High modulus self-compacting ultra-high strength steel tube reinforced concrete and preparation method thereof

Abstract

The application relates to the technical field of building materials, in particular to high-modulus self-compacting super-high-strength steel pipe concrete and a preparation method thereof, wherein the concrete is prepared from the following raw materials in parts by mass: silicate cement 282-380 parts, ferric aluminate cement 134-206 parts, microbeads 89-107 parts, superfine microbeads 6-10 parts, silica fume 65-75 parts, composite expansion component 39-45 parts, high-strength high-modulus fine aggregate 506-865 parts, high-strength ceramic sand 70-145 parts, high-strength high-modulus coarse aggregate 960-1100 parts, mixing water 126-145 parts, steel fiber 40-64 parts, high-efficiency water reducing agent 12-16 parts, silicon carbide whisker 15-25 parts and nano-alumina 6-10 parts; the problems of the existing super-high-strength steel pipe concrete, such as the mismatch between the core concrete and the elastic deformation of the outer steel pipe, the weakening of the hoop effect, the insufficient structural rigidity and the excessive deformation, are solved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a high-modulus self-compacting ultra-high-strength steel-tube concrete and its preparation method. Background Technology

[0002] Concrete-steel tubular (SST) members significantly improve the load-bearing capacity and ductility of a structure by utilizing the synergistic effect of the outer steel tube and the core concrete, employing the confinement effect of the steel tube on the concrete (i.e., the confinement effect). They are widely used in high-rise buildings, bridges, and long-span structures. Under incremental compressive loads, the core concrete exhibits elastoplastic behavior. In the initial stage, its stress and strain show a linear relationship, and the elastic modulus at this stage is a key parameter for calculating stress, deformation, deflection, and crack control in structural design. The elastic modulus of ordinary concrete is approximately 30 GPa, while ultra-high-strength concrete (strength grade C100 and above), although its compressive strength can reach 3-4 times that of ordinary concrete, only increases its elastic modulus to 45-50 GPa, approximately 1.5 times that of ordinary concrete, a much smaller increase than the increase in strength.

[0003] In concrete-filled steel tube structures, the elastic modulus of the outer steel tube is typically as high as 200 GPa, resulting in a significant difference in elastic deformation between the outer steel tube and the core concrete. This leads to a strain mismatch between the two under load. As stress increases, this deformation mismatch becomes more pronounced, weakening the effective constraint of the steel tube on the core concrete and affecting the full utilization of the confinement effect. Especially in ultra-high strength concrete-filled steel tubes, although the strength meets design requirements, the relatively low stiffness of the core concrete may lead to excessive overall deformation of the member, causing premature failure, reducing structural safety, and limiting its engineering application under high load conditions.

[0004] Therefore, it is necessary to invent a high-modulus self-compacting ultra-high-strength steel-tube concrete and its preparation method to solve the above problems. Summary of the Invention

[0005] To address the problems of insufficient structural stiffness and excessive deformation caused by the mismatch in elastic deformation between the core concrete and the outer steel tube in existing ultra-high strength steel-concrete composites, this invention provides a high-modulus self-compacting ultra-high strength steel-concrete composite and its preparation method.

[0006] This invention is achieved using the following technical solution:

[0007] A high-modulus self-compacting ultra-high-strength steel-tube concrete is composed of the following raw materials in parts by weight: 282-380 parts silicate cement, 134-206 parts aluminoferrite cement, 89-107 parts microspheres, 6-10 parts ultrafine microspheres, 65-75 parts silica fume, 39-45 parts composite expansion component, 506-865 parts high-strength high-modulus fine aggregate, 70-145 parts high-strength ceramic sand, 960-1100 parts high-strength high-modulus coarse aggregate, 126-145 parts mixing water, 40-64 parts steel fiber, 12-16 parts high-efficiency water-reducing agent, 15-25 parts silicon carbide whiskers, and 6-10 parts nano-alumina.

[0008] Furthermore, both the high-strength, high-modulus fine aggregate and the high-strength, high-modulus coarse aggregate are obtained by screening high-strength, high-modulus aggregate; the high-strength, high-modulus fine aggregate is formed by screening and blending high-strength, high-modulus aggregate, and its gradation includes: aggregate with a particle size between 1.18-2.36 mm, aggregate with a particle size between 0.6-1.18 mm, and aggregate with a particle size less than 0.6 mm; the above three types of aggregate are blended in a mass ratio of 3:5:2; the high-strength, high-modulus coarse aggregate is the high-strength, high-modulus aggregate with a particle size between 4.75-13.2 mm.

[0009] Furthermore, the preparation method of the high-strength and high-modulus aggregate includes the following steps: dry mixing coal gangue, bauxite fine powder raw meal, aluminum fluoride, and vanadium pentoxide in a mass ratio of 31-42: 58-68: 2-5: 3-6, pressing the mixture, and then calcining and crushing it in a rotary kiln to obtain the high-strength and high-modulus aggregate.

