A mixed aggregate based on steel slag and lithium slag, and a preparation method and application thereof

Abstract

The present application relates to a kind of based on steel slag and lithium slag mixed aggregate and its preparation method and application.The preparation method of based on steel slag and lithium slag mixed aggregate includes the following steps: steel slag under first temperature condition is cooled to second temperature, is crushed, obtains the steel slag containing active substance;Lithium slag and the steel slag containing active substance dry mix to obtain mixed material, water is added to mixed material so that the water content of mixed material is 15~19wt%, to obtain precursor material;After the granulation of precursor material, curing is obtained based on steel slag and lithium slag mixed aggregate.The present application also provides a kind of mixed aggregate prepared by the preparation method as described in the present application.The present application also provides a kind of mixed aggregate prepared by the preparation method as described in the present application as gravel in concrete, and the present application also provides a kind of concrete and its preparation method.The present application simultaneously realizes the resource application of steel slag and lithium slag.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of slag resource utilization, and particularly relates to a mixed aggregate based on steel slag and lithium slag, a preparation method and application thereof. BACKGROUND

[0002] Steelmaking involves precise control of carbon content (usually no more than 2 wt%), while removing harmful elements such as P, S, O, N, and retaining or increasing beneficial elements such as Si, Mn, Ni, Cr, etc., by adjusting the proportion of these elements to achieve the best performance. In the steelmaking process, steel slag is formed floating on the surface of the molten steel. Steel slag is mainly composed of oxides of silicon, manganese, phosphorus, sulfur and other impurities in iron ore formed during the smelting process, and salts generated by the reaction of these oxides with flux. The typical composition of steel slag includes 2 wt% to 8 wt% of metallic iron, 40 wt% to 60 wt% of calcium oxide, 3 wt% to 10 wt% of magnesium oxide, 1 wt% to 8 wt% of manganese oxide, 0.1 wt% to 2 wt% of sulfur, and relatively more silicon dioxide. Its mineral composition is mainly tricalcium silicate, followed by dicalcium silicate, solid solution of magnesium iron manganese oxide, dicalcium ferrite and free calcium oxide, and most of the sulfur mainly exists in the form of manganese sulfide and iron sulfide. Steel slag is large in quantity, complex in composition and low in recycling rate. If traditional treatment methods such as dumping and landfill are used for steel slag, it will cause great damage to the environment. Therefore, seeking new methods for resource utilization of steel slag not only helps to reduce environmental pollution, but also provides new raw material sources for industrial production.

[0003] Mixed sulfate roasting of spodumene concentrate produces a large amount of lithium slag after water leaching of the roasted material. In Yichun City, Jiangxi Province alone, at least 10 million tons of lithium slag are produced every year. These lithium slags contain a large amount of toxic metal elements such as thallium and beryllium, which pollute the water quality and destroy the ecological environment. The main components of lithium slag include lithium oxide, aluminum oxide, silicon dioxide, etc. Currently, lithium smelting plants generally use two ways to dispose of lithium slag. One is to temporarily store these hazardous wastes in a special warehouse; the other is to temporarily store lithium slag in a special disposal site. However, with the continuous expansion of the spodumene lithium extraction industry, the amount of lithium slag produced is also increasing year by year, leading to rising costs of warehouse rental and disposal fees of disposal sites, which brings great pressure to the operation of lithium smelting plants. In addition, long-term storage of lithium slag also has environmental risks. Once leakage or accidents occur, it will cause immeasurable damage to the surrounding environment.

[0004] Artificial aggregate balls are a kind of granules made by processing powdery industrial waste or construction waste. This aggregate can replace natural sand aggregate to reduce dependence on natural resources and handle a large amount of industrial waste. However, the current artificial aggregate balls have a generally high crushing value, higher than 38 wt%, or the production process needs to be passed through 1000o C Above high-temperature sintering and other hardening treatments can be used for building materials, resulting in huge solid waste treatment costs. SUMMARY

[0005] Therefore, the present application aims to provide a mixed aggregate based on steel slag and lithium slag, a preparation method and application thereof, so as to realize the resource utilization of steel slag and lithium slag and solve the problem that the crushing value of the existing artificial aggregate ball is generally higher than 38wt%, resulting in weak compressive strength, poor durability and poor structural stability.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a mixed aggregate based on steel slag and lithium slag, comprising the following steps:

[0008] S1, cooling the steel slag under a first temperature condition to a second temperature, crushing to obtain unhydrated steel slag with gel activity;

[0009] S2, dry mixing the lithium slag and the unhydrated steel slag with gel activity to obtain a mixture, adding water to the mixture so that the water content of the mixture is 15-19wt%, to obtain a precursor material;

[0010] S3, granulating and curing the precursor material to obtain a mixed aggregate based on steel slag and lithium slag.

[0011] By using industrial waste steel slag and lithium slag as raw materials to prepare the mixed aggregate, the resource utilization of steel slag and lithium slag is realized at the same time, the pollution to the environment is reduced, the synergistic use of steel slag and lithium slag gives the mixed aggregate better mechanical properties and durability, solves the problem that the crushing value of the existing artificial aggregate ball is generally higher than 38wt%, resulting in weak compressive strength, poor durability and poor structural stability, and widens the application range of the material; by using industrial waste as raw material, the raw material cost is reduced, and the waste treatment cost is also reduced; the method includes simple cooling, crushing, dry mixing, water adding and curing steps, and is easy to realize industrial production; the cooling and crushing of steel slag are carried out at a relatively low temperature, reducing energy consumption and greenhouse gas emissions; by adjusting the water content of the mixture and the curing conditions, the performance of the final mixed aggregate can be controlled to meet different engineering requirements.

[0012] Preferably, in S1, the first temperature is 1500-1700℃.

