A low-shrinkage, high-cohesion ultra-high performance concrete and its preparation method

Abstract

This invention discloses a low-shrinkage, high-bonding ultra-high performance concrete, comprising the following raw materials in parts by weight: 680-775 parts cement, 140-200 parts fly ash, 160-220 parts silica fume, 45-80 parts ultrafine zeolite powder, 60-90 parts composite expansion agent, 1.6-2.1 parts graphene oxide, 940-1120 parts high-titanium heavy slag sand, 25.3-31.6 parts water-reducing agent, 0.025-0.063 parts defoamer, 160-200 parts steel fiber, and 185-202 parts water. The low-shrinkage, high-bonding ultra-high performance concrete of this invention possesses characteristics such as low shrinkage and high bonding strength, effectively solving problems such as deformation and cracking of concrete joints in bridge decks, concrete cracking, and poor durability. It ensures the performance of bridge deck expansion joint concrete from multiple perspectives, effectively extending the service life of bridge engineering projects.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a low-shrinkage, high-bonding, ultra-high performance concrete and its preparation method. Background Technology

[0002] Bridge deck expansion joints are gaps of a certain width pre-installed in the concrete surface layer of a bridge deck to prevent stress caused by the shrinkage and expansion of concrete due to temperature changes and other factors, thereby ensuring the flatness and stability of the bridge deck. To ensure the performance of bridge deck expansion joints, special concrete is used to fill the gaps; this concrete is called bridge deck expansion joint concrete. Bridge deck expansion joint concrete typically uses high-strength, high-durability, high-flowability, and high-impermeability concrete to adapt to the complex environment of long-term vehicle loads, wind, and rain on the bridge deck.

[0003] Ultra-high performance concrete possesses superior mechanical properties and excellent durability, effectively addressing the following issues that may arise during the use of bridge deck expansion joint concrete: ① Joint deformation: Due to factors such as temperature, humidity, and load, the expansion joints may deform, leading to cracking, fracture, or spalling of the concrete; ② Concrete cracking: In bridge deck expansion joint concrete, cracking may occur due to temperature changes and load effects, allowing moisture, air, and chemicals to penetrate and accelerate concrete degradation; ③ Durability issues: Bridge deck expansion joint concrete is exposed to complex environments over long periods, such as water, climate, and chemicals, which may cause corrosion and spalling, thus reducing its durability.

[0004] However, traditional ultra-high performance concrete has a high amount of cementitious materials and a low water-cement ratio. It uses a single shrinkage reduction method, resulting in large shrinkage and easy cracking. At the same time, it does not consider improving the interlayer bond between the old and new concrete in the post-cast strip, which can easily lead to problems such as the failure of the expansion joint concrete bond. Therefore, the long-term performance has not been well improved, which is not conducive to improving the quality of bridge deck expansion joints. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, the main objective of this invention is to provide a low-shrinkage, high-bonding ultra-high performance concrete for bridge deck expansion joints. This concrete features low shrinkage and high bonding properties, effectively solving problems such as concrete joint deformation and cracking, concrete crazing, and poor durability in bridge deck expansion joints. It also improves upon the limitations of traditional ultra-high performance concrete shrinkage control technologies, which are often limited in scope, prone to shrinkage cracking, and suffer from poor bonding and structural failure. This invention ensures the performance of bridge deck expansion joint concrete from multiple perspectives and extends the service life of bridge engineering projects.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A low-shrinkage, high-bonding, ultra-high-performance concrete comprises the following raw materials in parts by weight: 680-775 parts cement, 140-200 parts fly ash, 160-220 parts silica fume, 45-80 parts ultrafine zeolite powder, 60-90 parts CaO-MgO composite expansive agent, 1.6-2.1 parts graphene oxide powder, 940-1120 parts fine aggregate, 25.3-31.6 parts shrinkage-reducing composite water-reducing agent, 0.025-0.063 parts defoamer, 160-200 parts steel fiber, and 185-202 parts water; wherein the shrinkage-reducing composite water-reducing agent is obtained by combining ether-based water-reducing masterbatch and ether-based slump-retaining masterbatch.

