Active powder concrete doped with steel slag and preparation process

Abstract

The present application relates to the technical field of concrete, and particularly relates to a kind of active powder concrete mixed with steel slag and a preparation process, comprising the following components: cement, pretreated steel slag powder, quartz powder, silica fume, functional additive, steel fiber, high efficiency water reducing agent;The functional additive includes modified LDHs material, repair agent and amino nano SiO2.Repair agent and modified LDHs material respond to Ca 2+ Concentration, release silicate, phosphate and oxalate, consume Ca 2+ / Mg 2+ Oxalate released from the outer layer of modified LDHs material forms interlayer vacancy, which efficiently captures phosphate and prevents its loss.Modified LDHs material surface is modified with quaternary ammonium salt, which further strengthens the capture of phosphate, and the inner layer of modified LDHs material slowly releases carbonate to generate stable calcium carbonate.Amino nano SiO2 can purify pore solution environment and provide strong mechanical support.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology, specifically an active powder concrete mixed with steel slag and its preparation process. Background Technology

[0002] Reactive powder concrete is a cement-based composite material with high strength, high toughness and excellent durability. Adding steel slag to it can not only significantly reduce raw material costs and environmental impact, but the micro-aggregate filling effect of steel slag powder can also make the concrete structure more compact, thereby significantly improving its impermeability, frost resistance and chemical erosion resistance.

[0003] Steel slag contains free calcium oxide (f-CaO) and free magnesium oxide (f-MgO), which are usually formed in the high-temperature environment of steelmaking. The high temperature results in extremely high lattice energy and a complete and dense crystal structure, which leads to extremely slow hydration reaction at room temperature and pressure. Furthermore, the high-strength CSH gel produced by the hydration of cement paste and silica fume in reactive powder concrete tightly encapsulates the steel slag, further hindering the hydration of f-CaO and f-MgO in the steel slag. Therefore, during concrete mixing and early hardening, they are encapsulated in the hardened dense structure in the form of "unstable particles", and the hydration rate is very slow, with almost no participation in the reaction. However, even with a dense CSH gel structure, there are nanoscale gel pores that allow water molecules to diffuse through concentration gradients. Especially under wet-dry cycles, freeze-thaw cycles, or external stress, micro-stress is generated inside the concrete, leading to micro-cracks that provide pathways for water to penetrate. Therefore, after several months or even years of service, the infiltration of moisture from the environment triggers the hydration of f-CaO and f-MgO, resulting in the expansion of the concrete volume. This continuous expansion stress occurring inside the hard concrete is sufficient to open up micro-cracks from the inside, causing structural cracking, surface spalling, and ultimately severely damaging the integrity and strength. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] The purpose of this invention is to provide an active powder concrete containing steel slag and its preparation process, so as to solve the problems of delayed hydration and volume expansion of free calcium oxide and free magnesium oxide in steel slag.

[0006] (2) Technical solution

[0007] To achieve the above objectives, on the one hand, the present invention provides an active powder concrete containing steel slag, comprising the following components in parts by weight: 70-100 parts cement, 30-50 parts pretreated steel slag powder, 1.5-3.5 parts functional additives, 20-50 parts quartz powder, 15-25 parts silica fume, 15-30 parts steel fiber, 1.5-2 parts high-efficiency water-reducing agent, and 25-35 parts water;

[0008] The functional additives include modified LDHs materials, repair agents, and aminated nano-SiO2, with a mass ratio of 1~2:0.5~1.5:0.5~1.5;

[0009] The modified LDHs material is an oxalate-carbonate intercalated LDH with quaternary ammonium salt groups modified on its surface;

[0010] The repair agent is Ca. 2+ Responsive silicate-phosphate composites.

[0011] Furthermore, the preparation method of the modified LDHs material includes the following steps:

[0012] S11. Dissolve magnesium chloride hexahydrate and aluminum chloride nonahydrate in deionized water to obtain a salt solution; dissolve anhydrous sodium carbonate and sodium hydroxide in deionized water to obtain a mixed alkaline solution;

[0013] S12. Under continuous nitrogen gas and mechanical stirring, the salt solution and mixed alkaline solution are simultaneously and slowly added dropwise to deionized water. The reaction is carried out under water bath heating. The resulting reaction solution is centrifuged, washed, vacuum dried, ground and sieved, and calcined under nitrogen protection to obtain carbonate-intercalated LDHs.

[0014] S13. Dissolve sodium oxalate and anhydrous sodium carbonate in deionized water to obtain an exchange solution. Slowly add carbonate-intercalated LDHs, disperse by ultrasonication, heat in a water bath to react, centrifuge and wash the resulting reaction solution, and vacuum dry to obtain oxalate-carbonate-intercalated LDHs.

