Steel slag-based in-situ grown hybrid nanoparticles and method of making same

Abstract

The application discloses a kind of steel slag-based in-situ growth hybrid nanoparticles and preparation method thereof, the steel slag-based in-situ growth hybrid nanoparticles include steel slag matrix, calcium-containing nanoparticles are in-situ grown on the surface of steel slag matrix, and nanometer silicon dioxide is in-situ grown with calcium-containing nanoparticles as nucleation site. Its preparation method includes sol-gel method for preparing steel slag-based in-situ growth hybrid nanometer calcium silicate hydrate and nanometer silicon dioxide, and carbonization method for preparing steel slag-based in-situ growth hybrid nanometer calcium carbonate and nanometer silicon dioxide. The application can improve the dispersibility of nanoparticles in cement-based materials, and also improve the cementing activity and volume stability of steel slag. In addition, the application can strengthen the bonding force between nanoparticles and matrix, and ensure the use effect of in-situ growth hybrid nanoparticles as nanometer additive or mineral admixture.

Description

TECHNICAL FIELD

[0001] The present application relates to a steel slag-based composite material and a preparation method thereof, in particular to a steel slag-based in-situ growth hybrid nanoparticles and a preparation method thereof. BACKGROUND

[0002] At present, the main nano materials commonly used for modifying cement-based materials are carbon nano materials (carbon nanotubes and graphene, etc.) and inorganic nanoparticles (nano-silicon dioxide, nano-calcium carbonate, nano-hydrated calcium silicate, nano-titanium dioxide and nano-aluminum oxide, etc.). Among them, nano-silicon dioxide, nano-hydrated calcium silicate and nano-calcium carbonate have received extensive attention. However, nano materials have large specific surface area and high specific surface energy, which makes them difficult to disperse and easy to agglomerate in the cement matrix, thereby limiting the exertion of the above effects.

[0003] Patents 201711143543.9 and 201810226554.1 respectively disclose a preparation method of in-situ growth of nanoparticles on the surface of solid waste and a method of in-situ growth of hydrated calcium silicate on the surface of mineral admixture. Both of the above two patents take fly ash and other solid waste as the matrix, and in-situ growth of nano-silicon dioxide, nano-calcium carbonate and nano-hydrated calcium silicate and other nanoparticles on the surface thereof, so as to obtain high-efficiency nano additives with good dispersion effect. In the above two patents, the solid waste is pretreated before in-situ growth of the nanoparticles, so as to facilitate the subsequent in-situ growth of the nanoparticles. This is mainly because the surface of fly ash and other solid waste is smooth and inert, which makes it difficult to provide nucleation sites for the in-situ growth of nanoparticles and is not conducive to the attachment and growth of nanoparticles on the solid waste matrix. Moreover, the smooth surface will weaken the bonding force between the nanoparticles and the solid waste, causing the in-situ growth nanoparticles on the surface of the solid waste to easily fall off during use (mixing with cement, etc.), which affects the use effect of the in-situ growth nanoparticles.

[0004] On the other hand, the production process of cement will cause a large amount of carbon emissions. Obviously, this does not meet the low-carbon, green and environmentally friendly concept. A large amount of steel slag stored in stockpiles has certain cementitious activity due to the presence of dicalcium silicate (C2S), tricalcium silicate (C3S), tricalcium aluminate (C3A) and tetracalcium aluminoferrite (C4AF), etc., and thus can be used as a mineral admixture to partially replace cement and reduce the amount of cement used in cement-based materials. However, steel slag has the problems of low cementitious activity and poor volume stability, which limits the large-scale resource utilization of steel slag in cement-based materials. At present, the methods for improving the cementitious activity and volume stability of steel slag mainly include physical modification (such as mechanical grinding), chemical modification (such as acetic acid modification) and reconstruction of steel slag mineral phase, etc. SUMMARY

[0005] The application aims to provide a steel slag-based in-situ growth hybrid nanoparticle with strong binding force between nanoparticles and a steel slag matrix, good nanoparticle dispersibility, high steel slag gel activity and good volume stability.

[0006] The second object of the application is to provide a preparation method of the above-mentioned steel slag-based in-situ growth hybrid nanoparticle.

[0007] The steel slag-based in-situ growth hybrid nanoparticle comprises a steel slag matrix, the surface of the steel slag matrix is in-situ growth with calcium-containing nanoparticles, and the calcium-containing nanoparticles are in-situ growth with nanosilica as nucleation sites.

[0008] The calcium-containing nanoparticles are nanometer hydrated calcium silicate or nanometer calcium carbonate.

[0009] The preparation method of the above-mentioned steel slag-based in-situ growth hybrid nanoparticle is a sol-gel method, and comprises the following steps:

[0010] (1) mixing water, anhydrous ethanol, ammonia and a surfactant to prepare solution A, and keeping solution A at a constant temperature; adding steel slag into solution A and stirring to obtain steel slag slurry A;

[0011] (2) mixing a silicon source and anhydrous ethanol, and dividing them into solution B and solution C;

[0012] (3) adding solution B into steel slag slurry A, and stirring to obtain steel slag slurry B;

[0013] (4) adding solution C into steel slag slurry B, and stirring to obtain steel slag slurry C; after washing and drying, the steel slag-based in-situ growth hybrid nanoparticle is obtained.

[0014] In step (1), the volume fractions of water, anhydrous ethanol and ammonia are 45-5 parts, 5-45 parts and 0-2 parts respectively, the mass fraction of the surfactant is 0-2 parts, and the mass fraction of the steel slag is 1-4 parts; the constant temperature of the solution is 30-60 DEG C. In step (2), the volume fractions of the silicon source and anhydrous ethanol are 0.5-2 parts and 5-10 parts respectively.

