Prefabricated coarse aggregate ultra-high performance concrete bridge deck and preparation method thereof

Abstract

The invention discloses a prefabricated coarse aggregate ultra-high performance concrete bridge deck slab and a preparation method thereof, and belongs to the technical field of concrete.The prefabricated coarse aggregate ultra-high performance concrete bridge deck slab comprises a prefabricated slab reinforcement cage and coarse aggregate reactive powder concrete for pouring a prefabricated slab, the coarse aggregate active powder concrete is prepared from the following raw material components in parts by weight: 300 to 500 parts of coarse aggregate, 600 to 1000 parts of fine aggregate, 900 to 1600 parts of active powder, 50 to 300 parts of steel fiber, 8 to 30 parts of compound water reducing agent and 100 to 300 parts of water, the active powder comprises the following components in parts by weight: 600 to 1000 parts of cement, 100 to 200 parts of silica fume, 100 to 200 parts of mineral powder and 100 to 200 parts of ultrafine fly ash; the compound water reducing agent comprises 5-20 parts of a polycarboxylic acid water reducing agent and 3-10 parts of a star-shaped water reducing agent. The star-shaped water reducing agent is compounded with the traditional comb-shaped water reducing agent, so that the compressive strength, the flexural tensile strength and the durability of the prefabricated bridge deck slab can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and specifically to a precast coarse aggregate ultra-high performance concrete bridge deck and a preparation method thereof. Background Art

[0002] In modern bridge construction, the application of precast bridge decks is becoming increasingly widespread. With the continuous growth of traffic demand, higher requirements are put forward for the speed, quality and safety of bridge construction. The construction period of traditional in-situ cast bridge decks is long, and it is greatly affected by factors such as weather, and the quality is difficult to be stably controlled. At the same time, with the acceleration of the urbanization process, the construction site space is limited, and the attention to construction efficiency and environmental impact is continuously increasing. Precast bridge decks can be standardized and produced in factories, and the quality can be strictly controlled to reduce quality defects. It can be constructed in parallel with the main bridge structure, accelerating the construction progress, reducing construction risks, and also reducing on-site pollution, meeting the requirements of sustainable development. However, the bridge deck system is composed of precast bridge deck components linked together. The correct geometric parameters of a single component cannot fully ensure good splicing between components. Moreover, the transportation distance between the precast factory and the actual construction site also puts forward higher requirements for the compressive strength, flexural tensile strength and durability of the precast bridge deck. At the same time, in order to meet the production efficiency of the precast bridge deck, it is required to minimize the time from pouring to form removal.

[0003] In recent years, with the rapid development of polycarboxylate water reducers, water reducers have become an indispensable and important part of concrete. At present, polycarboxylate water reducers are widely used in many large-scale projects such as high-speed railways, urban rail transit, water conservancy and hydropower facilities, and nuclear power projects. However, some problems have also emerged in the use of polycarboxylate water reducers. For example, (1) polycarboxylate water reducers are sensitive to mud, and the content of clay and mica needs to be strictly controlled in sand and gravel materials. Otherwise, it will have a serious impact on the construction and mechanical properties of concrete and accelerate the slump loss. Therefore, in the process of concrete preparation, secondary water washing treatment of coarse aggregates such as crushed stones is often required, increasing the construction difficulty and cost; (2) the vast majority of polycarboxylates are retarding to cement hydration if not compounded, and the increase in water reduction rate is not obvious either. However, the research and application progress of polycarboxylate compounding technology is relatively slow. Many companies use fixed commercially available formulations and cannot make certain fine-tuning according to temperature seasons and application occasions. Summary of the Invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a precast coarse aggregate ultra-high performance concrete bridge deck, including a precast slab steel reinforcement cage and a coarse aggregate reactive powder concrete for casting the precast slab. Among them, a star-shaped water reducer is introduced and compounded with a traditional comb-shaped water reducer in the coarse aggregate reactive powder concrete, achieving the effects of anti-mud and early strength, thereby improving the compressive strength, flexural tensile strength and durability of the precast bridge deck.