[0015] S14. Oxalate-carbonate intercalated LDHs were stirred and dispersed in anhydrous toluene, and N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride solution was slowly added dropwise. The mixture was heated in an oil bath and refluxed. The resulting reaction solution was centrifuged, Soxhlet extracted, and vacuum dried to obtain the modified LDHs material.

[0016] Furthermore, the concentration of the exchange solution is 0.1~0.3 mol / L, and the ion exchange reaction time in step S13 is 2~6 h.

[0017] Furthermore, the preparation method of the repair agent includes the following steps:

[0018] S21. Dissolve sodium silicate nonahydrate and sodium hexametaphosphate in deionized water and stir magnetically until completely transparent to obtain solution A; slowly add sodium alginate to deionized water, stir to dissolve, and let stand to remove bubbles to obtain solution B; stir and dissolve chitosan in a mixed solution of deionized water and glacial acetic acid to obtain solution C; dissolve calcium chloride in deionized water to obtain solution D;

[0019] S22. Mix solutions A and B to obtain a core material mixture; mix liquid paraffin and Span-80 to obtain an oil phase, add the core material mixture, and homogenize and emulsify at high speed to obtain a W / O emulsion;

[0020] S23. Slowly add solution D to the W / O emulsion, stir and react, then slowly add solution C, continue stirring and reacting, let the resulting reaction solution stand to precipitate, pour off the upper oil phase, wash and centrifuge, collect the precipitate, vacuum dry, and sieve to obtain the repair agent.

[0021] Furthermore, the preparation method of the aminated nano-SiO2 includes the following steps:

[0022] S31. Tetraethyl orthosilicate and anhydrous ethanol are mixed evenly and slowly added dropwise to an ammonia-ethanol mixture. The mixture is stirred and reacted. The resulting product is sealed and aged, then centrifuged and washed to obtain nano-SiO2 wet gel.

[0023] S32. Disperse the nano-SiO2 wet gel in anhydrous ethanol, slowly add KH550, heat in an oil bath, reflux the reaction, centrifuge and wash the resulting reaction solution, vacuum dry, grind and sieve to obtain aminated nano-SiO2.

[0024] Furthermore, the pretreated steel slag powder is obtained by crushing and grinding converter steel slag and then aging it in the open air.

[0025] On the other hand, based on the same inventive concept, the present invention also provides a preparation process for active powder concrete mixed with steel slag, applied to the aforementioned active powder concrete mixed with steel slag, comprising the following steps:

[0026] S1. Add cement, pretreated steel slag powder, quartz powder, functional additives, silica fume, and steel fibers to a mixer and mix evenly to obtain dry material;

[0027] S2. Dissolve the high-efficiency water-reducing agent in water, slowly add the dry material, stir and mix well to obtain the slurry;

[0028] S3. Inject the slurry into the mold, vibrate to compact it, cover with plastic film, let it stand to demold, and steam cure to obtain active powder concrete.

[0029] Because of the dense structure of free calcium oxide and magnesium oxide in steel slag, and the tight encapsulation of high-strength CSH gel in cement with the steel slag, the hydration of f-CaO and f-MgO in the steel slag is hindered, leading to delayed hydration. This results in the appearance of microcracks within the concrete later, accelerating the penetration of moisture from the environment, causing the concrete to expand and severely damaging its integrity and strength. Therefore, this invention adds a repair agent. When microcracks appear in the concrete and moisture penetrates, the steel slag particles begin delayed hydration, releasing excess CaO. 2+At that time, the repair agent shell is effective against Ca. 2+ It is sensitive; excessively high concentrations will cause it to break down immediately, releasing silicates and phosphates. The silicates then rapidly diffuse with Ca. 2+ The reaction generates a CSH gel network in situ, preventing further water penetration. Simultaneously, PO4... 3- After being released, it will be with Ca 2+ / Mg 2+ The reaction generates a dense, low-solution-product phosphate protective layer that firmly coats the surface of the unhydrated particles.

