Ultra-high performance concrete for lightweight bridge decks and its preparation method

Abstract

This invention relates to the field of cement-based building materials technology, and in particular to a lightweight bridge deck ultra-high performance concrete and its preparation method. The invention uses silicate cement and aluminoferrite cement as composite cement, adds active metakaolin powder, ultrafine fly ash and microsilica powder as composite admixtures, and combines them with self-healing aggregates and POM fibers. A self-made polycarboxylate superplasticizer is added to control the concrete's workability, and a composite expansion agent is added to prepare a lightweight bridge deck ultra-high performance concrete with low density, high strength and low shrinkage.

Description

Technical Field

[0001] This invention relates to the field of cement-based building materials technology, and in particular to a lightweight bridge deck ultra-high performance concrete and its preparation method. Background Technology

[0002] The continuous development of the transportation and logistics industry has driven the rapid development of bridge engineering and marine engineering in the engineering field, and long-span bridges are constantly breaking engineering records.

[0003] However, ordinary high-performance concrete currently has high density and low strength, and its high water-cement ratio makes it prone to cracking, causing construction difficulties and increasing the amount of repair work, which limits the development and application of bridges.

[0004] Therefore, there is an urgent need to develop lightweight, high-strength, self-healing, volumetrically stable, and easy-to-construct ultra-high-performance concrete materials for bridge decks, in order to further reduce the self-weight of bridge structures, increase bridge spans, and enable rapid construction and subsequent use, so as to meet the ever-increasing construction demands. Summary of the Invention

[0005] To overcome the problems existing in the prior art, the present invention provides an ultra-high performance concrete for lightweight bridge decks. Specifically, the present invention uses silicate cement and aluminoferrite cement as composite cement, adds active metakaolin powder, ultrafine fly ash and microsilica powder as composite admixtures, and combines them with self-healing aggregates and POM fibers. A self-made polycarboxylate superplasticizer is added to control the concrete's workability, and a composite expansion agent is added to prepare an ultra-high performance concrete for lightweight bridge decks with low density, high strength and low shrinkage.

[0006] Specifically, the ultra-high performance concrete for lightweight bridge decks of the present invention is composed of the following raw materials in parts by weight:

[0007] 600-650 parts silicate cement, 50-100 parts aluminoferrite cement, 100-120 parts activated metakaolin powder, 120-180 parts ultrafine fly ash, 100-150 parts microsilica, 700-900 parts self-healing aggregate, 15-20 parts activated calcium oxide, 5-10 parts activated magnesium oxide, 25-30 parts POM fiber, 24-30 parts polycarboxylate superplasticizer, and 320-350 parts water.

[0008] This invention uses silicate cement and aluminoferrite cement as composite cement, and adds active metakaolin powder, ultrafine fly ash and microsilica powder as composite admixtures, which have excellent hydration activity and provide a guarantee for the mechanical properties of concrete; active calcium oxide and active magnesium oxide are used as composite expansion agents to counteract concrete shrinkage.

[0009] Preferably, the self-healing aggregate preparation process is as follows:

[0010] a. Mix 80-90 parts of porous silicate powder and 5-10 parts of sodium carbonate evenly, calcine at high temperature, maintain the temperature, and then rapidly cool to obtain modified porous silicate powder.

[0011] b. Mix 50-75 parts of steel slag powder, 35-45 parts of modified porous silicate powder, 8-15 parts of silicate cement, and 2-5 parts of microsilica powder evenly to obtain a powder.

[0012] c. Add 95-105 parts of powder to a cylindrical granulator, slowly spray in 18-25 parts of water, and granulate by rotation to obtain a 2.36-4.75mm blank.

[0013] d. Carbonize and cure the billet, dry it, vacuum immerse it in water glass, and air dry it naturally to obtain the final product.

[0014] The self-healing aggregate prepared by this invention has numerous interconnected pores, and its crush resistance is enhanced after carbonation curing, resulting in a lightweight and high-strength aggregate. Furthermore, the use of POM fibers instead of steel fibers significantly reduces the density of ultra-high performance concrete, thus reducing the load on the bridge deck from its own weight. The self-healing aggregate encapsulates water glass, which acts as both a primary self-healing agent and activator within the aggregate. During drying, the water glass reacts with CO2 in the air to form a surface-inert, sealed capsule. During the mixing of ultra-high performance concrete, this surface passivation film ruptures, releasing the internal water glass and promoting the hydration of the admixtures. In particular, the water glass has a strength-enhancing effect on the reaction of reactive metakaolinite, thereby improving the strength of the ultra-high performance concrete.

