CN118183760A - A silica sol modified ferrochrome slag aggregate and preparation method thereof - Google Patents

Abstract

The invention relates to a silica sol modified ferrochrome slag aggregate and a preparation method thereof, comprising the following steps: the rice hull ash is subjected to acid washing treatment by adopting a sol-gel method to remove metal ions, and NaOH solution is added after drying, stirred and filtered to obtain brown sodium silicate solution. Adjusting the pH value of the water glass solution to 8-10 by acid titration, aging and centrifuging to obtain nano silica sol gel, drying and grinding for later use; preparing nano silica sol into silica sol solution with a certain fraction, dispersing the silica sol solution under an ultrasonic cleaning machine, and then immersing ferrochrome slag aggregate into the solution and fully immersing the ferrochrome slag aggregate; adding a modifier and a cross-linking agent into the fully soaked solution to strengthen the aggregate, and adding a small amount of initiator and accelerator to accelerate the reaction; and (3) placing the modified aggregate into a specific environment for curing, and drying and curing for standby. The modification method is green and environment-friendly, and has the advantages of simple process, low cost, safety and innocuity. The surface pores of the obtained modified ferrochrome slag aggregate are obviously reduced, and the crushing value and the water absorption are obviously reduced. The concrete prepared from the modified ferrochrome slag aggregate has more stable and reliable performance, and is expected to realize more excellent permeation resistance, durability and strength performance especially in high-performance concrete application.

Description

A silica sol modified ferrochrome slag aggregate and preparation method thereof

Technical Field

The invention relates to a silica sol modified ferrochrome slag aggregate and a preparation method thereof, belonging to the technical field of building materials.

Background technique

High-carbon ferrochrome slag is a byproduct of smelting ferrochrome alloys. According to statistics, as of last year, China's annual high-carbon ferrochrome smelting waste slag has exceeded 8.4 million tons. The traditional treatment method - simple landfill or stacking, has caused a huge waste of land resources and is also a hidden danger to the environment: the leachable Cr ⁶⁺ in the slag is highly toxic, affecting the growth of animals and plants, and long-term contact can cause skin and respiratory diseases. Therefore, the resource utilization of ferrochrome slag is imperative.

Ferrochrome slag is an inorganic non-metallic material with magnesium olivine and spinel as the main phases. According to the different cooling methods, it can be simply divided into water-cooled and air-cooled ferrochrome slag. Water-cooled slag has a fast cooling rate, fine particles and numerous pores, and a metastable glass phase, which affects the strength; while air-cooled slag is usually larger and coarser, and the formed phase is mostly crystals. Since ferrochrome slag contains a large amount of silicon and aluminum, standardized tailings can be widely used in metallurgy, ceramics, refractory materials and other fields after adjusting the component ratio. In the construction field, there is a precedent for using ferrochrome slag as a mineral admixture and aggregate. By detecting and controlling the leaching amount of Cr ⁶⁺ , it can be ensured that it complies with local environmental standards and regulations. However, due to the low content of active silicon in ferrochrome slag and its overall inertness, its application as an inert fine particle filler and supplementary cementitious materials (SCMs) has little effect. At present, there are examples in practice that ferrochrome slag can completely replace natural sand and gravel as aggregate. It should be noted that its porous morphology and high water absorption rate may affect the durability and strength of the material.

Nano-silica sol is a colloidal solution in which nano-scale SiO ₂ is stably dispersed in a medium. It has excellent adsorption and large specific surface area, and its mesoporous structure provides reactive sites. At the same time, since silica sol has good permeability to cement-based materials, the added colloidal particles can play a filling role. At the same time, considering the compatibility of silica sol with ferrochrome slag, the Ca ²⁺ in calcium acrylate can quickly combine with the active Si-OH group of cement-based materials to form CSH gel, effectively closing the pores and reducing water absorption. In addition, calcium acrylate will form a calcium polyacrylate skeleton structure under the action of initiators and crosslinkers, further improving the compressive and flexural strength of aggregates.

Summary of the invention

Technical problem: The purpose of the present invention is to provide a silica sol modified ferrochrome slag aggregate and a preparation method thereof, which is low-cost, green and environmentally friendly, and has a simple process. The method solves the problem of rough, porous and high water absorption of ferrochrome slag, so that the surface of the modified ferrochrome slag aggregate is smooth, and the porosity and water absorption are significantly reduced, thereby optimizing the workability of the fresh concrete slurry and improving the mechanical properties and durability of the concrete.