[0013] Preferably, in S1, the second temperature is 80-100℃.

[0014] Preferably, in S1, the cooling speed is 50-100℃ / min.

[0015] By controlling the temperature and speed in the cooling process, the atomic arrangement of the cooled steel slag at high temperature is effectively promoted, so that the steel slag is not hydrated and has gel activity, thereby effectively reducing the crushing value of the mixed aggregate obtained by combining the steel slag with the lithium slag, and improving the compressive strength, durability and structural stability of the mixed aggregate. At the same time, through the ingenious design of the temperature and speed in the cooling process, the compressive strength, durability and structural stability of the mixed aggregate can be ensured without adding any other reagents or substances, not only reducing the production cost, but also improving the production efficiency, and further avoiding the possibility of secondary pollution to the environment caused by the addition of new reagents or substances, which has significant economic and environmental benefits.

[0016] Preferably, the composition of the non-hydrated and gel-active steel slag includes dicalcium silicate, tricalcium silicate, free calcium oxide, calcium ferrite, RO phase (FeO-MgO-MnO solid solution), etc.

[0017] Preferably, the composition of the lithium slag includes lithium oxide, calcium sulfate, calcium fluoride, iron oxide, sodium oxide, aluminum oxide and silicon dioxide.

[0018] Preferably, in S1, the particle size of the non-hydrated and gel-active steel slag is greater than or equal to 90wt% of the steel slag with a particle size of -80 mesh.

[0019] Among them, through experimental research, it is found that fine particles can accelerate hydration and improve gel activity due to high specific surface area, but too high proportion of superfine particles will cause shrinkage stress concentration; while coarse particles can form a mechanical interlocking structure, but the gel activity is low. Therefore, by accurately controlling the particle size range of the steel slag, the material performance of the mixed aggregate is effectively ensured.

[0020] Preferably, in S2, the water content of the lithium slag is less than or equal to 22wt%.

[0021] Preferably, in S2, the mass ratio of the lithium slag with a water content of 0 to the non-hydrated and gel-active steel slag is 1:1~1:1.5.

[0022] By accurately controlling the mass ratio of the lithium slag with a water content of 0 to the non-hydrated and gel-active steel slag, the lithium slag and the gel-active steel slag are more tightly bonded, and cracking is not caused; if the mass ratio is less than 1:1, the lithium slag and the steel slag are not tightly bonded; if the mass ratio is greater than 1:1.5, the mixed aggregate is prone to cracking in the later stage.

[0023] Among them, in order to facilitate calculation, the lithium slag with a water content of less than or equal to 22wt% is converted into lithium slag with a water content of 0 and non-hydrated and gel-active steel slag for mass conversion, and the actual processing process does not perform drying and other operations on the lithium slag with water content.

[0024] Preferably, in the S3, the curing mode is curing for 6-8 hours under the condition of temperature of 100-180 DEG C and pressure of 0.1-0.8 MPa, and then curing for 28 days under the condition of normal temperature and normal pressure.

[0025] By curing under the condition of temperature of 100-180 DEG C and pressure of 0.1-0.8 MPa, the hydration reaction of silicate in the mixed aggregate ball is effectively accelerated, so that the hydrate gradually fills the gap between the particles, forming a hard matrix, thereby effectively improving the strength and hardness of the mixed aggregate ball.

[0026] The curing process of curing for 6-8 hours under the condition of temperature of 100-180 DEG C and pressure of 0.1-0.8 MPa is carried out in a high-pressure autoclave.

[0027] Preferably, the steel slag is derived from Xinyu Iron and Steel Plant; and the lithium slag is derived from Jiangxi Guoxuan Kefeng New Material Co., Ltd. or Yichun Wanzai Times New Energy Co., Ltd.

[0028] Preferably, the content of thallium in the lithium slag leaching solution is greater than 20 ppb, and the content of beryllium is greater than 1 ppb; and the content of thallium in the mixed aggregate leaching solution is less than or equal to 5 ppb, and the content of beryllium is less than or equal to 0.5 ppb.

[0029] It is known through experiments that the lithium slag not combined with the steel slag is detected according to the toxicity leaching method, and it is found that the content of thallium in the lithium slag leaching solution is very high, and direct stacking can easily cause environmental pollution, and after being combined with the steel slag and the process condition being skillfully controlled, not only the mixed aggregate prepared has excellent crushing value, but also the heavy metals in the lithium slag are fixed, achieving the advantages of killing two birds with one stone.

[0030] The application further provides a mixed aggregate prepared by the preparation method.

[0031] The application further provides a mixed aggregate prepared by the preparation method as gravel used in concrete.

[0032] The application further provides a concrete comprising cement, fly ash, water, fine aggregate, coarse aggregate and water reducing agent.

[0033] The coarse aggregate is the mixed aggregate prepared by the preparation method.

[0034] Preferably, in the concrete, the amount of cement is 330-350 kg / m 3 , the amount of fly ash is 70-80 kg / m 3 , the amount of water is 160-200 kg / m 3 , and the amount of fine aggregate is about 700-800 kg / m 3The amount of coarse aggregate is about 1100-1200 kg / m 3 The amount of water reducing agent is about 5-7 kg / m 3 .

[0035] Preferably, the fine aggregate is selected from sand.

[0036] Preferably, the water reducing agent is selected from polycarboxylate-based water reducing agent, which includes polycarboxylic acid and ester polymer, the main chain is polyacrylic acid or methacrylic acid, and the side chain is polyoxyethylene ether (PEG).

[0037] The application further provides a preparation method of the concrete, comprising the following steps:

[0038] Mixing the coarse aggregate, the fine aggregate, the cement and the fly ash by dry mixing, then adding water and the water reducing agent, and continuously stirring to obtain a mixed slurry;

[0039] Layered pouring, vibrating and curing the mixed slurry to obtain the concrete.

