Alkali-activated steel slag and slag curing agent and method for preparing road base material by using same

Abstract

The invention belongs to the technical field of curing of muck, and discloses an alkali-activated steel slag and slag curing agent which is prepared from the following components in percentage by weight: 80-90% of muck, 5-10% of steel slag, 5-10% of slag and CaO. CaO which is low in cost and remarkably low in carbon emission is adopted as an exciting agent, alkali-activated steel slag and slag are prepared to serve as a soil curing agent, key performance indexes such as mechanical strength and water-resistant stability of a cured soil body are effectively improved, high-added-value resource utilization of three types of bulk industrial solid waste including steel slag, slag and muck is achieved, and the method is suitable for industrial production. By optimizing the material ratio and the excitation process, the carbon footprint in the traditional curing material production process is greatly reduced while the production cost is remarkably reduced, and remarkable synergistic improvement of economic benefits and environmental benefits is formed, so that the cured soil material shows more excellent performance suitability in the field of road base application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of slag solidification, and particularly relates to an alkali-activated steel slag and mineral slag solidifying agent and a method for preparing a road base material. BACKGROUND

[0002] In recent years, the rapid economic development in China has driven a large amount of infrastructure construction, which has generated a huge amount of construction waste, with a total stock of 20 billion tons and an annual increase of about 3.5 billion tons, accounting for about 40% of the total amount of urban solid waste. Construction slag is the main construction waste, accounting for about 70% of the total mass.

[0003] At present, the main treatment method for slag in the industry is landfill, which not only wastes land resources but also causes environmental pollution. Only a small part of the slag is treated by solidification and used as road materials. In response to the overall policy of energy conservation and environmental protection and solid waste recycling, it is urgent to treat a large amount of engineering slag on a large scale and with high quality. The solidification methods of slag are usually divided into physical methods and chemical methods. The physical methods mainly include mechanical compaction, electrical treatment and thermal treatment, which can change the physical properties of slag to affect the grading, firmness and other properties of slag. The chemical method is to change the properties of slag by adding chemical active materials, which can be called solidifying agent, and is mainly divided into ion type, colloid type and biological enzyme solidifying agent. The performance of slag improved by the physical method is very limited. The ion type and biological enzyme solidifying agent in the chemical method can effectively improve the performance of slag but the cost is very high. The colloid type solidifying agent mainly includes cement, lime and fly ash, which are cheap and widely available, but have significant shortcomings. The early strength of the solidified soil is low, the water resistance is poor, the late volume stability is poor, and it is difficult to meet the application requirements. In addition, although the alkali-activated cementitious material solidifying agent currently promoted has good solidification effect, the commonly used precursor mineral slag has a price comparable to cement in some areas of China, and the activator used is water glass and sodium hydroxide with high cost and high carbon emission. Such activator needs to be prepared as a solution during use, and the solution has high alkalinity and high risk during use. Therefore, it needs to be improved. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides an alkali-activated steel slag and mineral slag solidifying agent and a method for preparing a road base material, which has the advantages of good mechanical properties, low cost and low carbon emission.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solution: an alkali-activated steel slag and mineral slag solidifying agent, the formula of which is composed of the following components: slag, steel slag, mineral slag and CaO, which are proportioned by weight percentage as follows: 80% to 90% of slag, 5% to 10% of steel slag, and 5% to 10% of mineral slag.

[0006] Preferably, the content of CaO is 20% of the total mass of steel slag and mineral slag, and the purity of CaO needs to be greater than or equal to 90%.

[0007] A method for preparing a road base material by using a steel slag and a mineral slag solidified by alkali activation, and the specific steps are as follows:

[0008] Step one: raw material preparation and pretreatment

[0009] Slag soil treatment: use a ball mill to grind the slag soil to a particle size of ≤2 mm, increase its specific surface area, and improve the contact efficiency with the cementitious material. Then, screen out the unground large particles through a 2 mm square hole screen to ensure uniformity of the slag soil particles and avoid the influence of coarse particles on material density. Finally, dry the slag soil to a moisture content of less than 1% to prevent residual moisture from interfering with the subsequent cementation reaction;

[0010] Steel slag and mineral slag treatment: dry to a moisture content of less than 1% to avoid introducing additional moisture that affects the accuracy of the proportioning;

[0011] CaO treatment: use industrial-grade calcium oxide, and the CaO needs to be prepared into powder through a grinding process to ensure uniformity of mixing and prevent local high alkalinity from causing volume expansion;

