A micro-expansion solid waste-based ultra-high performance concrete

Abstract

This invention relates to the field of ultra-high performance concrete (UHPC) technology, specifically disclosing a micro-expansion solid waste-based UHPC, comprising the following components: 10-90 parts slag powder, 5-30 parts gypsum powder, 2-50 parts fly ash, 1-20 parts steel slag powder, 5-20 parts silica fume, 1.5-20 parts alkali activator, 0-5 parts nano-silica, 0.7-5 parts water-reducing agent, 0.25-3 parts modifier powder, 80-120 parts fine aggregate, 0.5-5 parts fiber, and a water-cement ratio of 0.17-0.22. The modifier exhibits a core-shell structure with internal LiBO2 and residual LiB(OH)4·nH2O, and an external three-dimensional dense shell. This invention utilizes the modifier to simultaneously improve the macroscopic mechanical properties and volume stability of the solid waste-based UHPC.

Description

Technical Field

[0001] This invention relates to the field of ultra-high performance concrete technology, specifically to a micro-expansion solid waste-based ultra-high performance concrete. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art 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, possessing exceptional durability and mechanical properties. However, to ensure the superior mechanical properties of UHPC, its preparation requires the addition of large amounts of finely ground silica sand, silicate cement clinker, silica fume, high-strength fibers, and high-efficiency water-reducing agents. The use of these raw materials significantly increases the production cost of UHPC. Furthermore, the high silicate cement content in UHPC (approximately 3-4 times that of ordinary concrete) increases CO2 emissions, exacerbating environmental problems, and also causes severe autogenous shrinkage during hydration, affecting 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, and gypsum. It possesses excellent properties such as micro-expansion, high later-stage strength, and resistance to sulfate attack. Completely replacing silicate cement clinker in ultra-high-performance concrete (UHPC) with SSC can not only reduce CO2 emissions (the calcination process of silicate cement clinker generates significant carbon emissions) but also improve the resource utilization rate of industrial waste. However, solid waste-based UHPC obtained in this way struggles to achieve the strength performance (not less than 100 MPa) of traditional UHPC. The main reason is that the early hydration products of solid waste-based UHPC are primarily ettringite (AFt). Due to its rapid formation rate, it not only disrupts the compactness of the microstructure but also easily triggers abnormal secondary ettringite enrichment due to the sulfate enrichment effect of the system, leading to exacerbated volume expansion and consequently a significant deterioration in the mechanical properties and volume stability of the concrete material. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a micro-expansion solid waste-based ultra-high performance concrete (UHPC), which utilizes a modifier to simultaneously improve the macroscopic mechanical properties and volumetric stability of the solid waste-based UHPC. Specifically, the technical solution of this invention is as follows.

[0006] A micro-expansion solid waste-based ultra-high performance concrete comprises the following raw materials: 10-90 parts slag powder, 5-30 parts gypsum powder, 2-50 parts fly ash, 1-20 parts steel slag powder, 5-20 parts silica fume, 1.5-20 parts alkali activator, 0.5-5 parts nano-silica, 0.7-5 parts water-reducing agent, 0.25-3 parts modifier powder, 80-120 parts fine aggregate, 0.5-5 parts fiber, and a water-cement ratio of 0.17-0.22. The "cement" comprises the aforementioned slag powder, gypsum powder, fly ash, steel slag powder, silica fume, and alkali activator. The modifier powder is prepared using the following method:

[0007] (1) Borate was added to the pretreated organophosphonic acid compound solution under a protective atmosphere and reacted under heating and stirring conditions. After the reaction was completed, polyacrylic acid was added and stirred until homogeneous to obtain a liquid colloid.

[0008] (2) The lithium-based compound solution is added to the liquid colloid and ultrasonically treated, then aged under heating and pressure, and dried to obtain the core-shell structured modifier powder.

[0009] Furthermore, the slag powder includes at least one of granulated blast furnace slag powder, converter slag powder, electric furnace slag powder, etc.

[0010] Furthermore, the gypsum includes at least one of the following: desulfurized gypsum, phosphogypsum, fluorogypsum, titanium gypsum, chemically pure gypsum, etc.