[0015] The principle of the sol-gel method is that the silicon source is added step by step, that is, part of the silicon source is added first, and after a period of reaction, the remaining silicon source is added. The silicon source added first grows nanometer hydrated calcium silicate in situ on the surface of the steel slag under the action of calcium ions released by the steel slag hydration and the basic environment. The silicon source added later hydrolyzes and condenses in the basic environment based on the nanometer hydrated calcium silicate, grows nanometer silicon dioxide in situ on the surface of the steel slag, and finally obtains steel slag-based in-situ growth hybrid nanometer hydrated calcium silicate and nanometer silicon dioxide. Specifically, the silicon source added first will hydrolyze and condense under alkaline conditions to generate silicic acid polymers. In this process, calcium ions released by steel slag hydration will combine with silicic acid polymers to generate nanometer hydrated calcium silicate, and the surface of the steel slag and the hydrated calcium silicate on the surface thereof will serve as nucleation sites for the nanometer particles containing calcium to grow in situ on the surface of the steel slag.

[0016] The above-mentioned preparation method of the steel slag-based in-situ growth hybrid nanometer particles, the nanometer particles containing calcium are nanometer calcium carbonate, and the preparation method is a carbonation method, which comprises the following steps:

[0017] (1) Mix water, anhydrous ethanol and a surfactant to prepare solution A, and keep the solution at a constant temperature; add steel slag to solution A and stir to obtain steel slag slurry A;

[0018] (2) Weigh silicon source A and silicon source B, add silicon source A to steel slag slurry A to obtain steel slag slurry B;

[0019] (3) Pass carbon dioxide gas into steel slag slurry B until the pH value of the steel slag slurry B is less than 8 to obtain steel slag slurry C;

[0020] (4) Add silicon source B to steel slag slurry C to obtain steel slag slurry D, pass carbon dioxide gas into steel slag slurry D until the pH value of the steel slag slurry D is less than 8 to obtain steel slag slurry E, wash and then dry to obtain steel slag-based in-situ growth hybrid nanometer particles.

[0021] In step (1), the constant temperature of the solution is 30-80°C; in step (2), the volume ratio of solution B to solution C is 1-3:9-7. The weight fractions of the steel slag, water, anhydrous ethanol and surfactant are 10-50 parts, 100-200 parts, 50-150 parts and 0-10 parts, respectively.

[0022] In step (3), the passing rate of the carbon dioxide gas is 150-350 ml / min, and the stirring speed is 200-400 rpm.

[0023] The principle of the carbonization method is that the silicon source is added step by step, and the carbonization reaction is carried out step by step, that is, a part of the silicon source is added first, then the first carbonization reaction is carried out, after a period of time, the remaining silicon source is added, and the second carbonization reaction is carried out.

[0024] The first added silicon source can chemically coprecipitate with calcium ions released by the steel slag hydration to grow nanometer calcium hydroxide in situ on the surface of the steel slag. Then, carbon dioxide gas is introduced to carry out the first carbonization reaction. The carbon dioxide gas dissolves in water and reacts with the nanometer calcium hydroxide grown in situ on the surface of the steel slag to generate mixed nanometer calcium carbonate and nanometer silicon dioxide. At the same time, the carbon dioxide dissolved in water also reacts with calcium ions in water to generate nanometer calcium carbonate, and due to the presence of the steel slag, the nanometer calcium carbonate grows in situ on the surface of the steel slag. Then, the remaining silicon source is added, and carbon dioxide gas is introduced to carry out the second carbonization reaction. The silicon ions in the silicon source react with the hydrogen ions produced by the dissolution of carbon dioxide in water to generate silicic acid. With the decrease of the pH value of the system, the silicic acid polymerizes into silicic acid dimers, further polymerizes into silicic acid trimers and silicic acid tetramers, and finally forms spherical nanometer silicon dioxide. And due to the chemical activity of the rough surface of the steel slag and the generation of mixed nanometer calcium carbonate and nanometer silicon dioxide by the first carbonization reaction, the steel slag can act as a nucleation site for the nanometer silicon dioxide generated by the second carbonization reaction, promoting the in-situ growth of nanometer silicon dioxide on it, and finally obtaining steel slag-based in-situ growth of mixed nanometer calcium carbonate and nanometer silicon dioxide.

[0025] Invention principle: The calcium element in the steel slag is used as the calcium source, and an intermediate transition layer containing calcium nanoparticles is first grown in situ on the surface of the steel slag, and then nanometer silicon dioxide is further grown in situ, thereby forming steel slag-based in-situ growth of mixed nanoparticles. That is, by means of the rough surface and cementitious activity of the steel slag, the bonding force between the calcium-containing nanoparticles and the steel slag matrix is strengthened, preventing the in-situ grown nanoparticles from detaching from the steel slag during use and ensuring the use effect. Compared with nanoparticles, the steel slag has a larger particle size and can be more uniformly dispersed in the cement matrix, and the nanoparticles grown in situ on the steel slag matrix can also be uniformly dispersed with the steel slag matrix in the cement matrix, thereby improving the dispersion effect of the nanoparticles in the cement matrix. The nanoparticles grown in situ on the steel slag matrix can promote the hydration of the hydraulic mineral phases in the cement and the steel slag, thereby improving the cementitious activity of the steel slag and realizing the large-volume application of the steel slag. When the in-situ grown nanoparticles are nanometer silicon dioxide, the nanometer silicon dioxide has high pozzolanic activity, which is more conducive to improving the cementitious activity of the steel slag.

