Steel slag-based nanocomposite grouting material and preparation method thereof

Abstract

The application belongs to the technical field of building materials, and discloses a steel slag-based nanocomposite grouting material and a preparation method thereof. Raw materials for preparing the steel slag-based nanocomposite grouting material include cement, active steel slag powder, spherical glass beads, nanosilica, carboxylated carbon nanotubes and the like. The active steel slag powder is active steel slag powder activated by a Na2SO3 solution. The steel slag-based nanocomposite grouting material effectively utilizes steel slag resources and is green and environmentally friendly. The preparation method uses sulphoaluminate cement and active steel slag powder as a composite cementitious material system, and cooperates with nanosilica and carboxylated carbon nanotubes to form a multi-scale reinforcing network. The obtained steel slag-based nanocomposite grouting material has high early strength and multiple requirements such as low shrinkage and high durability. The application is suitable for the production of building grouting materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of building materials, and relates to a cement-based grouting material, in particular to a steel slag-based nanocomposite grouting material and a preparation method thereof. BACKGROUND

[0002] With the rapid development of the construction industry, grouting material as a key material for foundation engineering, structural repair and equipment installation directly affects the engineering quality and durability. However, traditional grouting materials still have many technical defects in practical application, especially poor environmental protection, high shrinkage rate and insufficient early compressive and flexural strength, which seriously restricts the development of engineering efficiency and green building.

[0003] On the one hand, traditional grouting material uses ordinary portland cement as the main cementitious material, which consumes a large amount of energy and releases a large amount of CO2 during production, which does not meet the current development trend of low-carbon building. In addition, in order to improve the early strength, the cement content usually needs to be increased, which further aggravates the carbon emission problem. On the other hand, the calcium silicate hydrate gel (C-S-H) generated in the early stage of the hydration reaction of traditional grouting material develops slowly in strength, which makes it difficult to meet the rapid bearing demand within 48 hours after construction. In the scenes of bridge support grouting, high-rise building foundation grouting, etc., insufficient early strength may cause structural micro-displacement or even bearing failure. Although increasing the cement content can partially improve the early strength, it will aggravate the accumulation of hydration heat, leading to an increase in the late shrinkage rate, forming a vicious cycle.

[0004] In addition, traditional grouting material is prone to irreversible volume shrinkage during hardening due to water evaporation, chemical shrinkage and autogenous shrinkage effect. This shrinkage will cause micro-cracks under restraint conditions, weakening the adhesion between the grouting layer and the matrix. Especially in a dry environment, when the surface water loss rate is too fast, through cracks may be formed within 24 hours, which seriously affects the long-term stability and durability of the structure.

[0005] Although there are many types of materials that can be selected for grouting material, the synergistic effect between different components is complex, making it extremely difficult to optimize the formula. For example, increasing early strength agents or adjusting the cement ratio to improve early strength often increases the shrinkage rate or reduces the fluidity at the same time. Grouting material that meets multiple requirements such as high strength, low shrinkage and high durability still needs to be developed. SUMMARY

[0006] To solve the above problems in the prior art, the present application aims to provide a steel slag-based nanocomposite grouting material, which uses sulphoaluminate cement and activated steel slag powder activated by Na2SO3 solution as a composite cementitious material system, and forms a multi-scale reinforcing network with spherical glass beads of a specific size, nanosilica and carboxylated carbon nanotubes, achieving the purposes of being green and environmentally friendly, low shrinkage rate, and high early compressive and flexural strength.

[0007] The application also provides a preparation method of the above-mentioned steel slag-based nanocomposite grouting material.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the application is as follows:

[0009] A steel slag-based nanocomposite grouting material, raw materials for effective components of which include cement 200-250 parts by weight, active steel slag powder 450-500 parts by weight, quartz sand 200-350 parts by weight, spherical glass beads 50-100 parts by weight, nanosilica 10-30 parts by weight, carboxylated carbon nanotubes 0.5-2 parts by weight, expanding agent 30-50 parts by weight, water reducing agent 8-12 parts by weight, water retaining agent 2-5 parts by weight, modified starch ether 0.3-1 part by weight, defoaming agent 0.5-1 part by weight, and water 120-190 parts by weight.