[0012] Step two: proportioning design and calculation

[0013] The slag soil, steel slag, and mineral slag are in a mass percentage of 80% to 90% slag soil, 5% to 10% steel slag, and 5% to 10% mineral slag. The CaO addition is 20% of the total mass of the steel slag and mineral slag, and the ratio of water to the total mass of solids (slag soil + steel slag + mineral slag + CaO) is 0.21;

[0014] Step three: mixing and molding process

[0015] Mixing sequence: first, put the slag soil, steel slag, and mineral slag into the mixer according to the proportion and dry mix for 3 minutes, then add CaO and continue to dry mix for 2 minutes to ensure uniform dispersion of CaO, and then add water and stir;

[0016] Step four: sample preparation and curing

[0017] Sample preparation: take the mixed mixture into a square mold, and use a hydraulic machine to press the test piece at a pressure of 15 MPa, with a pressure holding time of 30 seconds;

[0018] Curing: immediately wrap the test piece with double preservative film after molding, cover the outer layer with a wet cloth to prevent water evaporation, set the temperature of the curing box to 20±2℃, and the relative humidity to >95%, and cure for 7 days and 28 days respectively. Avoid vibration or temperature fluctuations during the curing period to ensure stable production of reaction products;

[0019] Step five: performance testing

[0020] According to the "Soil Solidification Admixture" (CJT486-2015), test the unconfined compressive strength and water stability coefficient of the solidified soil.

[0021] Preferably, the material in step two is 1m 3 Taking the amount of road base material as an example, only the cost used in the production stage is calculated, and the carbon dioxide emission is calculated based on the calculation boundary, and the total carbon emission in the production stage is calculated according to the following formula:

[0022]

[0023] In the formula, Em is the total carbon emission in the production stage, and the unit is kgCO2; Mi is the consumption of the ith material, and the unit is kg; Fi is the carbon emission factor of the ith material, and the unit is kgCO2 / kg.

[0024] Preferably, the stirring speed in step three is 30 to 50 r / min.

[0025] Preferably, in step four, the surface of the test piece is sprayed with atomized water every 24 hours during the curing period, and the spraying amount is 1% of the mass of the test piece, so as to maintain the constant wet cloth humidity.

[0026] Preferably, in step three, the CaO should be added in a quantitative and uniform speed, and the CaO is put into the stirrer by means of the continuous operation of the stirrer, so as to realize uniform dispersion of the CaO in the mixing system.

[0027] Preferably, in step one, the steel slag needs to be crushed in advance, and then dried to make the water content of the steel slag less than 1%, so as to avoid introducing additional water to affect the accuracy of the proportioning.

[0028] Preferably, in step three, the water is added in three equal amounts, and the stirring time after each water addition is not less than 1 minute and not more than 2 minutes, and after the stirring is completed, the mixture is placed for 5 minutes before sampling, so as to reduce the internal bubbles of the mixture.

[0029] Compared with the prior art, the beneficial effects of the present application are as follows:

[0030] CaO with low cost and significantly lower carbon emission is used as an activator to prepare alkali-activated steel slag and slag as a soil solidifying agent, which not only effectively improves the key performance indicators such as mechanical strength and water stability of the solidified soil body, but also realizes high-value resource utilization of three types of industrial solid waste, i.e., steel slag, slag and slag soil, through optimization of material proportioning and activation process, significantly reduces the carbon footprint in the production process of traditional solidifying materials, forms significant economic and environmental benefits, and makes the solidified soil material exhibit more excellent performance adaptability in the field of road base. DETAILED DESCRIPTION

[0031] All other embodiments obtained by one of ordinary skill in the art without creative work based on the embodiments of the present application shall fall within the scope of protection of the present application.

[0032] Embodiment one

[0033] The embodiment of the present application provides a kind of alkali-activated steel slag and slag solidification agent, formula is composed of following components: slag, steel slag, slag and CaO, it is proportioned by weight percentage as follows: slag 90%, steel slag 5%, slag 5%.

[0034] Using CaO as activator, prepare alkali-activated steel slag and slag as soil solidification agent, not only effectively improve the key performance indicators such as mechanical strength, water stability of solidified soil, more realize the high value-added resource utilization of steel slag, slag and slag three kinds of bulk industrial solid waste.

[0035] Wherein, CaO content is 20% of the total mass of steel slag and slag, and the purity of CaO needs to be greater than or equal to 90%.

