Micro-expansive solid waste-based ultra-high performance concrete

Abstract

The invention relates to the technical field of ultra-high performance concrete, and particularly discloses micro-expansive solid waste-based ultra-high performance concrete, which is prepared from the following components: 10 to 90 parts of slag powder, 5 to 30 parts of gypsum powder, 2 to 50 parts of fly ash, 1 to 20 parts of steel slag powder, 5 to 20 parts of silica fume, 1.5 to 20 parts of alkali activator, 0 to 5 parts of nano silicon dioxide, 0.7 to 5 parts of water reducing agent, 0.25 to 3 parts of modifier powder, 80 to 120 parts of fine aggregate and 0.5 to 5 parts of fiber, and the water-binder ratio is 0.17 to 0.22. The modifier has the core-shell structure characteristics that LiBO2 and residual LiB (OH) 4. NH2O are arranged inside the modifier, and the surface of the modifier is a three-dimensional compact shell layer. The modifier is utilized to realize synchronous improvement of the macroscopic mechanical property and the volume stability of the solid waste-based UHPC.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high performance concrete, and in particular to a micro-expansive solid waste-based ultra-high performance concrete. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Ultra-High Performance Concrete (UHPC) is hailed as one of the most innovative cement-based engineering materials of the past three decades, boasting exceptional durability and mechanical properties. However, to ensure UHPC's superior mechanical properties, the preparation process requires the addition of large quantities of finely ground quartz sand, Portland cement clinker, silica fume, high-strength fiber, and high-efficiency water reducers. This significantly increases UHPC production costs. Furthermore, the high Portland cement content in UHPC (approximately 3-4 times that of conventional concrete) increases CO2 emissions, exacerbating environmental concerns. It also causes significant autogenous shrinkage during hydration, impacting volume stability.

[0004] Supersulfated cement (SSC) is a low-carbon cement composed of a small amount of cement clinker or lime, a large amount of aluminosilicate industrial waste residue, and gypsum. It exhibits excellent properties such as minimal expansion, high late-stage strength, and resistance to sulfate attack. Completely replacing Portland cement clinker in UHPC with SSC not only reduces CO2 emissions (the firing process of Portland cement clinker generates significant carbon emissions) but also improves the resource utilization of industrial waste residue. However, solid waste-based UHPC produced in this manner struggles to achieve the strength properties of conventional UHPC (minimum 100 MPa). This is primarily due to the rapid early hydration product of solid waste-based UHPC, primarily ettringite (AFt). This rapid generation rate not only compromises the microstructural compactness but also, due to the sulfate enrichment effect in the system, leads to abnormal secondary ettringite accumulation, exacerbating volume expansion and significantly degrading the concrete's mechanical properties and volume stability. Summary of the Invention

[0005] To address the above issues, the present invention provides a micro-expansive solid waste-based ultra-high performance concrete (UHPC). This modifier utilizes a modifier to simultaneously enhance the macroscopic mechanical properties and volume stability of solid waste-based UHPC. Specifically, the technical solution of the present invention is as follows.

[0006] A micro-expansive solid waste-based ultra-high performance concrete, the raw materials of which include the following components: 10-90 parts of slag powder, 5-30 parts of gypsum powder, 2-50 parts of fly ash, 1-20 parts of steel slag powder, 5-20 parts of silica fume, 1.5-20 parts of alkali activator, 0.5-5 parts of nano-silica, 0.7-5 parts of water reducer, 0.25-3 parts of modifier powder, 80-120 parts of fine aggregate, 0.5-5 parts of fiber, and a water-binder ratio of 0.17-0.22. The "binder" includes the above-mentioned slag powder, gypsum powder, fly ash, steel slag powder, silica fume, and alkali activator. The modifier powder is prepared by the following method: (1) Add borate to the pretreated organic phosphonic acid compound solution in a protective atmosphere and allow the reaction to proceed under heating and stirring conditions. After the reaction is complete, add polyacrylic acid and stir evenly to obtain a liquid colloid.