[0040] Preferably, the curing mode is curing at normal temperature.

[0041] The concrete of the present application has the following advantages: 1) The lithium slag and steel slag have high hardness, which can improve the compressive strength and flexural strength of the concrete. The high strength characteristics of the steel slag can provide good skeletal support for the concrete, and the active ingredients of the lithium slag can react with the cement hydration products to further enhance the strength of the concrete. At the same time, the steel slag has a certain toughness, which can improve the anti-cracking performance of the concrete. The fine particles of the lithium slag can fill the micro-pores inside the concrete, reduce the stress concentration points, and thus improve the overall toughness of the concrete. 2) The particles of the lithium slag and steel slag are relatively dense, which can reduce the porosity inside the concrete and improve the impermeability of the concrete. At the same time, the pozzolanic activity of the lithium slag can generate more hydration products to fill the pores of the concrete, further reducing the permeability. The addition of lithium slag and steel slag can also improve the microstructure of the concrete, reducing the internal connected pores, thereby improving the frost resistance of the concrete. In the freezing and thawing cycle, the water inside the concrete is not easy to freeze and expand, reducing the freeze-thaw damage. And the steel slag contains a certain amount of calcium oxide and other ingredients, which can neutralize the acidic substances produced by sulfate attack, thereby improving the sulfate resistance of the concrete. 3) The particle shape and size distribution of the lithium slag and steel slag are reasonable, which can improve the fluidity of the concrete. Compared with traditional gravel or pebbles, the surface of the lithium slag and steel slag particles is relatively rough, which can improve the cohesiveness of the concrete and reduce the segregation phenomenon. At the same time, the fine particles of the lithium slag can absorb a certain amount of water, reducing the water loss of the concrete during mixing and transportation, thereby improving the water retention of the concrete and preventing bleeding. 4) The lithium slag and steel slag are both industrial waste, which can realize the recycling of resources, reduce the piling and landfill of waste, and reduce the pollution to the environment. At the same time, using lithium slag and steel slag as coarse aggregate can replace part of the natural aggregate, reducing the production cost of concrete. 5) The construction method of layered pouring and vibrating can ensure the compactness of the concrete and reduce internal defects. The high strength and high toughness characteristics of the lithium slag and steel slag make the concrete not easy to segregate during vibration, further improving the construction quality. At the same time, the active ingredients of the lithium slag and steel slag continue to react with the cement hydration products during curing to generate more hydration products, further improving the strength and durability of the concrete. 6) The fine particles of the lithium slag and steel slag can fill the micro-pores inside the concrete, making the microstructure of the concrete more dense. This densification effect can improve the impermeability, frost resistance and corrosion resistance of the concrete. At the same time, the lithium slag has a certain pozzolanic activity, which can react with calcium hydroxide in the cement hydration products to generate more calcium silicate gel, further improving the strength and durability of the concrete.

[0042] In summary, the preparation method of the concrete of the present application uses lithium slag and steel slag as coarse aggregate, which not only improves the mechanical properties and durability of the concrete, but also optimizes the workability of the concrete, and has significant environmental protection and economic advantages. It provides a new way for the resource utilization of industrial waste slag and has broad application prospects.

[0043] The present application has the following advantages:

[0044] The preparation method of the mixed aggregate based on steel slag and lithium slag of the present application uses industrial waste steel slag and lithium slag as raw materials to prepare mixed aggregate, which realizes the resource utilization of steel slag and lithium slag, reduces environmental pollution, and the mixed use of steel slag and lithium slag may give the mixed aggregate better mechanical properties and durability, solves the problem that the crushing value of the existing artificial aggregate ball is generally higher than 38wt%, which leads to weak compressive strength, poor durability and poor structural stability, and widens the application range of the material; by using industrial waste as raw material, the raw material cost is reduced, and the waste treatment cost is also reduced; the method includes simple cooling, crushing, dry mixing, water adding and curing steps, and is easy to realize industrial production; and high-pressure curing is an effective method to improve the strength of the aggregate ball. In the high-pressure curing process, the mixed aggregate ball is treated in a high-temperature and high-pressure environment, which can accelerate the hydration reaction of silicates, and these hydrates gradually fill the voids between the particles to form a hard matrix, thereby improving the strength and hardness. At the same time, the steel slag is crushed at a relatively low temperature, which reduces energy consumption and greenhouse gas emissions; by adjusting the water content of the mixed material and the curing conditions, the performance of the final mixed aggregate can be controlled to meet different engineering requirements, and the method has application value in the field of slag resource utilization application technology. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 A physical map of the mixed aggregate based on steel slag and lithium slag prepared by the method of the present application;

[0046] Figure 2 A physical map of the concrete prepared in Example 4;

[0047] Figure 3 A compression test result map of the concrete prepared in Example 4. DETAILED DESCRIPTION

[0048] Following, the embodiments of the present application will be described with reference to the preferred embodiments. Those skilled in the art can easily understand other advantages and functions of the present application from the contents disclosed in the present specification. The present application can be implemented or applied in other different specific embodiments, and the details in the present specification can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for illustrating the present application, but not for limiting the protection scope of the present application.

[0049] The present application intends to disclose a mixed aggregate based on steel slag and lithium slag, a preparation method and application thereof, so as to realize the resource utilization of steel slag and lithium slag.

[0050] The preparation method of the mixed aggregate based on steel slag and lithium slag comprises the following steps:

[0051] S1, cooling the steel slag under a first temperature condition to a second temperature, crushing to obtain the steel slag which is not hydrated and has a gel;

[0052] S2, dry mixing the lithium slag and the steel slag which is not hydrated and has a gel to obtain a mixed material, adding water to the mixed material so that the water content of the mixed material is 15-19wt%, to obtain a precursor material;

[0053] S3, granulating the precursor material and curing to obtain the mixed aggregate based on steel slag and lithium slag.