[0026] In addition, the steel slag-based in-situ growth hybrid nanoparticles can improve the volume stability of the steel slag by consuming free calcium oxide f-CaO in the steel slag and the pozzolanic reaction. During the preparation of the steel slag-based in-situ growth hybrid nanoparticles, part of the f-CaO in the steel slag reacts with water and is consumed, thereby reducing the content of f-CaO in the steel slag. During the use of the steel slag-based in-situ growth hybrid nanoparticles, with the progress of hydration, f-CaO reacts with water to generate calcium hydroxide CH, but the nano-silicon dioxide in-situ grown on the steel slag matrix has high pozzolanic activity and can react with CH generated by f-CaO to generate calcium silicate hydrate C-S-H gel, thereby reducing the negative impact of f-CaO in the steel slag on the volume stability of the hardened cement-based material. The above two work together to improve the volume stability of the steel slag.

[0027] Beneficial effects: Compared with the prior art, the present application has the following remarkable effects: (1) The cementitious activity and volume stability of the steel slag are improved, which is beneficial to realize the large-dosage application of the steel slag as a mineral admixture; the bonding force between the nanoparticles and the steel slag matrix is strengthened, which ensures the use effect of the steel slag-based in-situ growth hybrid nanoparticles as a nano-additive or a mineral admixture; (2) The controllable preparation of the steel slag-based in-situ growth hybrid nano-calcium silicate and nano-silicon dioxide is realized by the sol-gel method; (3) The efficient and green preparation of the steel slag-based in-situ growth hybrid nano-calcium carbonate and nano-silicon dioxide is realized by the carbonization method; (4) The dispersibility of the nanoparticles in the cement-based material is improved, which is beneficial to the popularization and application of the nano-additive in the cement-based material. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 SEM image of the raw steel slag used in Example 1, magnified by 40000 times;

[0029] Figure 2 SEM image of the dried steel slag slurry A obtained in step (2) of Example 1, magnified by 150000 times;

[0030] Figure 3 SEM image of the dried steel slag slurry B obtained in step (4) of Example 1, magnified by 150000 times;

[0031] Figure 4 EDS spectrum of the dried steel slag slurry B obtained in step (4) of Example 1;

[0032] Figure 5 SEM image of the steel slag-based in-situ growth hybrid nanoparticles obtained in Example 1, magnified by 150000 times;

[0033] Figure 6 FT-IR image of the steel slag-based in-situ growth hybrid nanoparticles obtained in Example 1;

[0034] Figure 7 SEM image of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 2, magnified 150000 times;

[0035] Figure 8 SEM image of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 3, magnified 300000 times;

[0036] Figure 9 SEM image of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 4, magnified 40000 times;

[0037] Figure 10 SEM image of the dried steel slag slurry C obtained in step (5) of Example 5, magnified 80000 times;

[0038] Figure 11 SEM image of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 5, magnified 300000 times;

[0039] Figure 12 XRD pattern of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 5;

[0040] Figure 13 SEM image of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 6, magnified 80000 times;

[0041] Figure 14 SEM image of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 7, magnified 300000 times;

[0042] Figure 15 SEM image of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 8, magnified 300000 times. DETAILED DESCRIPTION

[0043] The present application will be further described in detail.

[0044] Example 1

[0045] The sol-gel method for preparing the steel slag-based in-situ grown hybrid nano-hydrocalumite and nano-silicon dioxide comprises the following steps:

[0046] (1) 35 parts of water, 5 parts of anhydrous ethanol and 1 part of ammonia water are measured by volume fraction, and 1 part of polyethylene glycol is weighed by weight fraction to prepare solution A, and solution A is kept at 40℃ constant temperature;

[0047] (2) 2 parts of steel slag are weighed by mass fraction, and the solution A obtained in step (1) is stirred at a speed of 300 rpm, and the steel slag is added thereto, and stirred for 5 min to obtain steel slag slurry A;

[0048] (3) Measure 1 part of tetraethyl orthosilicate and 10 parts of anhydrous ethanol by volume, mix them evenly, and then divide them into solution B and solution C according to a volume ratio of 3:7.

[0049] (4) While stirring the steel slag slurry A obtained in step (2) at a speed of 300 rpm, add solution B dropwise to it. After the addition is completed, continue stirring for 30 minutes to obtain steel slag slurry B.

[0050] (5) While stirring the steel slag slurry B obtained in step (4), add solution C dropwise to it. After the addition is completed, continue stirring for 3 hours to obtain steel slag slurry C.

[0051] (6) The steel slag slurry C obtained in the centrifugal washing step (5) is vacuum dried at 60°C to constant weight to obtain steel slag-based in-situ grown mixed nanoparticles, namely steel slag-based in-situ grown mixed nano-hydrated calcium silicate and nano-silica.

[0052] Example 2

[0053] The preparation of in-situ grown hybrid nano-hydrated calcium silicate and nano-silica on steel slag substrate by sol-gel method includes the following steps:

[0054] (1) Measure 35 parts water, 5 parts anhydrous ethanol and 1 part ammonia water by volume, and weigh 1 part polyethylene glycol by weight to prepare solution A. Keep solution A at a constant temperature of 40°C.

[0055] (2) Weigh 2 parts of steel slag according to the mass fraction, and add the steel slag to the solution A obtained in step (1) while stirring at a speed of 300 rpm. Stir for 5 minutes to obtain steel slag slurry A.

[0056] (3) Measure 0.5 parts of tetraethyl orthosilicate and 10 parts of anhydrous ethanol by volume, mix them evenly, and then divide them into solution B and solution C according to a volume ratio of 3:7.

[0057] (4) While stirring the steel slag slurry A obtained in step (2) at a speed of 300 rpm, add solution B dropwise to it. After the addition is completed, continue stirring for 30 minutes to obtain steel slag slurry B.