[0008] In the above scheme, the shrinkage-reducing composite water-reducing agent is a high-water-reducing and shrinkage-reducing polycarboxylate water-reducing agent with a water reduction rate of ≥40%. The water-reducing agent has good compatibility with powder materials such as cement, fly ash microspheres, silica fume, zeolite powder, and expansion agents, and can be effectively adsorbed on the surface of powder materials, increasing free water and reducing viscosity. In addition, the water-reducing agent has a low surface tension, which can reduce the capillary pressure inside the cement matrix, change the pore size distribution in the cement paste, reduce the content of pores smaller than 50nm, affect the internal moisture evaporation rate, and thus effectively reduce the shrinkage rate of concrete.

[0009] In the above scheme, the solid content of the ether-based water-reducing masterbatch is 40-50%; the solid content of the ether-based slump-retaining masterbatch is 40-50%.

[0010] In the above scheme, the mass ratio of the ether-based water-reducing masterbatch to the ether-based slump-retaining masterbatch is 1:0.5~1.

[0011] Furthermore, the ether-based water-reducing masterbatch is obtained by polymerization of acrylic acid, methyl allyl polyoxyethylene ether-AGE, and mercaptopropionic acid as the main raw materials; wherein the mass ratio of mercaptopropionic acid, acrylic acid, and methyl allyl polyoxyethylene ether-AGE is 1:8~12:85~90.

[0012] Furthermore, the polymerization reaction adopts an oxidation-reduction system, which includes an oxidant and a reducing agent. The oxidant can be ammonium persulfate, etc., and the reducing agent can be vitamin C, etc. The mass ratio of oxidant, reducing agent and mercaptopropionic acid is 0.45~0.6:0.4~0.55:1.

[0013] In the above scheme, the polymerization reaction is carried out at a temperature of 30~35℃ for 7~8 hours.

[0014] In the above scheme, the molecular weight of the methyl allyl polyoxyethylene ether-AGE is 2150-2650.

[0015] Furthermore, the methyl allyl polyoxyethylene ether-AGE is prepared by reacting methyl allyl polyoxyethylene ether with C12-C14 alkyl glycidyl ether (AGE) using a ring-opening reaction between hydroxyl groups and epoxy groups; wherein the mass ratio of methyl allyl polyoxyethylene ether, AGE, and potassium persulfate is 100:8~15:0.5~1.2.

[0016] Furthermore, the molecular weight of the methyl allyl polyoxyethylene ether is 2640-3000.

[0017] In the above scheme, the ring-opening reaction is carried out at a temperature of 150~180℃ for 5~6 hours; the catalyst is potassium sulfate.

[0018] In the above scheme, the ether-based slump-preserving masterbatch is obtained by polymerization of acrylic acid, hydroxyethyl acrylate, methyl allyl polyoxyethylene ether-AGE, and mercaptopropionic acid as the main raw materials; wherein, the mass ratio of mercaptopropionic acid, acrylic acid, hydroxyethyl acrylate, and methyl allyl polyoxyethylene ether-AGE is 1:4~5:5~8:85~95.

[0019] In the above scheme, the polymerization reaction adopts an oxidation-reduction system, which includes an oxidant and a reducing agent. The oxidant can be ammonium persulfate, etc., and the reducing agent can be vitamin C, etc. The mass ratio of oxidant, reducing agent and mercaptopropionic acid is 0.55~0.65: 0.35~0.45:1.

[0020] In the above scheme, the polymerization reaction is carried out at a temperature of 30~40℃ for 6~8 hours.

[0021] In the above scheme, the preparation steps of the methyl allyl polyoxyethylene ether-AGE are the same as those of ether-based water-reducing masterbatch.

[0022] In the above scheme, the cement is silicate or ordinary silicate cement, and its specific surface area is not less than 360m². 2 / kg, with a strength grade of 52.5 or higher.

[0023] In the above scheme, the fly ash is ultrafine fly ash with a fineness (D50) ≤ 5μm, a water requirement ratio ≤ 95%, and a 28d strength activity index ≥ 100%.

[0024] In the above scheme, the silica fume is semi-densified silica fume with a specific surface area of ​​15m³. 2 The content of silica is above 92.0 wt%, the 28-day strength activity index is ≥105%, and the silica content is above 92.0 wt%.