[0054] In some embodiments, in S1, the first temperature is 1500-1700℃.

[0055] In some embodiments, in S1, the second temperature is 80-100℃.

[0056] In some embodiments, in S1, the cooling speed is 50-100℃ / min.

[0057] In some embodiments, the components of the steel slag which is not hydrated and has a gel activity include dicalcium silicate, tricalcium silicate, free calcium oxide, calcium ferrite-aluminate, RO phase (FeO-MgO-MnO solid solution).

[0058] In some embodiments, the components of the lithium slag include lithium oxide, calcium sulfate, calcium fluoride, iron oxide, sodium oxide, aluminum oxide and silicon dioxide.

[0059] In some embodiments, in S1, the steel slag with a particle size of-80 mesh accounts for more than 90wt% in the steel slag which is not hydrated and has a gel activity.

[0060] In some embodiments, in S2, the water content of the lithium slag is less than or equal to 22wt%.

[0061] In some embodiments, in S2, the mass ratio of lithium slag with a water content of 0 to steel slag containing active substances is 1:1-1.5. Wherein, the lithium slag with a water content of 0 is the mass of the actual lithium slag minus the water content therein.

[0062] In some embodiments, in S3, the curing method is curing at a temperature of 100-180℃ and a pressure of 0.1-0.8 MPa for 6-8h, and then curing at normal temperature and pressure for 28 days.

[0063] Wherein, the curing process of curing at a temperature of 100-180℃ and a pressure of 0.1-0.8 MPa for 6-8h is carried out in a high-pressure autoclave.

[0064] In some embodiments, the steel slag is derived from Xinyu Iron and Steel Plant; and the lithium slag is derived from Jiangxi Guoxuan Kefeng New Material Co., Ltd. or Yichun Wanzai Times New Energy Co., Ltd.

[0065] In some embodiments, the thallium content in the lithium slag leaching solution is 26ppb, and the beryllium content is 1ppb; the thallium content in the mixed aggregate leaching solution is less than or equal to 5ppb, and the beryllium content is less than or equal to 0.5ppb.

[0066] In some embodiments, a mixed aggregate prepared by the preparation method is also provided.

[0067] In some embodiments, a mixed aggregate prepared by the preparation method is also provided as a gravel in concrete.

[0068] In some embodiments, a concrete is also provided, comprising cement, fly ash, water, fine aggregate, coarse aggregate and water reducing agent.

[0069] The coarse aggregate is a mixed aggregate prepared by the preparation method.

[0070] In some embodiments, in the concrete, the amount of cement is 330-350 kg / m 3 , the amount of fly ash is 70-80 kg / m 3 , the amount of water is 160-200 kg / m 3 , the amount of fine aggregate is about 700-800 kg / m 3 , the amount of coarse aggregate is about 1100-1200 kg / m 3 , and the amount of water reducing agent is about 5-7 kg / m 3 .

[0071] Wherein, the fine aggregate is selected from sand. The water reducing agent is selected from polycarboxylate type water reducing agent, which includes polycarboxylic acid and ester polymer thereof, the main chain is polyacrylic acid or methacrylic acid, and the side chain is polyoxyethylene ether (PEG).

[0072] In some embodiments, a method for preparing concrete is also provided, comprising the following steps:

[0073] mixing the coarse aggregate, the fine aggregate, the cement and the fly ash by dry mixing, then adding water and the water reducing agent, and continuously stirring to obtain a mixed slurry;

[0074] layer-casting the mixed slurry, vibrating, curing to obtain the concrete.

[0075] The curing mode is curing at room temperature.

[0076] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the preparation method of the mixed aggregate of steel slag and lithium slag will be further described in detail below in combination with specific embodiments and drawings. Obviously, the specific embodiments described are only part of the embodiments of the present application, rather than all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application. Based on the specific embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0077] Unless otherwise specified in the specific embodiments, the technology or conditions are carried out according to the technology or conditions described in the literature in the art or according to the product manual. The reagents or instruments used are not specified by the manufacturer, but are conventional products that can be obtained by purchase.

[0078] Embodiment 1

[0079] A preparation method of a mixed aggregate based on steel slag and lithium slag, comprising the following steps:

[0080] S1, cooling the steel slag under a first temperature condition to a second temperature, and crushing to obtain steel slag which is not hydrated and has gel activity, specifically comprising:

[0081] The steel slag with a temperature of 1600℃±5℃ is poured into a ladle lined with cast iron and magnesia insulation material, and is cooled to 90℃ in air at a cooling rate of 75℃ / min, and is ground to obtain steel slag with a particle size of 90wt% of -80 mesh, which is unhydrated and has gel activity; wherein the steel slag is from Xinyu Iron and Steel Plant, and the composition of the steel slag mainly includes CaO, MgO, SiO2, FeO, and a small amount of P2O5 and Al2O3, and the steel slag is composed of complex compounds of these substances. The contents of Ca, Mg, Fe and Al are determined by atomic absorption spectrophotometry, and then converted into CaO, MgO, FeO and Al2O3 respectively; the content of SiO2 is determined by the silicon molybdenum blue method; the content of P2O5 is determined by the ammonium phosphomolybdate spectrophotometric method. After detection, the content of CaO is 39.23wt%, the content of MgO is 4.76wt%, the content of FeO is 21.35wt%, the content of SiO2 is 22.13wt%, the content of P2O5 is 0.87wt%, the content of Al2O3 is 2.45wt% and other trace substances; the unhydrated and gel active steel slag includes dicalcium silicate, tricalcium silicate, free calcium oxide and calcium aluminate.