[0005] The technical solution for achieving the object of the present invention is as follows:

[0006] A precast ultra-high performance concrete bridge deck, the bridge deck comprising a precast slab steel reinforcement cage and a coarse aggregate reactive powder concrete for casting the precast slab. The raw materials of the coarse aggregate reactive powder concrete, calculated by weight, include the following components: 300-500 parts of coarse aggregate, 600-1000 parts of fine aggregate, 900-1600 parts of reactive powder, 50-300 parts of steel fiber, 8-30 parts of compound superplasticizer, and 100-300 parts of water; the reactive powder includes 600-1000 parts of cement, 100-200 parts of silica fume, 100-200 parts of mineral powder, and 100-200 parts of superfine fly ash; the compound superplasticizer includes 5-20 parts of polycarboxylate superplasticizer and 3-10 parts of star-shaped superplasticizer; the star-shaped superplasticizer is prepared by the following steps:

[0007] S1. Heat isopentenyl polyoxyethylene ether until it is completely melted, add boron trifluoride diethyl ether solution as a catalyst, continuously dropwise add epichlorohydrin, and stir and react at 60-70 °C for 1-4 hours. Remove the unreacted substances by vacuum distillation to obtain monomer 1;

[0008] S2. Under a nitrogen atmosphere, add β-cyclodextrin and monomer 1 to DMF, add sodium hydroxide to adjust the pH to 12-13, stir and react at 70-90 °C for 1-5 hours, then cool to room temperature, precipitate with cold acetone, then wash with acetone at least once, and dry to obtain polyether-modified cyclodextrin;

[0009] S3. Under a nitrogen atmosphere, add polyether-modified cyclodextrin, 12-mercaptododecyl phosphoric acid, and 3-mercaptopropyltrimethoxysilane to DMF, stir, add tripropylphosphine as a catalyst, stir and react at room temperature for 10-20 hours, wash with acetone at least once, and dry to obtain the star-shaped superplasticizer.

[0010] The present invention uses a star-shaped water reducer and a traditional comb-shaped water reducer for compounding. The star-shaped water reducer contains a large number of short side chains in its molecule, with less entanglement between molecules and small intermolecular forces. Its intrinsic viscosity is much smaller than that of linear molecules. Moreover, the spatial volume of the three-dimensional spherical structure is larger than that of a linear polymer with the same molecular weight, having a stronger steric hindrance effect. The star-shaped water reducer with a star structure has higher adaptability and dispersing effect. The molecular structure of β-cyclodextrin is slightly conical, with a large number of hydroxyl groups outside the conical cavity showing hydrophilicity and hydrophobicity inside the conical cavity. Its molecular weight is 1135, the spatial diameter is 0.8 nm, and the cavity depth is about 0.7 - 0.8 nm, having a significant steric hindrance effect. Using cyclodextrin as the core of the star-shaped water reducer, arms with polyether segments and olefin functional groups are introduced through the ring-opening reaction of epichlorohydrin at the C-6 primary hydroxyl group of its glucose unit to prepare a star-shaped water reducer with a star structure. Further, a phosphate group and a siloxane group are introduced through the click reaction of an olefin double bond and a mercapto group. Among them, the cyclodextrin group has been proven to have dispersing performance, slump retention performance, and anti-clay performance when applied in water reducers. The phosphate group has better dispersing performance and sulfate tolerance than the carboxylic acid group. When competing for adsorption with sulfate ions, the phosphate group will be preferentially adsorbed by cement particles, showing better sulfate tolerance in macroscopic properties, having a better adsorption effect on cement, and effectively preventing clay from intercalating and adsorbing the water reducer, thus having an anti-clay effect. The siloxane group hydrolyzes under alkaline conditions and condenses with the silicon hydroxyl groups on the surface of calcium silicate hydrate to form an irreversible chemical bond to adsorb the water reducer on the surface of the hydration product, accelerating the early hydration of the cement paste, optimizing the pore structure of the cement-based material, reducing the number of capillary pores larger than 100 nm, increasing the number of gel pores smaller than 10 nm, and improving the early strength and durability of the bridge deck. By using cyclodextrin as the core and polyether segments as the arms, a star-shaped water reducer with polyether segments, phosphate end groups, and siloxane end groups is prepared. When compounded with the traditional comb-shaped water reducer, it can further improve the compressive strength, flexural strength, and durability of precast bridge decks.

[0011] Preferably, the mass ratio of the polycarboxylate water reducer to the star-shaped water reducer is (1.5 - 2.5):1.

[0012] Preferably, in step S1, the molar ratio of isopentenyl polyoxyethylene ether to epichlorohydrin is 1:(1.2 - 1.5); in step S2, the molar ratio of β-cyclodextrin to monomer 1 is 1:(7 - 9).