[0010] The active steel slag powder is active steel slag powder activated by a Na2SO3 solution.

[0011] Preferably, the concentration of the Na2SO3 solution is 5-8 wt%.

[0012] Preferably, the water reducing agent is at least one of a naphthalene series water reducing agent or a polycarboxylic acid water reducing agent.

[0013] Preferably, the water retaining agent is hydroxypropyl methylcellulose.

[0014] Preferably, the defoaming agent is an organic silicon defoaming agent or a polyether defoaming agent.

[0015] As a limitation of the application, the active steel slag powder is a mixture of ball-milled steel slag and electric furnace slag with a mass ratio of 3-5:1.

[0016] The specific surface area of the active steel slag powder is ≥500 m 2 / kg.

[0017] The active steel slag powder, as an industrial solid waste with potential cementitious activity, is fully released in activity after being ball-milled and mixed with electric furnace slag in a certain proportion, and forms a composite cementitious system with sulphoaluminate cement, thereby improving the strength and durability of the grouting material, significantly improving the microstructure of the material, reducing the porosity, and improving the compactness.

[0018] As a further limitation of the application, the particle size of the spherical glass beads is 0.2-0.5 mm.

[0019] As a further limitation of the present invention, the particle size of the nano-silica is 10-30 nm; nano-silica can refine the microstructure of hydration products and significantly improve the strength and durability of grouting materials.

[0020] The carboxylated carbon nanotubes have a diameter of 10-20 nm and a length of 5-20 μm. Unlike other carbon nanotubes, carboxylated carbon nanotubes can form a good interfacial bond with the cement matrix, further improving the tensile strength and crack resistance of the grout.

[0021] As a further limitation of the present invention, the particle size of the quartz sand is 40-70 mesh, and the silica content in the quartz sand is ≥95wt%;

[0022] The modified starch ether has a fineness of 50-80 μm. As a thickener, the modified starch ether can improve the rheological properties of the grout and prevent bleeding and segregation.

[0023] As a further limitation of the present invention, the cement is sulfoaluminate cement; the expanding agent is magnesium oxide expanding agent.

[0024] The present invention also provides a method for preparing steel slag-based nanocomposite grouting material, wherein active steel slag powder and Na2SO3 solution are taken at a solid-liquid ratio of 1:0.2-0.4, and mixed and stirred for 20-40 minutes to obtain grout;

[0025] Nano-silica and carboxylated carbon nanotubes were dispersed in an ethanol solution and ultrasonicated for 30-45 min to obtain a dispersion.

[0026] Take the slurry, dispersion, cement, quartz sand, spherical glass beads, expanding agent, water-reducing agent, water-retaining agent, modified starch ether, defoamer and water, and stir for 8-10 minutes to obtain grouting material;

[0027] The grouting material is cured under CO2 pressure to obtain the steel slag-based nanocomposite grouting material.

[0028] As a further limitation of the present invention, the ethanol solution contains polyvinylpyrrolidone (PVP).

[0029] The mass-to-volume ratio of polyvinylpyrrolidone to ethanol is 1%.

[0030] In the system of this invention, PVP is used to prevent the aggregation of nano-silica and carboxylated carbon nanotubes, ensuring their uniform dispersion in ethanol solution.

[0031] As a further limitation of the present invention, the CO2 pressure curing involves placing the grouting material in a CO2 pressure curing kettle after pouring it, and curing it for 1.5-3 hours under conditions of pressure of 0.2-0.3 MPa and temperature of 40-60℃.

[0032] Under high-pressure CO2 environment, free calcium oxide in steel slag reacts chemically with CO2 to generate calcite (CaCO3), which can not only improve the density and strength of grout, but also solidify CO2 in the grout, reduce carbon emissions, and achieve green environmental protection.