[0082] S2, dry mixing the lithium slag and the unhydrated and gel active steel slag to obtain a mixture, and adding water to the mixture to obtain a precursor material, the specific steps including:

[0083] The lithium slag with a water content of 22wt% is uniformly dry mixed with the unhydrated and gel active steel slag to obtain a mixture, and water is sprayed into the mixture to control the total water content in the mixture to 17wt% to obtain a precursor material; wherein the mass ratio of the lithium slag with a water content of 0 to the unhydrated and gel active steel slag is 1:1.25, the lithium slag is from Jiangxi Guoxuankefeng New Material Co., Ltd., and the composition of the lithium slag includes 52.32wt% of silicon dioxide, 23.21wt% of Al2O3, 8.21wt% of CaF2, 5.12wt% of Fe2O3, 3.54wt% of CaSO4, 2.12wt% of Na2O and other trace substances;

[0084] S3, granulating and curing the precursor material to obtain a mixed aggregate based on the steel slag and the lithium slag, the specific steps including:

[0085] A template with fixed-diameter holes is arranged inside the roller granulator, the precursor material is poured into the roller granulator, a mixture of mixed aggregates and powdery material based on steel slag and lithium slag with a diameter of 4 mm is obtained, after screening, the powdery material is returned to the granulation, then the obtained mixed aggregates with a diameter of 4 mm are loaded into a high-pressure autoclave with a temperature of 100 DEG C and a pressure of 0.1 MPa for 7 hours of curing, then cured for 28 days under normal temperature and pressure conditions, and after hardening, mixed aggregates based on steel slag and lithium slag are obtained, which can replace gravel in concrete.

[0086] Example 2

[0087] A preparation method of mixed aggregates based on steel slag and lithium slag, comprising the following steps:

[0088] S1, cooling the steel slag under the first temperature condition to a second temperature, crushing to obtain unhydrated and gel active steel slag, specifically comprising:

[0089] Pour the steel slag with a temperature of 1700 DEG C ± 5 DEG C into a ladle lined with cast iron magnesium oxide insulation material, and cool to 100 DEG C at a cooling rate of 100 DEG C / min in air, crush and grind, so that the steel slag with a particle size of -80 mesh accounts for 93wt%, to obtain unhydrated and gel active steel slag; wherein the steel slag is derived from Xinyu Iron and Steel Plant, and the composition of the steel slag is the same as that in Example 1;

[0090] S2, dry mixing lithium slag and unhydrated and gel active steel slag to obtain a mixture, adding water to the mixture to make the water content of the mixture 15-19wt%, to obtain a precursor material, specifically comprising:

[0091] Dry mix lithium slag with a water content of 12wt% and unhydrated and gel active steel slag uniformly, and spray water into the mixture, control the total water content in the mixture to be 19wt%, to obtain a precursor material; wherein the mass ratio of lithium slag with a water content of 0 to unhydrated and gel active steel slag is 1:1.5, the lithium slag is derived from Jiangxi Guoxuankefeng New Material Co., Ltd., and the composition of the lithium slag is the same as that in Example 1;

[0092] S3, curing after granulating the precursor material to obtain mixed aggregates based on steel slag and lithium slag, specifically comprising:

[0093] A template with fixed-diameter holes is arranged inside the roller granulator, the precursor material is poured into the roller granulator, a mixture of mixed aggregates and powdery material based on steel slag and lithium slag with a diameter of 4 mm is obtained, after screening, the powdery material is returned to the granulation, then the obtained mixed aggregates with a diameter of 4 mm are loaded into a high-pressure autoclave with a temperature of 180 DEG C and a pressure of 0.8 MPa for 8 hours of curing, then cured for 28 days under normal temperature and pressure conditions, and after hardening, the mixed aggregates based on steel slag and lithium slag are obtained, which can replace the gravel in concrete.

[0094] Example 3

[0095] A preparation method of mixed aggregates based on steel slag and lithium slag, comprising the following steps:

[0096] S1, cooling the steel slag under the first temperature condition to a second temperature, crushing to obtain unhydrated and gel active steel slag, specifically comprising:

[0097] Pour the steel slag with a temperature of 1500 DEG C ± 5 DEG C into a ladle lined with cast iron magnesium oxide insulation material, and cool it to 100 DEG C at a cooling rate of 100 DEG C / min in air, crush and grind, so that the steel slag with a particle size of -80 mesh accounts for 95wt%, to obtain unhydrated and gel active steel slag; wherein the steel slag is derived from Xinyu Iron and Steel Plant, and the composition of the steel slag is the same as that in Example 1;

[0098] S2, dry mixing lithium slag and unhydrated and gel active steel slag to obtain a mixture, adding water to the mixture to make the water content of the mixture 15-19wt%, to obtain a precursor material, specifically comprising:

[0099] Dry mix lithium slag with a water content of 0wt% and unhydrated and gel active steel slag uniformly to obtain a mixture, spray water into the mixture, control the total water content in the mixture to be 15wt%, to obtain a precursor material; wherein the mass ratio of lithium slag with a water content of 0 to steel slag is 1:1.0, the lithium slag is derived from Jiangxi Guoxuankefeng New Material Co., Ltd., and the composition of the lithium slag is the same as that in Example 1;

[0100] S3, curing after granulating the precursor material to obtain mixed aggregates based on steel slag and lithium slag, specifically comprising:

[0101] A template with fixed-diameter holes is arranged inside the roller granulator, the precursor material is poured into the roller granulator, a mixture of mixed aggregates and powdery material based on steel slag and lithium slag with a diameter of 4 mm is obtained, after screening, the powdery material is returned to the granulation, then the obtained mixed aggregates with a diameter of 4 mm are loaded into a high-pressure autoclave with a temperature of 140 DEG C and a pressure of 0.4 MPa for 6 hours of curing, then cured for 28 days under normal temperature and pressure conditions, and after hardening, mixed aggregates based on steel slag and lithium slag are obtained, which can replace the gravel in concrete.