[0013] Preferably, in step S3, the molar ratio of polyether-modified cyclodextrin to 12-mercaptododecyl phosphate and 3-mercaptopropyltrimethoxysilane is 1:(4 - 6):(3 - 4).

[0014] Preferably, the specific surface area of the ultra-fine fly ash ≥ 500 m 2 / kg.

[0015] Preferably, the precast slab steel reinforcement cage is a two-layer steel mesh, and the binding process of the steel reinforcement cage is as follows: both ends of the longitudinal steel bars of the bottom-layer steel mesh are fixed to the formwork tension reaction frame by bolts, and the tension force of a single steel bar is 7-9 kN; the bottom-layer transverse steel bars are bound relying on the longitudinal steel bars, and the tension force of a single steel bar is 9-11 kN; both ends of the transverse steel bars of the top-layer steel mesh are fixed to the formwork tension reaction frame by bolts, and the tension force of a single steel bar is 9-11 kN; the top-layer longitudinal steel bars are bound relying on the transverse steel bars, and the tension force of a single steel bar is 7-9 kN.

[0016] Preferably, the coarse aggregate is crushed stone, the maximum nominal particle size of the crushed stone is ≤8 mm, and the content of particles with a nominal particle size less than 5 mm is ≤5 wt%.

[0017] Preferably, the fine aggregate is natural river sand, and the fineness modulus is 2.6-3.0.

[0018] Another object of the present invention is to protect the preparation method of the precast coarse aggregate ultra-high performance concrete bridge deck, including the following steps:

[0019] (1) Use the longitudinal and transverse baselines of the formwork to position the embedded parts and end forms of each precast slab, so that multiple sets of formworks work under a unified positioning coordinate system, control the relative positions of the dovetail grooves, steel bars and embedded parts of each precast slab to be fixed positions, and bind the precast slab steel mesh on the formwork according to the positioning.

[0020] (2) Put the reactive powder, coarse aggregate and fine aggregate into the mixer, dry mix for no more than 4 minutes, add water and the compound water reducing agent liquid material, continue to stir for 2-3 minutes, put in the steel fiber, and stir for 2-3 minutes, then discharge to obtain the concrete.

[0021] (3) Put the concrete into the distributor, and the distributor pours the concrete on the precast slab steel mesh through the hopper and levels it preliminarily. The thickness of the mixture after placing is not less than the designed thickness of the bridge deck and not more than 10 mm of the designed thickness of the bridge deck.

[0022] (4) The row vibrator vibrates the whole bridge deck, the vibration frequency is 50-200 Hz, and then the flat vibrator levels and vibrates the bridge deck again. The vibration time for every 400 mm width is not more than 10 s. After the concrete surface at the vibrating place oozes out slurry and no longer sinks, the flat vibrator continues to operate forward until the whole bridge deck is vibrated.

[0023] (5) Cover the surface of the bridge deck after re-vibrating and leveling with a plastic film, and move it to the static stop and water-jet roughening area for form removal and curing treatment.

[0024] Preferably, after the precast bridge deck is moved to the static flushing area, the side formwork is removed for flushing treatment. The degree of flushing is based on exposing the coarse aggregate and steel fiber. After 24 hours, the plastic film is removed, the water-retaining film is covered, and after 72 hours of moisture conservation and curing, demolding is carried out. After demolding, continue water curing for 15 days and transport it to the storage area for moisture conservation and curing.

[0025] Beneficial effects

[0026] The present invention provides a precast ultra-high performance concrete bridge deck, including a precast slab steel reinforcement cage and the coarse aggregate reactive powder concrete for casting the precast slab. A compound superplasticizer is used in the coarse aggregate reactive powder concrete, including a traditional polycarboxylate superplasticizer and a star-shaped superplasticizer. By using cyclodextrin as the core and polyether chain segments as the arms, a star-shaped superplasticizer with polyether chain segments, phosphoric acid end groups, and siloxane end groups is prepared. When compounded with the traditional comb-shaped superplasticizer, it can further improve the compressive strength, flexural tensile strength, and durability of the precast bridge deck. Description of the drawings

[0027] Figure 1 It is the preparation path of the star-shaped superplasticizer;

[0028] Figure 2 It is the infrared spectrum of β-cyclodextrin, polyether-modified cyclodextrin, and star-shaped superplasticizer. Specific embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0030] In the embodiments, the experimental methods used are all conventional methods unless otherwise specified, and the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0031] Now, the raw materials used in the examples and comparative examples are described as follows:

[0032] Cement: Portland cement, PII 52.5R, produced by Yingde Conch Cement Co., Ltd.;

[0033] Silica fume: SiO with an average particle size of 0.1 - 0.3 μm 2 , purchased from Guangdong Jusan Industry Co., Ltd.;

[0034] Ultra-fine fly ash: specific surface area ≥ 500 m 2 / Kg, Huzhou Lanyun Ore Powder Co., Ltd.