[0015] Meanwhile, the present invention uses a lower water-cement ratio, which can also promote the improvement of concrete strength. The lower water-cement ratio will also retain some cementitious materials that have not been hydrated. When microcracks appear in ultra-high performance concrete, the intrusion of moisture and water vapor will cause the self-healing aggregate to release sodium silicate solution, which will re-activate the hydration activity of the cementitious materials, cause a hydration reaction, and heal the microcracks.

[0016] Preferably, the polycarboxylate superplasticizer is polymerized from monomers of 15-20 parts acrylic acid, 70-80 parts methyl allyl alcohol polyoxyethylene ether, 3-8 parts sodium methacrylate sulfonate, and 2-4 parts 2-hydroxyethyl methacrylate phosphate.

[0017] To enhance the workability of concrete prepared with high-cementing materials, low water-cement ratio, and self-healing aggregates, this invention prepares a special polycarboxylate superplasticizer to ensure the workability of ultra-high performance concrete slurry.

[0018] Preferably, the silicate cement is P·Ⅱ52.5 cement.

[0019] Preferably, the active metakaolin powder is made by calcining kaolin at 850℃ and then grinding it, and has a specific surface area ≥800m².2 / kg.

[0020] Preferably, the specific surface area of ​​the ultrafine fly ash is ≥1500 m². 2 / kg, 28d activity index ≥100%.

[0021] Preferably, the microsilica powder is monocrystalline microsilica powder with a specific surface area ≥18000 m². 2 / kg, SiO2 content ≥96%.

[0022] Preferably, in the self-healing aggregate preparation process, the porous silicate powder in step a is diatomaceous earth, containing 88.95% SiO2 by mass, with an average pore diameter of 56.2 nm, a particle size ≤0.075 mm, and a loss on ignition of 0.39%.

[0023] Preferably, in the self-healing aggregate preparation process, step a involves heating to 900-1100℃ for calcination and holding for 1-2 hours.

[0024] Preferably, in the self-healing aggregate preparation process, the carbonization pressure in step d, carbonization curing, is 0.1-0.5 MPa, the temperature is 20-24℃, the relative humidity is 50-70%, and the carbonization curing time is 24-48 h.

[0025] Preferably, in the self-healing aggregate preparation process, the water glass modulus in step d is 1.3-1.5, the mass concentration is 30-35%, and the vacuum soaking time is 10-20 min.

[0026] This invention also relates to a method for preparing ultra-high performance concrete for lightweight bridge decks, specifically comprising the following steps:

[0027] 1) Weigh each raw material according to its weight.

[0028] 2) Add the self-healing aggregate and some water to the mixer and mix to pre-wet.

[0029] 3) Add silicate cement, aluminoferrate cement, activated metakaolin powder, ultrafine fly ash, microsilica powder, activated calcium oxide, and activated magnesium oxide to the mixing tank and mix thoroughly. Add POM fiber and mix thoroughly.

[0030] 4) Mix the polycarboxylate superplasticizer with the remaining water until homogeneous to obtain the admixture solution.

[0031] 5) Add the additive solution to the mixer and mix thoroughly to obtain a slurry.

[0032] 6) The slurry is then molded and cured to obtain the final product.

[0033] Preferably, the maintenance is performed using standard maintenance.

[0034] This invention has the following technical advantages:

[0035] 1. This invention uses composite admixtures in combination with composite cement and reduces the water-cement ratio to ensure the mechanical properties of concrete.

[0036] 2. This invention utilizes self-healing aggregates to achieve self-healing properties. After micro-cracks appear in concrete, its strength can be partially restored after curing in a humid environment.

[0037] 3. The use of self-healing aggregates and organic fibers in this invention can effectively reduce the density of concrete and has the characteristics of high strength and low shrinkage, which is conducive to promoting its efficient application in structural engineering fields such as bridges and marine engineering where there are higher requirements for structural self-weight. Detailed Implementation

[0038] To characterize the technical effects of this invention, concrete was prepared and its performance was tested. During the experiment, P·Ⅱ52.5 silicate cement was used, and the active metakaolin powder was made by calcining kaolin at 850℃ and then grinding it, with a specific surface area of ​​850 m². 2 / kg, the specific surface area of ​​ultrafine fly ash is 1600m² 2 / kg, 28d activity index is 105%, microsilica powder is single crystal microsilica powder with SiO2 content of 96%, porous silicate powder is diatomaceous earth from Linjiang City, Jilin Province, with SiO2 mass fraction of 88.95%, average pore diameter of 56.2nm, particle size ≤0.075mm, loss on ignition of 0.39%, water glass modulus of 1.5, and mass concentration of 30%.