[0011] Furthermore, the steel slag powder includes at least one of the following: converter steel slag powder, electric furnace steel slag powder, blast furnace steel slag powder, etc.

[0012] Furthermore, the alkali activator includes at least one of the following: silicate cement clinker, sulfoaluminate cement, calcium oxide, sodium hydroxide, potassium hydroxide, sodium silicate, potassium silicate, etc.

[0013] Furthermore, the water-reducing agent includes at least one of the following: polycarboxylate water-reducing agent, naphthalene-based water-reducing agent, sulfonate water-reducing agent, etc.

[0014] Further, the fine aggregate includes at least one of river sand, quartz sand, manufactured sand, basalt sand, etc. Optionally, the fine aggregate is composed of particles with particle sizes of 0.075~0.30mm, 0.30mm~0.60mm, 0.6~1.18mm, and 1.18~2.36mm, graded at a mass ratio of 1:2~3:2~4:3~5.

[0015] Furthermore, the fiber has a length of 5-15 mm and a diameter of 0.2-0.3 mm.

[0016] Furthermore, in the preparation method, the mass ratio of borate, organophosphonic acid compound, lithium-based compound, and polyacrylic acid is 1~3:2~5:2~4:0.08~0.5.

[0017] Further, in step (1), the borate includes at least one of borax, boric acid, sodium metaborate, potassium borate, and ammonium borate.

[0018] Further, in step (1), the organophosphonic acid compound includes at least one of the following: hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, glyphosate sodium, glyphosate ammonium, phosphonoacetic acid, etc.

[0019] Further, in step (1), the pretreated organophosphonic acid compound solution refers to an organophosphonic acid compound solution with the pH adjusted to 6.2 ± 0.5, such as an aqueous solution of an organophosphonic acid compound with pH = 6.2 ± 0.5. Optionally, the protective atmosphere includes at least one of nitrogen, argon, etc.

[0020] Further, in step (1), the mass fraction of the organophosphonic acid compound solution is 10-20%. In this step, the organophosphonic acid compound utilizes its phosphonic acid group (-PO3H2) to react with the borate ion (B(OH)3 or B(OH)4) of the borate. - The borate group forms a [B(OPO3H2)(OH)]n complex. Simultaneously, the borate group utilizes its hydroxyl group (-OH) to form hydrogen bonds with the phosphonic acid group (-PO3H2), thereby jointly constructing a cross-linked network structure for the colloidal particles. The polyacrylic acid utilizes its carboxylic acid group to form a -COO... - Increasing the negative charge on the surface of colloidal particles and the steric hindrance effect inhibit the aggregation of colloidal particles, thereby ensuring the stability of colloidal particles in the liquid colloid.

[0021] Further, in step (1), the heating temperature is 50~60℃, the reaction time is 10~20min, and the stirring rate is 800~1200rpm.

[0022] Further, in step (2), the lithium-based compound includes at least one of lithium nitrate, lithium formate, lithium acetate, lithium chromate, and lithium iodide. Optionally, in step (2), the mass fraction of the lithium-based compound solution is 10-20%.

[0023] Further, in step (2), the ultrasonic treatment power is 300~700W, and the treatment time is 20~30min. During this process, the lithium-based compound provides Li... +The complex reacts with the compound to form LiB(OH)4·nH2O particles, generating free phosphonic acid groups (-PO3H2) distributed in the surrounding environment. The ultrasonic treatment disperses locally formed crystal nuclei throughout the system, preventing aggregation and promoting Li… + The homogeneous reaction with the complex.

[0024] Further, in step (2), the heating temperature is 75~90℃, the pressurization pressure is 0.6~0.8MPa, and the ripening time is 3~5 hours. During this process, the LiB(OH)4·nH2O particles gradually ripen into LiBO2. At the same time, the LiBO2 on the particle surface and the aforementioned free phosphonic acid groups (-PO3H2) react first to form an amorphous dense outer shell layer, which coats the surface of the particles to prevent further ripening of LiB(OH)4·nH2O, ultimately yielding the modifier with a core-shell structure consisting of a three-dimensional dense outer shell layer on the surface and LiBO2 and residual LiB(OH)4·nH2O in the core.