[0058] (5) While stirring the steel slag slurry B obtained in step (4), add solution C dropwise to it. After the addition is completed, continue stirring for 1.5 hours to obtain steel slag slurry C.

[0059] (6) The steel slag slurry C obtained in the centrifugal washing step (5) is vacuum dried at 60°C to constant weight to obtain steel slag-based in-situ grown mixed nanoparticles, namely steel slag-based in-situ grown mixed nano-hydrated calcium silicate and nano-silica.

[0060] Example 3

[0061] The preparation of in-situ grown hybrid nano-hydrated calcium silicate and nano-silica on steel slag substrate by sol-gel method includes the following steps:

[0062] (1) Measure 10 parts water, 30 parts anhydrous ethanol and 2 parts ammonia water by volume, and weigh 2 parts polyethylene glycol by weight to prepare solution A. Keep solution A at a constant temperature of 30°C.

[0063] (2) Weigh out 1 part of steel slag according to the mass fraction, and add the steel slag to the solution A obtained in step (1) while stirring at a speed of 300 rpm. Stir for 5 minutes to obtain steel slag slurry A.

[0064] (3) Measure 1 part of tetraethyl orthosilicate and 10 parts of anhydrous ethanol by volume, mix them evenly, and then divide them into solution B and solution C according to a volume ratio of 1:9.

[0065] (4) While stirring the steel slag slurry A obtained in step (2) at a speed of 200 rpm, add solution B dropwise to it. After the addition is completed, continue stirring for 60 min to obtain steel slag slurry B.

[0066] (5) While stirring the steel slag slurry B obtained in step (4), add solution C dropwise to it. After the addition is completed, continue stirring for 8 hours to obtain steel slag slurry C.

[0067] (6) The steel slag slurry C obtained in the centrifugal washing step (5) is vacuum dried at 60°C to constant weight to obtain steel slag-based in-situ grown mixed nanoparticles, namely steel slag-based in-situ grown mixed nano-hydrated calcium silicate and nano-silica.

[0068] Example 4

[0069] The preparation of in-situ grown hybrid nano-hydrated calcium silicate and nano-silica on steel slag substrate by sol-gel method includes the following steps:

[0070] (1) Measure 40 parts water and 0.5 parts ammonia water by volume, and weigh 0.5 parts polyethylene glycol by weight to prepare solution A. Keep solution A at a constant temperature of 60°C.

[0071] (2) Weigh 4 parts of steel slag according to the mass fraction, and add the steel slag to the solution A obtained in step (1) while stirring at a speed of 400 rpm. Stir for 5 minutes to obtain steel slag slurry A.

[0072] (3) Measure 2 parts of tetraethyl orthosilicate and 10 parts of anhydrous ethanol by volume, mix them evenly, and then divide them into solution B and solution C according to a volume ratio of 2:8.

[0073] (4) While stirring the steel slag slurry A obtained in step (2) at a speed of 300 rpm, add solution B dropwise to it. After the addition is completed, continue stirring for 10 minutes to obtain steel slag slurry B.

[0074] (5) While stirring the steel slag slurry B obtained in step (4), add solution C dropwise to it. After the addition is completed, continue stirring for 1 hour to obtain steel slag slurry C.

[0075] (6) The steel slag slurry C obtained in the centrifugal washing step (5) is vacuum dried at 60°C to constant weight to obtain steel slag-based in-situ grown mixed nanoparticles, namely steel slag-based in-situ grown mixed nano-hydrated calcium silicate and nano-silica.

[0076] Example 5

[0077] The preparation of in-situ grown hybrid nano-calcium carbonate and nano-silica on steel slag basis by carbonation method includes the following steps:

[0078] (1) Weigh 200 parts water, 50 parts anhydrous ethanol and 5 parts polyethylene glycol according to the weight ratio, and prepare solution A. Keep solution A at a constant temperature of 40°C.

[0079] (2) Weigh 25 parts of steel slag according to the weight ratio, and add the steel slag to the solution A obtained in step (1) while stirring at a speed of 400 rpm. Stir for 5 minutes to obtain steel slag slurry A.

[0080] (3) Weigh 15 parts of sodium metasilicate with zero water according to the weight ratio, and divide them into silicon source A and silicon source B according to the weight ratio of 1:9;

[0081] (4) Add the silicon source A obtained in step (3) to the steel slag slurry A obtained in step (2) to obtain steel slag slurry B;

[0082] (5) While stirring the steel slag slurry B obtained in step (4) at a speed of 400 rpm, carbon dioxide gas is introduced into it at a flow rate of 250 ml / min until the pH value of the steel slag slurry B is less than 8, and steel slag slurry C is obtained.

[0083] (6) Add the silicon source B obtained in step (3) to the steel slag slurry C obtained in step (5) to obtain steel slag slurry D;

[0084] (7) While stirring the steel slag slurry D obtained in step (6) at a speed of 400 rpm, carbon dioxide gas is introduced into it at a flow rate of 250 ml / min until the pH value of the steel slag slurry D is less than 8, and steel slag slurry E is obtained.

[0085] (8) The steel slag slurry E obtained from the centrifugal washing step (7) is vacuum dried at 60°C to constant weight to obtain steel slag-based in-situ grown mixed nanoparticles, namely steel slag-based in-situ grown mixed nano calcium carbonate and nano silica.

[0086] Example 6

[0087] The preparation of in-situ grown hybrid nano-calcium carbonate and nano-silica on steel slag basis by carbonation method includes the following steps:

[0088] (1) Weigh 200 parts water, 50 parts anhydrous ethanol and 5 parts polyethylene glycol according to the weight ratio, and prepare solution A. Keep solution A at a constant temperature of 40°C.