[0039] Example 1

[0040] Concrete, characterized in that it is composed of the following raw materials in parts by weight:

[0041] 620 parts silicate cement, 60 parts aluminoferrite cement, 100 parts activated metakaolin powder, 160 parts ultrafine fly ash, 110 parts microsilica, 850 parts self-healing aggregate, 18 parts activated calcium oxide, 7 parts activated magnesium oxide, 26 parts POM fiber, 27 parts polycarboxylate superplasticizer, and 340 parts water.

[0042] The self-healing aggregate preparation process is as follows:

[0043] a. Mix 80 parts of porous silicate powder and 6 parts of sodium carbonate evenly, heat to 1000℃ and calcine, hold at that temperature for 1.5 hours, then rapidly cool to obtain modified porous silicate powder.

[0044] b. Mix 75 parts of steel slag powder, 45 parts of modified porous silicate powder, 12 parts of silicate cement, and 2 parts of microsilica powder evenly to obtain a powder.

[0045] c. Add 100 parts of powder to a cylindrical granulator, slowly spray in 25 parts of water, and granulate by rotation to obtain a blank with a diameter of 2.36-4.75 mm.

[0046] d. Carbonize and cure the billet in an environment with a pressure of 0.3 MPa, a temperature of 20℃, and a relative humidity of 60% for 24 hours, dry it, vacuum immerse it in water glass for 15 minutes, and then air dry it naturally to obtain the final product.

[0047] The polycarboxylate superplasticizer is polymerized from monomers of 20 parts acrylic acid, 78 parts methyl allyl alcohol polyoxyethylene ether, 5 parts sodium methacrylate sulfonate, and 4 parts 2-hydroxyethyl methacrylate phosphate.

[0048] Tests showed that the initial spread of the concrete was 580 mm, the spread after 2 hours was 545 mm, and the apparent density was 2016 kg / m³. 3 28-day compressive strength: 145.3 MPa; flexural strength: 14.9 MPa; tensile strength: 7.4 MPa; elastic modulus: 38.4 GPa; drying shrinkage: 66 × 10⁻⁶. -6 .

[0049] Example 2

[0050] Concrete, characterized in that it is composed of the following raw materials in parts by weight:

[0051] 640 parts silicate cement, 70 parts aluminoferrite cement, 100 parts activated metakaolin powder, 130 parts ultrafine fly ash, 150 parts microsilica, 880 parts self-healing aggregate, 20 parts activated calcium oxide, 8 parts activated magnesium oxide, 28 parts POM fiber, 29 parts polycarboxylate superplasticizer, and 340 parts water.

[0052] The self-healing aggregate preparation process is as follows:

[0053] a. Mix 90 parts of porous silicate powder and 9 parts of sodium carbonate evenly, heat to 1000℃ and calcine, hold at that temperature for 1.5 hours, then rapidly cool to obtain modified porous silicate powder.

[0054] b. Mix 60 parts of steel slag powder, 45 parts of modified porous silicate powder, 14 parts of silicate cement, and 4 parts of microsilica powder evenly to obtain a powder.

[0055] c. Add 100 parts of powder to a cylindrical granulator, slowly spray in 25 parts of water, and granulate by rotation to obtain a blank with a diameter of 2.36-4.75 mm.

[0056] d. Carbonize and cure the billet in an environment with a pressure of 0.3 MPa, a temperature of 20℃, and a relative humidity of 60% for 24 hours, dry it, vacuum immerse it in water glass for 15 minutes, and then air dry it naturally to obtain the final product.

[0057] The polycarboxylate superplasticizer is polymerized from monomers of 20 parts acrylic acid, 75 parts methyl allyl alcohol polyoxyethylene ether, 5 parts sodium methacrylate sulfonate, and 3 parts 2-hydroxyethyl methacrylate phosphate.

[0058] Tests showed that the initial spread of the concrete was 570 mm, the spread after 2 hours was 550 mm, and the apparent density was 2034 kg / m³. 3 28-day compressive strength: 147.0 MPa; flexural strength: 15.3 MPa; tensile strength: 8.1 MPa; elastic modulus: 39.2 GPa; drying shrinkage: 62 × 10⁻⁶. -6 .