[0033] By adopting the above-described technical solution, the beneficial effects achieved by this invention compared to the prior art are as follows:

[0034] This invention solves the technical problem of simultaneously improving early strength and reducing shrinkage in grouting materials. It uses sulfoaluminate cement and activated steel slag powder activated by Na2SO3 solution as a composite cementitious material system, combined with spherical glass beads of specific size, nano-silica, and carboxylated carbon nanotubes to form a multi-scale reinforcing network, thereby improving the mechanical properties of the material. Nano-silica, with its ultra-high specific surface area and pozzolanic activity, rapidly fills the nanopores in the cementitious phase, increasing the density of the matrix. Carboxylated carbon nanotubes form a three-dimensional crack-resistant network through chemical bonding of surface carboxyl groups with cement hydration products, improving flexural strength while limiting crack width, reducing shrinkage, and significantly improving impermeability and durability.

[0035] This invention also solves the technical problem of simultaneously improving the early strength and flowability of grouting materials. By using spherical glass beads of a specific particle size in the raw materials of steel slag-based nanocomposite grouting material as micro-aggregates to fill the gaps between quartz sand, the compactness and compressive strength of the grouting material are improved. At the same time, the smooth surface of the spherical glass beads helps to improve the flowability of the grouting material.

[0036] In the steel slag-based nanocomposite grouting material of this invention, sulfoaluminate cement and active steel slag powder serve as cementitious materials. Utilizing the rapid hardening and early strength characteristics of sulfoaluminate cement, it can form high-strength hydration products in a short time, providing excellent early strength for the grouting material.

[0037] The preparation method of the steel slag-based nanocomposite grout of the present invention effectively destroys the passivation layer on the surface of steel slag powder with Na2SO3, so that the potential activity of steel slag powder can be fully released. The activated steel slag powder can participate in the hydration reaction more effectively when used together with sulfoaluminate cement as a composite cementitious material system, thereby significantly improving the strength and durability of the grout.

[0038] The preparation method of the steel slag-based nanocomposite grout of the present invention uses a CO2 pressure curing process to react free CaO in steel slag with CO2 to generate calcite, which can reduce carbon emissions and is more green and environmentally friendly than traditional grouting materials.

[0039] This invention is applicable to the utilization of steel slag waste and the production and processing of cement-based grouting materials. Detailed Implementation

[0040] The present invention will be further described in detail below through specific embodiments. It should be understood that the described embodiments are only used to explain the present invention and do not limit the present invention.

[0041] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art.

[0042] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0043] Unless otherwise specified in the embodiments or comparative examples, the cement used is sulfoaluminate cement; the activated steel slag powder is a mixture of ball mill steel slag and electric furnace slag in a mass ratio of 3-5:1; the specific surface area of ​​the activated steel slag powder is ≥500m². 2 / kg; the particle size of nano-silica is 10-30nm; the diameter of carboxylated carbon nanotubes is 10-20nm and the length is 5-20μm; the particle size of quartz sand is 40-70 mesh and the SiO2 content is ≥95%; the expanding agent is magnesium oxide, the water reducing agent is naphthalene-based water reducing agent, the water retaining agent is hydroxypropyl methylcellulose water retaining agent, and the defoamer is organosilicon defoamer;

[0044] Example 1

[0045] Example 1 is a steel slag-based nanocomposite grout J1. The raw materials for its effective components are: 200 kg of sulfoaluminate cement, 450 kg of activated steel slag powder, 225 kg of quartz sand, 50 kg of spherical glass beads with a particle size of 0.2-0.5 mm, 20 kg of nano silica, 1.5 kg of carboxylated carbon nanotubes, 174 kg of water, 40 kg of magnesium oxide expanding agent, 9.5 kg of naphthalene-based water-reducing agent, 3 kg of hydroxypropyl methylcellulose water-retaining agent, 0.5 kg of modified starch ether with a fineness of 50-80 μm, and 0.7 kg of organosilicon defoamer.

[0046] Among them, the activated steel slag powder is activated by a 5wt% Na2SO3 solution, and the specific surface area of ​​the activated steel slag powder is ≥500m². 2 / kg is a mixture of ball mill slag and electric furnace slag in a mass ratio of 3:1.