[0007] (2) Adding the lithium-based compound solution to the liquid colloid for ultrasonic treatment, and then performing aging treatment under heating and pressurizing conditions, and drying after completion to obtain the modifier powder with a core-shell structure.

[0008] Furthermore, the slag powder includes at least one of granulated blast furnace slag powder, converter slag powder, electric furnace slag powder, etc.

[0009] Furthermore, the gypsum includes at least one of desulfurized gypsum, phosphogypsum, fluorinated gypsum, titanium gypsum, and chemically pure gypsum.

[0010] Furthermore, the steel slag powder includes at least one of converter steel slag powder, electric furnace steel slag powder, blast furnace steel slag powder, etc.

[0011] Furthermore, the alkali activator includes at least one of: Portland cement clinker, sulfoaluminate cement, calcium oxide, sodium hydroxide, potassium hydroxide, sodium silicate, potassium silicate, etc.

[0012] Furthermore, the water reducer includes at least one of a polycarboxylate water reducer, a naphthalene water reducer, a sulfonate water reducer, and the like.

[0013] Furthermore, the fine aggregate includes at least one of river sand, quartz sand, machine-made sand, and basalt sand. Optionally, the fine aggregate is graded with particles having diameters of 0.075-0.30 mm, 0.30 mm-0.60 mm, 0.6-1.18 mm, and 1.18-2.36 mm in a mass ratio of 1:2-3:2-4:3-5.

[0014] Furthermore, the length of the fiber is 5-15 mm, and the diameter is 0.2-0.3 mm.

[0015] Furthermore, in the preparation method, the mass ratio of borate, organic phosphonic acid compound, lithium compound and polyacrylic acid is 1-3:2-5:2-4:0.08-0.5.

[0016] Furthermore, in step (1), the borate includes at least one of borax, boric acid, sodium metaborate, potassium borate, ammonium borate, etc.

[0017] Furthermore, in step (1), the organic phosphonic acid compound includes at least one of hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, sodium glyphosate, ammonium glyphosate, phosphonoacetic acid, etc.

[0018] Furthermore, in step (1), the pretreated organic phosphonic acid compound solution refers to an organic phosphonic acid compound solution having a pH adjusted to 6.2±0.5, such as an aqueous solution of an organic phosphonic acid compound having a pH of 6.2±0.5. Optionally, the protective atmosphere comprises at least one of nitrogen, argon, and the like.

[0019] Furthermore, in step (1), the mass fraction of the organic phosphonic acid compound solution is 10-20%. In this step, the organic phosphonic acid compound utilizes its phosphonic acid group (-PO3H2) to react with the borate radical (B(OH)3 or B(OH)4 - ) forms [B(OPO3H2)(OH)] n At the same time, the borate group forms a hydrogen bond with the phosphonic acid group (-PO3H2) by using its hydroxyl group (-OH), thereby jointly constructing a cross-linked network structure formed by colloidal particles. The polyacrylic acid forms a cross-linked network structure by using the -COO - The negative charge on the surface of the colloidal particles is increased, and the steric hindrance effect inhibits the aggregation of the colloidal particles, thereby ensuring the stability of the colloidal particles in the liquid colloid.

[0020] Furthermore, in step (1), the heating temperature is 50-60° C., the reaction time is 10-20 min, and the stirring rate is 800-1200 rpm.

[0021] Furthermore, in step (2), the lithium-based compound includes at least one of lithium nitrate, lithium formate, lithium acetate, lithium chromate, lithium iodide, etc. Optionally, in step (2), the mass fraction of the lithium-based compound solution is 10-20%.

[0022] Furthermore, in step (2), the power of the ultrasonic treatment is 300-700W, and the treatment time is 20-30min. In this process, the Li +The complex reacts to form LiB(OH)4·nH2O particles and generates free phosphonic acid groups (-PO3H2) distributed in the surrounding environment. The ultrasonic treatment can disperse the locally formed crystal nuclei into the entire system, prevent aggregation, and promote Li + Homogeneous reaction with the complex.