[0010] Furthermore, the specific calcination process includes:

[0011] First heating stage: Heat from room temperature to 960℃ at a heating rate of 3-5℃ / min, and hold for 1-1.5 hours;

[0012] The second heating stage: the temperature is increased from 960℃ to 1550℃ at a heating rate of 2-4℃ / min, held for 1-1.5h, and then cooled with the furnace.

[0013] Furthermore, the specific pressing process includes: dry mixing the raw materials of high-strength and high-modulus aggregates for 0.5 hours, then aging for 3-5 days, and pressing for 3-5 minutes under a pressure of 3-5 MPa, with a loading rate not exceeding 0.1 MPa / s.

[0014] Furthermore, the aluminoferrite cement is a modified aluminoferrite cement, which is prepared by mixing a standard aluminoferrite cement, boric acid, and lithium carbonate in a mass ratio of 99.45: 0.5: 0.05.

[0015] Furthermore, the composite expansion component is obtained by mixing HCSA expansion agent, MgO expansion agent and gypsum in a mass ratio of 58:30:12 and grinding them to a particle size ≤80μm; the HCSA expansion agent is obtained by mixing oyster shell, phosphogypsum and bauxite powder in a mass ratio of 103:68:42 and calcining it at 1350℃ for 30min; the MgO expansion agent is obtained by calcining periclase at 1200℃ for 1h.

[0016] A method for preparing high-modulus self-compacting ultra-high-strength steel-tube concrete, the method comprising the following steps:

[0017] S1: Mix the formula amount of high-efficiency water-reducing agent, nano alumina, ultrafine beads with part of the mixing water, stir for 5-10 minutes to obtain a nano solution;

[0018] S2: Mix the high-strength, high-modulus coarse aggregate, high-strength ceramic sand and high-strength, high-modulus fine aggregate according to the formula, stir for 0.5-1 min, then add the silicate cement, aluminoferrite cement, microspheres, silica fume, composite expansion component and silicon carbide whiskers according to the formula, stir again for 0.5-1 min, mix evenly to obtain the mixture;

[0019] S3: Add 2 / 3 of the remaining mixing water and 2 / 3 of the total amount of nano solution prepared in S1 to the mixture obtained in S2, stir for 1-2 minutes to obtain a flowable concrete matrix.

[0020] S4: Add the steel fibers of the formula to the concrete matrix prepared in S3 evenly, then add the remaining mixing water and the remaining nano solution, and stir for 1-1.5 minutes to obtain the high modulus self-compacting ultra-high strength steel pipe concrete.

[0021] Furthermore, in step S1, the amount of the mixed water used is 50-70 parts by weight.

[0022] Further, in step S2, the high-strength ceramic sand is pre-wetted before preparing the mixture. The pre-wetting treatment method includes the following steps: placing the high-strength ceramic sand in a treatment tank, adding pre-wetting water until it is completely submerged, controlling the water temperature at 20-25℃, and letting it stand for 24 hours; then draining the pre-wetting water, taking out the high-strength ceramic sand, and spreading it out to dry in a ventilated environment for 1-2 hours until it is surface dry.

[0023] Compared with the prior art, the present invention has the following significant advantages:

[0024] On the one hand, this invention uses aluminoferrite cement to replace part of silicate cement, taking advantage of the micro-expansion characteristic of aluminoferrite cement during hydration to reduce the amount of expansion agent and improve the mechanical properties of concrete. At the same time, the extremely high Al / Si ratio of aluminoferrite cement gives its hydration products a higher elastic modulus, thus improving the elastic modulus of concrete from the perspective of cementitious materials.

[0025] On the other hand, this invention uses coal gangue, a solid waste material, as a raw material to calcine high-strength, high-modulus aggregates. Utilizing the principle that carbon in coal gangue can generate gas channels during the venting process before 1000℃, mullite is synthesized via a gas-phase method, effectively reducing the reaction activation energy. A large number of long columnar mullite crystals generated in situ in the reaction products intersect within the corundum matrix, significantly improving the elastic modulus of the aggregates. With a fixed water-cement ratio, aggregates are a key factor determining the elastic modulus of concrete; the use of these high-strength, high-modulus aggregates significantly increases the elastic modulus of concrete. Simultaneously, this technology rationally utilizes solid waste resources, reduces calcination energy consumption, and decreases carbon emissions, making it an effective way to achieve cost reduction and efficiency improvement in green concrete technology. Attached Figure Description

[0026] Figure 1 This is a comparison chart of the shrinkage properties of concrete prepared in Examples 4, 7, and 9 of this invention and Comparative Examples 11, 15-18.