[0059] Comparative Example 1

[0060] Concrete, characterized in that it is composed of the following raw materials in parts by weight:

[0061] 640 parts silicate cement, 70 parts aluminoferrite cement, 100 parts mineral powder, 130 parts ultrafine fly ash, 150 parts microsilica, 880 parts self-healing aggregate, 20 parts activated calcium oxide, 8 parts activated magnesium oxide, 78 parts steel fiber, 29 parts polycarboxylate superplasticizer, and 340 parts water.

[0062] The self-healing aggregate preparation process is as follows:

[0063] a. Mix 90 parts of porous silicate powder and 9 parts of sodium carbonate evenly, heat to 1000℃ and calcine, hold at that temperature for 1.5 hours, then rapidly cool to obtain modified porous silicate powder.

[0064] b. Mix 60 parts of steel slag powder, 45 parts of modified porous silicate powder, 14 parts of silicate cement, and 4 parts of microsilica powder evenly to obtain a powder.

[0065] c. Add 100 parts of powder to a cylindrical granulator, slowly spray in 25 parts of water, and granulate by rotation to obtain a blank with a diameter of 2.36-4.75 mm.

[0066] d. Carbonize and cure the billet in an environment with a pressure of 0.3 MPa, a temperature of 20℃, and a relative humidity of 60% for 24 hours, dry it, vacuum immerse it in water glass for 15 minutes, and then air dry it naturally to obtain the final product.

[0067] The polycarboxylate superplasticizer is polymerized from monomers of 20 parts acrylic acid, 75 parts methyl allyl alcohol polyoxyethylene ether, 5 parts sodium methacrylate sulfonate, and 3 parts 2-hydroxyethyl methacrylate phosphate.

[0068] Tests showed that the initial spread of the concrete was 550 mm, the spread after 2 hours was 500 mm, and the apparent density was 2510 kg / m³. 328-day compressive strength: 128.4 MPa; flexural strength: 10.9 MPa; tensile strength: 6.3 MPa; elastic modulus: 37.0 GPa; drying shrinkage: 121 × 10⁻⁶. -6 .

[0069] Comparative Example 2

[0070] Concrete, characterized in that it is composed of the following raw materials in parts by weight:

[0071] 640 parts silicate cement, 70 parts aluminoferrite cement, 100 parts activated metakaolin powder, 130 parts ultrafine fly ash, 150 parts microsilica, 880 parts 2.36-4.75mm ceramsite sand, 20 parts activated calcium oxide, 8 parts activated magnesium oxide, 28 parts POM fiber, 29 parts polycarboxylate superplasticizer, and 340 parts water.

[0072] The polycarboxylate superplasticizer is polymerized from monomers of 20 parts acrylic acid, 75 parts methyl allyl alcohol polyoxyethylene ether, 5 parts sodium methacrylate sulfonate, and 3 parts 2-hydroxyethyl methacrylate phosphate.

[0073] Tests showed that the initial spread of the concrete was 540 mm, it showed no fluidity after 2 hours, and its apparent density was 2130 kg / m³. 3 28-day compressive strength: 92.6 MPa; flexural strength: 8.7 MPa; tensile strength: 5.9 MPa; elastic modulus: 34.3 GPa; drying shrinkage: 115 × 10⁻⁶. -6 .

[0074] Comparative Example 3

[0075] Concrete, characterized in that it is composed of the following raw materials in parts by weight:

[0076] 640 parts silicate cement, 70 parts aluminoferrite cement, 100 parts activated metakaolin powder, 130 parts ultrafine fly ash, 150 parts microsilica, 880 parts self-healing aggregate, 20 parts activated calcium oxide, 8 parts activated magnesium oxide, 28 parts POM fiber, 29 parts polycarboxylate superplasticizer, and 340 parts water.

[0077] The self-healing aggregate preparation process is as follows:

[0078] a. Mix 90 parts of porous silicate powder and 9 parts of sodium carbonate evenly, heat to 1000℃ and calcine, hold at that temperature for 1.5 hours, then rapidly cool to obtain modified porous silicate powder.

[0079] b. Mix 55 parts of modified porous silicate powder, 34 parts of silicate cement, and 24 parts of microsilica powder evenly to obtain a powder.

[0080] c. Add 100 parts of powder to a cylindrical granulator, slowly spray in 25 parts of water, and granulate by rotation to obtain a blank with a diameter of 2.36-4.75 mm.

[0081] d. Cur the billet according to standard for 24 hours, dry it, immerse it in water glass vacuum for 15 minutes, and then air dry it naturally to obtain the final product.