[0102] Example 4

[0103] A method for preparing concrete, comprising the following steps:

[0104] The mixed aggregates based on steel slag and lithium slag obtained after hardening in Example 1 are used as coarse aggregate, sand is used as fine aggregate, cement and fly ash are mixed and dry-mixed, then water and polycarboxylate-based superplasticizer are added, and continuous stirring is performed to obtain a mixed slurry;

[0105] In the concrete, the amount of cement is 340 kg / m 3 , the amount of fly ash is 70 kg / m 3 , the amount of water is 180 kg / m 3 , the amount of fine aggregate is 750 kg / m 3 , the amount of coarse aggregate is 1100 kg / m 3 , and the amount of polycarboxylate-based superplasticizer is 6 kg / m 3 .

[0106] The mixed slurry is poured in layers, each layer has a thickness of 25 cm, a vibrator is used to vibrate the concrete to remove air bubbles in the concrete and make the concrete more dense, and after water curing at room temperature for 28 days, the physical map of the obtained concrete is as shown in Figure 2 .

[0107] Comparative Example 1

[0108] A method for preparing mixed aggregates based on steel slag and lithium slag, comprising the following steps:

[0109] S1, cooling the steel slag under the first temperature condition to a second temperature, crushing to obtain unhydrated steel slag with gel activity, specifically comprising:

[0110] The steel slag with a temperature of 1600 DEG C ± 5 DEG C is poured into a ladle lined with cast iron magnesium oxide insulation material, and cooled to 90 DEG C at a cooling rate of 75 DEG C / min in air, and then crushed and ground to make the steel slag with a particle size of -80 mesh accounting for 90wt%, to obtain unhydrated steel slag with gel activity; wherein the steel slag is derived from Xinyu Iron and Steel Plant, and the composition of the steel slag is the same as that of Example 1.

[0111] S2, dry-mixing the lithium slag and the steel slag which is not hydrated and has gel activity to obtain a mixed material, adding water to the mixed material so that the water content of the mixed material is 15-19 wt%, to obtain a precursor material, specifically comprising:

[0112] uniformly dry-mixing the lithium slag with a water content of 22 wt% with the steel slag cement to obtain a mixed material, spraying water into the mixed material, and controlling the total water content in the mixed material to be 17 wt% to obtain a precursor material; wherein the mass ratio of the lithium slag with a water content of 0 to the steel slag is 1:0.5, the lithium slag is from Jiangxi Guoxuankefeng New Material Co., Ltd., and the composition of the lithium slag is the same as in Example 1;

[0113] S3, curing the precursor material after granulation to obtain a mixed aggregate based on the steel slag and the lithium slag, specifically comprising:

[0114] A template with fixed-diameter pores is arranged inside the roller granulator, the precursor material is poured into the roller granulator to obtain a mixture of the mixed aggregate based on the steel slag and the lithium slag with a diameter of 4 mm and a powdery material, after screening, the powdery material is returned to granulation, and the obtained mixed aggregate based on the steel slag and the lithium slag is cured in a high-pressure autoclave at a temperature of 100°C and a pressure of 0.1 MPa for 7 hours, and then cured at room temperature for 28 days, to obtain a mixed aggregate which can replace gravel in concrete after hardening.

[0115] Comparative Example 2

[0116] A preparation method of a mixed aggregate based on steel slag and lithium slag, comprising the following steps:

[0117] S1, cooling the steel slag under a first temperature condition to a second temperature, and crushing to obtain steel slag containing active substances, specifically comprising:

[0118] The steel slag with a temperature of 1700°C±5°C is poured into a ladle lined with cast iron and magnesium oxide heat preservation material, and cooled in air at a cooling rate of 100°C / min to 100°C, and ground so that the steel slag with a particle size of -80 mesh accounts for 93 wt% in the steel slag to obtain steel slag containing active substances; wherein the steel slag is from Xinyu Iron and Steel Plant, and the composition of the steel slag is the same as in Example 1;

[0119] S2, dry-mixing the lithium slag and the steel slag containing active substances to obtain a mixed material, adding water to the mixed material so that the water content of the mixed material is 15-19 wt%, to obtain a precursor material, specifically comprising:

[0120] The lithium residue with a water content of 12wt% is uniformly dry-mixed with the steel slag cement to obtain a mixture, and water is sprayed into the mixture to control the water content of the mixture to be 19wt% to obtain a precursor material; wherein the mass ratio of the lithium residue with a water content of 0 to the steel slag is 1:1.5, the lithium residue is from Jiangxi Guoxuan Kefeng New Material Co., Ltd., and the composition of the lithium residue is the same as in Example 1;

[0121] S3, curing the precursor material after granulation to obtain a mixed aggregate based on steel slag and lithium residue, specifically comprising:

[0122] A template with fixed-diameter pores is arranged inside the roller granulator, the precursor material is poured into the roller granulator to obtain a mixture of the mixed aggregate based on steel slag and lithium residue (for example, with a diameter of 4mm) and powdery material, after screening, the powdery material is returned to granulation, and the mixed aggregate based on steel slag and lithium residue is cured in a reaction kettle at a temperature of 25°C and a pressure of 0.1MPa for 8 hours, and then cured at room temperature for 28 days, to obtain a mixed aggregate that can replace gravel in concrete after hardening.