[0025] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0026] As mentioned above, the excessively rapid formation rate of ettringite (AFt), a hydration product of solid waste-based UHPC, not only disrupts the compactness of the microstructure but also easily triggers abnormal secondary ettringite enrichment due to the sulfate enrichment effect of the system, resulting in a significant deterioration of the mechanical properties and volume stability of the concrete material. Therefore, the solid waste-based ultra-high performance concrete of this invention achieves multi-level regulation of ettringite formation through the aforementioned modifier, effectively inhibiting the excessively rapid formation of ettringite and significantly improving the volume stability and mechanical properties of solid waste-based UHPC. This is because:

[0027] (1) After the modifier powder is added to concrete, under the action of the heat of hydration released by the gradual hydration of the cementitious components and the alkaline environment formed by hydration, the outer shell of the modifier gradually dissolves to form substances containing phosphonic acid groups, borates, and releases Li. + 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+ Reducing the supersaturation raises the critical free energy barrier required for nucleation, thus decreasing the formation rate of AFt. Simultaneously, the borates preferentially adsorb onto the AFt crystal via the (040) / (220) crystal plane, interfering with the polymerization of aluminum-oxygen octahedrons (Al-O-Al), thereby inhibiting the growth rate of AFt along the C-axis and transforming it from a fibrous to a short columnar structure. This helps eliminate stress concentration points and improves volume stability. The released Li...+ It can also preferentially adsorb onto the negative potential points of the hydrated product AFt crystal plane (such as oxygen atoms exposed on the [AlO6] octahedron) through electrostatic interaction, forming steric hindrance and hindering Ca. 2+ With SO4 2- Further integration of these elements suppresses the epitaxial growth of the AFt crystal plane. Additionally, the Li... + By enhancing the Ca in the early solution 2+ and OH - The concentration gradient accelerates the formation of CSH gel, a hydration product, making the microstructure of the concrete matrix more compact. This helps improve the early strength of concrete while also reducing porosity, thereby reducing sulfate ions (SO42-). 2- The migration of AFt inhibits secondary ettringite enrichment. This invention effectively overcomes the problem of excessively rapid ettringite formation and promotes the early strength development of concrete through the dual mechanism of inhibiting AFt epitaxial growth and promoting CSH gel formation.

[0028] (2) The modifier of the present invention has a core-shell structure with an interior of LiBO2 and residual LiB(OH)4·nH2O and an outer layer of three-dimensional dense shell. On the one hand, the shell can preferentially form a load-transfer skeleton in the early stage of hydration, sharing external stress and improving the packing density of the concrete matrix. On the other hand, the shell can also act as a physical barrier to prevent the modifier from being consumed prematurely during the hydration stage of concrete, and the core dissolves relatively slowly. This allows the modifier of the present invention to continuously release Li throughout the hydration stage. + It plays a role in suppressing the excessively rapid generation of AFt, ensuring its continued effectiveness during the explosive generation of AFt. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention and do not constitute an undue limitation of the invention.

[0030] Figure 1 The image shows a sample of the modifier powder prepared in Example 1 below.

[0031] Figure 2 Scanning electron microscope (SEM) image of the modifier powder prepared in Example 1 below.

[0032] Figure 3 The following is a diagram showing the compressive strength test results for Example 1.

[0033] Figure 4 The following is a graph showing the expansion rate test results for Example 1.

[0034] Figure 5 The image shows a sample of the modifier powder prepared in Example 2 below.

[0035] Figure 6 Scanning electron microscope (SEM) image of the modifier powder prepared in Example 2 below.

[0036] Figure 7 The following is a graph showing the expansion rate test results for Example 2.

[0037] Figure 8 The image shows a sample of the modifier powder prepared in Example 3 below.

[0038] Figure 9 Scanning electron microscope (SEM) image of the modifier powder prepared in Example 3 below.

[0039] Figure 10 The following is a graph showing the expansion rate test results for Example 3. Detailed Implementation

[0040] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as those skilled in the art. The preferred embodiments and materials described in this invention are for illustrative purposes only. The technical solutions of the present invention will now be further described with reference to specific embodiments.