[0047] Example 2

[0048] Example 2 is a steel slag-based nanocomposite grout J2. The raw materials for its effective components are: 230 kg of sulfoaluminate cement, 500 kg of active steel slag powder, 300 kg of quartz sand, 80 kg of spherical glass beads with a particle size of 0.2-0.5 mm, 30 kg of nano silica, 2 kg of carboxylated carbon nanotubes, 190 kg of water, 50 kg of magnesium oxide expanding agent, 12 kg of naphthalene-based water reducing agent, 5 kg of hydroxypropyl methylcellulose water retaining agent, 1 kg of modified starch ether with a fineness of 50-80 μm, and 1 kg of organosilicon defoamer.

[0049] Among them, the activated steel slag powder is activated by a 5wt% Na2SO3 solution, and the specific surface area of ​​the activated steel slag powder is ≥500m². 2 / kg is a mixture of ball mill slag and electric furnace slag in a mass ratio of 3:1.

[0050] Example 3

[0051] Example 3 is a steel slag-based nanocomposite grout J3. The raw materials for its effective components are: 200 kg of cement, 450 kg of activated steel slag powder, 200 kg of quartz sand, 100 kg of spherical glass beads with a particle size of 0.2-0.5 mm, 20 kg of nano-silica, 1.5 kg of carboxylated carbon nanotubes, 174 kg of water, 40 kg of magnesium oxide expanding agent, 9.5 kg of naphthalene-based water-reducing agent, 3 kg of hydroxypropyl methylcellulose water-retaining agent, 0.5 kg of modified starch ether with a fineness of 50-80 μm, and 0.7 kg of organosilicon defoamer.

[0052] Among them, the activated steel slag powder is activated by an 8wt% Na2SO3 solution, and the specific surface area of ​​the activated steel slag powder is ≥500m². 2 / kg is a mixture of ball mill slag and electric furnace slag in a mass ratio of 3:1.

[0053] Example 4

[0054] Example 4 is a steel slag-based nanocomposite grout J4. The raw materials for its effective components are: 230 kg of cement, 480 kg of active steel slag powder, 350 kg of quartz sand, 50 kg of spherical glass beads with a particle size of 0.2-0.5 mm, 30 kg of nano silica, 2 kg of carboxylated carbon nanotubes, 190 kg of water, 50 kg of magnesium oxide expanding agent, 12 kg of naphthalene-based water reducing agent, 5 kg of hydroxypropyl methylcellulose water retaining agent, 1 kg of modified starch ether with a fineness of 50-80 μm, and 1 kg of organosilicon defoamer.

[0055] Among them, the activated steel slag powder is activated by a 6wt% Na2SO3 solution, and the specific surface area of ​​the activated steel slag powder is ≥500m². 2 / kg is a mixture of ball mill slag and electric furnace slag in a mass ratio of 5:1.

[0056] Example 5

[0057] Example 5 is a steel slag-based nanocomposite grout J5. The raw materials for its effective components are: 250 kg of sulfoaluminate cement, 500 kg of activated steel slag powder, 300 kg of quartz sand, 80 kg of spherical glass beads with a particle size of 0.2-0.5 mm, 10 kg of nano silica, 0.5 kg of carboxylated carbon nanotubes, 120 kg of water, 30 kg of expansion agent, 8 kg of naphthalene-based water-reducing agent, 2 kg of hydroxypropyl methylcellulose water-retaining agent, 0.3 kg of modified starch ether with a fineness of 50-80 μm, and 0.5 kg of organosilicon defoamer.

[0058] Among them, the activated steel slag powder is activated by a 5wt% Na2SO3 solution, and the specific surface area of ​​the activated steel slag powder is ≥500m². 2 / kg is a mixture of ball mill slag and electric furnace slag in a mass ratio of 4:1.