[0036] CaO as activator has multiple advantages in alkali-activated steel slag and slag cementitious material solidified slag: the strong alkaline environment (high pH value) generated by its contact with water not only directly provides a large amount of Ca 2+ Cations, replace water molecules adsorbed on the surface of slag particles through cation exchange mechanism, reduce the particle spacing to Below, Van der Waals force dominates and promotes particle flocculation and coalescence, significantly reduces specific surface area and water affinity, and enhances overall connectivity of slag; at the same time, the alkaline conditions activated by CaO can efficiently activate active silicate and aluminate in steel slag and slag, promote the system to generate uniform and dense C-(A)-S-H gel, fully fill the soil pores, and combine with the synergistic strengthening effect of calcite and mullite crystals, greatly improve the mechanical strength and water stability of solidified soil; in addition, the synergistic effect of high concentration Ca 2+ , Al 3+ and other multivalent cations and high pH value further optimizes ion exchange efficiency, ensures that the solidification effect is significantly better than single activation system.

[0037] A method for preparing road base material using alkali-activated steel slag and slag solidification agent, the specific steps are as follows:

[0038] Step one: raw material preparation and pretreatment

[0039] Slag treatment: use a ball mill to grind the slag to a particle size of ≤2mm, increase its specific surface area, and improve the contact efficiency with cementitious materials, then screen out large particles that have not been ground through a 2mm square hole screen, to ensure uniformity of slag particles and avoid affecting material density due to coarse particles, finally dry the slag to a moisture content of less than 1% to prevent residual moisture from interfering with subsequent cementation reaction;

[0040] Steel slag treatment: dry to a moisture content of less than 1% to avoid introducing additional moisture affecting the accuracy of the proportioning;

[0041] CaO treatment: industrial-grade calcium oxide is used. The CaO needs to be prepared into powder through a grinding process to ensure uniform mixing and prevent local alkali content from being too high, causing volume expansion;

[0042] Control group A material treatment: dry cement and slag soil to a moisture content of less than 1%;

[0043] Step two: proportioning design and calculation

[0044] Slag soil, steel slag, and slag are mixed in a mass percentage of 90% slag soil, 5% steel slag, and 5% slag. The CaO addition is 20% of the total mass of steel slag and slag. The water to solid ratio is 0.21, with the total mass of slag soil, steel slag, slag, and CaO.

[0045] Control group A: the mass ratio of slag soil and cement is 90:10, and the water to solid ratio is 0.21, with the total mass of slag soil and cement.

[0046] Step three: mixing and molding process

[0047] Mixing sequence: first, mix the slag soil, steel slag, and slag in the proportioning machine for 3 minutes, then add CaO and continue to mix for 2 minutes to ensure uniform dispersion of CaO, and then add water and stir.

[0048] Control group A: first, mix the slag soil and cement in the proportioning machine for 3 minutes, then add the designed amount of water and stir for at least 3 minutes.

[0049] Step four: sample preparation and curing

[0050] Sample preparation: place the mixed mixture into a square mold and press the test piece with a hydraulic machine at a pressure of 15 MPa for 30 seconds.

[0051] Curing: immediately wrap the test piece with double-layer cling film after molding, cover the outer layer with a wet cloth to prevent water evaporation, set the curing box temperature to 20±2℃, and the relative humidity to >95%. Curing for 7 days and 28 days, respectively, avoid vibration or temperature fluctuations during curing to ensure stable product formation.

[0052] Step five: performance testing

[0053] According to the "Soil Solidification Admixture" (CJT486-2015), test the unconfined compressive strength and water stability coefficient of the solidified soil.

[0054] The unconfined compressive strength and water stability coefficient test results are shown in the following table:

[0055]

[0056] From the data in the table, it can be seen that the unconfined compressive strength and water stability coefficient of alkali-activated steel slag and slag solidified soil increase with the increase of steel slag and slag content, and meet the relevant requirements of "Highway Subgrade Construction Specification" (JTG / T3610-2019), and the results are better than that of cement solidified soil.

[0057] In step two, the material is 1m 3 Taking the amount of road base material as an example, only the cost used in the production stage is calculated, and the carbon dioxide emission is calculated based on this calculation boundary. The total carbon emission in the production stage is calculated by the formula:

[0058]

[0059] In the formula, Em is the total carbon emission in the production stage, unit: kgCO2; Mi is the consumption of the ith material, unit: kg; Fi is the carbon emission factor of the ith material, unit: kgCO2 / kg.