[0025] In the above scheme, the zeolite powder is ultrafine zeolite powder, which is a white powder with a median particle size of 3.8~5.2μm and a 28-day activity index of over 95%.

[0026] In the above scheme, the CaO-MgO composite expansion agent is obtained by combining CaO and MgO as dual expansion sources; wherein the mass ratio of CaO to MgO is 5.8~7.2:4.2~2.8, the restricted expansion rate in water after 7 days is not less than 0.15%, and the restricted expansion rate in air after 21 days is not less than -0.01%.

[0027] Furthermore, the CaO-MgO composite expanding agent is prepared by mixing calcined calcium oxide clinker and magnesium oxide clinker at a mass ratio of 5.8~7.2:4.2~2.8, then mixing them with the dispersible carrier zeolite powder at a mass ratio of 100:5~10, and finally grinding the mixture until the specific surface area is less than 400 m². 2 It is prepared by / kg.

[0028] In the above scheme, the graphene oxide is reduced graphene oxide powder, which is prepared by chemical oxidation-reduction method using natural flake graphite as raw material (reduced graphene oxide powder prepared by other methods has a significant impact on the workability of the ultra-high performance concrete of this invention), and its specific surface area is 350~450m². 2 / kg, fineness (D50) ≤5μm, number of layers is 1~5.

[0029] Preferably, the fine aggregate is obtained by compounding high-titanium heavy slag sand and high-titanium heavy slag powder in a mass ratio of 7.5~9.2:2.5~0.8; wherein the high-titanium heavy slag sand produced by crushing is high-titanium heavy slag sand obtained by a rapid cooling process, has continuous gradation, a fineness modulus of 2.2~2.4, and an apparent density of 3050~3150 kg / m³. 3 The saturated surface-dry moisture content is 4.6~6.2%; the high-titanium heavy slag sand powder is obtained by crushing and screening high-titanium heavy slag, and its specific surface area is 300~350m². 2 / kg, 20-25% residue on 45 μm sieve.

[0030] Preferably, the defoamer is a polyether defoamer, which is a pale yellow liquid with a pH value of 5.0~8.0 and a viscosity (25℃) of 100~700 mPa.s; it can eliminate harmful bubbles generated during stirring and setting, and improve the strength and bonding performance of ultra-high performance concrete.

[0031] Preferably, the steel fiber is a copper-plated microfiber steel fiber, which is straight, has an average diameter of 0.20~0.22mm, a length of 12~14mm, and a tensile strength ≥2450MPa.

[0032] The above-mentioned method for preparing low-shrinkage, high-bondage, ultra-high-performance concrete for bridge deck expansion joints includes the following steps:

[0033] S1. Weigh out cement, fly ash, silica fume, ultrafine zeolite powder, CaO-MgO composite expansion agent and graphene oxide powder according to the proportions, put them into the mixer and mix evenly.

[0034] S2. The fine aggregate is first subjected to pre-wetting and water absorption treatment (the amount of water absorbed is not included in the water used in the formulation) to obtain pre-wetted aggregate;

[0035] S3. Add water, composite additives (mixed with defoamer and shrinkage-reducing composite water-reducing agent), and pre-wetted aggregates according to the proportion, and stir until the powder material is completely fluidized into a plastic state.

[0036] S4. Add steel fiber according to the ratio and stir (4~6 min) to obtain ultra-high performance concrete mixture, pour and mold it, and cure it according to standard to obtain the low shrinkage and high bonding ultra-high performance concrete.

[0037] The low-shrinkage, high-bondage, ultra-high-performance concrete prepared according to the above scheme has a spread of 660~720mm, an air content of ≤3.5%, and a density of ≤2550kg / m³. 3 It has a 28-day compressive strength of 142~155MPa, a flexural strength of 24.2~27.5MPa, a tensile strength of 7.4~8.2MPa, a splitting bond strength of 6.12~6.96MPa, and a 365-day drying shrinkage of ≤150 microstrain. It has excellent working performance, mechanical properties, bonding performance and volume stability.