[0082] The polycarboxylate superplasticizer is polymerized from monomers of 20 parts acrylic acid, 75 parts methyl allyl alcohol polyoxyethylene ether, 5 parts sodium methacrylate sulfonate, and 3 parts 2-hydroxyethyl methacrylate phosphate.

[0083] Tests showed that the initial spread of the concrete was 550 mm, the spread after 2 hours was 500 mm, and the apparent density was 2170 kg / m³. 3 28-day compressive strength: 102.4 MPa; flexural strength: 11.7 MPa; tensile strength: 6.6 MPa; elastic modulus: 36.0 GPa; drying shrinkage: 98 × 10⁻⁶. -6 .

[0084] Comparative Example 4

[0085] Concrete, characterized in that it is composed of the following raw materials in parts by weight:

[0086] 640 parts silicate cement, 70 parts sulfoaluminate cement, 100 parts activated metakaolin powder, 130 parts ultrafine fly ash, 150 parts microsilica, 880 parts self-healing aggregate, 28 parts UEA expansion agent, 28 parts POM fiber, 29 parts polycarboxylate superplasticizer, and 340 parts water.

[0087] The self-healing aggregate preparation process is as follows:

[0088] a. Mix 90 parts of porous silicate powder and 9 parts of sodium carbonate evenly, heat to 1000℃ and calcine, hold at that temperature for 1.5 hours, then rapidly cool to obtain modified porous silicate powder.

[0089] b. Mix 60 parts of steel slag powder, 45 parts of modified porous silicate powder, 14 parts of silicate cement, and 4 parts of microsilica powder evenly to obtain a powder.

[0090] c. Add 100 parts of powder to a cylindrical granulator, slowly spray in 25 parts of water, and granulate by rotation to obtain a blank with a diameter of 2.36-4.75 mm.

[0091] d. Carbonize and cure the billet in an environment with a pressure of 0.3 MPa, a temperature of 20℃, and a relative humidity of 60% for 24 hours, dry it, vacuum immerse it in water glass for 15 minutes, and then air dry it naturally to obtain the final product.

[0092] The polycarboxylate superplasticizer is polymerized from monomers of 20 parts acrylic acid, 75 parts methyl allyl alcohol polyoxyethylene ether, 5 parts sodium methacrylate sulfonate, and 3 parts 2-hydroxyethyl methacrylate phosphate.

[0093] Tests showed that the initial spread of the concrete was 560 mm, the spread after 2 hours was 510 mm, and the apparent density was 2095 kg / m³. 3 28-day compressive strength: 133.8 MPa; flexural strength: 12.3 MPa; tensile strength: 7.0 MPa; elastic modulus: 36.2 GPa; drying shrinkage: 276 × 10⁻⁶. -6 .

[0094] Comparative Example 5

[0095] Concrete, characterized in that it is composed of the following raw materials in parts by weight:

[0096] 640 parts silicate cement, 70 parts aluminoferrite cement, 100 parts activated metakaolin powder, 130 parts ultrafine fly ash, 150 parts microsilica, 880 parts self-healing aggregate, 20 parts activated calcium oxide, 8 parts activated magnesium oxide, 28 parts POM fiber, 29 parts polycarboxylate superplasticizer, and 340 parts water.

[0097] The self-healing aggregate preparation process is as follows:

[0098] a. Mix 90 parts of porous silicate powder and 9 parts of sodium carbonate evenly, heat to 1000℃ and calcine, hold at that temperature for 1.5 hours, then rapidly cool to obtain modified porous silicate powder.

[0099] b. Mix 60 parts of steel slag powder, 45 parts of modified porous silicate powder, 14 parts of silicate cement, and 4 parts of microsilica powder evenly to obtain a powder.

[0100] c. Add 100 parts of powder to a cylindrical granulator, slowly spray in 25 parts of water, and granulate by rotation to obtain a blank with a diameter of 2.36-4.75 mm.

[0101] d. Carbonize and cure the billet in an environment with a pressure of 0.3 MPa, a temperature of 20℃, and a relative humidity of 60% for 24 hours, dry it, vacuum immerse it in water glass for 15 minutes, and then air dry it naturally to obtain the final product.

[0102] The polycarboxylate superplasticizer is polymerized from monomers of 20 parts acrylic acid, 78 parts methyl allyl alcohol polyoxyethylene ether, and 5 parts sodium methacrylate.