[0035] Mineral powder: purchased from Huzhou Lanyun Ore Powder Co., Ltd.;

[0036] Fine aggregate: natural river sand, fineness modulus is 2.8, produced in Qingyuan, Guangdong;

[0037] Coarse aggregate: diabase crushed stone, produced in Ganzhou City, Jiangxi Province, with a particle size of 5-8mm;

[0038] Steel fiber: end hook type steel fiber, SF100 / 60BP, purchased from Bolpais;

[0039] Polycarboxylate water reducer: -Ⅰ series polycarboxylic acid high performance water reducer, purchased from Jiangsu Subot;

[0040] Water: Guangzhou tap water, in compliance with the requirements of the standard "Mixing Water for Concrete" (JGJ 63-2006);

[0041] Isoprenoic acid polyoxyethylene ether: TPEG 2400, average molecular weight 2400D, purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.;

[0042] Boron trifluoride ether solution: 47wt% boron trifluoride and 53wt% ether mixed; analytical grade, commercially available;

[0043] Epichlorohydrin: analytical grade, purchased from Aladdin;

[0044] 12-Mercaptododecylphosphoric acid: purity 95%, purchased from Sigma-Aldrich;

[0045] 3-Mercaptopropyltrimethoxysilane: purity: 98%, purchased from Hubei Changfu Chemical Co., Ltd.;

[0046] Tripropyl phosphine: purity 98%, purchased from Shanghai Yien Chemical Technology Co., Ltd.;

[0047] Star-shaped water reducer 1: Homemade, the preparation method is as follows:

[0048] S1. Preparation of Monomer 1: 1 eq of isopentanol polyoxyethylene ether was heated to 65 ° C and completely melted, a boron trifluoride ether solution was added as a Lewis acid catalyst, 1.25 eq of epichlorohydrin was continuously added dropwise within half an hour, and the reaction was stirred at 65 ° C for 2 hours, and the unreacted substances were removed by distillation under reduced pressure to obtain Monomer 1;

[0049] S2. Under a nitrogen atmosphere, 1 eq of β-cyclodextrin and 7.5 eq of monomer 1 were added to DMF and stirred to a suspension state, sodium hydroxide was added to adjust the pH to 13, and the mixture was stirred at 80°C for 3 hours and then cooled to room temperature, precipitated with cold acetone, and then washed with acetone 3 times, and dried in vacuo at 40°C to obtain polyether-modified cyclodextrin;

[0050] S3. Under a nitrogen atmosphere, polyether-modified cyclodextrin, 12-mercaptododecylphosphonic acid, and 3-mercaptopropyltrimethoxysilane are added to DMF. The molar ratio of polyether-modified cyclodextrin, 12-mercaptododecylphosphonic acid, and 3-mercaptopropyltrimethoxysilane is 1:4.5:3.5. After stirring for a period of time, tripropylphosphine is added as a catalyst, and the addition amount of the catalyst is 2 mol% of the molar amount of polyether-modified cyclodextrin. Stir and react at room temperature for 20 hours, wash 3 times with acetone, and vacuum dry at 40 °C to obtain star-shaped water reducer 1. Among them, the preparation route of the star-shaped water reducer is as Figure 1 shown. The infrared spectra of β-cyclodextrin, polyether-modified cyclodextrin, and star-shaped water reducer are as Figure 2 shown. It can be seen from the infrared spectra that a special absorption peak of C═C can be observed at 1630 cm -1 in the infrared spectrum of polyether-modified cyclodextrin. In the infrared spectrum of the star-shaped water reducer, characteristic absorption peaks of phosphate groups appear at 1066 cm -1 and 1014 cm -1 . At the same time, a weak characteristic vibration peak of Si-O-C is detected at 795 cm -1 , which may be related to the low content of siloxane, indicating the successful preparation of the star-shaped water reducer.