[0060] The amount of solidified soil material (kg / m 3 ) is shown in the following table:

[0061]

[0062]

[0063] The cost analysis of solidified soil (Yuan / m 3 ) is shown in the following table:

[0064]

[0065] The carbon emission analysis of solidified soil (kgCO2 / m 3 ) is shown in the following table:

[0066]

[0067] From the data in the table, it can be seen that under the condition of the same amount of solidifying agent, the cost and carbon emission of cement solidifying agent are significantly higher than those of alkali-activated steel slag and slag solidifying agent, especially in terms of carbon emission.

[0068] In step three, the speed of the mixer is 30 to 50 r / min.

[0069] By controlling the speed of the mixer, the uniform dispersion of the cementitious material can be effectively ensured, the stability of the reaction system can be maintained, and the mechanical properties of the final product can be guaranteed.

[0070] In step four, the surface of the test piece is sprayed with atomized water every 24 hours during the curing period, and the spraying amount is 1% of the mass of the test piece, so as to maintain the constant humidity of the wet cloth.

[0071] The timed spraying of atomized water during maintenance can continuously maintain the moisture of the surface of the test piece, avoid the interruption of the hydration reaction due to water evaporation, ensure the full generation of C-(A)-S-H gel, and significantly improve the water stability and long-term strength of the solidified soil.

[0072] In step three, CaO should be added in a quantitative and uniform manner into the blender, and the continuous operation of the blender is used to ensure the uniform dispersion of CaO in the mixed system.

[0073] By adding CaO in a quantitative and uniform manner, the activator can uniformly activate the active ingredients in the steel slag and slag, improving the reliability of the overall performance of the material.

[0074] In step one, the steel slag needs to be pre-crushed and then dried to make the water content less than 1%, so as to avoid introducing additional water to affect the accuracy of the proportioning.

[0075] The pre-crushing and drying of the steel slag can control the water content and prevent water from affecting the accuracy of the proportioning, thereby improving the binding effect of the solidifying agent and the slag soil and the durability of the material.

[0076] In step three, when adding water and stirring, the same amount of water is added three times, the stirring time after each addition of water is not less than 1 minute and not more than 2 minutes, and after stirring is completed, the mixture is left to stand for 5 minutes before sampling, so as to reduce the internal bubbles of the mixture.

[0077] Adding water in several times and controlling the stirring time can promote the full contact between water and solid particles, reduce the internal bubbles and stratification of the mixture, enhance the material density, and finally improve the unconfined compressive strength of the solidified soil.

[0078] Example two:

[0079] The embodiment of the present application provides a kind of alkali-activated steel slag and slag solidifying agent, formula is composed of following components: slag soil, steel slag, slag and CaO, it is proportioned by weight percentage as follows: slag soil 85%, steel slag 7.5%, slag 7.5%.

[0080] Using CaO as an activator to prepare an alkali-activated steel slag and slag soil solidifying agent not only effectively improves the mechanical strength, water stability and other key performance indicators of the solidified soil, but also realizes the high-value resource utilization of the three types of industrial solid waste, i.e., steel slag, slag and slag soil.

[0081] The content of CaO is 20% of the total mass of steel slag and slag, and the purity of CaO needs to be greater than or equal to 90%.

[0082] As an activator, CaO has multiple advantages in alkali-activated steel slag and slag cementitious material solidified slag soil: the strong alkaline environment (high pH value) generated by CaO when it comes into contact with water not only directly provides a large amount of Ca2+ Cations replace water molecules adsorbed on the surface of particles by a cation exchange mechanism, reducing the particle spacing to The following, Van der Waals forces dominate and promote the flocculation of particles, significantly reduce the specific surface area and water affinity, enhance the overall connectivity of the soil; At the same time, the alkaline conditions stimulated by CaO can efficiently activate the active silicate and aluminate in steel slag and slag, prompting the system to generate uniform and dense C-(A)-S-H gel, fully filling the soil pores, and combined with the synergistic strengthening effect of calcite and mullite crystals, greatly improving the mechanical strength and water stability of the solidified soil; In addition, high concentration Ca 2+ In combination with Al 3+ The synergistic effect of multiple valence cations and high pH value further optimizes the ion exchange efficiency, ensuring that the solidification effect is significantly better than that of a single activation system.