[0089] (2) Weigh 25 parts of steel slag according to the weight ratio, and add the steel slag to the solution A obtained in step (1) while stirring at a speed of 400 rpm. Stir for 5 minutes to obtain steel slag slurry A.

[0090] (3) Weigh 5 parts of sodium metasilicate with zero water according to the weight ratio, and divide them into silicon source A and silicon source B according to the weight ratio of 1:9;

[0091] (4) Add the silicon source A obtained in step (3) to the steel slag slurry A obtained in step (2) to obtain steel slag slurry B;

[0092] (5) While stirring the steel slag slurry B obtained in step (4) at a speed of 400 rpm, carbon dioxide gas is introduced into it at a flow rate of 250 ml / min until the pH value of the steel slag slurry B is less than 8, and steel slag slurry C is obtained.

[0093] (6) Add the silicon source B obtained in step (3) to the steel slag slurry C obtained in step (5) to obtain steel slag slurry D;

[0094] (7) While stirring the steel slag slurry D obtained in step (6) at a speed of 400 rpm, carbon dioxide gas is introduced into it at a flow rate of 250 ml / min until the pH value of the steel slag slurry D is less than 8, and steel slag slurry E is obtained.

[0095] (8) The steel slag slurry E obtained from the centrifugal washing step (7) is vacuum dried at 60°C to constant weight to obtain steel slag-based in-situ grown mixed nanoparticles, namely steel slag-based in-situ grown mixed nano calcium carbonate and nano silica.

[0096] Example 7

[0097] The preparation of in-situ grown hybrid nano-calcium carbonate and nano-silica on steel slag basis by carbonation method includes the following steps:

[0098] (1) Weigh out 100 parts water, 150 parts anhydrous ethanol and 5 parts cetyltrimethylammonium bromide according to the weight ratio, and prepare solution A. Keep solution A at a constant temperature of 30°C.

[0099] (2) Weigh 25 parts of steel slag according to the weight ratio, and add the steel slag to the solution A obtained in step (1) while stirring at a speed of 400 rpm. Stir for 5 minutes to obtain steel slag slurry A.

[0100] (3) Weigh 10 parts of sodium metasilicate with zero water according to the weight ratio, and divide them into silicon source A and silicon source B according to the weight ratio of 2:8;

[0101] (4) Add the silicon source A obtained in step (3) to the steel slag slurry A obtained in step (2) to obtain steel slag slurry B;

[0102] (5) While stirring the steel slag slurry B obtained in step (4) at a speed of 400 rpm, carbon dioxide gas is introduced into it at a flow rate of 150 ml / min until the pH value of the steel slag slurry B is less than 8, and steel slag slurry C is obtained.

[0103] (6) Add the silicon source B obtained in step (3) to the steel slag slurry C obtained in step (5) to obtain steel slag slurry D;

[0104] (7) While stirring the steel slag slurry D obtained in step (6) at a speed of 400 rpm, carbon dioxide gas is introduced into it at a flow rate of 150 ml / min until the pH value of the steel slag slurry D is less than 8, and steel slag slurry E is obtained.

[0105] (8) The steel slag slurry E obtained from the centrifugal washing step (7) is vacuum dried at 60°C to constant weight to obtain steel slag-based in-situ grown mixed nanoparticles, namely steel slag-based in-situ grown mixed nano calcium carbonate and nano silica.

[0106] Example 8

[0107] The preparation of in-situ grown hybrid nano-calcium carbonate and nano-silica on steel slag basis by carbonation method includes the following steps:

[0108] (1) Weigh 150 parts water, 100 parts anhydrous ethanol and 10 parts cetyltrimethylammonium bromide according to the weight ratio, prepare solution A, and keep solution A at a constant temperature of 80°C.

[0109] (2) Weigh 25 parts of steel slag according to the weight ratio, and add the steel slag to the solution A obtained in step (1) while stirring at a speed of 400 rpm. Stir for 5 minutes to obtain steel slag slurry A.

[0110] (3) Weigh 25 parts of sodium metasilicate with zero water according to the weight ratio, and divide them into silicon source A and silicon source B according to the weight ratio of 1:9;

[0111] (4) Add the silicon source A obtained in step (3) to the steel slag slurry A obtained in step (2) to obtain steel slag slurry B;

[0112] (5) While stirring the steel slag slurry B obtained in step (4) at a speed of 400 rpm, carbon dioxide gas is introduced into it at a flow rate of 350 ml / min until the pH value of the steel slag slurry B is less than 8, and steel slag slurry C is obtained.

[0113] (6) Add the silicon source B obtained in step (3) to the steel slag slurry C obtained in step (5) to obtain steel slag slurry D;

[0114] (7) While stirring the steel slag slurry D obtained in step (6) at a speed of 400 rpm, carbon dioxide gas is introduced into it at a flow rate of 350 ml / min until the pH value of the steel slag slurry D is less than 8, and steel slag slurry E is obtained.

[0115] (8) The steel slag slurry E obtained from the centrifugal washing step (7) is vacuum dried at 60°C to constant weight to obtain steel slag-based in-situ grown mixed nanoparticles, namely steel slag-based in-situ grown mixed nano calcium carbonate and nano silica.

[0116] The steel slag-based in-situ grown hybrid nanoparticles obtained in Examples 1-8 were characterized and tested, and then used to modify cement-based materials, as detailed below:

[0117] (1) The steel slag-based in-situ grown hybrid nanoparticles obtained in Examples 1 to 4 were characterized by the following tests:

[0118] Figure 1 The image shows the SEM image of the undisturbed steel slag used in Example 1. It can be seen that the surface of the steel slag is relatively rough.