[0041] Example 1

[0042] A method for preparing micro-expansion solid waste-based ultra-high performance concrete includes the following steps:

[0043] (1) Weigh each component according to the mass ratio of borate (borax), organophosphonic acid compound (hydroxyethylidene diphosphonic acid), lithium-based compound (lithium nitrate), and polyacrylic acid = 2:3.5:3:0.25. Then dissolve the organophosphonic acid compound in water to form a 10% mass fraction solution, and adjust the pH of the solution to 6.2 using NaOH to obtain a pretreated organophosphonic acid compound solution. Dissolve the lithium-based compound in water to form a 10% mass fraction lithium-based compound solution for later use.

[0044] (2) Under a nitrogen protective atmosphere, the borate is added to the pretreated organophosphonic acid compound solution, heated to 60°C and stirred for 10 min at a stirring rate of 1000 rpm. After completion, the polyacrylic acid is added and stirred for 2 min to obtain a liquid colloid for later use.

[0045] (3) The lithium-based compound solution was added to the liquid colloid and ultrasonically treated for 30 minutes at a power of 500W. Then, it was aged for 4 hours under heating and pressurization conditions (temperature 80℃, pressure 0.7MPa). After completion, the resulting reactants were spray-dried to obtain the modifier powder, such as... Figure 1 , Figure 2 As shown.

[0046] (4) The following raw materials are taken 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, 1.5 parts of the modifier powder described in this embodiment, 100 parts fine aggregate, 2 parts steel fiber, and a water-cement ratio of 0.21. The "cement" includes the above-mentioned slag powder, gypsum powder, fly ash, steel slag powder, silica fume, and alkali activator. Among them, the alkali activator is silicate cement clinker powder, and the fly ash is Grade I fly ash with a particle size ≤5μm. The fine aggregate is composed 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 1:2:2:3. The particle size of the modifier powder is mainly distributed between 30 and 80 μm. The steel fiber has a length of 10 mm and a diameter of 0.2 mm. After mixing and stirring the above raw materials evenly, solid waste-based ultra-high performance concrete is obtained.

[0047] Performance Testing: 1. The solid waste-based ultra-high performance concrete prepared in this embodiment is poured into a mold, then transferred to a curing chamber (temperature 20±3℃, relative humidity RH≥95%) for curing for 24 hours before demolding. It is then cured in the same chamber for 3 days and 28 days. The 3-day compressive strength and 28-day compressive strength of the obtained specimens are tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081-2019). Figure 3 (As shown). 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 (e.g., ...). Figure 4 (As shown in the table below). The test results for the above performance indicators are shown in the table below.

[0048]

[0049] Example 2

[0050] A method for preparing micro-expansion solid waste-based ultra-high performance concrete includes the following steps:

[0051] (1) Weigh each component according to the mass ratio of borate (boric acid), organophosphonic acid compound (aminotrimethylenephosphonic acid), lithium-based compound (lithium formate), and polyacrylic acid = 1:2:2:0.08. Then dissolve the organophosphonic acid compound in water to form a 15% mass fraction solution, and adjust the pH of the solution to 6.7 using NaOH to obtain a pretreated organophosphonic acid compound solution. Dissolve the lithium-based compound in water to form a 15% mass fraction lithium-based compound solution for later use.

[0052] (2) Under a nitrogen protective atmosphere, the borate was added to the pretreated organophosphonic acid compound solution, heated to 50°C and stirred for 20 min at a stirring rate of 800 rpm. After the reaction was completed, the polyacrylic acid was added and stirred for 2 min to obtain a liquid colloid for later use.

[0053] (3) The lithium-based compound solution was added to the liquid colloid and ultrasonically treated for 25 minutes at a power of 300W. Then, it was aged for 3 hours under heating and pressurization conditions (temperature 90℃, pressure 0.8MPa). After completion, the resulting reactants were spray-dried to obtain the modifier powder, such as... Figure 5 , Figure 6 As shown, for future reference.

