of sand and gravel around metallurgical enterprises that needs to be utilized.

[0006] A method for preparing high-strength concrete from tailings waste rock containing fly ash (application number: CN201210238942.4) utilizes various solid wastes such as mining waste rock, mineral processing tailings, fly ash, desulfurization gypsum, and slag. The drawback is that the cementitious materials need to be ground twice to achieve the required specific surface area, making the process cumbersome, time-consuming, and energy-intensive, and difficult to apply industrially. Simply utilizing waste rock and tailings, due to the influence of the waste rock's strength and crushing value, prevents a significant increase in concrete strength. A sintering flue gas desulfurization ash early-strength agent used as a fine admixture in concrete (application number: CN03121115.1) uses active silica, which is the so-called silica fume. Free calcium and magnesium oxides can easily cause products to expand and crack during future use; a method for producing active admixtures for concrete using iron tailings (application number: CN200710118711.9) uses iron tailings and desulfurized gypsum to produce active admixtures at high temperature. The process is complicated, energy consumption is high, and the components in the desulfurized gypsum are easily decomposed at high temperature.

[0007] Therefore, how to develop and utilize metallurgical solid waste for concrete preparation has become an important issue that urgently needs to be addressed. Summary of the Invention

[0008] Therefore, the purpose of this invention is to provide a method for preparing concrete using metallurgical solid waste, thereby improving the resource utilization rate of iron ore waste rock, iron tailings, and sintering flue gas desulfurization ash in the field of concrete, and meeting the application performance requirements such as concrete strength indicators.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing concrete using metallurgical solid waste, comprising the following steps: S1: 196-332 parts of iron ore waste rock artificial crushed stone as coarse aggregate, and 59-104 parts of iron tailings sand and 26-236 parts of iron ore waste rock artificial sand are mixed to form a continuous particle size distribution as fine aggregate. S2: Add 62-73 parts cement, 12-18 parts slag powder, 7-13 parts modified sintering flue gas desulfurization ash and 8-10 parts fly ash and mix evenly; S3: Add 2-2.4 parts of water-reducing agent and 32-61 parts of water, mix and stir for ≥3 minutes to obtain concrete.

[0011] Among them, the continuous particle size distribution state is a state in which the particle size specifications from large to small are complete, and the number of particles of each size exists in a certain proportion.

[0012] Cement, slag powder, modified sintering flue gas desulfurization ash, and fly ash together constitute the cementitious material.

[0013] Among them, artificial crushing of iron ore waste rock is referred to as artificial crushing, and artificial sand made from iron ore waste rock is referred to as artificial sand.

[0014] Among them, the stirring method in S3 is simple and convenient to operate, which is conducive to industrial production and widespread application.

[0015] Concrete prepared using this method can be cured at temperatures of 25-35℃ and humidity of 40-60%RH.

[0016] The number of parts refers to the number of mass parts.

[0017] Based on the above technical solution, further, iron ore waste with a crushing index ≤8% is processed to a size ≤20mm and a crushing index ≤10%; iron ore waste with a size <5mm is made into iron ore waste artificial sand, and iron ore waste with a size of 5-20mm is made into iron ore waste artificial crushed stone.

[0018] Among them, iron ore waste rock is mainly composed of iron-bearing quartzite with high silicon content.

[0019] Among them, iron ore waste with a crushing index of ≤8% is processed to a size of ≤20mm using specialized grinding equipment.

[0020] Based on the above technical solution, the modified sintering flue gas desulfurization ash is obtained by modifying the sintering flue gas desulfurization ash to CaSO3 < 3%, and the fineness of the modified sintering flue gas desulfurization ash is ≥ 400 mesh.

[0021] Among them, the CaSO3 content of the modified sintering flue gas desulfurization ash is less than 3%, which avoids the CaSO3 from continuing to transform and expand during future use, causing cracks in the products.

[0022] The modification process specifically involves dissolving the desulfurization ash from sintered flue gas in water, adding acidic additives (such as sulfuric acid, hydrochloric acid, citric acid, etc.), adjusting the pH to 4.0-6.0, introducing air to oxidize CaSO3 to CaSO4, and then separating the solid and liquid phases to obtain the modified desulfurization ash from sintered flue gas.

[0023] Based on the above technical solution, the crushing value of the iron tailings sand is further ≤30%.

[0024] Based on the above technical solution, the iron ore waste rock is further composed of the following substances in mass percentage: SiO2: 50%-78%, Al2O3: 5%-18%, FeO: 0.5%-8%, Fe2O3: 1%-8%, TFe: 0.3%-8%, CaO: 2%-10%, MgO: 1%-5%, K2O: 0%-4%, Na2O: 0%-4%, the remainder being impurities.