[0030] However, PO4 3- The process of forming a protective layer is relatively slow, during which time the released PO4... 3- It is prone to leakage and may have adverse effects with other ions; therefore, this invention incorporates modified LDHs materials. When Ca... 2+ / Mg 2+ When the concentration locally increases, the oxalate ions in the outer layer of the modified LDHs material are preferentially released and react with Ca. 2+ / Mg 2+ The formation of oxalate precipitate further prevents the volume expansion of concrete. After the release of oxalate ions, the modified LDHs material layers become positively charged, and the resulting interlayer vacancies have a strong anion adsorption capacity, which can efficiently capture free PO4. 3- Simultaneously, the surface of the modified LDHs material is modified with quaternary ammonium salts to further enhance the resistance to PO4. 3- The capture capacity. Furthermore, the carbonate ions in the inner layer of the modified LDHs material are slowly released in the later stages, reacting with Ca... 2+ The reaction produces stable calcium carbonate, which can actively fill existing microcracks, further densifying the matrix. It can also convert unstable Ca(OH)2 produced by hydration into stable CaCO3, improving long-term durability.

[0031] To prevent the interlayer vacancies formed after the release of oxalate from the outer layer of the modified LDHs material from other anions in the environment, this invention incorporates aminated nano-SiO2. The amino groups on its surface can form hydrogen bonds and coordination complexes with corrosive anions, effectively adsorbing corrosive anions such as sulfate and chloride ions, purifying the pore solution environment. Furthermore, nano-SiO2 can continuously consume Ca(OH)2 to generate high-strength CSH gel, greatly strengthening and compacting the matrix, and providing solid mechanical support.

[0032] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0033] 1. The response of repair agents and modified LDHs materials to Ca 2+ Concentration, releases silicates, phosphates and oxalates, consumes the Ca produced by steel slag hydration 2+ / Mg 2+ This prevents the concrete from expanding in volume, and the interlayer vacancies formed after the release of oxalate from the outer layer of the modified LDHs material efficiently capture phosphate ions, preventing their loss.

[0034] 2. The surface of the modified LDHs material is modified with quaternary ammonium salt to further enhance the capture of phosphate ions. Furthermore, the carbonate ions in the inner layer of the modified LDHs material are slowly released during long-term service to generate stable calcium carbonate, achieving beneficial self-repair, compensating for shrinkage and healing microcracks.

[0035] 3. Aminated nano-SiO2 can effectively adsorb corrosive anions such as sulfate and chloride ions, purifying the pore solution environment. Furthermore, nano-SiO2 can continuously consume Ca(OH)2 to generate high-strength CSH gel, greatly strengthening and compacting the matrix and providing solid mechanical support. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1: This example discloses an active powder concrete mixed with steel slag, comprising the following components in parts by weight: 100 parts cement, 50 parts pretreated steel slag powder, 3.5 parts functional additives, 50 parts quartz powder, 25 parts silica fume, 30 parts steel fiber, 2 parts high-efficiency water-reducing agent, and 35 parts water.

[0038] The functional additives include modified LDHs materials, repair agents, and aminated nano-SiO2 in a mass ratio of 1.5:1:1.

[0039] The modified LDHs material is an oxalate-carbonate intercalated LDH with quaternary ammonium salt groups modified on its surface;

[0040] The repair agent is Ca. 2+ Responsive silicate-phosphate composites.

[0041] The preparation method of the modified LDHs material includes the following steps:

[0042] S11. Dissolve 12.2g magnesium chloride hexahydrate and 4.8g aluminum chloride nonahydrate in 200mL of deionized water to obtain a salt solution; dissolve 3.7g anhydrous sodium carbonate and 5.6g sodium hydroxide in 200mL of deionized water to obtain a mixed alkaline solution;

[0043] S12. Under continuous nitrogen purging and mechanical stirring, the salt solution and mixed alkali solution were simultaneously and slowly added dropwise to 50 mL of deionized water. The reaction was carried out in a water bath at 65 °C for 20 h. The resulting reaction solution was centrifuged, washed alternately with deionized water and anhydrous ethanol, dried under vacuum at 80 °C for 24 h, ground through a 200-mesh sieve, and calcined at 450-500 °C for 4 h under nitrogen protection to obtain carbonate-intercalated LDHs.

[0044] S13. Dissolve 6.7g sodium oxalate and 1.5g anhydrous sodium carbonate in 500mL of deionized water to obtain an exchange solution. While hot, slowly add 5g carbonate-intercalated LDHs, sonicate for 15min, heat in a 60℃ water bath for 6h, centrifuge the resulting reaction solution, wash with 60℃ hot deoxygenated deionized water, and vacuum dry at 80℃ for 12h to obtain oxalate-carbonate-intercalated LDHs.

[0045] S14. 5g of oxalate-carbonate intercalated LDHs were stirred and dispersed in 150mL of anhydrous toluene. 10mL of N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride solution was slowly added dropwise. The mixture was heated in an oil bath at 90℃ and refluxed for 18h. The resulting reaction solution was separated and extracted with anhydrous ethanol as a solvent using Soxhlet extraction. The mixture was then dried under vacuum at 60℃ for 12h to obtain the modified LDHs material.