[0023] Furthermore, in step (2), the heating temperature is 75-90°C, the pressurizing pressure is 0.6-0.8 MPa, and the aging treatment time is 3-5 hours. During this process, the LiB(OH)4·nH2O particles gradually mature into LiBO2. At the same time, the LiBO2 on the surface of the particles and the above-mentioned free phosphonic acid groups (-PO3H2) first react to form an amorphous dense shell layer, which coats the surface of the particles to prevent the LiB(OH)4·nH2O from further maturation, and finally obtains the core-shell structure of the modifier having a three-dimensional dense shell layer on the surface and a core of LiBO2 and residual LiB(OH)4·nH2O.

[0024] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: As previously mentioned, the rapid generation rate of ettringite (AFt), a hydration product of solid waste-based UHPC, not only destroys the compactness of the microstructure but also easily leads to abnormal enrichment of secondary ettringite due to the sulfate enrichment effect of the system, resulting in significant degradation of the mechanical properties and volume stability of the concrete material. Therefore, the solid waste-based ultra-high performance concrete of the present invention achieves multi-level regulation of ettringite formation through the modifier, effectively inhibiting the excessive generation of ettringite and significantly improving the volume stability and mechanical properties of solid waste-based UHPC. This is due to the following reasons: (1) After the modifier powder is added to the concrete, the outer shell of the modifier gradually dissolves to form substances containing phosphonic acid groups, borates and release Li under the action of the hydration heat released by the gradual hydration of the gelling components and the alkaline environment formed by hydration. + The LiBO2 in the core will gradually dissolve to form borates and release Li + The phosphonic acid group can selectively chelate Ca in the hydrated liquid phase. 2+ and Al 3+ By reducing the supersaturation, the critical free energy barrier required for nucleation is increased, and the generation rate of AFt is reduced. At the same time, the borate is preferentially adsorbed on the AFt crystal through the (040) / (220) crystal plane to interfere with the polymerization of aluminum oxide octahedron (Al-O-Al), thereby inhibiting the growth rate of AFt along the C axis direction, and transforming AFt from a fibrous structure to a short columnar structure, which helps to eliminate stress concentration points and improve volume stability. The released Li +It can also preferentially adsorb on the negative potential points of the hydrated product AFt crystal surface (such as the exposed oxygen atoms of the [AlO6] octahedron) through electrostatic interaction to form steric hindrance, hindering the Ca 2+ With SO4 2- Further combination of the Li + By enhancing the Ca 2+ and OH - The concentration gradient accelerates the formation of hydration product CSH gel, making the microstructure of the concrete matrix denser, which helps to improve the early strength of concrete and reduce porosity, thereby reducing sulfate ion (SO4 2- The present invention effectively overcomes the problem of excessively rapid ettringite formation and promotes the development of early concrete strength through the dual mechanism of preventing AFt epitaxial growth and promoting CSH gel formation.

[0025] (2) The modifier of the present invention has a core-shell structure with LiBO2 and residual LiB(OH)4·nH2O inside and a three-dimensional dense shell on the outside. On the one hand, the shell can preferentially form a load transfer skeleton in the early stage of hydration, share external stress, and improve the packing density of the concrete matrix. On the other hand, the shell can also serve as a physical barrier to prevent the modifier from being consumed prematurely during the hydration stage of concrete. In addition, the dissolution of the core is relatively slow. This allows the modifier of the present invention to continuously release Li throughout the entire hydration stage. + It plays a role in inhibiting the excessive generation of AFt, ensuring that it continues to function when the AFt is generated explosively. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute a part of the present invention, are used to provide further understanding of the present invention and are not intended to constitute an improper limitation of the present invention.

[0027] Figure 1 This is a sample of the modifier powder prepared in Example 1 below.

[0028] Figure 2 This is a scanning electron microscope (SEM) image of the modifier powder prepared in the following Example 1.

[0029] Figure 3 This is a compressive strength test diagram of the following Example 1.