[0038] The principle of this invention is as follows:

[0039] (1) Shrinkage control of ultra-high performance concrete in bridge deck expansion joints;

[0040] First, the shrinkage-reducing water-reducing agent designed and synthesized in this invention contains oleophilic AGE components at the branch ends, which can reduce the surface tension of the capillary solution in the ultra-high performance concrete mixture, reduce the negative pressure and additional pressure caused by water consumption, and thus reduce the early shrinkage of ultra-high performance concrete. Second, the composite expansive agent used in the low-shrinkage, high-bonding ultra-high performance concrete of this invention is a dual-expansion-source expansive agent. The composite expansive agent CaO expansive agent has high hydration activity, fast expansion speed, and is very suitable for UHPC with large early self-shrinkage. The hydration of the composite expansive agent produces physicochemically stable products with adjustable expansion process design. The composite expansive agent can effectively improve the deformation performance of ultra-high performance concrete and reduce its shrinkage and cracking risks. Finally, this invention adds appropriate amounts of zeolite powder and high-titanium heavy slag sand. These two materials have good water absorption properties and can regulate the humidity of ultra-high performance concrete. When the internal humidity of ultra-high performance concrete drops to a critical value, the humidity compensation medium begins to release the internally stored water, playing a role in internal curing to reduce shrinkage. They play a role in adsorbing and releasing water during the initial hydration process of ultra-high performance concrete. Moreover, this humidity-compensating medium contains abundant silica, which can undergo a pozzolanic reaction and also act as a fine mineral admixture to some extent, helping to reduce the internal shrinkage of ultra-high performance concrete. By controlling the shrinkage of ultra-high performance concrete through cement hydration reaction and temperature, humidity, and stress control at multiple levels, the low-shrinkage, high-bondability ultra-high performance concrete used for bridge deck expansion joints achieves long-term volume stability with a shrinkage of ≤150 microstrain over 365 days while maintaining excellent workability and mechanical properties.

[0041] (2) Regarding the bonding performance of ultra-high performance concrete for bridge deck expansion joints;

[0042] The mineral admixtures used in this invention, fly ash microspheres and silica fume, possess extremely strong pozzolanic activity. They can undergo a secondary hydration reaction with the cement hydration product Ca(OH)2 to generate insoluble, high-quality hydration product silicate CSH gel, which is deposited in the voids at the aggregate-cement interface, optimizing the pore structure and improving the basic mechanical properties of ultra-high performance concrete. High-quality CSH has a large rigidity and specific surface area, and the van der Waals forces and chemical bonds between high-quality CSH particles are stronger, which can improve the interlaminar shear force of hardened ultra-high performance concrete at the microscopic and submicroscopic levels, and enhance the adhesion of ultra-high performance concrete. However, ultrafine zeolite powder and heavy high-titanium slag sand have certain water absorption and release effects for internal curing, resulting in a higher water consumption required to achieve the designed workability, reducing the strength and adhesion of the matrix. This invention further combines a shrinkage-reducing composite water-reducing agent, which has good shrinkage reduction effect and ultra-high water reduction rate, to achieve the preparation of ultra-high performance concrete with low water-cement ratio by admixture internal curing materials, and improves the problems of insufficient hydration degree of internal curing materials, weak interlaminar force and weak adhesion of CSH. Secondly, by incorporating multilayer graphene oxide powder, this invention utilizes the excellent strength and strain hardening characteristics of graphene itself, dispersed among the hydration products of cement, to enhance the nanoscale CSH structure, inhibit the initiation and formation of microcracks in ultra-high performance concrete, and further improve the interlayer shear capacity and bond strength of ultra-high performance concrete. This invention also utilizes the volcanic activity, micro-aggregate effect, and enhanced interlayer shear force of silica fume and reduced graphene oxide powder to further optimize the pore structure and interface transition zone of ultra-high performance concrete, improve the bonding performance of ultra-high performance concrete, enhance the service performance of bridge deck expansion joint concrete, and extend the service life of bridge engineering structures.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] 1) The low-shrinkage, high-adhesion ultra-high performance concrete of the present invention has the characteristics of low shrinkage and high adhesion, which can effectively solve the problems of deformation and cracking of concrete joints in bridge deck expansion joints, concrete cracking, and poor durability, and ensure the performance of bridge deck expansion joint concrete from multiple aspects, effectively extending the service life of bridge engineering.