[0059] Example 6

[0060] Example 6 describes a method for preparing steel slag-based nanocomposite grouting material J1, which specifically includes the following steps:

[0061] Prepare an ethanol solution containing polyvinylpyrrolidone at a mass-to-volume ratio of 1% to ethanol; mix activated steel slag powder and Na2SO3 solution at a solid-liquid ratio of 1:0.2 and stir for 20 minutes to obtain a slurry.

[0062] According to the amount of raw materials used in Example 1, the weighed nano-silica and carboxylated carbon nanotubes were dispersed in an ethanol solution and ultrasonically treated for 30 minutes to obtain a dispersion.

[0063] Take the slurry, dispersion, cement, quartz sand, spherical glass beads, expanding agent, water-reducing agent, water-retaining agent, modified starch ether, defoamer and water, and stir for 8 minutes to obtain grouting material;

[0064] After the grout is poured, it is placed in a CO2 pressure curing kettle and cured for 1.5 hours at a pressure of 0.2 MPa and a temperature of 40℃ to obtain steel slag-based nanocomposite grout J1.

[0065] Example 7

[0066] Example 7 describes a method for preparing steel slag-based nanocomposite grouting material J2, which specifically includes the following steps:

[0067] Prepare an ethanol solution containing polyvinylpyrrolidone at a mass-to-volume ratio of 1% to ethanol; mix activated steel slag powder and Na2SO3 solution at a solid-liquid ratio of 1:0.4 and stir for 40 minutes to obtain a slurry.

[0068] According to the amount of raw materials used in Example 2, the weighed nano-silica and carboxylated carbon nanotubes were dispersed in an ethanol solution and ultrasonically treated for 45 min to obtain a dispersion.

[0069] Take the slurry, dispersion, cement, quartz sand, spherical glass beads, expanding agent, water-reducing agent, water-retaining agent, modified starch ether, defoamer and water, stir for 10 minutes to obtain grouting material;

[0070] After the grout is poured, it is placed in a CO2 pressure curing kettle and cured for 3 hours at a pressure of 0.3 MPa and a temperature of 60℃ to obtain steel slag-based nanocomposite grout J2.

[0071] Comparative Example 1

[0072] This comparative example is a steel slag-based grouting material without carboxylated carbon nanotubes. The raw material composition is as follows: 230 kg of sulfoaluminate cement, 500 kg of activated steel slag powder, 300 kg of quartz sand, 80 kg of spherical glass beads with a particle size of 0.2-0.5 mm, 30 kg of nano silica, 190 kg of water, 50 kg of expanding agent, 12 kg of water-reducing agent, 5 kg of water-retaining agent, 1 kg of modified starch ether, and 1 kg of defoamer.

[0073] Comparative Example 2

[0074] This comparative example is a steel slag-based grouting material without nano-silica compared to Example 2. The raw material composition is as follows: 230 kg of sulfoaluminate cement, 500 kg of activated steel slag powder, 300 kg of quartz sand, 80 kg of spherical glass beads with a particle size of 0.2-0.5 mm, 2 kg of carboxylated carbon nanotubes, 190 kg of water, 50 kg of expanding agent, 12 kg of water-reducing agent, 5 kg of water-retaining agent, 1 kg of modified starch ether with a fineness of 50-80 μm, and 1 kg of defoamer.

[0075] Comparative Example 3

[0076] This comparative example is a steel slag-based grout with a lower content of expanding agent compared to Example 2. The raw material composition is as follows: 230 kg of sulfoaluminate cement, 500 kg of activated steel slag powder, 300 kg of quartz sand, 80 kg of spherical glass beads with a particle size of 0.2-0.5 mm, 30 kg of nano-silica, 2 kg of carboxylated carbon nanotubes, 190 kg of water, 25 kg of expanding agent, 12 kg of water-reducing agent, 5 kg of water-retaining agent, 1 kg of modified starch ether with a fineness of 50-80 μm, and 1 kg of defoamer.