Technical solution: A silica sol modified ferrochrome slag aggregate, wherein the ferrochrome slag aggregate is immersed in nano silica sol and fully soaked, and then a modifier, a cross-linking agent, an initiator and an accelerator are added to react and strengthen the aggregate, and finally the aggregate is dried and solidified after curing for use; the nano silica sol is obtained by using a sol-gel method with rice husk ash as a raw material, acid washing, reacting with NaOH, and then adjusting the pH value to 8-10 with acid and then aging.

In the pickling process, the pH value needs to be adjusted to 4-5, and the acid used is nitric acid or acrylic acid.

The modifier is calcium acrylate, and the addition amount is 10wt% to 20wt% of the nano-silica sol solution. The cross-linking agent is tris (3-aziridine) propionate (molecular formula is C ₂₀ H ₃₃ N ₃ O ₇ ), the initiator is potassium persulfate, and the accelerator is triethanolamine.

The mass ratio of the modifier, the cross-linking agent, the accelerator and the initiator is 100:5:1:2.5.

The method for preparing the silica sol modified ferrochrome slag aggregate comprises the following steps:

1) The rice husk ash is pickled by a sol-gel method to remove metal ions, and after drying, a NaOH solution is added, stirred and filtered to obtain a brown sodium silicate solution;

2) adjusting the water glass solution to pH=8-10 by acid titration, aging and centrifuging to obtain nano-silica sol gel, drying and grinding for later use;

3) preparing the nano-silica sol into a silica sol solution and dispersing it under an ultrasonic cleaning machine, and then immersing the ferrochrome slag aggregate into the solution and fully soaking it;

4) Add modifier and cross-linking agent to the fully soaked solution to strengthen the aggregate, and add a small amount of initiator and accelerator to accelerate the reaction;

5) The modified aggregate is cured, dried and solidified for later use.

The amount of NaOH substance in step 1) is 0.6-0.8 mol.

The aging time required for the aging centrifugation step described in step 2) is 2 to 3 days, and the centrifugal speed is 3500 to 4000 rpm.

The nano-silica sol solution of a certain mass fraction is dispersed in the ultrasonic cleaning machine described in step 3), the dispersion time of the ultrasonic cleaning machine is 20 to 30 minutes, the ultrasonic frequency is 30 to 40 KHz, and the nano-silica sol solution is 5wt to 10wt%.

The curing conditions described in step 4) are 20±2° C., relative humidity 95%, and curing time 3 days.

The drying temperature in steps 1), 2) and 4) is 110-140° C. and the drying time is 12-18 hours.

Beneficial effects:

1) The method uses rice husk ash as raw material to prepare nano-silica sol, abandons the toxicity caused by traditional metal alkoxide as silicon source, effectively alleviates environmental pressure, and the process does not require high equipment complexity and precision, and is easy to realize industrial production;

2) The nano-silica sol used in this method has stronger permeability than nano- _SiO2 powder, and is easier to achieve uniform dispersion in the medium, so that it can fully contact with the aggregate to be modified. When the excess nano-silica sol solution reacts with calcium acrylate, it not only achieves a sealing effect, but also retains active nano _-SiO2 particles on the surface and inside, playing a key role in interface bonding and microstructure optimization. At the same time, under the action of the cross-linking agent, the skeleton structure formed by calcium acrylate further strengthens the overall mechanical properties of the aggregate, allowing its reinforcing effect in concrete to be fully exerted.

3) The porosity and water absorption of the modified ferrochrome slag aggregate are reduced, the surface is smoother, and the interior is relatively stable. In the process of using the modified aggregate to form concrete, the water demand is significantly reduced and the workability of the fresh slurry is optimized. The strength of the concrete produced is significantly improved, the chloride ion diffusion coefficient is reduced, the interface structure between the aggregate and the slurry is optimized, and the mechanical properties and durability of the concrete are effectively improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the 28d chloride ion diffusion coefficients of the modified ferrochrome slag aggregate concrete of Examples 1-5 and the control example.

FIG. 2 shows the 28d chloride ion carbonization depth of the modified ferrochrome slag aggregate concrete of Examples 1-5 and the control example.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments.

The coarse and fine aggregates used in the embodiments of the present invention are obtained by crushing and screening air-cooled high-carbon ferrochrome slag. The particle size range of the coarse aggregate is 5 to 20 mm; the particle size range of the fine aggregate is 0.75 to 5 mm.