[0083] A method for preparing a road base material with an alkali-activated steel slag and slag solidifying agent, the specific steps are as follows:

[0084] Step one: raw material preparation and pretreatment

[0085] Soil treatment: use a ball mill to grind the slag to a particle size of ≤2mm, increase its specific surface area, and improve the contact efficiency with the cementitious material, then screen out the unground large particles through a 2mm square hole screen to ensure uniformity of the slag particles and avoid the influence of coarse particles on material density, finally dry the slag to a moisture content of less than 1% to prevent residual water from interfering with subsequent cementation reactions;

[0086] Steel slag and slag treatment: dry to a moisture content of less than 1% to avoid introducing additional water that affects the accuracy of the proportioning;

[0087] CaO treatment: industrial-grade calcium oxide is used, and CaO needs to be prepared into powder through a grinding process to ensure uniformity and prevent local high alkalinity from causing volume expansion;

[0088] Control group A material treatment: dry the cement and slag to a moisture content of less than 1%;

[0089] Step two: proportioning design and calculation

[0090] The slag, steel slag and slag are in a mass percentage of 85% slag, 7.5% steel slag and 7.5% slag, and the CaO addition is 20% of the total mass of steel slag and slag, and the ratio of water to total solid mass (slag + steel slag + slag + CaO) is 0.21;

[0091] Control group A: the mass ratio of slag to cement is 85:15, and the ratio of water to total solid mass (slag + cement) is 0.21;

[0092] Step three: mixing and molding process

[0093] Mixing sequence: first put the slag, steel slag, and slag into the mixer in proportion and dry mix for 3 minutes, then add CaO and continue to dry mix for 2 minutes to ensure uniform dispersion of CaO, then add water and stir;

[0094] Control group A: first put the slag and cement into the mixer in proportion and dry mix for 3 minutes, then add the designed water amount and stir for at least 3 minutes;

[0095] Step four: sample preparation and curing

[0096] Sample preparation: take the mixed mixture into a square mold and press the test piece with a hydraulic machine at a pressure of 15 MPa for 30 seconds;

[0097] Curing: immediately wrap the test piece with double preservative film after molding, cover the outer layer with wet cloth to prevent water evaporation, set the curing box temperature to 20±2℃, and the relative humidity to >95%, cure for 7 days and 28 days respectively, avoid vibration or temperature fluctuation during curing to ensure stable production of reaction products;

[0098] Step five: performance test

[0099] According to "Soil Solidification Admixture" (CJT486-2015), the unconfined compressive strength and water stability coefficient of solidified soil are tested.

[0100] The unconfined compressive strength and water stability coefficient test results are shown in the following table:

[0101]

[0102] From the data in the table, it can be seen that the alkali-activated steel slag and slag solidified soil has higher unconfined compressive strength and water stability coefficient with the increase of steel slag and slag content, and meets the relevant requirements of "Highway Subgrade Construction Specification" (JTG / T3610-2019), and the results are better than those of cement solidified soil.

[0103] In step two, the materials are 1m 3 Taking the amount of road base material as an example, only the cost used in the production stage is calculated, and the carbon dioxide emission is calculated based on this calculation boundary. The total carbon emission in the production stage is calculated by the formula:

[0104]

[0105] In the formula, Em is the total carbon emission in the production stage, unit is kgCO2; Mi is the consumption of the ith material, unit is kg; Fi is the carbon emission factor of the ith material, unit is kgCO2 / kg.

[0106] The amount of solidified soil material (kg / m 3 ) is shown in the following table:

[0107]

[0108] Solidified soil cost analysis (Yuan / m 3 ) as shown in the following table:

[0109]

[0110] Solidified soil carbon emission analysis (kgCO2 / m 3 ) as shown in the following table:

[0111]

[0112] From the data in the table, under the condition of the same dosage of solidifying agent, the cost and carbon emission of cement solidifying agent are obviously higher than that of alkali-activated steel slag and slag solidifying agent, especially in terms of carbon emission.

[0113] Among them, the stirring speed of step three is 30 to 50 r / min.

[0114] By controlling the stirring speed, the uniform dispersion of the cementing material can be effectively ensured, the stability of the reaction system can be maintained, and the mechanical properties of the final product can be ensured.

[0115] Among them, during the curing period in step four, the surface of the test piece is sprayed with atomized water every 24 hours, and the spraying amount is 1% of the mass of the test piece, so as to maintain the constant humidity of the wet cloth.

[0116] The surface humidity of the test piece can be maintained by spraying atomized water during the curing period, so as to avoid the interruption of the hydration reaction due to water evaporation, ensure the full generation of C-(A)-S-H gel, and significantly improve the water stability and long-term strength of the solidified soil.