[0046] The concentration of the exchange solution is 0.1 mol / L, and the water bath heating reaction time in step S13 is 6 h.

[0047] The preparation method of the repair agent includes the following steps:

[0048] S21. Dissolve 4g of sodium silicate nonahydrate and 2g of sodium hexametaphosphate in 30mL of deionized water and stir magnetically until completely transparent to obtain solution A; slowly add 1.5g of sodium alginate to 100mL of deionized water, stir to dissolve, and let stand to remove bubbles to obtain solution B; stir and dissolve 0.5g of chitosan in a mixed solution of 50mL of deionized water and 5mL of glacial acetic acid to obtain solution C; dissolve 5g of calcium chloride in 100mL of deionized water to obtain solution D;

[0049] S22. Mix solutions A and B to obtain a core material mixture; mix 200 mL of liquid paraffin and 1 mL of Span-80 to obtain an oil phase; add the core material mixture and homogenize at 8000~10000 rpm for 3~5 min to obtain a W / O emulsion.

[0050] S23. Slowly add solution D to the W / O emulsion, stir at 300~500 rpm for 30 min, then slowly add solution C, continue stirring for 1 h, let the resulting reaction solution stand to precipitate, discard the upper oil phase, wash with anhydrous ethanol, centrifuge, collect the precipitate, vacuum dry at 40℃ for 24 h, and sieve through a 200 mesh standard sieve to obtain the repair agent.

[0051] The preparation method of the aminated nano-SiO2 includes the following steps:

[0052] S31. Mix 10 mL of tetraethyl orthosilicate and 20 mL of anhydrous ethanol evenly, and slowly add it dropwise to 85 mL of ammonia-ethanol mixture (80 mL of anhydrous ethanol + 5 mL of ammonia). Stir and react at 30 °C for 6 h. Seal and age the product for 24 h. Wash it with anhydrous ethanol by centrifugation to obtain nano-SiO2 wet gel.

[0053] S32. Disperse the nano-SiO2 wet gel in 80 mL of anhydrous ethanol, slowly add 2 mL of KH550, heat in an oil bath at 70 °C, reflux for 4 h, centrifuge the resulting reaction solution, wash with anhydrous ethanol and deionized water in sequence, vacuum dry at 60 °C for 12 h, grind through a 300-mesh sieve to obtain aminated nano-SiO2.

[0054] The pretreated steel slag powder is made by crushing and grinding converter steel slag, aging it in the open air at room temperature for 3 to 5 months, spraying water 1 to 2 times a week to keep the surface of the material moist but not waterlogged, and turning it over 1 to 2 times a month.

[0055] The preparation process of the active powder concrete mixed with steel slag includes the following steps:

[0056] S1. Add cement, pretreated steel slag powder, quartz powder, functional additives, silica fume, and steel fibers to a mixer and mix evenly to obtain dry material;

[0057] S2. Dissolve the high-efficiency water-reducing agent in water, slowly add the dry material, stir and mix well to obtain the slurry;

[0058] S3. Inject the slurry into the mold, vibrate to compact it, cover with plastic film, let it stand to demold, and steam cure to obtain active powder concrete.

[0059] Example 2: This example is based on Example 1, but differs from Example 1 in that it includes the following components in parts by weight: 85 parts cement, 40 parts pretreated steel slag powder, 2 parts functional additives, 35 parts quartz powder, 20 parts silica fume, 22 parts steel fiber, 1.7 parts high-efficiency water-reducing agent, and 30 parts water.

[0060] The other components and preparation methods are the same as in Example 1.

[0061] Example 3: This example is based on Example 1, but differs from Example 1 in that it includes the following components in parts by weight: 70 parts cement, 30 parts pretreated steel slag powder, 1.5 parts functional additives, 20 parts quartz powder, 15 parts silica fume, 15 parts steel fiber, 1.5 parts high-efficiency water-reducing agent, and 25 parts water.

[0062] The other components and preparation methods are the same as in Example 1.

[0063] Example 4: This example is based on Example 1, but differs from Example 1 in that the functional additives in this example include modified LDHs materials, repair agents and aminated nano-SiO2, with a mass ratio of 1:0.5:0.5.

[0064] The other components and preparation methods are the same as in Example 1.

[0065] Example 5: This example is based on Example 1, but differs from Example 1 in that the functional additives in this example include modified LDHs materials, repair agents and aminated nano-SiO2, with a mass ratio of 2:1.5:1.5.

[0066] The other components and preparation methods are the same as in Example 1.