The present invention introduces a method for preparing a silica sol modified ferrochrome slag aggregate, which comprises the following steps:

1) The rice husk ash is pickled by a sol-gel method to remove metal ions, and then dried, a NaOH solution is added, stirred and filtered to obtain a brown sodium silicate solution.

2) adjusting the water glass solution to pH=8-10 by acid titration, aging and centrifuging to obtain nano-silica sol gel, drying and grinding for later use;

3) preparing the nano-silica sol into a silica sol solution with a certain fraction and dispersing it under an ultrasonic cleaning machine, and then immersing the ferrochrome slag aggregate into the solution and fully soaking it;

4) Add modifiers and cross-linking agents to the fully immersed solution to strengthen the aggregate, and add a small amount of initiator and promoter to accelerate the reaction.

5) Place the modified aggregate in a specific environment for curing, then dry and solidify for later use.

in:

In the pickling process described in step 1), the pH value needs to be adjusted to 4-5, and the acid used is nitric acid or acrylic acid.

The amount of NaOH substance in step 1) is 0.6-0.8 mol.

The aging time required for the aging centrifugation step described in step 2) is 2 to 3 days, and the centrifugal speed is 3500 to 4000 rpm.

The nano-silica sol solution of a certain mass fraction is dispersed in the ultrasonic cleaning machine described in step 3), the dispersion time of the ultrasonic cleaning machine is 20 to 30 minutes, the ultrasonic frequency is 30 to 40 KHz, and the nano-silica sol solution is 5wt to 10wt%.

The modifier described in step 4) is calcium acrylate, and its addition amount is 10wt% to 20wt% of the dispersed nano-silica sol solution. The cross-linking agent is tris (3- _aziridinyl ) propionate (molecular formula is _C20H33N3O7 ), the initiator is potassium _persulfate , and the accelerator is _{triethanolamine} . The proportion of the modifier, the cross-linking agent, the accelerator, and the initiator is 100:5:1:2.5.

The curing conditions described in step 4) are 20±2° C., relative humidity 95%, and curing time 3 days.

The drying temperatures in steps 1), 2) and 4) are all 110-140° C. and the drying time is 12-18 hours.

Embodiment 1:

A method for preparing silica sol modified ferrochrome slag aggregate, the method comprising the following steps:

1) preparing nano-silica sol particles made from rice husk ash into a nano-silica sol solution with a mass fraction of 5% using water as a solvent, and ultrasonically dispersing it in an ultrasonic cleaner with a frequency of 40 kHz for 20 minutes, and soaking the coarse and fine aggregates of ferrochrome slag in the ultrasonically treated solution for 3 days;

2) After soaking, open the sealing cover and add calcium acrylate with a mass fraction of 20% of the soaking liquid. Based on the mass of calcium acrylate, add tris(3-aziridinyl) propionate, triethanolamine and potassium persulfate in a ratio of 100:5:1:2.5, mix well and let stand;

3) Place the fully soaked ferrochrome slag aggregate in a standard curing room at 20±2°C and 95% relative humidity for curing, and take it out after 3 days for drying and standby use;

4) Take 312 parts of P·II52.5 cement, 156 parts of metakaolin, 748 parts of modified ferrochrome slag fine aggregate, including 343 parts of 5-10 mm modified ferrochrome slag coarse aggregate, including 685 parts of 10-20 mm modified ferrochrome slag coarse aggregate, 151 parts of water, and 4.6 parts of water reducer.

Embodiment 2:

A method for preparing silica sol modified ferrochrome slag aggregate, the method comprising the following steps:

1) preparing nano-silica sol particles made from rice husk ash into a nano-silica sol solution with a mass fraction of 5% using water as a solvent, and ultrasonically dispersing it in an ultrasonic cleaner with a frequency of 40 kHz for 20 minutes, and soaking the coarse and fine aggregates of ferrochrome slag in the ultrasonically treated solution for 3 days;

2) After soaking, open the sealing cover and add calcium acrylate with a mass fraction of 20% of the soaking liquid. Based on the mass of calcium acrylate, add tris(3-aziridinyl) propionate, triethanolamine and potassium persulfate in a ratio of 100:5:1:2.5, mix well and let stand;

3) Place the fully soaked ferrochrome slag aggregate in a standard curing room at 20±2°C and 95% relative humidity for curing, and take it out after 3 days for drying and standby use;

4) Take 312 parts of P·II52.5 cement, 156 parts of metakaolin, 799 parts of ferrochrome slag fine aggregate, 326 parts of 5-10 mm ferrochrome slag coarse aggregate, including 651 parts of 10-20 mm ferrochrome slag coarse aggregate, 151 parts of water, and 4.6 parts of water reducer.