[0030] Figure 4 This is a graph showing the expansion rate test of Example 1 below.

[0031] Figure 5 This is a sample of the modifier powder prepared in Example 2 below.

[0032] Figure 6 This is a scanning electron microscope (SEM) image of the modifier powder prepared in the following Example 2.

[0033] Figure 7 This is the expansion rate test diagram of the following Example 2.

[0034] Figure 8 This is a sample of the modifier powder prepared in Example 3 below.

[0035] Figure 9 This is a scanning electron microscope (SEM) image of the modifier powder prepared in the following Example 3.

[0036] Figure 10 This is the expansion rate test diagram of the following Example 3. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. Unless otherwise defined, all professional and scientific terms used in the present invention have the same meanings as those familiar to those skilled in the art. The preferred implementation methods and materials described in the present invention are for exemplary purposes only. The technical solutions of the present invention will now be further described with reference to specific embodiments.

[0038] Example 1 A method for preparing ultra-high performance concrete based on micro-expansive solid waste comprises the following steps: (1) Weigh the components according to the mass ratio of borate (borax), organic phosphonic acid compound (hydroxyethylidene diphosphonic acid), lithium compound (lithium nitrate), and polyacrylic acid = 2:3.5:3:0.25. Then, dissolve the organic phosphonic acid compound in water to form a 10% by mass solution, and adjust the pH of the solution to 6.2 using NaOH to obtain a pretreated organic phosphonic acid compound solution. Dissolve the lithium compound in water to form a 10% by mass lithium compound solution for later use.

[0039] (2) Add the borate to the pretreated organic phosphonic acid compound solution under a nitrogen atmosphere, heat to 60°C, and stir for 10 minutes at a stirring rate of 1000 rpm. After completion, add the polyacrylic acid and stir for 2 minutes to obtain a liquid colloid, which is then set aside.

[0040] (3) Add the lithium-based compound solution to the liquid colloid and ultrasonically treat for 30 minutes at a power of 500W. Then, mature it under heating and pressurizing conditions (temperature 80°C, pressure 0.7MPa) for 4 hours. After completion, spray dry the obtained reactant to obtain a modifier powder, such as Figure 1 、 Figure 2 shown.

[0041] (4) Take the following raw materials in the following weight ratios: 60 parts of granulated blast furnace slag powder, 20 parts of desulfurized gypsum powder, 30 parts of fly ash, 13 parts of converter steel slag powder, 15 parts of silica fume, 10 parts of alkali activator, 2.5 parts of nano-silica, 4 parts of polycarboxylic acid water reducer, 1.5 parts of the modifier powder of this embodiment, 100 parts of fine aggregate, 2 parts of steel fiber, and a water-binder ratio of 0.21. The "binder" includes the above-mentioned slag powder, gypsum powder, fly ash, steel slag powder, silica fume, and alkali activator. The alkali activator is silicate cement clinker powder, and the fly ash is Class I fly ash with a particle size of ≤5μm. The fine aggregate is made of river sand with a particle size distribution of 0.075-0.30mm, 0.30mm-0.60mm, 0.6-1.18mm, and 1.18-2.36mm in a mass ratio of 1:2:2:3. The particle size of the modifier powder is mainly distributed between 30 and 80 μm. The steel fiber is 10 mm long and 0.2 mm in diameter. The above raw materials are mixed and stirred uniformly to obtain solid waste-based ultra-high performance concrete.

[0042] Performance test: 1. The solid waste-based ultra-high performance concrete prepared in this embodiment was poured into a mold, and then transferred to a curing box (temperature 20±3°C, relative humidity RH≥95%) for curing for 24 hours before demoulding. The concrete was then cured in the curing box until the age of 3 days and 28 days. The 3d compressive strength and 28d compressive strength of the specimens were tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081-2019). Figure 3 2. According to the "Standard for Test Methods of Long-term Performance and Durability of Concrete" (GB / T 50082-2024), the expansion rate of the solid waste-based ultra-high performance concrete prepared in this embodiment was tested (as shown). Figure 4 The test results of the above performance indicators are shown in the following table.