[0103] Testing revealed an initial concrete spread of 600 mm, slight floating of self-healing aggregate, no fluidity after 2 hours, and an apparent density of 2100 kg / m³. 3 28-day compressive strength: 120.8 MPa; flexural strength: 10.9 MPa; tensile strength: 6.7 MPa; elastic modulus: 36.1 GPa; drying shrinkage: 173 × 10⁻⁶. -6 .

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A type of ultra-high performance concrete for lightweight bridge decks, characterized in that, Composed of the following raw materials in parts by weight: 600-650 parts silicate cement, 50-100 parts aluminoferrite cement, 100-120 parts activated metakaolin powder, 120-180 parts ultrafine fly ash, 100-150 parts microsilica, 700-900 parts self-healing aggregate, 15-20 parts activated calcium oxide, 5-10 parts activated magnesium oxide, 25-30 parts POM fiber, 24-30 parts polycarboxylate superplasticizer, and 320-350 parts water. The self-healing aggregate preparation process is as follows: a. Mix 80-90 parts of porous silicate powder and 5-10 parts of sodium carbonate evenly, calcine at high temperature, maintain the temperature, and then rapidly cool to obtain modified porous silicate powder. b. Mix 50-75 parts of steel slag powder, 35-45 parts of modified porous silicate powder, 8-15 parts of silicate cement, and 2-5 parts of microsilica powder evenly to obtain a powder. c. Add 95-105 parts of powder to a cylindrical granulator, slowly spray in 18-25 parts of water, and granulate by rotation to obtain a 2.36-4.75mm blank. d. Carbonize and cure the billet, dry it, then vacuum immerse it in water glass and air dry it naturally to obtain the final product. The polycarboxylate superplasticizer is polymerized from monomers of 15-20 parts acrylic acid, 70-80 parts methyl allyl alcohol polyoxyethylene ether, 3-8 parts sodium methacrylate sulfonate, and 2-4 parts 2-hydroxyethyl methacrylate phosphate.

2. The ultra-high performance concrete for lightweight bridge decks according to claim 1, characterized in that, The silicate cement is P·Ⅱ52.5 cement.

3. The ultra-high performance concrete for lightweight bridge decks according to claim 1, characterized in that, The active metakaolin powder is made by calcining kaolin at 850℃ and then grinding it finely, with a specific surface area ≥800m². 2 / kg.

4. The ultra-high performance concrete for lightweight bridge decks according to claim 1, characterized in that, The ultrafine fly ash has a specific surface area ≥1500m² 2 / kg, 28d activity index ≥100%.

5. The ultra-high performance concrete for lightweight bridge decks according to claim 1, characterized in that, The microsilica powder is monocrystalline microsilica powder with a specific surface area ≥18000m². 2 / kg, SiO2 content ≥96%.

6. The ultra-high performance concrete for lightweight bridge decks according to claim 1, characterized in that, In the self-healing aggregate preparation process, the porous silicate powder in step a is diatomaceous earth, containing 88.95% SiO2 by mass, with an average pore diameter of 56.2 nm, a particle size ≤0.075 mm, and a loss on ignition of 0.39%.

7. The ultra-high performance concrete for lightweight bridge decks according to claim 1, characterized in that, In the self-healing aggregate preparation process, step a involves heating to 900-1100℃ for calcination and holding for 1-2 hours.

8. The ultra-high performance concrete for lightweight bridge decks according to claim 1, characterized in that, In the self-healing aggregate preparation process, the carbonization pressure in step d, carbonization curing, is 0.1-0.5 MPa, the temperature is 20-24℃, the relative humidity is 50-70%, and the carbonization curing time is 24-48 h.

9. The ultra-high performance concrete for lightweight bridge decks according to claim 1, characterized in that, In the self-healing aggregate preparation process, the water glass modulus in step d is 1.3-1.5, the mass concentration is 30-35%, and the vacuum soaking time is 10-20 min.

10. The method for preparing ultra-high performance concrete for lightweight bridge decks according to any one of claims 1-9, characterized in that, Includes the following steps: 1) Weigh each raw material according to its weight. 2) Add the self-healing aggregate and some water to the mixer and mix to pre-wet. 3) Add silicate cement, aluminoferrite cement, activated metakaolin powder, ultrafine fly ash, microsilica powder, activated calcium oxide, and activated magnesium oxide to the mixer and mix thoroughly. Add POM fiber and mix thoroughly. 4) Mix the polycarboxylate superplasticizer with the remaining water until homogeneous to obtain the admixture solution. 5) Add the additive solution to the mixer and mix thoroughly to obtain a slurry. 6) The slurry is then molded and cured to obtain the final product.