[0077] Comparative Example 4

[0078] This comparative example is a steel slag-based grouting material produced without Na2SO3 solution activation treatment, compared to Example 2. The raw material composition is as follows: 230 kg of sulfoaluminate cement, 500 kg of activated steel slag powder, 300 kg of quartz sand, 80 kg of spherical glass beads with a particle size of 0.2-0.5 mm, 30 kg of nano-silica, 2 kg of carboxylated carbon nanotubes, 190 kg of water, 50 kg of expanding agent, 12 kg of water-reducing agent, 5 kg of water-retaining agent, 1 kg of modified starch ether with a fineness of 50-80 μm, and 1 kg of defoamer. The activated steel slag powder was not activated with Na2SO3 solution.

[0079] Comparative Example 5

[0080] This comparative example is a steel slag-based grouting material that uses small-diameter spherical glass beads instead of Example 2. The raw material composition is as follows: 230 kg of sulfoaluminate cement, 500 kg of activated steel slag powder, 300 kg of quartz sand, 80 kg of spherical glass beads, 30 kg of nano-silica, 2 kg of carboxylated carbon nanotubes, 190 kg of water, 50 kg of expanding agent, 12 kg of water-reducing agent, 5 kg of water-retaining agent, 1 kg of modified starch ether with a fineness of 50-80 μm, and 1 kg of defoamer. The particle size of the spherical glass beads is less than 0.1 mm.

[0081] Comparative Example 6

[0082] This comparative example is a steel slag-based grouting material that uses large-diameter spherical glass beads instead of Example 2. The raw material composition is as follows: 230 kg of sulfoaluminate cement, 500 kg of activated steel slag powder, 300 kg of quartz sand, 80 kg of spherical glass beads, 30 kg of nano-silica, 2 kg of carboxylated carbon nanotubes, 190 kg of water, 50 kg of expanding agent, 12 kg of water-reducing agent, 5 kg of water-retaining agent, 1 kg of modified starch ether with a fineness of 50-80 μm, and 1 kg of defoamer. The particle size of the spherical glass beads is 0.6-0.9 mm.

[0083] Comparative Example 7

[0084] This comparative example is a steel slag-based grouting material that uses a conventional curing process instead of Example 2. The raw material composition is as follows: 230 kg of sulfoaluminate cement, 500 kg of activated steel slag powder, 300 kg of quartz sand, 80 kg of spherical glass beads, 30 kg of nano-silica, 2 kg of carboxylated carbon nanotubes, 190 kg of water, 50 kg of expanding agent, 12 kg of water-reducing agent, 5 kg of water-retaining agent, 1 kg of modified starch ether with a fineness of 50-80 μm, and 1 kg of defoamer. In the preparation steps, conventional curing is used instead of CO2 pressure curing.

[0085] Comparative Example 8

[0086] This comparative example is a steel slag-based grouting material that uses aminated carbon nanotubes instead of Example 1. The raw material composition is as follows: 200 kg of sulfoaluminate cement, 450 kg of activated steel slag powder, 225 kg of quartz sand, 50 kg of spherical glass beads with a particle size of 0.2-0.5 mm, 20 kg of nano-silica, 1.5 kg of aminated carbon nanotubes, 174 kg of water, 40 kg of expanding agent, 9.5 kg of water-reducing agent, 3 kg of water-retaining agent, 0.5 kg of modified starch ether with a fineness of 50-80 μm, and 0.7 kg of defoamer.

[0087] Comparative Example 9

[0088] This comparative example is a steel slag-based grouting material that uses sulfonated carbon nanotubes instead of Example 1. The raw material composition is as follows: 200 kg of sulfoaluminate cement, 450 kg of activated steel slag powder, 225 kg of quartz sand, 50 kg of spherical glass beads with a particle size of 0.2-0.5 mm, 20 kg of nano silica, 1.5 kg of sulfonated carbon nanotubes, 174 kg of water, 40 kg of expanding agent, 9.5 kg of water-reducing agent, 3 kg of water-retaining agent, 0.5 kg of modified starch ether with a fineness of 50-80 μm, and 0.7 kg of defoamer.

[0089] Effect verification example

[0090] The compressive strength and flexural strength of the steel slag-based nanocomposite grouts J1 and J2 prepared in Examples 1-2, and the steel slag-based grouts prepared in Comparative Examples 1-9 were tested at 24h and 28d respectively, according to the Technical Specification for Application of Cement-based Grouting Materials (GB / T 50488-2015).