[0051] Star-shaped water reducer 2: The difference in the preparation method compared with star-shaped water reducer 1 is that: the molar ratio of polyether-modified cyclodextrin, 12-mercaptododecylphosphonic acid, and 3-mercaptopropyltrimethoxysilane is 1:5.5:2.5;

[0052] Star-shaped water reducer 3: The difference in the preparation method compared with star-shaped water reducer 1 is that: 3-mercaptopropyltrimethoxysilane is not added, and the molar ratio of polyether-modified cyclodextrin and 12-mercaptododecylphosphonic acid is 1:7.5;

[0053] Star-shaped water reducer 4: The difference in the preparation method compared with star-shaped water reducer 1 is that: 12-mercaptododecylphosphonic acid is not added, and the molar ratio of polyether-modified cyclodextrin and 3-mercaptopropyltrimethoxysilane is 1:7.5.

[0054] Unless otherwise specified, the component raw materials used in each example and comparative example of the present invention are all commercially available raw materials, and the component raw materials used in each parallel experiment are all of the same kind.

[0055] Examples and Comparative Examples

[0056] A precast coarse aggregate ultra-high performance concrete bridge deck, with a width of 17.1 meters, a length of 3.37 meters, and a thickness of 180 millimeters. The preparation method is as follows:

[0057] (1) Use the longitudinal and transverse baselines of the formwork to position the embedded parts and end formwork of each precast slab, enabling multiple sets of formwork to work under a unified positioning coordinate system, controlling the relative positions of the dovetail grooves, steel bars, and embedded parts of each precast slab to fixed positions, and binding the steel bar mesh of the precast slab on the formwork according to the positioning.

[0058] Among them, the steel bar cage of the precast slab is divided into two layers of steel bar meshes. The specific binding process is as follows: ① First, fix the longitudinal steel bars at both ends of the bottom layer steel bar mesh to the formwork tension reaction frame by bolts, with the tension of a single steel bar being 8 kN; ② The transverse steel bars of the bottom layer are bound relying on the longitudinal steel bars, with the tension of a single steel bar being 10 kN; ③ Fix the transverse steel bars at both ends of the top layer steel bar mesh to the formwork tension reaction frame by bolts, with the tension of a single steel bar being 10 kN; ④ The longitudinal steel bars of the top layer are bound relying on the transverse steel bars, with the tension of a single steel bar being 8 kN; ⑤ The longitudinal and transverse steel bars are connected by binding; after the steel bars are tensioned, the distance between the sleeve end and the adjacent side formwork is preferably 2 - 3 mm.

[0059] (2) Put the reactive powder, coarse aggregate, and fine aggregate into the mixer, dry mix for no more than 4 minutes, add water and the compound water-reducing agent liquid material, continue to mix for 2 - 3 minutes, put in the steel fiber, and mix for 2 - 3 minutes, then discharge to obtain the concrete; the compound water-reducing agent liquid material is an aqueous solution of the compound water-reducing agent.

[0060] (3) Put the concrete into the distributor, and the distributor pours the concrete on the steel bar mesh of the precast slab through the hopper and initially levels it. The thickness of the mixture after placing is not less than the designed thickness of the bridge deck and not more than 10 mm greater than the designed thickness of the bridge deck.

[0061] (4) The row vibrator vibrates the bridge deck as a whole along the bridge deck, with the vibration frequency being 50 - 200 Hz. The flat vibrator and screed vibrate and level the bridge deck again. The vibration time for every 400 mm width is not more than 10 s. After the concrete surface oozes out mortar and no longer sinks, the flat vibrator and screed move forward and repeat the above operations.

[0062] (5) Cover the surface of the bridge deck after re-vibrating and leveling with a plastic film, move it to the static stop and surface roughening area to remove the side formwork, and conduct surface roughening treatment. The degree of surface roughening is based on exposing the coarse aggregate and steel fiber. After 24 hours, remove the plastic film, cover with a water-retaining film, keep moist for 72 h and then demold. After demolding, continue water curing for 15 d, and transport it to the storage area for moisture conservation. The specific composition and ratio of the concrete are shown in Table 1.

[0063] Table 1 Specific composition and ratio of coarse aggregate reactive powder concrete

[0064]

[0065]

[0066] Performance test

[0067] For every 100 precast bridge decks produced, randomly select 1 for the cutting plate test. The plane size of the test plate is 1500mm×350mm×180mm. Test the compressive strength, flexural tensile strength, initial cracking flexural tensile strength, and the nominal stress of the characteristic crack widths of 0.05mm and 0.10mm (which can be used to judge the durability of concrete). The results are shown in Table 2.