[0117] Among them, in step three, when CaO is added, a quantitative and uniform feeding method should be adopted to put CaO into the mixer, and the continuous operation of the mixer is used to ensure the uniform dispersion of CaO in the mixed system.

[0118] By adding CaO in a quantitative and uniform manner, the uniform activation of the active ingredients in steel slag and slag by the activator can be ensured, and the reliability of the overall performance of the material can be improved.

[0119] Among them, in step one, the steel slag needs to be pre-crushed and then dried to make the water content of the steel slag less than 1%, so as to avoid the introduction of additional water to affect the accuracy of the proportioning.

[0120] Pre-crushing and drying of steel slag can control the water content to prevent water from affecting the accuracy of the proportioning, thereby improving the combination effect of the solidifying agent and slag soil and the durability of the material.

[0121] In step three, the water is added in three equal portions, and each time the water is added, the stirring time is not less than 1 minute and not more than 2 minutes, and after the stirring is completed, the mixture is left to stand for 5 minutes before sample preparation, so as to reduce the internal bubbles of the mixture.

[0122] The step of adding water in portions and controlling the stirring time can promote the full contact between water and solid particles, reduce the internal bubbles and stratification of the mixture, enhance the material density, and finally improve the unconfined compressive strength of the solidified soil.

[0123] Example three:

[0124] The embodiment of the present application provides a kind of alkali-activated steel slag and slag solidification agent, formula is composed of following components: slag, steel slag, slag and CaO, and the proportion of weight percentage is 80% of slag, 10% of steel slag, 10% of slag.

[0125] Using CaO as activator, the alkali-activated steel slag and slag are used as soil solidification agent, which not only effectively improves the key performance indicators such as mechanical strength and water stability of solidified soil, but also realizes the high value-added resource utilization of three types of industrial solid waste, i.e., steel slag, slag and slag.

[0126] The content of CaO is 20% of the total mass of steel slag and slag, and the purity of CaO needs to be greater than or equal to 90%.

[0127] CaO as activator has multiple advantages in alkali-activated steel slag and slag cementitious material solidified slag: the strong alkaline environment (high pH value) generated by CaO when meeting water not only directly provides a large amount of Ca 2+ Cations replace water molecules adsorbed on the surface of slag particles through cation exchange mechanism, reduce the particle spacing to Van der Waals force dominates and promotes particle flocculation and coalescence, significantly reduces specific surface area and water affinity, and enhances overall connectivity of slag; at the same time, the alkaline conditions activated by CaO can efficiently activate active silicate and aluminate in steel slag and slag, promote the system to generate uniform and dense C-(A)-S-H gel, fully fill soil pores, and combine with the synergistic strengthening effect of calcite and mullite crystals, greatly improve the mechanical strength and water stability of solidified soil; in addition, the synergistic effect of high concentration Ca 2+ and Al 3+ and other multivalent cations and high pH value further optimizes ion exchange efficiency, ensures that the solidification effect is significantly better than single activation system.

[0128] A method for preparing road base material by using alkali-activated steel slag and slag solidification agent, the specific steps are as follows:

[0129] Step one: raw material preparation and pretreatment

[0130] Slag treatment: use a ball mill to grind the slag to a particle size of ≤2 mm, increase its specific surface area, improve the contact efficiency with cementitious materials, then screen out the unground large particles through a 2 mm square hole screen to ensure uniformity of the slag particles and avoid the influence of coarse particles on material density, and finally dry the slag to a moisture content of less than 1% to prevent residual moisture from interfering with subsequent cementation;

[0131] Steel slag and slag treatment: dry to a moisture content of less than 1% to avoid introducing additional moisture to affect the accuracy of the proportioning;

[0132] CaO treatment: use industrial-grade calcium oxide, which needs to be ground into powder to ensure uniformity and prevent local alkali content from causing volume expansion;

[0133] Control group A material treatment: dry the cement and slag to a moisture content of less than 1%;

[0134] Step two: proportioning design and calculation

[0135] Slag, steel slag and slag are in a mass percentage of 80% slag, 10% steel slag and 10% slag, CaO is added in an amount of 20% of the total mass of steel slag and slag, and the ratio of water to total solid mass (slag + steel slag + slag + CaO) is 0.21;

[0136] Control group A: the mass ratio of slag and cement is 80:20, and the ratio of water to total solid mass (slag + cement) is 0.21;

[0137] Step three: mixing and molding process

[0138] Mixing sequence: first, put the slag, steel slag and slag into the mixer in the right proportion and dry mix for 3 minutes, then add CaO and continue to dry mix for 2 minutes to ensure uniform dispersion of CaO, and then add water and stir;