[0045] 2) The preparation method involved in this invention is relatively simple and easy to implement, and is suitable for widespread application. Detailed Implementation

[0046] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

[0047] In the following embodiments, the cement is type II Portland cement with a strength grade of 52.5 and a specific surface area of ​​375 m². 2 / kg; the fly ash is ultrafine fly ash with a water requirement ratio of 87% and a 28-day strength activity index of 112%; the silica fume is semi-dense silica fume with a specific surface area of ​​16m³. 2 / g, 28d strength activity index 127%, silica content 96.0wt%; zeolite powder is ultrafine zeolite powder, white powder, particle size 2.7-14.6μm, median particle size 4.7μm, its 28d activity index is 97%.

[0048] The fine aggregate used is a composite of high-titanium heavy slag sand and high-titanium heavy slag powder in a mass ratio of 9:1; the high-titanium heavy slag sand is produced by a rapid cooling process, is continuously graded, has a fineness modulus of 2.4, and an apparent density of 3100 kg / m³. 3 The saturated surface-dry moisture content is 4.9%; the high-titanium heavy slag sand powder is obtained by crushing and screening high-titanium heavy slag, and its specific surface area is 325 m². 2 / kg, 20.9% residue on 45 μm sieve.

[0049] The shrinkage-reducing composite water-reducing agent used is a self-synthesized high water-reducing polycarboxylate water-reducing agent with a water reduction rate of 45%. The specific preparation method includes the following steps:

[0050] 1) Ether-based water-reducing masterbatch: Acrylic acid, methyl allyl polyoxyethylene ether 3000-AGE, and mercaptopropionic acid were polymerized in an aqueous solution at 30°C under ammonium persulfate-vitamin C redox catalysis for 7 hours to obtain an ether-based water-reducing masterbatch. The mass ratio of acrylic acid, allyl polyoxyethylene ether 3000-AGE, mercaptopropionic acid, ammonium persulfate, vitamin C, and water was 12:88:1:0.6:0.4:102. The solid content of the obtained ether-based water-reducing masterbatch was 50%.

[0051] The methyl allyl polyoxyethylene ether 3000-AGE is prepared by reacting methyl allyl polyoxyethylene ether and dodecyl glycidyl ether (AGE) with the ring-opening reaction of hydroxyl groups and epoxy at 170°C and under the catalysis of potassium persulfate for 5 hours. The mass ratio of methyl allyl polyoxyethylene ether 3000, AGE and potassium persulfate is 100:10:0.8.

[0052] 2) Ether-based slump-preserving masterbatch: Acrylic acid, hydroxyethyl acrylate, methyl allyl polyoxyethylene ether 3000-AGE, and mercaptopropionic acid were polymerized in an aqueous solution at 30°C under ammonium persulfate-vitamin C redox catalysis for 7 hours to obtain an ether-based slump-preserving masterbatch. The mass ratio of acrylic acid, hydroxyethyl acrylate, methyl allyl polyoxyethylene ether 3000-AGE, mercaptopropionic acid, ammonium persulfate, vitamin C, and water was 5:7:88:1:0.6:0.4:102. The preparation steps of methyl allyl polyoxyethylene ether 3000-AGE were the same as in Example 1, and the solid content of the obtained ether-based slump-preserving masterbatch was 50%.

[0053] 3) The composite water-reducing agent is obtained by compounding ether-based water-reducing masterbatch and ether-based slump-retaining masterbatch at a mass ratio of 1:1 at room temperature.

[0054] The CaO-MgO composite expander used is obtained by combining CaO and MgO. CaO is calcined at 950-1050℃, and MgO is calcined at 1150-1250℃. The resulting calcium oxide clinker and magnesium oxide clinker are then mixed at a mass ratio of 7:3, and further mixed with zeolite powder (a dispersible carrier) at a mass ratio of 10:1. The mixture is then ground until the specific surface area is below 400 m². 2 It is prepared by / kg.

[0055] The steel fiber is commercially available copper-plated microfiber steel fiber, with a straight structure, an average diameter of 0.20~0.22mm, a length of 13mm, and a tensile strength ≥2450MPa; the graphene oxide is reduced graphene oxide powder, prepared from natural flake graphite through a chemical oxidation-reduction method, with a specific surface area of ​​350~450m². 2 / kg, fineness (D50) ≤5μm, number of layers 1-5.