[0054] (4) The following raw materials are taken in the following weight ratios: 10 parts converter slag powder, 5 parts phosphogypsum powder, 2 parts fly ash, 1 part electric furnace steel slag powder, 5 parts silica fume, 1.5 parts alkali activator, 0.5 parts nano silica, 0.7 parts polycarboxylate superplasticizer, 0.25 parts of the modifier powder described in this embodiment, 80 parts fine aggregate, 0.5 parts steel fiber, and a water-cement ratio of 0.17. The "cement" includes the above-mentioned slag powder, gypsum powder, fly ash, steel slag powder, silica fume, and alkali activator. Among them, the alkali activator is sodium silicate, and the fly ash is Grade I fly ash with a particle size ≤5μm. The fine aggregate is composed 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 has a length of 5 mm and a diameter of 0.2 mm. After mixing and stirring the above raw materials evenly, solid waste-based ultra-high performance concrete is obtained.

[0055] Performance testing: The 3-day compressive strength, 28-day compressive strength, and expansion rate (e.g., as described in Example 1) of the solid waste-based ultra-high performance concrete prepared in this example were tested using the same method as in Example 1 above. Figure 7 (As shown in the figure), the results are shown in the table below.

[0056]

[0057] Example 3

[0058] A method for preparing micro-expansion solid waste-based ultra-high performance concrete includes the following steps:

[0059] (1) Weigh each component according to the mass ratio of borate (sodium metaborate), organophosphonic acid compound (aminotrimethylenephosphonic acid), lithium-based compound (lithium acetate), and polyacrylic acid = 3:5:4:0.5. Then dissolve the organophosphonic acid compound in water to form a 20% mass fraction solution, and adjust the pH of the solution to 5.7 using NaOH to obtain a pretreated organophosphonic acid compound solution. Dissolve the lithium-based compound in water to form a 20% mass fraction lithium-based compound solution for later use.

[0060] (2) Under a nitrogen protective atmosphere, the borate was added to the pretreated organophosphonic acid compound solution, heated to 55°C and stirred for 20 min at a stirring rate of 1200 rpm. After the reaction was completed, the polyacrylic acid was added and stirred for 3 min to obtain a liquid colloid for later use.

[0061] (3) The lithium-based compound solution was added to the liquid colloid and ultrasonically treated for 20 minutes at a power of 700W. Then, it was aged for 5 hours under heating and pressurization conditions (temperature 75℃, pressure 0.6MPa). After completion, the resulting reactants were spray-dried to obtain the modifier powder, such as... Figure 8 , Figure 9 As shown, for future reference.

[0062] (4) Take the following raw materials in the following weight ratios: 90 parts granulated blast furnace slag powder, 30 parts fluorogypsum powder, 50 parts fly ash, 20 parts blast furnace steel slag powder, 20 parts silica fume, 20 parts alkali activator, 5 parts nano silica, 5 parts sodium lignosulfonate water-reducing agent, 3 parts of the modifier powder described in this embodiment, 120 parts fine aggregate, 5 parts steel fiber, and a water-cement ratio of 0.22. The "cement" includes the above-mentioned slag powder, gypsum powder, fly ash, steel slag powder, silica fume, and alkali activator. Among them, the alkali activator is calcium oxide powder, and the fly ash is Grade I fly ash with a particle size ≤5μm. The fine aggregate is composed 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 has a length of 15 mm and a diameter of 0.3 mm. After mixing and stirring the above raw materials evenly, solid waste-based ultra-high performance concrete is obtained.

[0063] Performance testing: The 3-day compressive strength, 28-day compressive strength, and expansion rate (e.g., as described in Example 1) of the solid waste-based ultra-high performance concrete prepared in this example were tested using the same method as in Example 1 above. Figure 10(As shown in the figure), the results are shown in the table below.

[0064]

[0065] Example 4

[0066] A method for preparing micro-expansion solid waste-based ultra-high performance concrete is the same as in Example 1 above, except that the modifier powder in this example is prepared using the following steps:

[0067] (1) Weigh each component according to the mass ratio of borate (borax), organophosphonic acid compound (hydroxyethylidene diphosphonic acid), and polyacrylic acid = 2:3.5:0.25. Then dissolve the organophosphonic acid compound in water to form a 10% mass fraction solution, and adjust the pH of the solution to 6.2 using NaOH to obtain a pretreated organophosphonic acid compound solution for later use.