[0119] Figure 2 The image shows the SEM image of the steel slag slurry A obtained in step (2) of Example 1 after drying. It can be seen that the steel slag underwent a certain degree of hydration reaction when it came into contact with water, and there were hydration products on its surface, namely the formation of hydrated calcium silicate.

[0120] Figure 3 The image shows the SEM image of the dried steel slag slurry B obtained in step (4) of Example 1. It can be seen that there are hemispherical nanoparticles on the surface of the steel slag, and these hemispherical nanoparticles are tightly bonded to the steel slag matrix.

[0121] Furthermore, the elemental composition of the hemispherical nanoparticles was analyzed. Figure 4The EDS spectrum of the steel slag slurry B obtained in step (4) of Example 1 after drying shows that the hemispherical particles on the surface of the steel slag are nano-hydrated calcium silicate with a low calcium-to-silicon ratio, wherein the calcium / silicon molar ratio is 0.2.

[0122] Figure 5 The image shows an SEM image of the in-situ grown mixed nanoparticles on the steel slag substrate obtained in Example 1. It can be seen that spherical nanoparticles with a particle size of about 40 nm are grown in situ on the surface of the steel slag.

[0123] Figure 6 This is the FT-IR image of the in-situ grown hybrid nanoparticles on the steel slag substrate obtained in Example 1. For the undisturbed steel slag, at 516 cm⁻¹... -1 An in-plane bending vibration peak of Si-O is present at this location. However, in the FT-IR spectrum of the obtained in-situ grown hybrid nanoparticles on steel slag substrate, this peak is significantly weakened, and instead, a peak appears at 461 cm⁻¹. -1 A distinct Si-O-Si bending vibration characteristic peak appeared at 985 cm⁻¹. Furthermore, the undisturbed steel slag showed a peak at 985 cm⁻¹. -1 An antisymmetric stretching vibration absorption peak of Si-O-Si appeared at [value missing], while in the obtained in-situ grown hybrid nanoparticles based on steel slag, this peak shifted significantly to the left, specifically to 1080 cm⁻¹. -1 This indicates a significant increase in the degree of polymerization of Si-O-Si, which is attributed to the hydrolytic condensation reaction of tetraethyl orthosilicate. Therefore, it can be concluded that the in-situ growth of hybrid nanoparticles, namely nano-hydrated calcium silicate and nano-silica, on the surface of steel slag can be achieved using the sol-gel method through the hydrolytic condensation reaction of tetraethyl orthosilicate.

[0124] Figures 7 to 9 The images show SEM images of the in-situ grown mixed nanoparticles on the steel slag substrate obtained in Examples 2-4. It can be seen that mixed nanoparticles are grown in situ on the surface of the steel slag.

[0125] (2) The steel slag-based in-situ grown hybrid nanoparticles obtained in Examples 5-8, namely steel slag-based in-situ grown hybrid nano-calcium carbonate and nano-silica, were characterized and tested as follows:

[0126] Figure 10 The image shows the SEM image of the steel slag slurry C obtained in step (5) of Example 5 after drying. It can be seen that nano-calcium carbonate and nano-silica are grown in situ on the surface of the steel slag, and the nano-silica is tightly bonded to the steel slag matrix.

[0127] Figure 11 The image shows an SEM image of the in-situ grown mixed nanoparticles on the steel slag substrate obtained in Example 5. It can be seen that nano-silica with a particle size of 30-50 nm is grown in situ on the surface of the steel slag.

[0128] Figure 12The XRD pattern of the in-situ grown hybrid nanoparticles on the steel slag substrate obtained in Example 5 shows that obvious characteristic diffraction peaks of calcium carbonate appear in the XRD pattern of the obtained in-situ grown hybrid nanoparticles on the steel slag substrate. In summary, it can be concluded that the in-situ growth of hybrid nanoparticles, namely nano-calcium carbonate and nano-silica, on the surface of steel slag can be achieved through the carbonization method.

[0129] Figures 13 to 15 The images shown are SEM images of the steel slag-based in-situ grown mixed nanoparticles obtained in Examples 6-8. It can be seen that mixed nanoparticles are grown in situ on the surface of the steel slag.

[0130] (3) Effect of steel slag-based in-situ grown hybrid nanoparticles obtained in Examples 1 and 5 as nano-additives on the properties of cement-based materials

[0131] The steel slag-based in-situ grown hybrid nanoparticles obtained in Example 1 and Example 5 were used as nano-additives and incorporated into cement paste, respectively. Thermogravimetric analysis showed that the content of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 1 was 11.64%, and the content of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 5 was 19.76%. Based on this, comparative examples 1, 2, and 9, as well as comparative examples 3, 4, and 10, were designed using the controlled variable method. Details are as follows:

[0132] Comparative Example 1

[0133] Weigh out 469.64 parts by weight of P.II 52.5 cement, 30.36 parts by weight of steel slag, and 200 parts by weight of water, and mix them to form a cement paste. Determine the fluidity of the freshly mixed cement paste according to GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures", and determine the compressive strength of the hardened cement paste according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0134] Comparative Example 2

[0135] Weigh out 469.64 parts by weight of P.II 52.5 cement, 30.36 parts by weight of steel slag, 4 parts by weight of commercial nano-silica with a particle size of approximately 40 nm, and 200 parts by weight of water, and mix them to form a cement paste. Determine the fluidity of the freshly mixed cement paste according to GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures", and determine the compressive strength of the hardened cement paste according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0136] Example 9