[0139] Control group A: first, put the slag and cement into the mixer in the right proportion and dry mix for 3 minutes, then add the designed amount of water and stir for at least 3 minutes;

[0140] Step four: sample preparation and curing

[0141] Sample preparation: take the mixed mixture and put it into a square mold, use a hydraulic machine to press the test piece at a pressure of 15 MPa, and keep the pressure for 30 seconds;

[0142] Curing: immediately after molding, wrap the test piece with double preservative film, cover the outer layer with wet cloth to prevent water evaporation, set the curing box temperature to 20±2℃, relative humidity >95%, and cure for 7 days and 28 days respectively, avoid vibration or temperature fluctuation during curing to ensure stable production of reaction products;

[0143] Step five: performance test

[0144] The unconfined compressive strength and water stability coefficient of the solidified soil are tested according to the Soil Solidification Admixture (CJT 486-2015).

[0145] The unconfined compressive strength and water stability coefficient test results are shown in the following table:

[0146]

[0147] As can be seen from the data in the table, the unconfined compressive strength and water stability coefficient of the alkali-activated steel slag and slag solidified soil increase with the increase of the steel slag and slag content, and meet the relevant requirements of the Highway Subgrade Construction Specification (JTG / T 3610-2019), and the results are better than those of the cement solidified soil.

[0148] In step two, the material is stirred at 1 m / s 3 Taking the amount of road base material as an example, only the cost used in the production stage is calculated, and the carbon dioxide emission is calculated based on this calculation boundary. The total carbon emission in the production stage is calculated by the formula:

[0149]

[0150] In the formula, Em is the total carbon emission in the production stage, with a unit of kgCO2; Mi is the consumption of the ith material, with a unit of kg; and Fi is the carbon emission factor of the ith material, with a unit of kgCO2 / kg.

[0151] The amount of solidified soil material (kg / m 3 ) is shown in the following table:

[0152]

[0153] The cost analysis of the solidified soil (Yuan / m 3 ) is shown in the following table:

[0154]

[0155] The carbon emission analysis of the solidified soil (kgCO2 / m 3 ) is shown in the following table:

[0156]

[0157] As can be seen from the data in the table, under the condition of the same solidifying agent content, the cost and carbon emission of the cement solidifying agent are significantly higher than those of the alkali-activated steel slag and slag solidifying agent, especially in terms of carbon emission.

[0158] In step three, the stirring speed of the mixer is 30 to 50 r / min.

[0159] By controlling the stirring speed, the cementitious material can be effectively ensured to be uniformly dispersed, the stability of the reaction system is maintained, and the mechanical properties of the final product are consistent.

[0160] In step four, the test piece surface is sprayed with atomized water every 24 hours during the curing period, and the spraying amount is 1% of the mass of the test piece, so as to maintain the constant wet cloth humidity.

[0161] The test piece surface humidity can be continuously maintained by spraying atomized water during the curing period, so as to avoid interruption of the hydration reaction due to water evaporation, ensure the full formation of C-(A)-S-H gel, and significantly improve the water stability and long-term strength of the solidified soil.

[0162] In step three, when CaO is added, a quantitative and uniform feeding method should be used to pour CaO into the stirrer, and the continuous operation of the stirrer is used to ensure the uniform dispersion of CaO in the mixed system.

[0163] By adding CaO in a quantitative and uniform manner, the reliability of the overall performance of the material can be ensured, and the active ingredients in the steel slag and slag are uniformly activated.

[0164] In step one, the steel slag needs to be pre-crushed and then dried to make the water content of the steel slag less than 1%, so as to avoid introducing additional water to affect the accuracy of the proportioning.

[0165] Pre-crushing and drying of the steel slag can control the water content to prevent water from affecting the accuracy of the proportioning, thereby improving the binding effect of the solidifying agent and the slag soil and the durability of the material.

[0166] In step three, when water is added and stirred, the same amount of water is added in three times, the stirring time after each water addition is not less than 1 minute and not more than 2 minutes, and the mixture is placed for 5 minutes after stirring is completed before sample preparation, so as to reduce the internal bubbles of the mixture.

[0167] Adding water in several times and controlling the stirring time can promote the full contact between water and solid particles, reduce the internal bubbles and stratification of the mixture, enhance the material density, and finally improve the unconfined compressive strength of the solidified soil.