[0027] Figure 2 These are microscopic property cloud maps of the interfacial transition zone (ITZ) of concrete prepared in Example 9 of this invention: (a) hardness cloud map; (b) modulus distribution cloud map.

[0028] Figure 3 These are microscopic property cloud maps of the interfacial transition zone (ITZ) of concrete prepared in Comparative Example 6 of this invention: (a) hardness cloud map; (b) modulus distribution cloud map.

[0029] Figure 4 This is a comparison diagram of the elastic modulus distribution of the interfacial transition zone (ITZ) of concrete prepared in Comparative Example 6 and Example 9 of this invention.

[0030] Figure 5 This is a SEM image of the interface transition zone of the specimen in Example 9 of the present invention after a 28-day compressive strength test.

[0031] Figure 6 This is a SEM image of the interface transition zone of specimen 6 in Comparative Example 6 of this invention after 28 days of compressive strength testing.

[0032] Figure 7 This is a cross-sectional SEM image of the same proportioned adhesive sample from Example 4 of this invention, three days after molding.

[0033] Figure 8This is a cross-sectional SEM image of the specimen with the same adhesive ratio from Comparative Example 10 of this invention, three days after molding. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] To verify the performance of the high-strength, high-modulus aggregate described in this invention, the following examples and comparative examples are provided. Example 1

[0036] A method for preparing high-strength, high-modulus aggregate includes the following steps: 36g of coal gangue, 62g of bauxite fine powder raw material, 3g of aluminum fluoride, and 4g of vanadium pentoxide are dry-mixed evenly and pressed into 50mm×50mm×50mm samples under 10MPa pressure. Then, the samples are calcined in a rotary kiln. The calcination is divided into two heating stages. In the first heating stage, the temperature is raised from room temperature to 960℃ at a heating rate of 3-5℃ / min and held for 1-1.5h. In the second heating stage, the temperature is raised uniformly from 960℃ to 1550℃ at a heating rate of 2-4℃ / min and held for 1-1.5h. The samples are then cooled in the furnace to obtain high-strength, high-modulus aggregate block samples. Example 2

[0037] The difference between this embodiment and embodiment 1 is that: 31g of coal gangue, 68g of bauxite fine powder raw material, 2g of aluminum fluoride, and 6g of vanadium pentoxide are weighed; the remaining preparation steps and process parameters are the same as in embodiment 1, and a high-strength, high-modulus aggregate block sample is prepared. Example 3

[0038] The difference between this embodiment and embodiment 1 is that: 42g of coal gangue, 58g of bauxite fine powder raw material, 5g of aluminum fluoride, and 3g of vanadium pentoxide are weighed; the remaining preparation steps and process parameters are the same as in embodiment 1, and a high-strength, high-modulus aggregate block sample is prepared. Comparative Example 1

[0039] The difference between this comparative example and Example 1 is that the addition of coal gangue was removed, while the dosage of other raw materials, preparation steps and process parameters were the same as in Example 1, and aggregate block samples were prepared. Comparative Example 2

[0040] The difference between this comparative example and Example 1 is that: alumina of equal mass is used instead of the bauxite fine powder raw material, and the dosage of other raw materials, preparation steps and process parameters are the same as in Example 1, and aggregate block samples are prepared.

[0041] Using a universal testing machine, the block compressive strength and elastic modulus of the specimens obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were tested according to GB / T 3001-2007. The apparent porosity and surface dry water absorption of the specimens were tested according to GB / T 2997-2015. The test results are shown in Table 1.

[0042] Table 1

[0043]

[0044] Comparing the compressive strength and elastic modulus of the samples from Example 1 and Comparative Example 1, it can be seen that the incorporation of coal gangue can significantly reduce the activation energy for mullite crystal phase formation, thereby lowering the mullite formation temperature. In Comparative Example 1, at 1550℃, due to low reactivity, the mullite phase failed to form in large quantities, resulting in lower compressive strength and elastic modulus than in Example 1. Furthermore, the carbon elements in the coal gangue decompose and are released at around 1000℃, creating gas channels, which significantly increases the apparent porosity and surface-dry water absorption rate of the sample from Example 1.

[0045] Meanwhile, by comparing the compressive strength, elastic modulus, and apparent porosity of the sample from Example 1 and Comparative Example 2, it can be seen that bauxite has similar properties to alumina, but the apparent porosity of the aggregate prepared from bauxite is slightly lower, indicating that its sintering density is higher and therefore its mechanical properties are superior.

[0046] The following examples and comparative examples illustrate in detail the specific implementation methods and effects of using the high-strength, high-modulus aggregate to prepare the high-modulus self-compacting ultra-high-strength steel-tube concrete of the present invention. Example 4

[0047] A high-modulus self-compacting ultra-high-strength steel-tube concrete is composed of the following raw materials by weight: 350 kg of silicate cement, 148 kg of aluminoferrite cement, 100 kg of microspheres, 8 kg of ultrafine microspheres, 72.5 kg of silica fume, 43.5 kg of composite expansion component, 610 kg of high-strength high-modulus fine aggregate, 105 kg of high-strength ceramic sand, 1012 kg of high-strength high-modulus coarse aggregate, 135 kg of mixing water, 56 kg of steel fiber, 13.5 kg of high-efficiency water-reducing agent, 20 kg of silicon carbide whiskers, and 8 kg of nano-alumina.