Embodiment 3:

A method for preparing silica sol modified ferrochrome slag aggregate, the method comprising the following steps:

1) preparing nano-silica sol particles made from rice husk ash into a nano-silica sol solution with a mass fraction of 5% using water as a solvent, and ultrasonically dispersing it in an ultrasonic cleaner with a frequency of 40 kHz for 20 minutes, and soaking the coarse and fine aggregates of ferrochrome slag in the ultrasonically treated solution for 3 days;

2) After soaking, open the sealing cover and add calcium acrylate with a mass fraction of 20% of the soaking liquid. Based on the mass of calcium acrylate, add tris(3-aziridinyl) propionate, triethanolamine and potassium persulfate in a ratio of 100:5:1:2.5, mix well and let stand;

3) Place the fully soaked ferrochrome slag aggregate in a standard curing room at 20±2°C and 95% relative humidity for curing, and take it out after 3 days for drying and standby use;

4) Take 312 parts of P·II52.5 cement, 156 parts of metakaolin, 799 parts of ferrochrome slag fine aggregate, 326 parts of 5-10 mm ferrochrome slag coarse aggregate, including 651 parts of 10-20 mm ferrochrome slag coarse aggregate, 151 parts of water, and 4.6 parts of water reducer.

Embodiment 4:

A method for preparing silica sol modified ferrochrome slag aggregate, the method comprising the following steps:

1) preparing nano-silica sol particles made from rice husk ash into a nano-silica sol solution with a mass fraction of 5% using water as a solvent, and ultrasonically dispersing it in an ultrasonic cleaner with a frequency of 40 kHz for 20 minutes, and soaking the coarse and fine aggregates of ferrochrome slag in the ultrasonically treated solution for 3 days;

2) After soaking, open the sealing cover and add calcium acrylate with a mass fraction of 20% of the soaking liquid. Based on the mass of calcium acrylate, add tris(3-aziridinyl) propionate, triethanolamine and potassium persulfate in a ratio of 100:5:1:2.5, mix well and let stand;

3) Place the fully soaked ferrochrome slag aggregate in a standard curing room at 20±2°C and 95% relative humidity for curing, and take it out after 3 days for drying and standby use;

4) Take 312 parts of P·II52.5 cement, 156 parts of metakaolin, 748 parts of ferrochrome slag fine aggregate, 343 parts of 5-10 mm ferrochrome slag coarse aggregate, including 685 parts of 10-20 mm ferrochrome slag coarse aggregate, 151 parts of water, and 4.6 parts of water reducer.

Embodiment 5:

A method for preparing silica sol modified ferrochrome slag aggregate, the method comprising the following steps:

1) preparing nano-silica sol particles made from rice husk ash into a nano-silica sol solution with a mass fraction of 5% using water as a solvent, and ultrasonically dispersing it in an ultrasonic cleaner with a frequency of 40 kHz for 20 minutes, and soaking the coarse and fine aggregates of ferrochrome slag in the ultrasonically treated solution for 3 days;

2) After soaking, open the sealing cover and add calcium acrylate with a mass fraction of 20% of the soaking liquid. Based on the mass of calcium acrylate, add tris(3-aziridinyl) propionate, triethanolamine and potassium persulfate in a ratio of 100:5:1:2.5, mix well and let stand;

3) Place the fully soaked ferrochrome slag aggregate in a standard curing room at 20±2°C and 95% relative humidity for curing, and take it out after 3 days for drying and standby use;

4) Take 312 parts of P·II52.5 cement, 156 parts of metakaolin, 799 parts of ferrochrome slag fine aggregate, 326 parts of 5-10 mm ferrochrome slag coarse aggregate, including 651 parts of 10-20 mm ferrochrome slag coarse aggregate, 151 parts of water, and 4.6 parts of water reducer.

Comparative Example

This control example is C60 concrete, which is made of the following raw materials in parts by weight: 312 parts of P·II52.5 cement, 156 parts of metakaolin, 799 parts of unmodified ferrochrome slag fine aggregate, including 326 parts of 5-10 mm unmodified ferrochrome slag coarse aggregate, 651 parts of 10-20 mm unmodified ferrochrome slag coarse aggregate, 151 parts of water, and 4.6 parts of water reducer.