[0137] Weigh out 469.64 parts by weight of P.II 52.5 cement, 34.36 parts by weight of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 1, and 200 parts by weight of water, and mix them to form a cement paste. The fluidity of the freshly mixed cement paste was determined according to GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures", and the compressive strength of the hardened cement paste was determined according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0138] Table 1 shows the performance indicators of the cement paste. Clearly, compared to Comparative Example 1 without nano-silica, the incorporation of ordinary nano-silica in Comparative Example 2 significantly reduced the fluidity of the fresh cement paste. However, in Example 9, the negative impact of the incorporation of the steel slag-based in-situ grown nano-hybrid particles obtained in Example 1 on the fluidity of the fresh cement paste was smaller. Furthermore, although both ordinary nano-silica and steel slag-based in-situ grown nanoparticles significantly improved the 3-day and 28-day compressive strength of the hardened cement paste, the steel slag-based in-situ grown hybrid nanoparticles showed a greater improvement in both 3-day and 28-day compressive strength. All these results indicate that, compared to ordinary nano-silica, steel slag-based in-situ grown hybrid nanoparticles have better dispersibility in the cement matrix and can better modify cement-based materials.

[0139] Table 1 Performance Indicators of Cement Paste

[0140] Group Fluidity / mm 3d compressive strength / MPa 28d compressive strength / MPa Comparative Example 1 120 42.5 62.3 Comparative Example 2 91 48.3 67.6 Example 9 103 53.2 72.7

[0141] Comparative Example 3

[0142] Weigh out 483.76 parts by weight of P.II 52.5 cement, 16.24 parts by weight of steel slag, and 200 parts by weight of water, and mix them to form a cement paste. Determine the fluidity of the freshly mixed cement paste according to GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures", and determine the compressive strength of the hardened cement paste according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0143] Comparative Example 4

[0144] Weigh out 483.76 parts by weight of P.II 52.5 cement, 16.24 parts by weight of steel slag, 4 parts by weight of commercial nano-silica with a particle size of approximately 40 nm, and 200 parts by weight of water, and mix them to form a cement paste. Determine the fluidity of the freshly mixed cement paste according to GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures", and determine the compressive strength of the hardened cement paste according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0145] Example 10

[0146] Weigh out 483.76 parts by weight of P.II 52.5 cement, 20.24 parts by weight of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 5, and 200 parts by weight of water, and mix them to form a cement paste. The fluidity of the freshly mixed cement paste was determined according to GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures", and the compressive strength of the hardened cement paste was determined according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0147] Table 2 shows the performance indicators of the cement paste. Clearly, compared to Comparative Example 3 without nano-silica, the incorporation of ordinary nano-silica in Comparative Example 4 significantly reduced the fluidity of the fresh cement paste. However, in Example 10, the negative impact of the incorporation of the steel slag-based in-situ grown nano-hybrid particles obtained in Example 1 on the fluidity of the fresh cement paste was smaller. Furthermore, although both ordinary nano-silica and steel slag-based in-situ grown nanoparticles significantly improved the 3-day and 28-day compressive strength of the hardened cement paste, the steel slag-based in-situ grown hybrid nanoparticles showed a greater improvement in both 3-day and 28-day compressive strength. All these results indicate that, compared to ordinary nano-silica, steel slag-based in-situ grown hybrid nanoparticles have better dispersibility in the cement matrix and can better modify cement-based materials.

[0148] Table 2 Performance Indicators of Cement Paste

[0149] Group Fluidity / mm 3d compressive strength / MPa 28d compressive strength / MPa Comparative Example 3 118 42.8 62.2 Comparative Example 4 87 51.2 68.7 Example 10 105 56.6 76.2

[0150] (4) Effect of steel slag-based in-situ grown hybrid nanoparticles obtained in Examples 2 and 6 as mineral admixtures on the properties of cement-based materials

[0151] The steel slag-based in-situ grown hybrid nanoparticles obtained in Example 2 and Example 6 were used as mineral admixtures, and their cementitious activity and volume stability were analyzed, as follows:

[0152] Comparative Example 5

[0153] Weigh out 315 parts by weight of P.II 52.5 cement, 135 parts by weight of steel slag, 1350 parts by weight of sand and 225 parts by weight of water, mix them into cement mortar, and determine the compressive strength of the hardened cement paste according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0154] Example 11

[0155] Weigh out 315 parts by weight of P.II 52.5 cement, 135 parts by weight of the steel slag-based in-situ grown mixed nanoparticles obtained in Example 2, 1350 parts by weight of sand and 225 parts by weight of water, mix them into cement mortar, and determine the compressive strength of the hardened cement paste according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0156] Example 12

[0157] Weigh out 315 parts by weight of P.II 52.5 cement, 135 parts by weight of the steel slag-based in-situ grown mixed nanoparticles obtained in Example 6, 1350 parts by weight of sand and 225 parts by weight of water, mix them into cement mortar, and determine the compressive strength of the hardened cement paste according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0158] Table 3 shows the 28-day compressive strength of cement mortar. Clearly, in-situ growth of steel slag mixed with nanoparticles effectively improves the 28-day compressive strength of cement mortar; that is, in-situ growth of steel slag-based mixed nanoparticles enhances the cementitious activity of steel slag. Obviously, the improved cementitious activity of steel slag facilitates its large-scale application in cement-based materials.

[0159] Table 3 Compressive strength of cement mortar

[0160] Group 28d compressive strength / MPa Comparative Example 5 42.8 Example 11 47.9 Example 12 49.6

[0161] Comparative Example 6

[0162] The volume stability of undisturbed steel slag was determined according to GB / T 1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The mass ratio of undisturbed steel slag to cement was 3:7.

[0163] Example 13

[0164] The volume stability of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 2 was determined according to GB / T 1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The mass ratio of the steel slag-based in-situ grown hybrid nanoparticles to cement obtained in Example 2 was 3:7.