[0068] (2) Under a nitrogen protective atmosphere, the borate is added to the pretreated organophosphonic acid compound solution, heated to 60°C and stirred for 10 min at a stirring rate of 1000 rpm. After completion, the polyacrylic acid is added and stirred for 2 min to obtain a liquid colloid for later use.

[0069] (3) The liquid colloid is aged for 4 hours under heating and pressurization conditions (temperature 80℃, pressure 0.7MPa). After completion, the reactants are spray-dried to obtain the modifier powder.

[0070] Performance testing: The 3-day compressive strength, 28-day 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 Example 1 above. The results are shown in the table below.

[0071]

[0072] Example 5

[0073] A method for preparing micro-expansion solid waste-based ultra-high performance concrete includes the following steps:

[0074] (1) Weigh each component according to the mass ratio of borate (boric acid), organophosphonic acid compound (aminotrimethylenephosphonic acid), lithium-based compound (lithium formate), and polyacrylic acid = 1:2:2:0.08. Then dissolve the organophosphonic acid compound in water to form a 15% mass fraction solution, and adjust the pH of the solution to 6.7 using NaOH to obtain a pretreated organophosphonic acid compound solution. Dissolve the lithium-based compound in water to form a 15% mass fraction lithium-based compound solution for later use.

[0075] (2) Under a nitrogen protective atmosphere, the borate was added to the pretreated organophosphonic acid compound solution, heated to 50°C and stirred for 20 min at a stirring rate of 800 rpm. After the reaction was completed, the polyacrylic acid was added and stirred for 2 min to obtain a liquid colloid for later use.

[0076] (3) The lithium-based compound solution is added to the liquid colloid and ultrasonically treated for 25 minutes at a power of 300W. After completion, the reactants are spray-dried to obtain the modifier powder.

[0077] Performance testing: The 3-day compressive strength, 28-day 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 Example 1 above. The results are shown in the table below.

[0078]

[0079] Example 6

[0080] A method for preparing micro-expansion solid waste-based ultra-high performance concrete includes the following steps:

[0081] (1) Weigh each component according to the mass ratio of borate (sodium metaborate), organophosphonic acid compound (aminotrimethylenephosphonic acid), and lithium-based compound (lithium acetate) of 3:5:4. Then dissolve the organophosphonic acid compound in water to form a 20% mass fraction solution, and adjust the pH of the solution to 5.7 using NaOH to obtain a pretreated organophosphonic acid compound solution. Dissolve the lithium-based compound in water to form a 20% mass fraction lithium-based compound solution for later use.

[0082] (2) The borate is added to the pretreated organophosphonic acid compound solution under a nitrogen protective atmosphere, heated to 55°C and stirred for 20 min at a stirring rate of 1200 rpm. After completion, a liquid reactant is obtained for later use.

[0083] (3) The lithium-based compound solution was added to the liquid reactant and ultrasonically treated for 20 minutes at a power of 700W. Then, it was aged for 5 hours under heating and pressurization conditions (temperature 75℃, pressure 0.6MPa). After completion, the reactant was spray-dried to obtain the modifier powder for later use.

[0084] Performance testing: The 3-day compressive strength, 28-day 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 Example 1 above. The results are shown in the table below.

[0085]

[0086] Example 7

[0087] A method for preparing solid waste-based ultra-high performance concrete includes the following steps:

[0088] The following raw materials are used 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-cement ratio of 0.21. The "cement" includes the aforementioned slag powder, gypsum powder, fly ash, steel slag powder, silica fume, and alkali activator. Specifically, the alkali activator is silicate cement clinker powder, and the fly ash is Grade I fly ash with a particle size ≤5μm. The fine aggregate is composed of river sand with particle sizes distributed at 0.075~0.30mm, 0.30mm~0.60mm, 0.6~1.18mm, and 1.18~2.36mm, graded in a mass ratio of 1:2:2:3. The particle size of the modifier powder is mainly distributed between 30 and 80 μm. The steel fiber has a length of 10 mm and a diameter of 0.2 mm. Mixing and stirring the above raw materials thoroughly yields solid waste-based ultra-high performance concrete.

[0089] Performance testing: The 3-day compressive strength, 28-day 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 Example 1 above. The results are shown in the table below.

[0090]

[0091] 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 foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention.