[0056] The defoamer used is a polyether defoamer with a pH of 6.6 and a viscosity (25℃) of 354 mPa.s.

[0057] In the following examples and comparative examples, the low-viscosity, high-adhesion ultra-high performance concrete was prepared using the following steps unless otherwise specified:

[0058] S1. Weigh out cement, fly ash, silica fume, ultrafine zeolite powder, CaO-MgO composite expansion agent and graphene oxide powder according to the proportions, put them into the mixer and mix evenly.

[0059] S2. The fine aggregate is pre-wetted and absorbed for 24 hours before use to obtain pre-wetted aggregate;

[0060] S3. Add water and composite additives (mixed with defoamer and shrinkage-reducing composite water-reducing agent) and pre-wetted aggregates to the mixer according to the proportion and stir until the powder material is completely fluidized into a plastic state.

[0061] S4. Add steel fiber according to the ratio and stir for 4-6 minutes to obtain ultra-high performance concrete mixture, which can be poured and molded, and cured according to standard for 28 days.

[0062] The low-shrinkage, high-bonding, ultra-high performance concrete comprises the following raw materials in parts by weight: 680-775 parts cement, 140-200 parts fly ash, 160-220 parts silica fume, 45-80 parts ultrafine zeolite powder, 60-90 parts CaO-MgO composite expansion agent, 1.6-2.1 parts graphene oxide, 940-1120 parts fine aggregate, 25.3-31.6 parts shrinkage-reducing composite water-reducing agent, 0.025-0.063 parts defoamer, 160-200 parts steel fiber, and 185-202 parts water.

[0063] Example 1

[0064] A type of low-viscosity, high-adhesion, ultra-high-performance concrete for bridge reinforcement comprises the following raw materials and their respective weight proportions: 750 parts cement, 150 parts fly ash, 200 parts silica fume, 60 parts ultrafine zeolite powder, 80 parts CaO-MgO composite expansion agent, 1.75 parts 5-layer graphene oxide, 1120 parts fine aggregate, 31.5 parts shrinkage-reducing composite water-reducing agent, 0.057 parts defoamer, 200 parts steel fiber, and 200 parts water.

[0065] Example 2

[0066] A type of low-viscosity, high-adhesion, ultra-high-performance concrete for bridge reinforcement comprises the following raw materials and their respective weight proportions: 700 parts cement, 180 parts fly ash, 160 parts silica fume, 80 parts ultrafine zeolite powder, 60 parts CaO-MgO composite expansion agent, 1.92 parts three-layer graphene oxide, 1050 parts fine aggregate, 25.5 parts shrinkage-reducing composite water-reducing agent, 0.046 parts defoamer, 180 parts steel fiber, and 194 parts water.

[0067] Example 3

[0068] A type of low-viscosity, high-adhesion, ultra-high-performance concrete for bridge reinforcement comprises the following raw materials and their respective weight proportions: 680 parts cement, 200 parts fly ash, 210 parts silica fume, 60 parts ultrafine zeolite powder, 90 parts CaO-MgO composite expansion agent, 2.1 parts one layer of graphene oxide, 1000 parts fine aggregate, 26.4 parts shrinkage-reducing composite water-reducing agent, 0.052 parts defoamer, 160 parts steel fiber, and 185 parts water.

[0069] Comparative Example 1

[0070] An ultra-high performance concrete material is prepared in a manner similar to that of Example 1, except that a commercially available ultra-high performance dry mix is ​​selected. The dry mix is ​​a premixed mixture of powder materials, steel fibers, powder composite admixtures, and other components, with a strength grade of C120 and a water-to-material ratio of 9.0%.

[0071] Comparative Example 2

[0072] This comparative example provides an ultra-high performance concrete material, the preparation method of which is roughly the same as that of Example 1, except that: a commercially available ultra-high performance dry mix is ​​selected, the dry mix being a premixed mixture of powder materials, steel fibers, liquid composite admixtures and other components, with a strength grade of C150 and a water-to-material ratio of 8.5%.