[0025] Based on the above technical solution, the iron tailings sand is further composed of the following substances in mass percentage: SiO2: 55%-82%, Al2O3: 0.2%-9%, FeO: 0.5%-12%, Fe2O3: 2%-22%, TFe: 5%-15%, CaO: 0%-8%, MgO: 0%-4%, K2O: 0%-1.8%, Na2O: 0%-1.8%, with the remainder being impurities.

[0026] TFe refers to the total amount of iron.

[0027] Based on the above technical solution, further, the fineness modulus of the iron tailings sand is 0.7-1.8, and the proportion of iron tailings sand with a particle size <0.16mm is >10%.

[0028] Among them, the fineness modulus of iron tailings sand is generally smaller than that of fine sand (the fineness modulus of fine sand is usually 1.6-2.2), and it belongs to extremely fine sand.

[0029] Based on the above technical solution, further, the fineness of the slag powder is ≥400 mesh, and the fineness of the fly ash is ≥400 mesh.

[0030] Among them, the slag powder grade is S75 or above, and the fly ash reaches the Class II standard or above.

[0031] Based on the above technical solution, the cement is ordinary silicate cement or composite silicate cement, and the water-reducing agent is naphthalene-based or polycarboxylate-based water-reducing agent.

[0032] Ordinary Portland cement is abbreviated as PO, composite Portland cement is abbreviated as PC, and the cement strength grade is 42.5.

[0033] Secondly, the present invention provides the application of the above-mentioned method for preparing concrete using metallurgical solid waste in the preparation of C20-C40 concrete.

[0034] This type of concrete is recommended for use in structural concrete components or buildings.

[0035] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention addresses the needs of concrete by utilizing iron ore waste as coarse and fine aggregates, while simultaneously using iron tailings sand produced by metallurgical enterprises as fine aggregate. Because iron tailings sand is extremely fine, it is necessary to combine iron ore waste with artificial sand and iron tailings sand as fine aggregates and perform continuous gradation treatment. Ultimately, this invention achieves the replacement of all natural sand and gravel in concrete with iron ore waste and iron tailings, saving on natural resource extraction, reducing concrete production costs, increasing the resource utilization rate of iron ore waste, iron tailings, and sintering flue gas desulfurization ash in the concrete field, and meeting the application performance requirements such as concrete strength indicators.

[0036] 2. This invention also uses sintering flue gas desulfurization ash to replace part of the cement, reducing the amount of cement used, which accounts for the highest cost of concrete, realizing the high-value utilization of sintering desulfurization ash, further reducing the production cost of concrete, and significantly reducing carbon dioxide emissions.

[0037] 3. In this invention, active oxides such as silica and alumina in iron ore waste rock and iron tailings react chemically with cementitious materials such as calcium hydroxide crystals and hydrated calcium silicate gel precipitated during cement hydration, as well as effective alkalis, sulfates, and chloride ions introduced by aggregates, which are detrimental to the strength and durability of cement stone and concrete. This reaction generates calcium aluminosilicate gel and other beneficial compounds that are beneficial to the strength and durability of cement stone and concrete. Furthermore, these compounds can react with components in cement during concrete hydration to form ettringite (Aft), enhancing the overall performance of concrete, improving the adhesion between the paste and aggregate interface, reducing harmful pores, and decreasing pore size. Their dense structure and volume stability enhance the concrete's resistance to various chemical attacks and inhibit alkali-aggregate reactions, significantly improving the durability of cement stone and concrete. They also improve the rheological properties, bleeding and segregation of fresh concrete, maintain a certain level of workability, and prevent heavy metals from leaching out.

[0038] 4. This invention provides a method for improving the utilization of iron ore waste rock, iron tailings, and desulfurization ash from sintering flue gas to prepare green concrete. It utilizes iron ore waste rock and iron tailings to completely replace natural sand and gravel, and uses an equal amount of desulfurization ash from sintering flue gas to replace cement in concrete preparation. This effectively reduces concrete production costs, provides a new approach to the utilization of metallurgical resources, ensures that the various properties of the concrete are not reduced, reduces the mining of natural sand and gravel, reduces cement usage, achieves high-value utilization of metallurgical solid waste, and simultaneously reduces CO2 emissions (the cement industry is a major emitter of carbon dioxide, emitting more than 0.6 tons of carbon dioxide per ton of cement produced). The strength and other performance indicators of the prepared concrete meet the standard requirements. The compressive strength of the concrete reaches 115% or more of the design strength. Detailed Implementation

[0039] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0040] Concrete is prepared using the process method provided by this invention, with the corresponding mass fractions of the substances in Tables 1 and 2 as raw materials.

[0041] The prepared concrete was tested for strength grade, compressive strength, and flexural strength according to the standard GB / T50081-2019.

[0042] The results are shown in Table 3. The concrete strengths obtained in Examples 1 to 3 are all higher than the design strength, and they have excellent compressive strength and flexural strength.

[0043] Table 1: Specific concrete mix design (unit: parts by mass).