Claims

1. A micro-expansion solid waste-based ultra-high performance concrete, characterized in that, The product comprises the following components: 10-90 parts slag powder, 5-30 parts gypsum powder, 2-50 parts fly ash, 1-20 parts steel slag powder, 5-20 parts silica fume, 1.5-20 parts alkali activator, 0.5-5 parts nano silica, 0.7-5 parts water-reducing agent, 0.25-3 parts modifier powder, 80-120 parts fine aggregate, 0.5-5 parts fiber, and a water-cement ratio of 0.17-0.22; the "cement" includes the aforementioned slag powder, gypsum powder, fly ash, steel slag powder, silica fume, and alkali activator; the modifier powder is prepared using the following method: (1) Add borates or boric acid to the pretreated organophosphonic acid compound solution under a protective atmosphere and react under heating and stirring conditions; After completion, polyacrylic acid is added and stirred evenly to obtain a liquid colloid; the organophosphonic acid compound includes at least one of the following: hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, glyphosate sodium, glyphosate ammonium, and phosphonoacetic acid; (2) The lithium-based compound solution is added to the liquid colloid and ultrasonically treated. Then, it is aged for 3 to 5 hours under heating and pressurization conditions at a temperature of 75 to 90°C and a pressure of 0.6 to 0.8 MPa. After completion, it is dried to obtain the core-shell structure of the modifier powder. The lithium-based compound includes at least one of lithium nitrate, lithium formate, lithium acetate, lithium chromate, and lithium iodide.

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

5.

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

4. The micro-expansion solid waste-based ultra-high performance concrete according to claim 1, characterized in that, In step (1), the pretreated organophosphonic acid compound solution refers to an organophosphonic acid compound solution with the pH adjusted to 6.2±0.

5.

5. The micro-expansion solid waste-based ultra-high performance concrete according to claim 1, characterized in that, In step (1), the protective atmosphere includes at least one of nitrogen and argon.

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

7. The micro-expansion solid waste-based ultra-high performance concrete according to claim 1, characterized in that, In step (1), the heating temperature is 50~60℃, the reaction time is 10~20min, and the stirring rate is 800~1200rpm.

8. The micro-expansion 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%.

9. The micro-expansion 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.

10. The micro-expansion solid waste-based ultra-high performance concrete according to any one of claims 1-9, characterized in that, The slag powder includes at least one of granulated blast furnace slag powder, converter slag powder, and electric furnace slag powder.

11. The micro-expansion solid waste-based ultra-high performance concrete according to any one of claims 1-9, characterized in that, The gypsum includes at least one of the following: desulfurized gypsum, phosphogypsum, fluorogypsum, titanium gypsum, and chemically pure gypsum.

12. The micro-expansion solid waste-based ultra-high performance concrete according to any one of claims 1-9, characterized in that, The steel slag powder includes at least one of the following: converter steel slag powder, electric furnace steel slag powder, and blast furnace steel slag powder.

13. The micro-expansion solid waste-based ultra-high performance concrete according to any one of claims 1-9, characterized in that, The alkali activator includes at least one of silicate cement clinker, sulfoaluminate cement, calcium oxide, sodium hydroxide, potassium hydroxide, sodium silicate, and potassium silicate.

14. The micro-expansion solid waste-based ultra-high performance concrete according to any one of claims 1-9, characterized in that, The water-reducing agent includes at least one of the following: polycarboxylate water-reducing agent, naphthalene-based water-reducing agent, and sulfonate water-reducing agent.

15. The micro-expansion solid waste-based ultra-high performance concrete according to any one of claims 1-9, characterized in that, The fine aggregate includes at least one of the following: river sand, quartz sand, manufactured sand, and basalt sand.

16. The micro-expansion solid waste-based ultra-high performance concrete according to any one of claims 1-9, characterized in that, The fine aggregate is composed of particles with particle sizes of 0.075~0.30mm, 0.30~0.60mm, 0.6~1.18mm, and 1.18~2.36mm, graded in a mass ratio of 1:2~3:2~4:3~5.

17. The micro-expansion solid waste-based ultra-high performance concrete according to any one of claims 1-9, characterized in that, The fiber has a length of 5-15 mm and a diameter of 0.2-0.3 mm.

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