[0048] Both the high-strength, high-modulus fine aggregate and the high-strength, high-modulus coarse aggregate are obtained by screening high-strength, high-modulus aggregate. The high-strength, high-modulus fine aggregate is formed by screening and blending high-strength, high-modulus aggregate, and its gradation includes: aggregate with a particle size between 1.18-2.36 mm, aggregate with a particle size between 0.6-1.18 mm, and aggregate with a particle size less than 0.6 mm. The above three types of aggregate are blended in a mass ratio of 3:5:2. The high-strength, high-modulus coarse aggregate is the high-strength, high-modulus aggregate with a particle size between 4.75-13.2 mm.

[0049] The preparation method of the high-strength and high-modulus aggregate includes the following steps: dry mixing four powdered raw materials, namely coal gangue, bauxite fine powder, aluminum fluoride and vanadium pentoxide, in a mass ratio of 36:62:3:4, and after pressing, calcining and crushing in a rotary kiln to obtain high-strength and high-modulus aggregate.

[0050] The specific calcination process includes:

[0051] First heating stage: Heat from room temperature to 960℃ at a heating rate of 3-5℃ / min, and hold for 1-1.5 hours;

[0052] The second heating stage: the temperature is uniformly increased from 960℃ to 1550℃ at a heating rate of 2-4℃ / min, held for 1-1.5h, and then cooled with the furnace.

[0053] The specific pressing process includes: placing the raw material of high-strength and high-modulus aggregate into a mixer and dry mixing for 0.5 hours. The mixing rod of the mixer rotates at a speed of 240 r / min, and the inner cylinder of the mixer rotates at a speed of 80 r / min. After aging for 3-5 days, the mixture is pressed for 3-5 minutes under a pressure of 3-5 MPa, with a loading rate not exceeding 0.1 MPa / s.

[0054] The silicate cement is PO 52.5 type silicate cement; the aluminoferrite cement is modified aluminoferrite cement, which is prepared by mixing standard aluminoferrite cement, boric acid, and lithium carbonate in a mass ratio of 99.45: 0.5: 0.05. The standard aluminoferrite cement is grade 52.5 aluminoferrite cement, which requires an Al2O3 content between 20-24% and an Fe2O3 content between 8-12%.

[0055] The composite expansion component is obtained by mixing HCSA expansion agent, MgO expansion agent and gypsum in a mass ratio of 58:30:12 and grinding them to a particle size ≤80μm; the HCSA expansion agent is obtained by mixing oyster shell, phosphogypsum and bauxite powder in a mass ratio of 103:68:42 and calcining it at 1350℃ for 30min; the MgO expansion agent is obtained by calcining periclase at 1200℃ for 1h.

[0056] The microspheres are micron-sized microspheres; the ultrafine microspheres are nano-sized microspheres with a particle size of 20-100 nm.

[0057] The silicon carbide whiskers are micron-sized materials with a particle size of 20-100 μm and a specific surface area of ​​56-78 m². 2 / g.

[0058] The nano-alumina has a particle size of 20-100 nm and a specific surface area of ​​160-200 m². 2 / g.

[0059] The high-strength ceramic sand used has a bulk density of 800-900 m³ / s. 2 / kg, apparent density is 1550-1650m³ 2 / kg, coal gangue ceramic sand with micro-connected pores.

[0060] The high-efficiency water-reducing agent is a UHPC-specific water-reducing agent.

[0061] The preparation method of high-modulus self-compacting ultra-high-strength steel-tube concrete described in this embodiment includes the following steps:

[0062] S1: Mix the formulated amount of high-efficiency water-reducing agent, nano-alumina, and ultrafine beads with a portion of the mixing water, and stir using a magnetic stirrer for 5-10 minutes to obtain a nano solution. The amount of the mixing water is 50-70 kg.

[0063] S2: Mix the high-strength, high-modulus coarse aggregate, high-strength ceramic sand, and high-strength, high-modulus fine aggregate according to the formula. After stirring for 0.5-1 min, add the silicate cement, aluminoferrite cement, microspheres, silica fume, composite expansion component, and silicon carbide whiskers according to the formula. Stir again for 0.5-1 min until uniformly mixed to obtain the mixture. The high-strength ceramic sand is pre-wetted before preparing the mixture. The pre-wetting treatment method includes the following steps: place the high-strength ceramic sand in a treatment tank, add pre-wetting water until completely submerged, control the water temperature at 20-25℃, and let it stand for 24 hours; then drain the pre-wetting water, take out the high-strength ceramic sand, and spread it out to dry in a ventilated environment for 1-2 hours until it is surface dry.