[0091] The test results show:

[0092] The steel slag-based nanocomposite grout J1 in Example 1 has a 24-hour compressive strength of 37.5 MPa, a 24-hour flexural strength of 4.1 MPa, a 28-day compressive strength of 83.4 MPa, a 28-day flexural strength of 8.2 MPa, and a shrinkage rate of 0.013%.

[0093] The steel slag-based nanocomposite grout J2 in Example 2 has a 24-hour compressive strength of 39.5 MPa, a 24-hour flexural strength of 4.2 MPa, a 28-day compressive strength of 86.1 MPa, a 28-day flexural strength of 8.6 MPa, and a shrinkage rate of 0.012%.

[0094] The steel slag-based grouting material of Comparative Example 1 exhibited a 24-hour compressive strength of 30.8 MPa, a 24-hour flexural strength of 3.3 MPa, a 28-day compressive strength of 64.6 MPa, a 28-day flexural strength of 7.1 MPa, and a shrinkage rate of 0.019%. The results indicate that carboxylated carbon nanotubes can enhance the interfacial bonding force of the cement matrix and significantly improve compressive / flexural strength.

[0095] The steel slag-based grouting material in Comparative Example 2 exhibited a 24-hour compressive strength of 27.5 MPa, a 24-hour flexural strength of 3.1 MPa, a 28-day compressive strength of 60.9 MPa, a 28-day flexural strength of 5.9 MPa, and a shrinkage rate of 0.021%. The results indicate that nano-silica contributes significantly to early strength by filling nanoscale pores and promoting secondary hydration.

[0096] The steel slag-based grout in Comparative Example 3 exhibited a 24-hour compressive strength of 34.6 MPa, a 24-hour flexural strength of 4.3 MPa, a 28-day compressive strength of 80.4 MPa, a 28-day flexural strength of 7.9 MPa, and a shrinkage rate of 0.017%. The results indicate that the content of the expanding agent affects the early compressive and flexural strength of the grout.

[0097] Compared with the steel slag-based grout in Example 4, the 24-hour compressive strength was 26.2 MPa, the 24-hour flexural strength was 2.6 MPa, the 28-day compressive strength was 65.6 MPa, the 28-day flexural strength was 5.9 MPa, and the shrinkage rate was 0.023%. The results show that the activation treatment significantly improves the early compressive and flexural strength of the grout.

[0098] The steel slag-based grouting material of Comparative Example 5 has a 24-hour compressive strength of 23.8 MPa, a 24-hour flexural strength of 2.4 MPa, a 28-day compressive strength of 59.4 MPa, a 28-day flexural strength of 4.7 MPa, and a shrinkage rate of 0.020%.

[0099] The steel slag-based grouting material of Comparative Example 6 has a 24-hour compressive strength of 28.4 MPa, a 24-hour flexural strength of 3.0 MPa, a 28-day compressive strength of 67.3 MPa, a 28-day flexural strength of 5.6 MPa, and a shrinkage rate of 0.018%.

[0100] The results of Comparative Examples 5 and 6 show that both excessively large and excessively small particle sizes of spherical glass beads affect the early compressive and flexural strength of steel slag-based grouting materials.

[0101] Compared with the steel slag-based grout of Comparative Example 7, the 24-hour compressive strength was 26.4 MPa, the 24-hour flexural strength was 3.4 MPa, the 28-day compressive strength was 66.6 MPa, the 28-day flexural strength was 6.3 MPa, the shrinkage rate was 0.024%, and the internal porosity of the specimen increased. The results show that CO2 pressure curing of the present invention can improve the density and strength of the grout.