[0043] Example 2 A method for preparing ultra-high performance concrete based on micro-expansive solid waste comprises the following steps: (1) Weigh the components of borate (boric acid), organic phosphonic acid compound (aminotrimethylenephosphonic acid), lithium compound (lithium formate), and polyacrylic acid in a mass ratio of 1:2:2:0.08. Then, dissolve the organic phosphonic acid compound in water to form a 15% by mass solution, and adjust the pH of the solution to 6.7 using NaOH to obtain a pretreated organic phosphonic acid compound solution. Dissolve the lithium compound in water to form a 15% by mass lithium compound solution for later use.

[0044] (2) Add the borate to the pretreated organic phosphonic acid compound solution under a nitrogen atmosphere, heat to 50°C, and stir for 20 minutes at a stirring rate of 800 rpm. After completion, add the polyacrylic acid and stir for 2 minutes to obtain a liquid colloid, which is then set aside.

[0045] (3) Add the lithium-based compound solution to the liquid colloid and ultrasonically treat for 25 minutes at a power of 300W. Then, mature for 3 hours under heating and pressurizing conditions (temperature 90°C, pressure 0.8MPa). After completion, the obtained reactant is spray-dried to obtain a modifier powder, such as Figure 5 、 Figure 6 As shown, spare.

[0046] (4) Take the following raw materials in the following weight ratios: 10 parts of converter slag powder, 5 parts of phosphogypsum powder, 2 parts of fly ash, 1 part of electric furnace steel slag powder, 5 parts of silica fume, 1.5 parts of alkali activator, 0.5 parts of nano-silica, 0.7 parts of polycarboxylic acid water reducer, 0.25 parts of the modifier powder of this embodiment, 80 parts of fine aggregate, 0.5 parts of steel fiber, and a water-binder ratio of 0.17. The "binder" includes the above-mentioned slag powder, gypsum powder, fly ash, steel slag powder, silica fume, and alkali activator. The alkali activator is sodium silicate, and the fly ash is Class I fly ash with a particle size of ≤5μm. The fine aggregate is made of river sand with a particle size distribution of 0.075-0.30mm, 0.30mm-0.60mm, 0.6-1.18mm, and 1.18-2.36mm, graded in a mass ratio of 1:3:4:5. The particle size of the modifier powder is mainly distributed between 30 and 80 μm. The steel fiber is 5 mm long and 0.2 mm in diameter. The above raw materials are mixed and stirred uniformly to obtain solid waste-based ultra-high performance concrete.

[0047] Performance test: The same method as in Example 1 was used to test the 3d compressive strength, 28d compressive strength and expansion rate of the solid waste-based ultra-high performance concrete prepared in this example (such as Figure 7 The results are shown in the following table.

[0048] Example 3 A method for preparing ultra-high performance concrete based on micro-expansive solid waste comprises the following steps: (1) Weigh the components of borate (sodium metaborate), organic phosphonic acid compound (aminotrimethylene phosphonic acid), lithium compound (lithium acetate), and polyacrylic acid in a mass ratio of 3:5:4:0.5. Then, dissolve the organic phosphonic acid compound in water to form a 20% by mass solution, and adjust the pH of the solution to 5.7 using NaOH to obtain a pretreated organic phosphonic acid compound solution. Dissolve the lithium compound in water to form a 20% by mass lithium compound solution for later use.

[0049] (2) Add the borate to the pretreated organic phosphonic acid compound solution under a nitrogen atmosphere, heat to 55°C, and stir for 20 minutes at a stirring rate of 1200 rpm. After completion, add the polyacrylic acid and stir for 3 minutes to obtain a liquid colloid, which is then set aside.

[0050] (3) Add the lithium-based compound solution to the liquid colloid and ultrasonically treat for 20 minutes at a power of 700W. Then, mature it under heating and pressurizing conditions (temperature 75°C, pressure 0.6MPa) for 5 hours. After completion, the obtained reactant is spray-dried to obtain a modifier powder, such as Figure 8 、 Figure 9 As shown, spare.