[0064] S3: Add 2 / 3 of the remaining mixing water and 2 / 3 of the total amount of nano solution prepared in S1 to the mixture obtained in S2, stir for 1-2 minutes to obtain a flowable concrete matrix.

[0065] S4: Add the steel fibers of the formula to the concrete matrix prepared in S3 using a vibrating screen, then add the remaining mixing water and the remaining nano solution, and stir for 1-1.5 minutes to obtain the high modulus self-compacting ultra-high strength steel pipe concrete. Example 5

[0066] The difference between this embodiment and embodiment 4 is that the amount of silicate cement is 282 kg, the amount of aluminoferrite cement is 206 kg, the amount of microspheres is 107 kg, the amount of ultrafine microspheres is 6 kg, the amount of silica fume is 75 kg, the amount of composite expansion component is 39 kg, and the amount of mixing water is 133.7 kg; the proportions of other raw materials, preparation steps and process parameters are the same as in embodiment 4, and high modulus self-compacting ultra-high strength steel pipe concrete is prepared. Example 6

[0067] The difference between this embodiment and embodiment 4 is that the amount of silicate cement is 380 kg, the amount of aluminoferrite cement is 134 kg, the amount of microspheres is 89 kg, the amount of ultrafine microspheres is 10 kg, the amount of silica fume is 65 kg, and the amount of composite expansion component is 45 kg; the proportions of other raw materials, preparation steps and process parameters are the same as in embodiment 4, and high modulus self-compacting ultra-high strength steel pipe concrete is prepared. Comparative Example 3

[0068] The difference between this comparative example and Example 4 is that basalt crushed stone (particle size 5mm-13mm) of equal volume is used instead of the high-strength, high-modulus coarse aggregate. The other raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 4

[0069] The difference between this comparative example and Example 4 is that limestone crushed stone (particle size 5mm-13mm) of equal volume is used instead of the high-strength, high-modulus coarse aggregate. The other raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 5

[0070] The difference between this comparative example and Example 4 is that: equal volume and same gradation of quartz sand are used instead of the high-strength and high-modulus fine aggregate, while the other raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 6

[0071] The difference between this comparative example and Example 4 is that: river sand with equal volume and natural gradation is used instead of the high-strength and high-modulus fine aggregate. The other raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 7

[0072] The difference between this comparative example and Example 4 is that: basalt crushed stone (particle size 5mm-13mm) of equal volume is used instead of the high-strength, high-modulus coarse aggregate, and quartz sand of equal volume and the same gradation is used instead of the high-strength, high-modulus fine aggregate. The remaining raw material ratios, preparation steps, and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 8

[0073] The difference between this comparative example and Example 4 is that: equal volume of basalt crushed stone (particle size 5mm-13mm) is used instead of the high-strength, high-modulus coarse aggregate, and equal volume of naturally graded river sand is used instead of the high-strength, high-modulus fine aggregate. The remaining raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 9

[0074] The difference between this comparative example and Example 4 is that the addition of silicon carbide whiskers was removed, while the other raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 10

[0075] The difference between this comparative example and Example 4 is that the incorporation of nano-alumina was removed, while the remaining raw material ratios, preparation steps, and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 11

[0076] The difference between this comparative example and Example 4 is that silicate cement of equal mass is used instead of the aluminoferrite cement, while the other raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 12

[0077] The difference between this comparative example and Example 4 is that: equal mass of Grade I fly ash is used instead of the microspheres, while the remaining raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 13

[0078] The difference between this comparative example and Example 4 is that the incorporation of ultrafine beads was removed, while the remaining raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 14

[0079] The difference between this comparative example and Example 4 is that an equal mass of ordinary high-performance concrete water-reducing agent is used instead of the high-efficiency water-reducing agent, while the other raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Example 7

[0080] The difference between this embodiment and embodiment 4 is that: 70 kg of high-strength ceramic sand, 678 kg of high-strength high-modulus fine aggregate, 145 kg of mixing water, and 12 kg of high-efficiency water-reducing agent are weighed; the proportions of other raw materials, preparation steps, and process parameters are the same as in embodiment 4, and concrete is prepared. Example 8

[0081] The difference between this embodiment and embodiment 4 is that: 145 kg of high-strength ceramic sand, 540 kg of high-strength high-modulus fine aggregate, 126 kg of mixing water, and 16 kg of high-efficiency water-reducing agent are weighed; the proportions of other raw materials, preparation steps, and process parameters are the same as in embodiment 4, and concrete is prepared. Example 9