First, the cement, metakaolin and other powder materials and ferrochrome slag coarse aggregate described in the above Examples 1-5 and the comparative example are put into a horizontal mixer and mixed evenly. Then, a portion of the mixing water is poured in and stirred for 2 minutes until the slurry becomes viscous, and then the fine aggregate is slowly poured in and stirred. Next, the remaining mixing water and water reducing agent are added and stirred for 3 minutes. After the slurry is evenly mixed, it is poured in layers, molded, vibrated, and coated. After 24 hours, the mold is removed and placed in a standard curing room.

The mechanical properties and durability of the concrete prepared in Examples 1-5 are better than those of the control example, with the compressive strength growth rate ranging from 3.1% to 25.3%, and the flexural strength growth rate ranging from 3.8% to 41.8%; the chloride ion diffusion coefficient and the carbonization layer depth are significantly reduced, proving that the modified ferrochrome slag aggregate has a significant effect on improving the mechanical properties and durability of concrete.

Table 1 Workability and mechanical properties of modified ferrochrome slag concrete

The above description is only an application embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes and substitutions that can be easily conceived by a technician familiar with the field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims (10)

1. A silica sol modified ferrochrome slag aggregate, characterized in that the ferrochrome slag aggregate is immersed in nano silica sol and fully soaked, then a modifier, a cross-linking agent, an initiator and an accelerator are added to react and strengthen the aggregate, and finally the aggregate is dried and solidified for standby use after curing; the nano silica sol is obtained by using a sol-gel method with rice husk ash as a raw material, acid washing, reacting with NaOH, adjusting the pH value to 8-10 with acid, and then aging. 2. The silica sol modified ferrochrome slag aggregate as claimed in claim 1, characterized in that during the pickling process, the pH value needs to be adjusted to 4-5, and the acid used is nitric acid or acrylic acid. 3. The silica sol modified ferrochrome slag aggregate according to claim 1, characterized in that the modifier is calcium acrylate, and the addition amount is 10wt% to _20wt % of the nano silica sol solution; the crosslinking agent is tris (3- _aziridinyl ) propionate (molecular formula is _C20H33N3O7 ), the initiator is potassium _persulfate , and the accelerator is triethanolamine. 4. The silica sol modified ferrochrome slag aggregate as claimed in claim 1, characterized in that the mass ratio of the modifier, the cross-linking agent, the accelerator and the initiator is 100:5:1:2.5. 5. The method for preparing the silica sol modified ferrochrome slag aggregate according to any one of claims 1 to 4, characterized in that it comprises the following steps: 1) The rice husk ash is pickled by a sol-gel method to remove metal ions, and after drying, a NaOH solution is added, stirred and filtered to obtain a brown sodium silicate solution; 2) adjusting the water glass solution to pH=8-10 by acid titration, aging and centrifuging to obtain nano-silica sol gel, drying and grinding for later use; 3) preparing the nano-silica sol into a silica sol solution and dispersing it under an ultrasonic cleaning machine, and then immersing the ferrochrome slag aggregate into the solution and fully soaking it; 4) Add modifier and cross-linking agent to the fully soaked solution to strengthen the aggregate, and add a small amount of initiator and accelerator to accelerate the reaction; 5) The modified aggregate is cured, dried and solidified for later use. 6. The method for preparing silica sol modified ferrochrome slag aggregate according to claim 5, characterized in that the amount of NaOH substance in step 1) is 0.6-0.8 mol. 7. The method for preparing silica sol modified ferrochrome slag aggregate as claimed in claim 5, characterized in that the aging time required for the aging centrifugal step in step 2) is 2 to 3 days, and the centrifugal speed is 3500 to 4000 rpm. 8. The method for preparing silica sol modified ferrochrome slag aggregate as claimed in claim 5, characterized in that: the nano silica sol solution of a certain mass fraction dispersed in the ultrasonic cleaning machine in step 3) has a dispersion time of 20 to 30 minutes, an ultrasonic frequency of 30 to 40 kHz, and a nano silica sol solution of 5wt to 10wt%. 9. The method for preparing silica sol modified ferrochrome slag aggregate according to claim 5, characterized in that: the curing conditions in step 4) are 20±2°C, relative humidity is 95%, and the curing time is 3 days. 10. The method for preparing silica sol modified ferrochrome slag aggregate according to claim 5, characterized in that the drying temperature in steps 1), 2) and 4) is 110-140°C and the drying time is 12-18 hours.