[0073] Comparative Example 3

[0074] An ultra-high performance concrete material is prepared in a manner largely similar to that of Example 1, except that the raw materials and their weight percentages are as follows: 790 parts cement, 150 parts fly ash, 200 parts silica fume, 100 parts commercially available UHPC composite expansion agent, 1120 parts fine aggregate, 42.5 parts commercially available water-reducing agent, 0.057 parts defoamer, 200 parts steel fiber, and 200 parts water. The commercially available UHPC composite expansion agent has a 7-day limited expansion rate of 0.21% in water and a 21-day limited expansion rate of 0.02% in air. The commercially available water-reducing agent has a water reduction rate of 28.3% and a 28-day shrinkage rate of 110%.

[0075] Comparative Example 4

[0076] An ultra-high performance concrete material is prepared in a manner largely similar to that of Example 2, except that the raw materials and their respective weight percentages are as follows: 700 parts cement, 180 parts fly ash, 160 parts silica fume, 60 parts commercially available UHPC composite expansion agent (same as Comparative Example 3), 1.92 parts 3-layer graphene oxide, 1050 parts fine aggregate, 35.7 parts commercially available UHPC water-reducing agent, 0.046 parts defoamer, 180 parts steel fiber, and 194 parts water. The commercially available UHPC water-reducing agent has a solids content of 35.6%, a water reduction rate of 41%, and a 28-day shrinkage rate of 105%.

[0077] The performance of the ultra-high performance concrete prepared in Examples 1, 2, 3, Comparative Examples 1, 2, 3, and 4 was tested. The spread, air content, compressive strength, flexural strength, and splitting bond strength were tested according to the relevant provisions of the industry standard "Test Procedures for Cement and Cement Concrete in Highway Engineering" (JG / J 3420). Tensile strength was tested according to the relevant provisions of the industry standard "Technical Requirements for Ultra-High Performance Concrete (UHPC)" (T / CECS 10107). 365-day drying shrinkage was tested according to the relevant provisions of the national standard "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" (GBT50082-2009).

[0078] The test results are shown in Table 1 below:

[0079] The low-shrinkage, high-bondage ultra-high performance concrete obtained by this invention has a spread of 660-720 mm, an air content of ≤3.5%, and a bulk density of ≤2550 kg / m³. 3 It has a 28-day compressive strength of 142-155 MPa, a flexural strength of 24.2-27.5 MPa, a tensile strength of 7.4-8.2 MPa, a splitting bond strength of 6.12-6.96 MPa, and a 365-day drying shrinkage of ≤250 micro-strain. It has excellent workability, bonding performance and volume stability, and is suitable for engineering fields such as bridge deck expansion joints.

[0080] Table 1. Concrete performance test results

[0081]

[0082] As shown in Table 1, both Example 1 and Comparative Example 2 incorporate 2.5% steel fiber by volume. However, Example 1 exhibits higher spreadability, lower air content, and lighter density while maintaining similar compressive and flexural strengths. Furthermore, its tensile and splitting strengths are superior to those of the Comparative Example, with a splitting bond strength increase of over 30% and a 365-day shrinkage reduction of over 40%. Examples 2 and 3, along with the Comparative Example, incorporate 2.0% steel fiber by volume. Similarly, the workability, basic mechanical properties, and volume stability of Examples 2 and 3 are superior to those of Comparative Example 1. This invention primarily utilizes the low-shrinkage, high-bonding ultra-high performance concrete for bridge expansion joints, employing a shrinkage-reducing composite water-reducing agent and CaO-MgO composite expansion agent to inhibit shrinkage. This allows for full-process control of the ultra-high performance concrete's shrinkage performance. Simultaneously, it incorporates moisture-compensating materials such as ultrafine zeolite powder and titanium slag sand, which act as water storage during the initial hydration process. When the internal humidity of the ultra-high performance concrete drops to a critical value, the moisture-compensating medium releases the stored moisture, providing internal curing and further reducing shrinkage. This mitigates problems such as high shrinkage and cracking common in traditional ultra-high performance concrete. Furthermore, the invention leverages the volcanic activity, micro-aggregate effect, and enhanced interlayer shear force of the inorganic mineral ultrafine powder composite system and graphene oxide powder to further optimize the pore structure and interface transition zone of the ultra-high performance concrete, improving its bonding performance and enhancing the adhesion between the bridge expansion joint and the post-cast strip. This reduces the likelihood of bonding failure and extends the service life of the bridge expansion joint.