[0082] The difference between this embodiment and embodiment 4 is that the high-strength ceramic sand is removed, and 815 kg of the high-strength, high-modulus fine aggregate is weighed. In preparation step S2, the high-strength, high-modulus coarse aggregate and the high-strength, high-modulus fine aggregate are pre-wetted before preparing the mixture. The pre-wetting treatment method includes the following steps: placing the high-strength, high-modulus coarse aggregate and the high-strength, high-modulus fine aggregate in a treatment tank, adding pre-wetting water until completely submerged, controlling the water temperature at 20-25℃, and letting it stand for 24 hours; then draining the pre-wetting water, taking out the high-strength, high-modulus coarse aggregate and the high-strength, high-modulus fine aggregate, and spreading them out to dry in a ventilated environment for 1-2 hours until they are surface-dry; the remaining raw material ratios, preparation steps, and process parameters are the same as in embodiment 4, and concrete is prepared. Comparative Example 15

[0083] The difference between this comparative example and Example 4 is that an equal mass of HCSA expanded clinker is used instead of the composite expanded component, while the remaining raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 16

[0084] The difference between this comparative example and Example 4 is that an equal mass of MgO expanded clinker is used instead of the composite expanded component, while the remaining raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 17

[0085] The difference between this comparative example and Example 4 is that: an equal mass of silicate cement is used instead of the composite expansion component, while the remaining raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Comparative Example 18

[0086] The difference between this comparative example and Example 4 is that: high-strength, high-modulus fine aggregate of equal volume without pre-wetting is used instead of the high-strength ceramic sand, while the other raw material ratios, preparation steps and process parameters are the same as in Example 4, and concrete is prepared. Example 10

[0087] The difference between this embodiment and embodiment 4 is that: 40 kg of steel fiber, 25 kg of silicon carbide whiskers, and 10 kg of nano-alumina are weighed; the remaining raw material ratios, preparation steps, and process parameters are the same as in embodiment 4, and concrete is prepared. Example 11

[0088] The difference between this embodiment and embodiment 4 is that: 64 kg of steel fiber, 15 kg of silicon carbide whiskers, and 6 kg of nano-alumina are weighed; the remaining raw material ratios, preparation steps, and process parameters are the same as in embodiment 4, and concrete is prepared.

[0089] Performance tests were conducted on concrete samples prepared in Examples 4-11 and Comparative Examples 3-18.

[0090] The concrete prepared in Examples 4-11 and Comparative Examples 3-11 was poured into standard molds and vibrated to obtain 100mm×100mm×100mm cubic standard specimens and 100mm×100mm×300mm prism standard specimens. The poured standard specimens were placed in a standard curing room at 20℃. Concrete standard specimens were taken at 3d, 7d, and 28d and tested according to the standard methods in GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The compressive strength of the concrete specimens at 3d, 7d, and 28d and the elastic modulus at 28d were determined. The specific results are shown in Table 2.

[0091] Table 2

[0092]

[0093] The concrete prepared in Examples 4, 7, and 9, as well as Comparative Examples 12 to 14, were tested according to the standard method of GB / T50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". The concrete spreadability, 1-hour spreadability loss, and T500 test were tested respectively. The specific results are shown in Table 3.

[0094] Table 3

[0095]

[0096] The concrete prepared in Examples 4, 7, and 9, as well as Comparative Examples 11 and 15-18, was poured into a standard mold and vibrated to obtain concrete shrinkage specimens of 100mm × 100mm × 515mm. A reflective target with a distance of not less than 400mm was used, and a non-contact concrete shrinkage tester was employed to test the concrete shrinkage deformation of the specimens over a period of 180 days. Specific results are shown in […]. Figure 1 .

[0097] The specimens from Example 9 and Comparative Example 6 were subjected to an indentation modulus and hardness distribution within the interfacial transition zone (ITZ) lattice microregions 28 days after molding using a TI-980 nanoindenter. Hardness and modulus distribution cloud maps were then plotted to characterize the micromechanical properties of the ITZ. Specific results are shown in [link to results]. Figure 2 , Figure 3 and Figure 4 .

[0098] The broken specimens from Example 9 and Comparative Example 6 after 28 days of compressive strength testing, as well as the mortar specimens from Example 4 and Comparative Example 10 with the same mix proportions, were examined using a field emission environment scanning electron microscope (SEM) to observe the ITZ zone of the fine aggregate and the cross-section of the mortar specimens after 3 days of molding. The obtained SEM images are shown below. Figures 5-8 As shown.

[0099] Examples 4, 7, and 9, as well as Comparative Examples 3, 5, 9-11, and 17, were subjected to frost resistance tests in accordance with GB / T50081-2019 "Standard for Test Methods of Long-Term Performance and Durability of Concrete". The specific results are shown in Table 4.