[0068] Initial cracking flexural tensile strength and the nominal stress of the characteristic crack widths of 0.05mm and 0.10mm: First, repeatedly load at 40% of the estimated cracking load for preloading, check the working conditions of the test system and the loading system, and eliminate the inelastic deformation until the deflections and strains during loading and unloading are approximately the same. Then, load in steps of 10 - 20kN to 80% of the estimated cracking load, hold the load steady for 5 - 10 minutes, and measure the deflections and strains; reduce the load step by 50%, carefully search for the cracking load, and the holding time of the specimen can be appropriately extended according to the deflections and strains of the previous load level. During the holding process, carefully search for cracks, record the load when the first crack appears, and calculate according to the formula f f =FL / bh 2 , where f f is the flexural tensile strength, F is the load at cracking (N), L is the distance between the support members (mm), b is the width of the specimen (mm), and h is the height of the specimen (mm). After cracking, continue to load in steps of 10 - 20kN to find the two characteristic cracks of 0.05mm and 0.10mm. During loading, the load step can be appropriately reduced according to the crack width. After holding the load steady, search for cracks, measure the maximum crack width and maximum height, record the loads when the two characteristic cracks of 0.05mm and 0.10mm appear, and calculate the nominal stress of the characteristic crack widths of 0.05mm and 0.10mm according to the formula f f =FL / bh 2 .

[0069] Compressive strength: Test the compressive strength at 28d in accordance with the national standard specification GB / T 50081-2019;

[0070] Flexural tensile strength: According to CECS13-2009 "Standard Test Method for Fiber Reinforced Concrete", measure its flexural tensile strength by the four-point loading method, and the loading speed is 0.08MPa / s.

[0071] Table 2 Performance Test of Precast Bridge Decks

[0072]

[0073]

[0074] As can be seen from the examples and comparative examples, the precast coarse aggregate ultra-high performance concrete bridge deck prepared by the present invention uses a compound of polycarboxylate water reducer and star-shaped water reducer, with a compressive strength ≥ 150 MPa, a flexural tensile strength ≥ 24 MPa, and an initial crack flexural tensile strength ≥ 8.5 MPa, and has good durability. Among them, as can be seen from Examples 3-7, when the mass ratio of polycarboxylate water reducer to star-shaped water reducer is within the preferred range of (1.5-2.5):1, the strength and durability performance are better; as can be seen from Examples 3, 8 and Comparative Examples 3, 4, when the phosphate group and siloxane group of the star-shaped water reducer are within a certain molar ratio range, the effect is better. This is because when the siloxane is in excess, it will undergo a condensation reaction with itself under the action of alkali, reducing the adsorption on cement, and when the phosphate group is in excess, the anionic charge density of the polymer main chain increases significantly, resulting in a large increase in the polymer adsorbed on the surface of cement particles, which will cause an increase in the viscosity of the concrete, poor fluidity, and difficulty in fully filling the corners of the formwork and the gaps between steel bars, resulting in defects such as cavities and honeycombs inside the concrete, reducing the compactness of the concrete. The internal defects will become stress concentration points, easily causing the generation and expansion of cracks, thereby reducing the strength of the concrete.

[0075] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A prefabricated coarse aggregate ultra-high performance concrete bridge deck, characterized in that: The bridge deck comprises a precast plate steel cage and a coarse aggregate active powder concrete for casting the precast plate. The raw materials of the coarse aggregate active powder concrete include the following components by weight: 300-500 parts of coarse aggregate, 600-1000 parts of fine aggregate, 900-1600 parts of active powder, 50-300 parts of steel fiber, 8-30 parts of compound water reducer, and 100-300 parts of water; the active powder includes 600-1000 parts of cement, 100-200 parts of silica fume, 100-200 parts of mineral powder, and 100-200 parts of ultra-fine fly ash; the compound water reducer includes 5-20 parts of polycarboxylate water reducer and 3-10 parts of star-shaped water reducer; the star-shaped water reducer is prepared by the following steps: S1. The isopentanol polyoxyethylene ether was heated until completely melted, a boron trifluoride ether solution was added as a catalyst, epichlorohydrin was continuously added dropwise, and the reaction was stirred at 60 to 70 ° C for 1 to 4 hours, and the unreacted substances were removed by distillation under reduced pressure to obtain monomer 1; S2. Under a nitrogen atmosphere, β-cyclodextrin and monomer 1 are added to DMF, sodium hydroxide is added to adjust the pH to 12-13, the mixture is stirred at 70-90° C. for 1-5 hours, and then cooled to room temperature, precipitated with cold acetone, and then washed with acetone at least once, and dried to obtain a polyether-modified cyclodextrin; S3. Under a nitrogen atmosphere, polyether-modified cyclodextrin, 12-mercaptododecyl phosphoric acid and 3-mercaptopropyltrimethoxysilane are added to DMF, and tripropyl phosphine is added as a catalyst after stirring. The mixture is stirred at room temperature for 10 to 20 hours, washed with acetone at least once, and dried to obtain a star-shaped water reducer.