[0123] Comparative Example 3

[0124] A method for preparing a mixed aggregate based on steel slag and lithium residue, comprising the following steps:

[0125] S1, cooling the steel slag under a first temperature condition to a second temperature, and crushing to obtain steel slag containing active substances, specifically comprising:

[0126] The steel slag with a temperature of 1500°C±5°C is poured into a ladle lined with cast iron and magnesium oxide heat preservation material, and cooled in air at a cooling rate of 5°C / min to 100°C, and ground to make the steel slag with a particle size of -80 mesh account for 95wt% in the steel slag to obtain steel slag containing active substances; wherein the steel slag is from Xinyu Iron and Steel Plant, and the composition of the steel slag, CaO, MgO, FeO, SiO2, P2O5, Al2O3 and other trace substances, is the same as in Example 1; however, because the cooling rate is too slow, the steel slag cannot retain the microstructure under high temperature, resulting in poor cementitious properties of the steel slag;

[0127] S2, dry-mixing the lithium residue and the steel slag containing active substances to obtain a mixture, and adding water to the mixture to make the water content of the mixture be 15-19wt% to obtain a precursor material, specifically comprising:

[0128] The lithium residue with a water content of 0wt% is uniformly dry-mixed with the steel slag cement to obtain a mixture, and water is sprayed into the mixture to control the water content of the mixture to be 15wt% to obtain a precursor material; wherein the mass ratio of the lithium residue with a water content of 0 to the steel slag is 1:1.0, the lithium residue is from Jiangxi Guoxuan Kefeng New Material Co., Ltd., and the composition of the lithium residue is the same as in Example 1;

[0129] S3, curing the precursor material after granulation to obtain a mixed aggregate based on steel slag and lithium slag, specifically comprising:

[0130] A template with fixed-diameter holes is arranged inside the roller granulator, the precursor material is poured into the roller granulator to obtain a mixture of mixed aggregate based on steel slag and lithium slag (for example, with a diameter of 4 mm) and powdery material, after screening, the powdery material is returned to granulation, and the mixed aggregate based on steel slag and lithium slag is cured in a high-pressure autoclave at a temperature of 140°C and a pressure of 0.4 MPa for 6 hours, and then cured at room temperature for 28 days, and the hardened mixed aggregate can replace gravel in concrete.

[0131] Detection analysis

[0132] 1) Crushing value test of mixed aggregate

[0133] The specific operation steps are: the mixed aggregate prepared in Examples 1 to 3 and Comparative Examples 1 to 3 is subjected to crushing value test.

[0134] Sample preparation: the sample is dried in an oven, the oven temperature should not exceed 100°C, and the drying time should not exceed 4 hours. After cooling to room temperature, sieve using 13.2 mm and 9.5 mm standard sieves, and take 3 groups of 9.5 mm-13.2 mm samples, each group about 3000g.

[0135] Sample treatment: the sample is divided into 3 equal parts and loaded into the test mold, the surface of the sample is leveled each time, and the hemispherical end of the metal rod is used to evenly tamp the surface of the stone 25 times. Finally, the surface is carefully leveled with a metal rod as a straight scraper.

[0136] Press operation: place the test mold containing the sample on the press, and at the same time, place the pressure head on the stone surface in the test cylinder, pay attention to make the pressure head flat, and do not wedge the test mold side wall. Start the press and apply the load evenly, reach the total load of 400 kN in about 10 minutes, and unload after 5 seconds of stable pressure.

[0137] Screening and weighing: remove the test mold from the press and take out the sample. Screen the crushed entire sample using a 2.36 mm standard sieve, which can be screened several times, and all need to be screened until there is no obvious sieve in 1 minute. Weigh the mass of the fine aggregate passing through the 2.36 mm sieve (m1), accurate to 1 g.

[0138] Result calculation: the stone crushing value calculation formula is: q n = m1 / m0, where qn is the crushing value, m1 is the mass of fine aggregate passing through the sieve, and m0 is the original mass of the sample.

[0139] The arithmetic average of the results of three parallel tests is taken as the measured value of the crushing value.

[0140] These steps ensure the accuracy and consistency of the crushing value test, which is suitable for evaluating the crushing resistance of coarse aggregate.

[0141] The results are shown in Table 1.

[0142] Table 1 Crushing values in Examples 1 to 3 and Comparative Examples 1 to 3

[0143]

[0144] Table 2 Crushing values of coarse aggregate and applicable highway types

[0145]

[0146] From the analysis of Table 1 and Table 2, it can be seen that in Comparative Example 1, the mass ratio of lithium slag to steel slag with water content of 0 is 1:0.5, and the proportion of steel slag is low, and the active substance is less, so the crushing value is 40%, which just meets the requirement of the crushing value of the sub-base of secondary and below secondary highway. In Comparative Example 2, the mixed aggregate prepared initially is cured at room temperature, and the crushing value is 38%, which is higher than that of Example 2, but it still meets the requirement of the crushing value of secondary and below secondary highway. In Comparative Example 3, the cooling speed of steel slag is too slow, causing complete transformation of the crystal form of the cooled steel slag, so the activity is not high, resulting in a crushing value of 51%, which is too high to meet the requirements of secondary and below secondary highway.

[0147] The crushing values of the mixed aggregates in Examples 1 to 3 are all below 35%, and the products can meet the standards of secondary and below secondary highway, and can be used to replace the gravel used for paving, with broad application prospects.

[0148] 2) Determination of thallium and beryllium content

[0149] The specific operation steps are: toxic leaching test is carried out on the lithium slag used in Examples 1 to 6 and the mixed aggregate prepared, and the thallium and beryllium content in the leaching solution is tested.

[0150] The results are shown in Table 3.