[0102] Comparative Example 8, a steel slag-based grout, exhibited a 24-hour compressive strength of 31.5 MPa, a 24-hour flexural strength of 3.7 MPa, a 28-day compressive strength of 76.1 MPa, a 28-day flexural strength of 7.6 MPa, and a shrinkage rate of 0.020%. The results indicate that the amino groups (-NH2) of aminated carbon nanotubes have relatively weak chemical reactivity with the cement matrix, resulting in weak interfacial bonding. Furthermore, the aminated carbon nanotubes are prone to agglomeration and exhibit poor dispersibility, thus failing to fully exert their reinforcing effect.

[0103] Comparative Example 9, the steel slag-based grout, exhibited a 24-hour compressive strength of 29.2 MPa, a 24-hour flexural strength of 3.1 MPa, a 28-day compressive strength of 65.4 MPa, a 28-day flexural strength of 6.6 MPa, and a shrinkage rate of 0.023%. The results indicate that the sulfonic acid groups (-SO3H) of sulfonated carbon nanotubes have poor chemical compatibility with the cement matrix, failing to form effective chemical bonds. Furthermore, the strong acidity of the sulfonic acid groups interferes with the formation of ettringite in sulfoaluminate cement, thereby reducing early strength.

[0104] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A steel slag-based nanocomposite grouting material, characterized in that, The raw materials used to make its effective components include 200-250 parts by weight of cement, 450-500 parts by weight of activated steel slag powder, 200-350 parts by weight of quartz sand, 50-100 parts by weight of spherical glass beads, 10-30 parts by weight of nano-silica, 0.5-2 parts by weight of carboxylated carbon nanotubes, 30-50 parts by weight of expansion agent, 8-12 parts by weight of water-reducing agent, 2-5 parts by weight of water-retaining agent, 0.3-1 parts by weight of modified starch ether, 0.5-1 parts by weight of defoamer, and 120-190 parts by weight of water. The activated steel slag powder is an activated steel slag powder that is composed of a mixture of ball mill steel slag and electric furnace slag in a mass ratio of 3-5:1 and activated by Na2SO3 solution. The spherical glass beads have a particle size of 0.2-0.5 mm; The cement is sulfoaluminate cement; The concentration of the Na2SO3 solution is 5-8 wt%.

2. The steel slag-based nanocomposite grouting material according to claim 1, characterized in that, The specific surface area of ​​the activated steel slag powder is ≥500 m². 2 / kg.

3. The steel slag-based nanocomposite grouting material according to claim 1 or 2, characterized in that, The particle size of the nano-silica is 10-30 nm; The carboxylated carbon nanotubes have a diameter of 10-20 nm and a length of 5-20 μm.

4. The steel slag-based nanocomposite grouting material according to claim 3, characterized in that, The quartz sand has a particle size of 40-70 mesh and a silica content of ≥95 wt%. The modified starch ether has a fineness of 50-80 μm.

5. The steel slag-based nanocomposite grouting material according to claim 4, characterized in that, The expanding agent is a magnesium oxide expanding agent.

6. A method for preparing the steel slag-based nanocomposite grouting material according to any one of claims 1-5, characterized in that, Take activated steel slag powder and Na2SO3 solution at a solid-liquid ratio of 1:0.2-0.4, mix and stir for 20-40 minutes to obtain a slurry; Nano-silica and carboxylated carbon nanotubes were dispersed in an ethanol solution and ultrasonicated for 30-45 min to obtain a dispersion. Take the slurry, dispersion, cement, quartz sand, spherical glass beads, expanding agent, water-reducing agent, water-retaining agent, modified starch ether, defoamer and water, and stir for 8-10 minutes to obtain grouting material; The grouting material is cured under CO2 pressure to obtain the steel slag-based nanocomposite grouting material.

7. The preparation method of the steel slag-based nanocomposite grouting material according to claim 6, characterized in that, The ethanol solution contains polyvinylpyrrolidone; The mass-to-volume ratio of polyvinylpyrrolidone to ethanol is 1%.

8. The method for preparing steel slag-based nanocomposite grouting material according to claim 6 or 7, characterized in that, The CO2 pressure curing involves pouring the grout and then placing it in a CO2 pressure curing vessel for 1.5-3 hours at a pressure of 0.2-0.3 MPa and a temperature of 40-60℃.