[0044]

[0045] Table 2: Cementitious Materials (Unit: Parts by Mass). Note: The total cementitious material consisting of cement, slag powder, sintering flue gas desulfurization ash, and fly ash is 100 parts.

[0046]

[0047] Table 3: Compressive and flexural strength of concrete.

[0048]

[0049] The raw materials used in this technology are inexpensive and readily available. With other mixing materials remaining constant, it can save 20-70 yuan / m³ in concrete mixing costs. 3 .

[0050] Using desulfurization ash from sintering flue gas as a cementing material to replace cement in equal quantities in concrete preparation, with cement prices above 300 yuan / ton, reduces the cost of cement, the most expensive component in concrete, thus further lowering overall costs.

[0051] Based on ordinary concrete calculations, the overall cost is reduced by more than 36 yuan / m³. Among them, using iron ore waste rock and iron tailings reduces concrete cost by more than 30 yuan / m³; and using desulfurization ash to replace cement in equal amounts reduces concrete cost by more than 6 yuan.

[0052] A large amount of iron ore waste rock and tailings sand are used in concrete preparation, completely replacing the amount of natural sand and gravel used in the concrete mixing process, greatly reducing the production cost of concrete, making metallurgical solid waste concrete more competitive in the market. If it is fully promoted in China, it will generate huge economic benefits and achieve the organic unity of economic, environmental and social benefits.

[0053] Based on the annual disposal of 20 million tons of iron ore waste rock and iron tailings, and the utilization of more than 2 million tons of sintering desulfurization ash (accounting for 1 / 10 of the national SDA emissions), waste is turned into treasure, achieving an annual economic benefit of nearly 1 billion yuan and reducing CO2 emissions by more than 3 million tons.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing concrete using metallurgical solid waste, characterized in that, Includes the following steps: S1: 196-332 parts of iron ore waste rock artificial crushed stone as coarse aggregate, and 59-104 parts of iron tailings sand and 26-236 parts of iron ore waste rock artificial sand are mixed to form a continuous particle size distribution as fine aggregate. S2: Add 62-73 parts cement, 12-18 parts slag powder, 7-13 parts modified sintering flue gas desulfurization ash and 8-10 parts fly ash and mix evenly; S3: Add 2-2.4 parts of water-reducing agent and 32-61 parts of water, mix and stir for ≥3 minutes to obtain concrete.

2. The method for preparing concrete using metallurgical solid waste according to claim 1, characterized in that, Iron ore waste with a crushing index ≤8% is processed to a size ≤20mm and a crushing index ≤10%; iron ore waste with a size <5mm is made into iron ore waste sand, and iron ore waste with a size of 5-20mm is made into iron ore waste crushed stone.

3. The method for preparing concrete using metallurgical solid waste according to claim 1, characterized in that, The modified sintering flue gas desulfurization ash is obtained by modifying sintering flue gas desulfurization ash to CaSO3 < 3%, and the fineness of the modified sintering flue gas desulfurization ash is ≥ 400 mesh.

4. The method for preparing concrete using metallurgical solid waste according to claim 1, characterized in that, The crushing value of the iron tailings is ≤30%.

5. The method for preparing concrete using metallurgical solid waste according to claim 2, characterized in that, The iron ore waste rock consists of the following substances in mass percentage: composition: SiO2: 50%-78%, Al2O3: 5%-18%, FeO: 0.5%-8%, Fe2O3: 1%-8%, TFe: 0.3%-8%, CaO: 2%-10%, MgO: 1%-5%, K2O: 0%-4%, Na2O: 0%-4%, the remainder being impurities.

6. The method for preparing concrete using metallurgical solid waste according to claim 1, characterized in that, The iron tailings sand consists of the following substances in mass percentage: composition: SiO2: 55%-82%, Al2O3: 0.2%-9%, FeO: 0.5%-12%, Fe2O3: 2%-22%, TFe: 5%-15%, CaO: 0%-8%, MgO: 0%-4%, K2O: 0%-1.8%, Na2O: 0%-1.8%, with the remainder being impurities.

7. The method for preparing concrete using metallurgical solid waste according to claim 1, characterized in that, The fineness modulus of the iron tailings is 0.7-1.8, and the proportion of iron tailings with a particle size <0.16mm is >10%.

8. The method for preparing concrete using metallurgical solid waste according to claim 1, characterized in that, The fineness of the slag powder is ≥400 mesh, and the fineness of the fly ash is ≥400 mesh.

9. The method for preparing concrete using metallurgical solid waste according to claim 1, characterized in that, The cement is ordinary silicate cement or composite silicate cement, and the water-reducing agent is naphthalene-based or polycarboxylate-based water-reducing agent.

10. The application of the method for preparing concrete using metallurgical solid waste as described in any one of claims 1 to 9 in the preparation of C20-C40 concrete.

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