[0051] (4) Take the following raw materials in the following weight ratios: 90 parts of granulated blast furnace slag powder, 30 parts of fluorgypsum powder, 50 parts of fly ash, 20 parts of blast furnace steel slag powder, 20 parts of silica fume, 20 parts of alkali activator, 5 parts of nano-silica, 5 parts of sodium lignin sulfonate water reducer, 3 parts of the modifier powder of this embodiment, 120 parts of fine aggregate, 5 parts of steel fiber, and a water-binder ratio of 0.22. The "binder" includes the above-mentioned slag powder, gypsum powder, fly ash, steel slag powder, silica fume, and alkali activator. The alkali activator is calcium oxide powder, and the fly ash is Class I fly ash with a particle size of ≤5μm. The fine aggregate is made of river sand with a particle size distribution of 0.075-0.30mm, 0.30mm-0.60mm, 0.6-1.18mm, and 1.18-2.36mm, graded in a mass ratio of 1:2.5:3:4. The particle size of the modifier powder is mainly distributed between 30 and 80 μm. The steel fiber is 15 mm long and 0.3 mm in diameter. The above raw materials are mixed and stirred uniformly to obtain solid waste-based ultra-high performance concrete.

[0052] Performance test: The same method as in Example 1 was used to test the 3d compressive strength, 28d compressive strength and expansion rate of the solid waste-based ultra-high performance concrete prepared in this example (such as Figure 10 The results are shown in the following table.

[0053] Example 4 A method for preparing ultra-high performance concrete based on micro-expansive solid waste is the same as that of Example 1, except that the modifier powder of this embodiment is prepared by the following steps: (1) Weigh the components according to the mass ratio of borate (borax), organic phosphonic acid compound (hydroxyethylidene diphosphonic acid), and polyacrylic acid = 2:3.5:0.25. Then, dissolve the organic phosphonic acid compound in water to form a solution with a mass fraction of 10%, and adjust the pH of the solution to 6.2 using NaOH to obtain a pretreated organic phosphonic acid compound solution for later use.

[0054] (2) Add the borate to the pretreated organic phosphonic acid compound solution under a nitrogen atmosphere, heat to 60°C, and stir for 10 minutes at a stirring rate of 1000 rpm. After completion, add the polyacrylic acid and stir for 2 minutes to obtain a liquid colloid, which is then set aside.

[0055] (3) The liquid colloid is aged under heating and pressurizing conditions (temperature 80°C, pressure 0.7 MPa) for 4 hours. After completion, the obtained reactant is spray-dried to obtain a modifier powder.

[0056] Performance test: The 3d compressive strength, 28d compressive strength and expansion rate of the solid waste-based ultra-high performance concrete prepared in this embodiment were tested using the same method as in the above embodiment 1. The results are shown in the following table.

[0057] Example 5 A method for preparing ultra-high performance concrete based on micro-expansive solid waste comprises the following steps: (1) Weigh the components of borate (boric acid), organic phosphonic acid compound (aminotrimethylenephosphonic acid), lithium compound (lithium formate), and polyacrylic acid in a mass ratio of 1:2:2:0.08. Then, dissolve the organic phosphonic acid compound in water to form a 15% by mass solution, and adjust the pH of the solution to 6.7 using NaOH to obtain a pretreated organic phosphonic acid compound solution. Dissolve the lithium compound in water to form a 15% by mass lithium compound solution for later use.

[0058] (2) Add the borate to the pretreated organic phosphonic acid compound solution under a nitrogen atmosphere, heat to 50°C, and stir for 20 minutes at a stirring rate of 800 rpm. After completion, add the polyacrylic acid and stir for 2 minutes to obtain a liquid colloid, which is then set aside.