[0151] Table 3 Thallium and beryllium content in toxic leaching solution

[0152]

[0153] Analysis of Table 3 shows that the thallium and beryllium contents in the toxic leachate of the mixed aggregates in Examples 1 to 3 are significantly lower than those in the lithium slag, and the thallium content in the toxic leachate of the mixed aggregates in Examples 1 to 3 is less than 5 ppb. In Comparative Example 1, the mass ratio of lithium slag with zero water content to steel slag is 1:0.5, with a lower proportion of steel slag and less active material; the thallium content in the toxic leachate is 5.45 ppb. In Comparative Example 2, the mixed aggregates were initially cured at room temperature, and the thallium content in the toxic leachate is 4.89 ppb. In Comparative Example 3, the steel slag cooled too slowly, resulting in a more complete crystal transformation after cooling, thus leading to low activity; the thallium content in the toxic leachate is 9.32 ppb. These data indicate that the activity of steel slag is the most significant factor affecting the thallium content in the toxic leachate.

[0154] 3) Compressive strength test

[0155] The concrete specimens cured in Example 4 were placed on a testing machine. The loading speed and loading method of the testing machine were adjusted to constant speed loading, with a loading rate of 0.3 MPa / s to 0.5 MPa / s. The measured compressive strength results are as follows: Figure 3 As shown.

[0156] from Figure 3 Analysis shows that the maximum compressive strength of the concrete specimens prepared in Example 4 is 29.6 MPa, which proves that the concrete prepared by the present invention has good compressive strength, is suitable for general building structures and components, and can meet the design requirements of most common building structures.

[0157] In summary, the method for preparing mixed aggregate based on steel slag and lithium slag of the present invention utilizes industrial waste steel slag and lithium slag as raw materials to prepare mixed aggregate, thereby realizing the resource utilization of steel slag and lithium slag, reducing environmental pollution. Furthermore, the mixed use of steel slag and lithium slag may impart better mechanical properties and durability to the mixed aggregate, broadening the application range of the material. Using industrial waste as raw material reduces raw material costs and waste disposal expenses. The method includes simple cooling, crushing, dry mixing, water addition, and curing steps, making it easy to implement industrial production. Crushing the steel slag at relatively low temperatures reduces energy consumption and greenhouse gas emissions. By adjusting the moisture content and curing conditions of the mixture, the performance of the final mixed aggregate can be controlled to meet different engineering needs, making it valuable for widespread application in the field of slag resource utilization technology.

[0158] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for preparing a mixed aggregate based on steel slag and lithium slag, characterized in that, The mixed aggregate is composed of steel slag and lithium slag; The preparation method comprises the following steps: S1, cooling the steel slag under a first temperature condition to a second temperature, crushing to obtain the steel slag which is not hydrated and has gel activity; S2, dry mixing the lithium slag and the steel slag which is not hydrated and has gel activity to obtain a mixture, adding water to the mixture so that the water content of the mixture is 15-19wt%, to obtain a precursor material, and the mass ratio of the lithium slag which has no water content to the steel slag which is not hydrated and has gel activity is 1:1-1:1.5; S3, granulating the precursor material and curing to obtain the mixed aggregate based on the steel slag and the lithium slag; In the S1, the first temperature is 1500-1700℃; In the S1, the second temperature is 80-100℃; In the S1, the cooling speed is 50-100℃ / min; The thallium content in the lithium slag leaching solution is greater than 20 ppb, and the beryllium content is greater than 1 ppb; The thallium content in the mixed aggregate leaching solution is less than or equal to 5 ppb, and the beryllium content is less than or equal to 0.5 ppb; By controlling the temperature and speed in the cooling process, the atomic arrangement of the cooled steel slag under high temperature is effectively promoted, so that the steel slag is not hydrated and has gel activity, thereby effectively reducing the crushing value of the mixed aggregate obtained by combining the steel slag and the lithium slag, and improving the compressive strength, durability and structural stability of the mixed aggregate. At the same time, through the ingenious design of the temperature and speed in the cooling process, the compressive strength, durability and structural stability of the mixed aggregate can be ensured without adding any other reagents or substances.

2. The production method according to claim 1, characterized by, The components of the steel slag which is not hydrated and has gel activity include dicalcium silicate, tricalcium silicate, free calcium oxide, calcium ferrite-aluminate and FeO-MgO-MnO solid solution; And / or, the components of the lithium slag include lithium oxide, calcium sulfate, calcium fluoride, iron oxide, sodium oxide, aluminum oxide and silicon dioxide; And / or, in the S1, the particle size of the steel slag which is not hydrated and has gel activity is greater than or equal to 90wt% of the steel slag with a particle size of-80 mesh.

3. The preparation method according to claim 1, characterized in that, In the S2, the water content of the lithium slag is less than or equal to 22wt%.

4. The production method according to claim 1, characterized by, In the S3, the curing mode is to cure for 6-8h under the conditions of a temperature of 100-180℃ and a pressure of 0.1-0.8MPa, and then to cure for 28 days under the conditions of normal temperature and normal pressure.

5. A mixed aggregate prepared by the preparation method of any one of claims 1-4.

6. Use of the mixed aggregate produced according to the method of any one of claims 1 to 4, characterized in that, The mixed aggregate is used as gravel in concrete.

7. A concrete, characterized by The cement, fly ash, water, fine aggregate, coarse aggregate and water reducing agent are mixed and dry-mixed, and then water and water reducing agent are added, and the mixture is continuously stirred to obtain a mixed slurry; The coarse aggregate, fine aggregate, cement and fly ash are mixed and dry-mixed, and then water and water reducing agent are added, and the mixture is continuously stirred to obtain a mixed slurry; 8. A method of producing concrete as claimed in claim 7, characterised in that, The mixed slurry is layered and poured, vibrated and cured to obtain the concrete. ​ ​

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