[0067] Example 6: This example is based on Example 1, but differs from Example 1 in that the concentration of the exchange solution in this example is 0.3 mol / L, and the ion exchange reaction time in step S13 is 6 h.

[0068] The other components and preparation methods are the same as in Example 1.

[0069] Comparative Example 1: This comparative example is based on Example 1, but differs from Example 1 in that the modified LDHs material described in this comparative example is a carbonate intercalated LDH with quaternary ammonium salt groups modified on the surface.

[0070] The preparation method of the carbonate-intercalated LDHs includes the following steps:

[0071] S11. Dissolve 12.2g magnesium chloride hexahydrate and 4.8g aluminum chloride nonahydrate in 200mL of deionized water to obtain a salt solution; dissolve 3.7g anhydrous sodium carbonate and 5.6g sodium hydroxide in 200mL of deionized water to obtain a mixed alkaline solution;

[0072] S12. Under continuous nitrogen purging and mechanical stirring, the salt solution and mixed alkali solution were simultaneously and slowly added dropwise to 50 mL of deionized water. The reaction was carried out in a water bath at 65 °C for 20 h. The resulting reaction solution was centrifuged, washed alternately with deionized water and anhydrous ethanol, dried under vacuum at 80 °C for 24 h, ground through a 200-mesh sieve, and calcined at 450-500 °C for 4 h under nitrogen protection to obtain carbonate-intercalated LDHs.

[0073] S13. 5g of carbonate-intercalated LDHs were stirred and dispersed in 150mL of anhydrous toluene. 10mL of N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride solution was slowly added dropwise. The mixture was heated in an oil bath at 90℃ and refluxed for 18h. The resulting reaction solution was separated and extracted with anhydrous ethanol as a solvent using a Soxhlet extractor. The mixture was then dried under vacuum at 60℃ for 12h to obtain the modified LDHs material.

[0074] The other components and preparation methods are the same as in Example 1.

[0075] Comparative Example 2: This comparative example is based on Example 1, but differs from Example 1 in that the modified LDHs material described in this comparative example is oxalate-intercalated LDHs with quaternary ammonium salt groups modified on the surface.

[0076] The preparation method of the modified LDHs material includes the following steps:

[0077] S11. Dissolve 12.2g of magnesium chloride hexahydrate and 4.8g of aluminum chloride nonahydrate in 200mL of deionized water to obtain a salt solution; dissolve 8g of sodium hydroxide in 200mL of deionized water to obtain an alkaline solution;

[0078] S12. Under continuous nitrogen purging and mechanical stirring, the salt solution and alkaline solution were simultaneously and slowly added dropwise to 50 mL of deionized water. The reaction was carried out at 65 °C in a water bath for 20 h. The resulting reaction solution was centrifuged, and the precipitate was collected and redispersed in 500 mL of 1 mol / L sodium oxalate solution. The reaction was carried out under nitrogen protection at 60 °C with stirring for 24 h. The resulting reaction solution was centrifuged, washed with 60 °C hot deoxygenated deionized water and ethanol, and vacuum dried at 80 °C for 12 h to obtain oxalate-intercalated LDHs.

[0079] S13. 5g of oxalate-intercalated LDHs were stirred and dispersed in 150mL of anhydrous toluene. 10mL of N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride solution was slowly added dropwise. The mixture was heated in an oil bath at 90℃ and refluxed for 18h. The resulting reaction solution was separated and extracted with anhydrous ethanol as a solvent using Soxhlet extraction. The mixture was then dried under vacuum at 60℃ for 12h to obtain the modified LDHs material.

[0080] The other components and preparation methods are the same as in Example 1.

[0081] Comparative Example 3: This comparative example is based on Example 1, but differs from Example 1 in that the modified LDHs material described in this comparative example is oxalate-carbonate intercalated LDHs.

[0082] The preparation method of the modified LDHs material includes the following steps:

[0083] S11. Dissolve 12.2g magnesium chloride hexahydrate and 4.8g aluminum chloride nonahydrate in 200mL of deionized water to obtain a salt solution; dissolve 3.7g anhydrous sodium carbonate and 5.6g sodium hydroxide in 200mL of deionized water to obtain a mixed alkaline solution;

[0084] S12. Under continuous nitrogen gas and mechanical stirring, the salt solution and mixed alkaline solution were simultaneously and slowly added dropwise to 50 mL of deionized water. The reaction was carried out at 65 °C in a water bath for 20 h. The resulting reaction solution was centrifuged, washed alternately with deionized water and anhydrous ethanol, dried under vacuum at 80 °C for 24 h, and ground through a 200-mesh sieve to obtain carbonate-intercalated LDHs.