[0059] (3) Add the lithium-based compound solution to the liquid colloid and ultrasonically treat for 25 minutes at a power of 300 W. After completion, spray dry the obtained reactant to obtain a modifier powder.

[0060] Performance test: The 3d compressive strength, 28d compressive strength and expansion rate of the solid waste-based ultra-high performance concrete prepared in this embodiment were tested using the same method as in the above embodiment 1. The results are shown in the following table.

[0061] Example 6 A method for preparing ultra-high performance concrete based on micro-expansive solid waste comprises the following steps: (1) Weigh the components of borate (sodium metaborate), organic phosphonic acid compound (aminotrimethylenephosphonic acid), and lithium compound (lithium acetate) in a mass ratio of 3:5:4. Then, dissolve the organic phosphonic acid compound in water to form a 20% solution, and adjust the pH of the solution to 5.7 using NaOH to obtain a pretreated organic phosphonic acid compound solution. Dissolve the lithium compound in water to form a 20% lithium compound solution, which is then set aside.

[0062] (2) Add the borate to the pretreated organic phosphonic acid compound solution in a nitrogen atmosphere, heat to 55° C., and stir for 20 min at a stirring rate of 1200 rpm. After completion, a liquid reactant is obtained for standby use.

[0063] (3) The lithium-based compound solution was added to the liquid reactant and ultrasonically treated for 20 minutes at a power of 700 W. The reactant was then aged under heating and pressurization conditions (temperature 75°C, pressure 0.6 MPa) for 5 hours. After completion, the obtained reactant was spray-dried to obtain a modifier powder for later use.

[0064] Performance test: The 3d compressive strength, 28d compressive strength and expansion rate of the solid waste-based ultra-high performance concrete prepared in this embodiment were tested using the same method as in the above embodiment 1. The results are shown in the following table.

[0065] Example 7 A method for preparing solid waste-based ultra-high performance concrete comprises the following steps: The following raw materials are prepared in the following weight ratios: 60 parts granulated blast furnace slag powder, 20 parts desulfurized gypsum powder, 30 parts fly ash, 13 parts converter steel slag powder, 15 parts silica fume, 10 parts alkali activator, 2.5 parts nano-silica, 4 parts polycarboxylate superplasticizer, 100 parts fine aggregate, 2 parts steel fiber, and a water-binder ratio of 0.21. The "binder" comprises the aforementioned slag powder, gypsum powder, fly ash, steel slag powder, silica fume, and alkali activator. The alkali activator is Portland cement clinker powder, and the fly ash is Grade I fly ash with a particle size of ≤5 μm. The fine aggregate is river sand with particle sizes ranging from 0.075 to 0.30 mm, 0.30 to 0.60 mm, 0.6 to 1.18 mm, and 1.18 to 2.36 mm, graded in a mass ratio of 1:2:2:3. The particle size of the modifier powder is mainly distributed between 30 and 80 μm. The length of the steel fiber is 10 mm and the diameter is 0.2 mm. The above raw materials are mixed and stirred uniformly to obtain solid waste-based ultra-high performance concrete.

[0066] Performance test: The 3d compressive strength, 28d compressive strength and expansion rate of the solid waste-based ultra-high performance concrete prepared in this embodiment were tested using the same method as in the above embodiment 1. The results are shown in the following table.

[0067] The foregoing 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 foregoing embodiments, those skilled in the art will appreciate that they may modify the technical solutions described in the foregoing embodiments or substitute equivalents for some of the technical features. Any such modifications, equivalent substitutions, and improvements shall be within the scope of protection of the present invention.