[0165] Example 14

[0166] The volume stability of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 6 was determined according to GB / T 1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The mass ratio of the steel slag-based in-situ grown hybrid nanoparticles to cement obtained in Example 6 was 3:7.

[0167] Comparative Example 7

[0168] The volume stability of undisturbed steel slag was determined according to GB / T 1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The mass ratio of undisturbed steel slag to cement was 6:4.

[0169] Example 15

[0170] The volume stability of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 2 was determined according to GB / T 1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The mass ratio of the steel slag-based in-situ grown hybrid nanoparticles to cement obtained in Example 2 was 6:4.

[0171] Example 16

[0172] The volume stability of the steel slag-based in-situ grown hybrid nanoparticles obtained in Example 6 was determined according to GB / T 1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The mass ratio of the steel slag-based in-situ grown hybrid nanoparticles to cement obtained in Example 6 was 6:4.

[0173] Table 4 shows the Reiter expansion values ​​of the cement paste. Clearly, when the steel slag content is 30 wt% of the total cementitious material, the in-situ grown steel slag with mixed nanoparticles (Examples 13 and 14) significantly reduces the Reiter expansion value of the cement paste compared to the undisturbed steel slag in Comparative Example 6. Furthermore, when the steel slag content is 50 wt% of the total cementitious material, the Reiter expansion value of Comparative Example 7, which contains undisturbed steel slag, is greater than 5 mm, indicating unsatisfactory volume stability. However, when the in-situ grown steel slag with mixed nanoparticles is 50 wt%, as shown in Examples 15 and 16, its Reiter expansion value is still less than 5 mm. This indicates that in-situ grown mixed nanoparticles on a steel slag base are beneficial for improving the volume stability of the steel slag.

[0174] Table 4. Stability of Cement Paste

[0175] Group Le Chatelier dilatation / mm Comparative Example 6 3.5 Example 13 1.0 Example 14 1.5 Comparative Example 7 5.5 Example 15 1.0 Example 16 2.0

Claims

1. A method for preparing steel slag-based in-situ grown hybrid nanoparticles, characterized in that, The in-situ grown hybrid nanoparticles on a steel slag matrix include a steel slag matrix, on the surface of which calcium-containing nanoparticles are in-situ grown, and nano-silica is in-situ grown using the calcium-containing nanoparticles as nucleation sites; the calcium-containing nanoparticles are nano-hydrated calcium silicate, and the preparation method is a sol-gel method, including the following steps: (1) Mix water, anhydrous ethanol, ammonia and surfactant to prepare solution A, and keep solution A at a constant temperature; add steel slag to solution A and stir to obtain steel slag slurry A; (2) Mix the silicon source and anhydrous ethanol, and separate them into solution B and solution C; (3) Add solution B dropwise to steel slag slurry A, and after stirring, obtain steel slag slurry B; (4) Add solution C dropwise to steel slag slurry B, and after stirring, obtain steel slag slurry C; After washing and drying, in-situ grown mixed nanoparticles based on steel slag were obtained.

2. The method for preparing steel slag-based in-situ grown hybrid nanoparticles according to claim 1, characterized in that, In step (1), the volume fractions of water, anhydrous ethanol and ammonia are 45-5 parts, 5-45 parts and 0-2 parts, respectively, the mass fraction of surfactant is 0-2 parts, and the mass fraction of steel slag is 1-4 parts.

3. The method for preparing steel slag-based in-situ grown hybrid nanoparticles according to claim 1, characterized in that, In step (2), the volume fractions of the silicon source and anhydrous ethanol are 0.5 to 2 parts and 5 to 10 parts, respectively.

4. The method for preparing steel slag-based in-situ grown hybrid nanoparticles according to claim 1, characterized in that, In step (1), the constant temperature of solution A is 30~60℃.

5. A method for preparing steel slag-based in-situ grown hybrid nanoparticles, characterized in that, The in-situ grown hybrid nanoparticles on a steel slag matrix include a steel slag matrix, on the surface of which calcium-containing nanoparticles are in-situ grown, and nano-silica is in-situ grown using the calcium-containing nanoparticles as nucleation sites; the calcium-containing nanoparticles are nano-calcium carbonate, and the preparation method is a carbonization method, including the following steps: (1) Mix water, anhydrous ethanol and surfactant to prepare solution A, and keep solution A at a constant temperature; add steel slag to solution A and stir to obtain steel slag slurry A; (2) Weigh silicon source A and silicon source B, add silicon source A to steel slag slurry A to obtain steel slag slurry B; (3) Carbon dioxide gas is introduced into steel slag slurry B until the pH value of steel slag slurry B is less than 8, thus obtaining steel slag slurry C; (4) Add silicon source B to steel slag slurry C to obtain steel slag slurry D; introduce carbon dioxide gas into steel slag slurry D until the pH value of steel slag slurry D is less than 8 to obtain steel slag slurry E. After washing, dry to obtain steel slag-based in-situ grown mixed nanoparticles.

6. The method for preparing steel slag-based in-situ grown hybrid nanoparticles according to claim 5, characterized in that, In step (1), the constant temperature of solution A is 30~80℃.

7. The method for preparing steel slag-based in-situ grown hybrid nanoparticles according to claim 5, characterized in that, In step (3), the carbon dioxide gas is introduced at a rate of 150~350 ml / min; in step (3), carbon dioxide gas is introduced under stirring conditions, and the stirring speed is 200~400 rpm.

8. The method for preparing steel slag-based in-situ grown hybrid nanoparticles according to claim 5, characterized in that, In step (1), the weight parts of the steel slag, water, anhydrous ethanol and surfactant are 10~50 parts, 100~200 parts, 50~150 parts and 0~10 parts, respectively.

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