[0085] S13. Dissolve 6.7g of sodium oxalate in 500mL of deionized water to obtain an exchange solution. Slowly add 5g of carbonate-intercalated LDHs, sonicate for 15min, heat in a 60℃ water bath, and perform an ion exchange reaction for 2h. Centrifuge the resulting reaction solution, wash with 60℃ hot deoxygenated deionized water, and vacuum dry at 80℃ for 12h to obtain the modified LDHs material.

[0086] The other components and preparation methods are the same as in Example 1.

[0087] Comparative Example 4: This comparative example differs from Example 1 in that the repair agent described in this comparative example is Ca-free. 2+ Response silicate-phosphate composites.

[0088] The preparation method of the repair agent includes the following steps:

[0089] S21. Dissolve 4g sodium silicate nonahydrate and 2g sodium hexametaphosphate in 30mL of deionized water and stir magnetically until completely transparent to obtain solution A; dissolve 3g gelatin in 70mL of deionized water by heating in a 40℃ water bath to obtain wall material liquid;

[0090] S22. Mix 200 mL of liquid paraffin and 1 mL of Span-80 to obtain the oil phase; mix solution A and wall material liquid, emulsify in the oil phase at 40 °C to form an emulsion, cool in an ice bath, stir at low temperature for 1 h, collect the precipitate by centrifugation, wash with cold ethanol, and vacuum dry at 25 °C to obtain the repair agent.

[0091] The other components and preparation methods are the same as in Example 1.

[0092] Comparative Example 5: This comparative example differs from Example 1 in that the repair agent used in this comparative example is Ca. 2+ Responsive silicate composites.

[0093] The preparation method of the repair agent includes the following steps:

[0094] S21. Dissolve 6g of sodium silicate nonahydrate in 30mL of deionized water using magnetic stirring until completely transparent to obtain solution A; slowly add 1.5g of sodium alginate to 100mL of deionized water, stir to dissolve, and allow to stand to remove bubbles to obtain solution B; dissolve 0.5g of chitosan in a mixture of 50mL of deionized water and 5mL of glacial acetic acid to obtain solution C; dissolve 5g of calcium chloride in 100mL of deionized water to obtain solution D.

[0095] S22. Mix solutions A and B to obtain a core material mixture; mix 200 mL of liquid paraffin and 1 mL of Span-80 to obtain an oil phase; add the core material mixture and homogenize at 8000~10000 rpm for 3~5 min to obtain a W / O emulsion.

[0096] S23. Slowly add solution D to the W / O emulsion, stir at 300~500 rpm for 30 min, then slowly add solution C, continue stirring for 1 h, let the resulting reaction solution stand to precipitate, discard the upper oil phase, wash with anhydrous ethanol, centrifuge, collect the precipitate, vacuum dry at 40℃ for 24 h, and sieve through a 200 mesh standard sieve to obtain the repair agent.

[0097] The other components and preparation methods are the same as in Example 1.

[0098] Comparative Example 6: This comparative example differs from Example 1 in that the repair agent used in this comparative example is Ca. 2+ Responsive phosphate composites.

[0099] The preparation method of the repair agent includes the following steps:

[0100] S21. Dissolve 5g of sodium hexametaphosphate in 30mL of deionized water and stir magnetically until completely transparent to obtain solution A; slowly add 1.5g of sodium alginate to 100mL of deionized water, stir to dissolve, and let stand to remove bubbles to obtain solution B; stir and dissolve 0.5g of chitosan in a mixed solution of 50mL of deionized water and 5mL of glacial acetic acid to obtain solution C; dissolve 5g of calcium chloride in 100mL of deionized water to obtain solution D.

[0101] S22. Mix solutions A and B to obtain a core material mixture; mix 200 mL of liquid paraffin and 1 mL of Span-80 to obtain an oil phase; add the core material mixture and homogenize at 8000~10000 rpm for 3~5 min to obtain a W / O emulsion.

[0102] S23. Slowly add solution D to the W / O emulsion, stir at 300~500 rpm for 30 min, then slowly add solution C, continue stirring for 1 h, let the resulting reaction solution stand to precipitate, discard the upper oil phase, wash with anhydrous ethanol, centrifuge, collect the precipitate, vacuum dry at 40℃ for 24 h, and sieve through a 200 mesh standard sieve to obtain the repair agent.

[0103] The other components and preparation methods are the same as in Example 1.

[0104] Comparative Example 7: This comparative example is based on Example 1, but differs from Example 1 in that the aminated nano-SiO2 described in this comparative example is not subjected to amino functionalization treatment.

[0105] The other components and preparation methods are the same as in Example 1.