Claims

1. A micro-expansive solid waste-based ultra-high performance concrete, characterized in that: The invention comprises the following components: 10-90 parts of slag powder, 5-30 parts of gypsum powder, 2-50 parts of fly ash, 1-20 parts of steel slag powder, 5-20 parts of silica fume, 1.5-20 parts of alkali activator, 0.5-5 parts of nano-silicon dioxide, 0.7-5 parts of water reducer, 0.25-3 parts of modifier powder, 80-120 parts of fine aggregate, 0.5-5 parts of fiber, and a water-binder ratio of 0.17-0.22; the modifier powder is prepared by the following method: (1) Adding borate to the pretreated organic phosphonic acid compound solution in a protective atmosphere and reacting under heating and stirring conditions; After completion, polyacrylic acid is added and stirred evenly to obtain a liquid colloid; the organic phosphonic acid compound includes at least one of hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, sodium glyphosate, ammonium glyphosate, and phosphonoacetic acid; (2) adding a lithium-based compound solution to the liquid colloid for ultrasonic treatment, then performing an aging treatment under heating and pressurizing conditions, and drying after completion to obtain the modifier powder having a core-shell structure; the lithium-based compound includes at least one of lithium nitrate, lithium formate, lithium acetate, lithium chromate, and lithium iodide.

2. The micro-expansive solid waste-based ultra-high performance concrete according to claim 1, characterized in that: In the preparation method, the mass ratio of borate, organic phosphonic acid compound, lithium compound and polyacrylic acid is 1-3:2-5:2-4:0.08-0.

5.

3. The micro-expansive solid waste-based ultra-high performance concrete according to claim 1, characterized in that: In step (1), the borate comprises at least one of borax, boric acid, sodium metaborate, potassium borate, and ammonium borate.

4. The micro-expansive solid waste-based ultra-high performance concrete according to claim 1, characterized in that: In step (1), the pretreated organic phosphonic acid compound solution refers to an organic phosphonic acid compound solution whose pH is adjusted to 6.2±0.5; Alternatively, in step (1), the protective atmosphere includes at least one of nitrogen and argon.

5. The micro-expansive solid waste-based ultra-high performance concrete according to claim 1, characterized in that: In step (1), the mass fraction of the organic phosphonic acid compound solution is 10-20%; Alternatively, in step (1), the heating temperature is 50-60° C., the reaction time is 10-20 min, and the stirring rate is 800-1200 rpm.

6. The micro-expansive solid waste-based ultra-high performance concrete according to claim 1, characterized in that: In step (2), the mass fraction of the lithium-based compound solution is 10-20%.

7. The micro-expansive solid waste-based ultra-high performance concrete according to claim 1, characterized in that: In step (2), the power of the ultrasonic treatment is 300-700W, and the treatment time is 20-30min; Alternatively, in step (2), the heating temperature is 75-90° C., the pressurizing pressure is 0.6-0.8 MPa, and the aging treatment time is 3-5 hours.

8. The micro-expansive solid waste-based ultra-high performance concrete according to any one of claims 1 to 7, characterized in that: The slag powder includes at least one of granulated blast furnace slag powder, converter slag powder, and electric furnace slag powder; Alternatively, the gypsum includes at least one of desulfurized gypsum, phosphogypsum, fluorinated gypsum, titanium gypsum, and chemically pure gypsum; Alternatively, the steel slag powder includes at least one of converter steel slag powder, electric furnace steel slag powder, and blast furnace steel slag powder.

9. The micro-expansive solid waste-based ultra-high performance concrete according to any one of claims 1 to 7, characterized in that: The alkali activator comprises at least one of: Portland cement clinker, sulphoaluminate cement, calcium oxide, sodium hydroxide, potassium hydroxide, sodium silicate and potassium silicate; Alternatively, the water reducer comprises at least one of a polycarboxylate water reducer, a naphthalene water reducer, and a sulfonate water reducer; Alternatively, the fine aggregate comprises at least one of river sand, quartz sand, machine-made sand, and basalt sand; Alternatively, the fine aggregate is graded by particles with particle sizes of 0.075-0.30 mm, 0.30 mm-0.60 mm, 0.6-1.18 mm, and 1.18-2.36 mm in a mass ratio of 1:2-3:2-4:3-5.

10. The micro-expansive solid waste-based ultra-high performance concrete according to any one of claims 1 to 7, characterized in that: The length of the fiber is 5-15 mm, and the diameter is 0.2-0.3 mm.

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