[0100] Table 4

[0101]

[0102] As shown in Examples 4, Comparative Examples 3-8, and Table 2, the incorporation of high-strength, high-modulus fine aggregate and high-strength, high-modulus coarse aggregate can significantly improve the compressive strength and elastic modulus of concrete, with a 28-day elastic modulus exceeding 65 GPa. Due to the porous nature of this aggregate, the bonding strength of its interfacial transition zone (ITZ) is much higher than that of equally high-strength quartz sand. Therefore, this material is superior to quartz sand in improving the mechanical properties of concrete. As shown in Examples 4, Comparative Examples 9-10, and Table 2, the incorporation of micro / nano materials such as silicon carbide whiskers and nano-alumina can not only improve the elastic modulus of concrete but also accelerate the early hydration rate of cementitious materials, thereby improving early mechanical properties. Furthermore, as shown in Examples 4, Comparative Example 11, and Table 2, the incorporation of aluminoferrite cement can effectively improve the elastic modulus of concrete to a certain extent.

[0103] Based on Examples 4, 7, and 9, Comparative Examples 12-14, and Tables 2 and 3, it can be seen that partially or completely replacing pre-wetted high-strength ceramsite with pre-wetted high-strength, high-modulus aggregate can increase the mechanical properties of concrete to a certain extent, but it will also affect its workability to some extent. Meanwhile, ultrafine particles have a positive effect on improving the workability of concrete. Finally, in order to meet the requirements of JGJ / T283-2012 "Technical Specification for Application of Self-Compacting Concrete", the preparation of this high-modulus self-compacting ultra-high-strength steel pipe concrete cannot use Class I fly ash to replace microspheres, nor can it use ordinary high-performance water-reducing agents to replace high-efficiency water-reducing agents.

[0104] In conjunction with Examples 4, 8, and 9, and Comparative Examples 11, 15-18, and Figure 1 It is evident that the incorporation of aluminoferrite cement, besides accelerating early hydration and increasing the elastic modulus of concrete, can also significantly compensate for shrinkage, thereby reducing the dosage of expansive agents. Furthermore, neither HCSA nor MgO expansive agents alone can meet the micro-expansion requirements of steel-tube concrete. HCSA expansive agents exhibit rapid early-stage activity development, achieving expansion in the early stages of concrete hydration, but later show volume reversal. MgO expansive agents show slow early-stage development and significant delayed expansion. The composite expansive component, however, provides stable expansion, achieving early expansion while preventing volume reversal, and converges to around 56 days. Finally, pre-wetted high-strength ceramic sand and high-strength, high-modulus aggregates can both play a role in internal curing, compensating for concrete shrinkage.

[0105] From Example 9, Comparative Example 6, and the ITZ micromodulus and hardness distribution of both, it can be seen that the matrix elastic modulus and ITZ elastic modulus of the high-strength, high-modulus aggregate are both higher than those of river sand. The high-strength, high-modulus aggregate can effectively enhance the mechanical properties of the ITZ in weak areas of concrete, thereby improving the overall elastic modulus of the concrete. Furthermore, from... Figure 5 , Figure 6 It can be seen that after the compressive strength test, cracks appeared between the aggregate and the concrete matrix in the specimen of Comparative Example 6, while after the compressive strength test, the aggregate and the concrete matrix remained tightly bonded. This also shows that the use of high-strength, high-modulus aggregate can improve the bonding strength with cement paste and improve the micromechanical properties of ITZ.

[0106] The cross-sectional SEM images of the same adhesive resin specimens from Example 4 and Comparative Example 10 show that... Figure 7 , Figure 8It can be seen that after incorporating nano-alumina, i.e. nano-Al2O3, the cross section of the mortar sample is almost completely covered by nano-Al2O3 particles. Al2O3 chemically bonds with hydration products such as CH in the cement matrix, accelerating the generation of C-(A)-SH, and further hydrating the large-particle-size nano-Al2O3, thus accelerating the early hydration rate of concrete overall.

[0107] Based on Examples 4, 7, and 9, as well as Comparative Examples 3, 5, 9-11, 17, and Table 4, it can be seen that the freeze-thaw resistance grade of the concrete reference mix is ​​greater than D300. The incorporation of pre-wetted high-strength and high-modulus aggregates, silicon carbide whiskers, nano-alumina, and aluminoferrite cement can improve the freeze-thaw resistance of concrete and enhance its durability.