[0106] Comparative Example 8: This comparative example is based on Example 1, but unlike Example 1, no modified LDHs material is added.

[0107] The other components and preparation methods are the same as in Example 1.

[0108] Comparative Example 9: This comparative example is based on Example 1, but unlike Example 1, no repair agent is added to this comparative example.

[0109] The other components and preparation methods are the same as in Example 1.

[0110] Comparative Example 10: This comparative example is based on Example 1, but unlike Example 1, no functional additives are added.

[0111] The other components and preparation methods are the same as in Example 1.

[0112] Experimental verification:

[0113] Experiment 1: Ca 2+ Response release test

[0114] (1) Add the repair agent to a 30 mmol / L Ca(OH)2 solution, stir in a constant temperature water bath at 25℃, and after 24 h, take a sample and centrifuge to determine the concentration of silicate and phosphate in the supernatant and calculate the release rate.

[0115] (2) The modified LDHs material was added to a 30 mmol / L Ca(OH)2 solution and stirred in a constant temperature water bath at 25°C. After 24 h, a sample was taken and centrifuged to determine the oxalate concentration in the supernatant and the release rate was calculated.

[0116] The modified LDHs material was added to a 30 mmol / L Ca(OH)2 solution and stirred in a constant temperature water bath at 25℃ for 4 h. The treated material was then added to a 50 mg / L phosphate solution. After 24 h, a sample was taken to determine the concentration of the remaining phosphate and the phosphate capture rate was calculated.

[0117] The modified LDHs material was dispersed in a CO2-free saturated Ca(OH)2 solution, sealed, and incubated at 25℃ for 90 days. Samples were then taken to determine the carbonate concentration and calculate the release rate.

[0118] Table 1. Ca 2+ Response release test:

[0119]

[0120] Ca 2+ The response release test results are shown in Table 1. Comparing Example 1 and Comparative Example 4, no Ca was observed. 2+ The silicates and phosphates of the responding repair agent dissolve slowly, resulting in a low release rate. Comparing Example 1 with Comparative Examples 1-3, it can be seen that the oxalate ions on the outer layer of the modified LDHs material can dissolve rapidly, consuming Ca. 2+ After the oxalate is released, the interlayer vacancies can efficiently capture phosphate. Quaternary ammonium salt modification enhances the phosphate capture ability, while the carbonate inner layer can provide long-term sustained-release repair performance.

[0121] Experiment 2: Performance Testing of Reactive Powder Concrete

[0122] (1) Compressive strength test: The reactive powder concrete was prepared into 40mm×40mm×40mm specimens, and the 28-day compressive strength was tested according to GB / T17671-2021 "Test method for strength of cement mortar (ISO method)".

[0123] (2) Compressive strength test: The reactive powder concrete was prepared into 40mm×40mm×160mm specimens, and the flexural strength was tested for 28 days according to GB / T17671-2021.

[0124] (3) Autoclaving expansion rate test: The reactive powder concrete was prepared into 25mm×25mm×280mm specimens. After standard curing for 24h, the initial length was tested. The specimens were placed in a pressure cooker at 2MPa and 215℃ for 3h. After cooling, the length change was tested and the autoclaving expansion rate was calculated.

[0125] (4) Freeze-thaw cycle test: The reactive powder concrete was prepared into 100mm×100mm×400mm specimens and subjected to freeze-thaw cycles at -18±2℃ to 5±2℃. After 150 cycles, the relative dynamic modulus of elasticity and mass loss rate were measured.

[0126] Table 2. Performance Tests of Reactive Powder Concrete:

[0127]

[0128] The performance test results of reactive powder concrete are shown in Table 2. As can be seen from the table, the mechanical properties, volume stability, and long-term durability of the example with added functional additives are better than those of the control example.