[0168] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0169] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. An alkali-activated steel slag slag curing agent, characterized in that: The formula consists of the following components: slag, steel slag, slag and CaO, and the weight percentage is 80% to 90% of slag, 5% to 10% of steel slag and 5% to 10% of slag.

2. The alkali-activated steel slag and slag curing agent according to claim 1, characterized in that: The CaO content is 20% of the total mass of the steel slag and slag, and the CaO purity needs to be greater than or equal to 90%.

3. A method for preparing road base materials using an alkali-activated steel slag and slag curing agent, characterized in that: The specific steps are as follows: Step 1: Raw material preparation and pretreatment Slag treatment: Use a ball mill to grind the slag to a particle size of ≤2mm to increase its specific surface area and improve the contact efficiency with the cementitious material. Then, use a 2mm square hole sieve to remove large particles that are not ground to ensure uniform slag particles and prevent coarse particles from affecting the density of the material. Finally, dry the slag to a moisture content of less than 1% to prevent residual moisture from interfering with the subsequent gelation reaction. Steel slag treatment: Dry to a moisture content of less than 1% to avoid the introduction of additional moisture that affects the ratio accuracy; CaO treatment: Use industrial-grade calcium oxide. CaO needs to be ground into powder to ensure mixing uniformity and prevent volume expansion caused by excessive alkalinity in some areas. Step 2: Ratio design and calculation The mass percentage of slag, steel slag and slag is 80% to 90% slag, 5% to 10% steel slag, and 5% to 10% slag. The amount of CaO added is 20% of the total mass of steel slag and slag. The ratio of water to total solid mass (slag + steel slag + slag + CaO) is 0.

21. Step 3: Mixing and molding process Mixing order: first put the slag, steel slag and slag into the mixer in proportion and dry mix for 3 minutes, then add CaO and continue dry mixing for 2 minutes to ensure that the CaO is evenly dispersed, and then add water and stir; Step 4: Sample preparation and maintenance Sample preparation: Place the mixed mixture into a square mold and press the specimen with a hydraulic press at a pressure of 15 MPa for 30 seconds; Curing: Immediately after forming, wrap the specimen with a double layer of plastic wrap and cover the outer layer with a wet cloth to prevent moisture evaporation. Set the temperature of the curing box to 20±2℃ and the relative humidity>95%. Cure for 7 days and 28 days respectively. Avoid vibration or temperature fluctuations during the curing period to ensure stable generation of the reaction product. Step 5: Performance Testing The unconfined compressive strength and water stability coefficient of the stabilized soil were tested in accordance with Soil Stabilization Admixtures (CJT486-2015).

4. The method for preparing a road base material using an alkali-activated steel slag and slag curing agent according to claim 3, characterized in that: The materials mentioned in step 2 are 1m 3 Taking the amount of road base materials as an example, only the cost used in the production stage is calculated, and the carbon dioxide emissions are calculated based on this as the calculation boundary. The total carbon emissions calculation formula for the production stage is: Where Em is the total carbon emissions in the production stage, in kgCO2; Mi is the consumption of the i-th material, in kg; Fi is the carbon emission factor of the i-th material, in kgCO2 / kg.

5. The method for preparing a road base material using an alkali-activated steel slag and slag curing agent according to claim 3, characterized in that: The stirring speed in step 3 is 30 to 50 r / min.

6. The method for preparing a road base material using an alkali-activated steel slag and slag curing agent according to claim 3, characterized in that: During the curing period described in step 4, the surface of the specimen is sprayed with atomized water every 24 hours, with a spraying amount of 1% of the mass of the specimen to maintain a constant humidity of the wet cloth.

7. The method for preparing a road base material using an alkali-activated steel slag and slag curing agent according to claim 3, characterized in that: When adding CaO in step 3, the CaO should be added into the mixer in a quantitative and uniform manner, and the continuous operation of the mixer ensures that the CaO is evenly dispersed in the mixing system.

8. The method for preparing a road base material using an alkali-activated steel slag and slag curing agent according to claim 3, characterized in that: The steel slag in step 1 needs to be crushed in advance and then dried to make the moisture content of the steel slag less than 1% to avoid the introduction of additional moisture that affects the ratio accuracy.

9. The method for preparing a road base material using an alkali-activated steel slag and slag curing agent according to claim 3, characterized in that: When adding water and stirring in step 3, add equal amounts of water three times, and stir for no less than 1 minute and no more than 2 minutes after each addition of water. After stirring, let it stand for 5 minutes before preparing the sample to reduce bubbles inside the mixture.

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