[0108] In the description of this invention, it should be understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0109] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-modulus self-compacting ultra-high-strength steel-tube concrete, characterized in that: It is composed of the following raw materials in parts by weight: 282-380 parts silicate cement, 134-206 parts aluminoferrite cement, 89-107 parts microspheres, 6-10 parts ultrafine microspheres, 65-75 parts silica fume, 39-45 parts composite expansion component, 506-865 parts high-strength high-modulus fine aggregate, 70-145 parts high-strength ceramic sand, 960-1100 parts high-strength high-modulus coarse aggregate, 126-145 parts mixing water, 40-64 parts steel fiber, 12-16 parts high-efficiency water-reducing agent, 15-25 parts silicon carbide whiskers, and 6-10 parts nano-alumina. Both the high-strength, high-modulus fine aggregate and the high-strength, high-modulus coarse aggregate are obtained by screening high-strength, high-modulus aggregate; The preparation method of the high-strength and high-modulus aggregate includes the following steps: dry mixing coal gangue, bauxite fine powder raw meal, aluminum fluoride, and vanadium pentoxide in a mass ratio of 31-42: 58-68: 2-5: 3-6, pressing the mixture, and then calcining and crushing it in a rotary kiln to obtain the high-strength and high-modulus aggregate. The aluminoferrite cement is a modified aluminoferrite cement, which is prepared by mixing standard aluminoferrite cement, boric acid, and lithium carbonate in a mass ratio of 99.45: 0.5: 0.

05. The composite expansion component is obtained by mixing HCSA expansion agent, MgO expansion agent and gypsum in a mass ratio of 58:30:12 and grinding them to a particle size ≤80μm; the HCSA expansion agent is obtained by mixing oyster shell, phosphogypsum and bauxite powder in a mass ratio of 103:68:42 and calcining it at 1350℃ for 30min; the MgO expansion agent is obtained by calcining periclase at 1200℃ for 1h.

2. The high-modulus self-compacting ultra-high-strength steel-tube concrete according to claim 1, characterized in that: The high-strength, high-modulus fine aggregate is composed of high-strength, high-modulus aggregate through screening and blending. Its gradation includes: aggregate with a particle size between 1.18 and 2.36 mm, aggregate with a particle size between 0.6 and 1.18 mm, and aggregate with a particle size less than 0.6 mm; the above three types of aggregate are blended in a mass ratio of 3:5:2; the high-strength, high-modulus coarse aggregate is the high-strength, high-modulus aggregate with a particle size between 4.75 and 13.2 mm.

3. The high-modulus self-compacting ultra-high-strength steel-tube concrete according to claim 1, characterized in that: The specific process of calcination using a rotary kiln includes: First heating stage: Heat from room temperature to 960℃ at a heating rate of 3-5℃ / min, and hold for 1-1.5 hours; The second heating stage: the temperature is increased from 960℃ to 1550℃ at a heating rate of 2-4℃ / min, held for 1-1.5h, and then cooled with the furnace.

4. The high-modulus self-compacting ultra-high-strength steel-tube concrete according to claim 1, characterized in that: The specific pressing process includes: dry mixing the raw materials of high-strength and high-modulus aggregates for 0.5 hours, then aging for 3-5 days, and pressing for 3-5 minutes under a pressure of 3-5 MPa, with a loading rate not exceeding 0.1 MPa / s.

5. A method for preparing high-modulus self-compacting ultra-high-strength steel-tube concrete, wherein the method is used to prepare the high-modulus self-compacting ultra-high-strength steel-tube concrete as described in any one of claims 1-4, characterized in that: Includes the following steps: S1: Mix the formula amount of high-efficiency water-reducing agent, nano alumina, ultrafine beads with part of the mixing water, stir for 5-10 minutes to obtain a nano solution; S2: Mix the high-strength, high-modulus coarse aggregate, high-strength ceramic sand and high-strength, high-modulus fine aggregate according to the formula, stir for 0.5-1 min, then add the silicate cement, aluminoferrite cement, microspheres, silica fume, composite expansion component and silicon carbide whiskers according to the formula, stir again for 0.5-1 min, mix evenly to obtain the mixture; S3: Add 2 / 3 of the remaining mixing water and 2 / 3 of the total amount of nano solution prepared in S1 to the mixture obtained in S2, stir for 1-2 minutes to obtain a flowable concrete matrix. S4: Add the steel fibers of the formula to the concrete matrix prepared in S3 evenly, then add the remaining mixing water and the remaining nano solution, and stir for 1-1.5 minutes to obtain the high modulus self-compacting ultra-high strength steel pipe concrete.

6. The method for preparing high-modulus self-compacting ultra-high-strength steel-tube concrete according to claim 5, characterized in that: In step S1, the amount of the mixed water used is 50-70 parts by weight.

7. The method for preparing high-modulus self-compacting ultra-high-strength steel-tube concrete according to claim 5, characterized in that: In step S2, the high-strength ceramic sand is pre-wetted before preparing the mixture. The pre-wetting treatment method includes the following steps: placing the high-strength ceramic sand in a treatment tank, adding pre-wetting water until it is completely submerged, controlling the water temperature at 20-25℃, and letting it stand for 24 hours; then draining the pre-wetting water, taking out the high-strength ceramic sand, and spreading it out to dry in a ventilated environment for 1-2 hours until it is surface dry.

Images