2. The bridge deck according to claim 1, characterized in that: The mass ratio of the polycarboxylate water reducer to the star-shaped water reducer is (1.5-2.5):

1.

3. The bridge deck according to claim 1, characterized in that: The molar ratio of isopentanol polyoxyethylene ether to epichlorohydrin in step S1 is 1:(1.2-1.5); the molar ratio of β-cyclodextrin to monomer 1 in step S2 is 1:(7-9).

4. The bridge deck according to claim 1, characterized in that: The molar ratio of the polyether-modified cyclodextrin to 12-mercaptododecylphosphoric acid and 3-mercaptopropyltrimethoxysilane in step S3 is 1:(4-6):(3-4).

5. The bridge deck according to claim 1, characterized in that: The specific surface area of ​​the ultrafine fly ash is ≥500m 2 / kg.

6. The bridge deck according to claim 1, characterized in that: The prefabricated plate steel cage is a two-layer steel mesh, and the binding process of the steel cage is as follows: the two ends of the longitudinal steel bars of the bottom steel mesh are bolted and fixed to the formwork tensioning reaction frame, and the tensioning force of a single steel bar is 7 to 9 kN; the bottom transverse steel bars are tied against the longitudinal steel bars, and the tensioning force of a single steel bar is 9 to 11 kN; the two ends of the transverse steel bars of the top steel mesh are bolted and fixed to the formwork tensioning reaction frame, and the tensioning force of a single steel bar is 9 to 11 kN; the top longitudinal steel bars are tied against the transverse steel bars, and the tensioning force of a single steel bar is 7 to 9 kN.

7. The bridge deck according to claim 1, characterized in that: The coarse aggregate is crushed stone, the maximum nominal particle size of the crushed stone is ≤8 mm, and the content of particles with a nominal particle size less than 5 mm is ≤5wt%.

8. The bridge deck according to claim 1, characterized in that: The fine aggregate is natural river sand with a fineness modulus of 2.6 to 3.

0.

9. The method for preparing a prefabricated coarse aggregate ultra-high performance concrete bridge deck according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) The embedded parts and end molds of each prefabricated panel are positioned using the longitudinal and transverse baselines of the mold platform, so that multiple sets of mold platforms work under a unified positioning coordinate system, and the relative positions of the dovetail notches, steel bars and embedded parts of each prefabricated panel are controlled to be fixed positions, and the steel mesh of the prefabricated panel is tied on the mold platform according to the positioning; (2) Add active powder, coarse aggregate and fine aggregate into a mixer, dry stir for no more than 4 minutes, add water and compound water reducing agent liquid, continue stirring for 2 to 3 minutes, add steel fiber, stir for 2 to 3 minutes, and discharge to obtain concrete; (3) The concrete is fed into the concrete placing machine, which pours the concrete on the precast slab steel mesh through the concrete placing hopper and initially levels it. The thickness of the mixture after placing is not less than the designed thickness of the bridge deck and not more than 10 mm of the designed thickness of the bridge deck; (4) The row vibrator vibrates the entire bridge deck at a frequency of 50 to 200 Hz. The flat-plate vibrator and leveler then re-vibrates and level the bridge deck. The vibration time for each 400 mm width is no more than 10 seconds. When the concrete surface at the vibrated location is slurry-free and no longer sinks, the flat-plate vibrator and leveler continue to move forward until the entire bridge deck is vibrated. (5) After re-vibration and leveling, the surface of the bridge deck is covered with a plastic film and moved to the static roughening area for demolding and maintenance.

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