[0129] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A reactive powder concrete doped with steel slag, characterized in that, The components include the following parts by weight: 70-100 parts cement, 30-50 parts pretreated steel slag powder, 1.5-3.5 parts functional additives, 20-50 parts quartz powder, 15-25 parts silica fume, 15-30 parts steel fiber, 1.5-2 parts high-efficiency water-reducing agent, and 25-35 parts water. The functional additives include modified LDHs materials, repair agents, and aminated nano-SiO2, with a mass ratio of 1~2:0.5~1.5:0.5~1.5; The modified LDHs material is oxalate-carbonate intercalated LDHs with quaternary ammonium salt groups modified on the surface; The repair agent is Ca 2+ Responsive silicate-phosphate composites The preparation method of the modified LDHs material includes the following steps: S11. Dissolve 12.2g magnesium chloride hexahydrate and 4.8g aluminum chloride nonahydrate in 200mL of deionized water to obtain a salt solution; dissolve 3.7g anhydrous sodium carbonate and 5.6g sodium hydroxide in 200mL of deionized water to obtain a mixed alkaline solution; S12. Under continuous nitrogen purging and mechanical stirring, the salt solution and mixed alkali solution were simultaneously and slowly added dropwise to 50 mL of deionized water. The reaction was carried out in a water bath at 65 °C for 20 h. The resulting reaction solution was centrifuged, washed alternately with deionized water and anhydrous ethanol, dried under vacuum at 80 °C for 24 h, ground through a 200-mesh sieve, and calcined at 450-500 °C for 4 h under nitrogen protection to obtain carbonate-intercalated LDHs. S13. Dissolve 6.7g sodium oxalate and 1.5g anhydrous sodium carbonate in 500mL of deionized water to obtain an exchange solution. While hot, slowly add 5g carbonate-intercalated LDHs, sonicate for 15min, heat in a 60℃ water bath for 6h, centrifuge the resulting reaction solution, wash with 60℃ hot deoxygenated deionized water, and vacuum dry at 80℃ for 12h to obtain oxalate-carbonate-intercalated LDHs. S14. 5g of oxalate-carbonate intercalated LDHs were stirred and dispersed in 150mL of anhydrous toluene. 10mL of N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride solution was slowly added dropwise. The mixture was heated in an oil bath at 90℃ and refluxed for 18h. The resulting reaction solution was separated and extracted with anhydrous ethanol as a solvent using Soxhlet extraction. The solution was then dried under vacuum at 60℃ for 12h to obtain the modified LDHs material. The preparation method of the repair agent includes the following steps: S21. Dissolve 4g of sodium silicate nonahydrate and 2g of sodium hexametaphosphate in 30mL of deionized water and stir magnetically until completely transparent to obtain solution A; slowly add 1.5g of sodium alginate to 100mL of deionized water, stir to dissolve, and let stand to remove bubbles to obtain solution B; stir and dissolve 0.5g of chitosan in a mixed solution of 50mL of deionized water and 5mL of glacial acetic acid to obtain solution C; dissolve 5g of calcium chloride in 100mL of deionized water to obtain solution D; S22. Mix solutions A and B to obtain a core material mixture; mix 200 mL of liquid paraffin and 1 mL of Span-80 to obtain an oil phase; add the core material mixture and homogenize at high speed to obtain a W / O emulsion. S23. Slowly add solution D to the W / O emulsion, stir and react, then slowly add solution C, continue stirring and reacting for 1 hour. Let the resulting reaction solution stand to precipitate, pour off the upper oil phase, wash with anhydrous ethanol and centrifuge, collect the precipitate and vacuum dry at 40°C for 24 hours, and sieve through a 200-mesh standard sieve to obtain the repair agent. The preparation method of the aminated nano-SiO2 includes the following steps: S31. Mix 10 mL of tetraethyl orthosilicate and 20 mL of anhydrous ethanol evenly, and slowly add it dropwise to 85 mL of ammonia-ethanol mixture. Stir at 30 °C for 6 h. The product is sealed and aged for 24 h. It is then washed by centrifugation with anhydrous ethanol to obtain nano-SiO2 wet gel. S32. Disperse the nano-SiO2 wet gel in 80 mL of anhydrous ethanol, slowly add 2 mL of KH550, heat in an oil bath at 70 °C, reflux for 4 h, centrifuge the resulting reaction solution, wash with anhydrous ethanol and deionized water in sequence, vacuum dry at 60 °C for 12 h, grind through a 300-mesh sieve to obtain aminated nano-SiO2.

2. The reactive powder concrete containing steel slag according to claim 1, characterized in that, The concentration of the exchange solution is 0.1~0.3 mol / L, and the water bath heating reaction time in step S13 is 6~12 h.

3. The reactive powder concrete containing steel slag according to claim 1, characterized in that, The pretreated steel slag powder is obtained by crushing and grinding converter steel slag and then aging it in the open air.

4. A process for preparing reactive powder concrete mixed with steel slag, applied to the preparation of reactive powder concrete mixed with steel slag as described in any one of claims 1 to 3, characterized in that, The process includes the following steps: S1. Add cement, pretreated steel slag powder, quartz powder, functional additives, silica fume, and steel fibers to a mixer and mix evenly to obtain dry material; S2. Dissolve the high-efficiency water-reducing agent in water, slowly add the dry material, stir and mix well to obtain the slurry; S3. Inject the slurry into the mold, vibrate to compact it, cover with plastic film, let it stand to demold, and steam cure to obtain active powder concrete.

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