[0083] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A low-shrinkage, high-bonding, ultra-high performance concrete, characterized in that, The raw materials include the following parts by weight: 680-775 parts cement, 140-200 parts fly ash, 160-220 parts silica fume, 45-80 parts ultrafine zeolite powder, 60-90 parts CaO-MgO composite expanding agent, 1.6-2.1 parts graphene oxide powder, 940-1120 parts fine aggregate, 25.3-31.6 parts shrinkage-reducing composite water-reducing agent, 0.025-0.063 parts defoamer, 160-200 parts steel fiber, and 185-202 parts water; the shrinkage-reducing composite water-reducing agent is obtained by combining ether-based water-reducing masterbatch and ether-based slump-retaining masterbatch. The ether-based water-reducing masterbatch is obtained by polymerization of acrylic acid, methyl allyl polyoxyethylene ether-AGE, and mercaptopropionic acid as main raw materials; wherein the mass ratio of mercaptopropionic acid, acrylic acid, and methyl allyl polyoxyethylene ether-AGE is 1:8~12:85~90; the ether-based slump-retaining masterbatch is obtained by polymerization of acrylic acid, methyl allyl polyoxyethylene ether-AGE, mercaptopropionic acid, and hydroxyethyl acrylate as main raw materials; wherein the mass ratio of mercaptopropionic acid, acrylic acid, hydroxyethyl acrylate, and methyl allyl polyoxyethylene ether-AGE is 1:4~5:5~8:85~95. The methyl allyl polyoxyethylene ether-AGE is prepared by reacting methyl allyl polyoxyethylene ether with C12-C14 alkyl glycidyl ether via a ring-opening reaction between hydroxyl groups and epoxy groups; wherein the mass ratio of methyl allyl polyoxyethylene ether to AGE is 100:8~15.

2. The low-shrinkage, high-bondage ultra-high performance concrete according to claim 1, characterized in that, The cement is silicate or ordinary silicate cement, with a specific surface area of ​​not less than 360 m². 2 / kg, strength grade 52.5 or above; fly ash is ultrafine fly ash with a fineness D50≤5μm, water requirement ≤95%, and 28-day strength activity index ≥100%; silica fume is semi-dense silica fume with a specific surface area of ​​15m³. 2 The zeolite powder is of the highest quality, with a 28-day strength activity index ≥105% and a silica content of ≥92.0wt%; the zeolite powder is ultrafine zeolite powder with a median particle size of 3.8~5.2μm and a 28-day activity index of ≥95%.

3. The low-shrinkage, high-bondage ultra-high performance concrete according to claim 1, characterized in that, The CaO-MgO composite expansion agent is obtained by combining CaO and MgO as dual expansion sources; wherein the mass ratio of CaO to MgO is 5.8~7.2:4.2~2.8, the restricted expansion rate in water after 7 days is not less than 0.15%, and the restricted expansion rate in air after 21 days is not less than -0.01%.

4. The low-shrinkage, high-bondage ultra-high performance concrete according to claim 1, characterized in that, The graphene oxide mentioned is reduced graphene oxide powder with a specific surface area of ​​350~450m². 2 / kg, fineness ≤5μm, number of layers 1~5.

5. The low-shrinkage, high-bondage ultra-high performance concrete according to claim 1, characterized in that, The fine aggregate is obtained by compounding high-titanium heavy slag sand and high-titanium heavy slag powder in a mass ratio of 7.5~9.2:2.5~0.8; wherein, the high-titanium heavy slag sand is continuously graded, with a fineness modulus of 2.2~2.4 and an apparent density of 3050~3150 kg / m³. 3 The saturated surface-dry moisture content is 4.6~6.2%; the high-titanium heavy slag sand powder is obtained by crushing and screening high-titanium heavy slag, and its specific surface area is 200~325 m². 2 / kg, 20-25% residue on 45 μm sieve.

6. The low-shrinkage, high-bondage ultra-high performance concrete according to claim 1, characterized in that, The defoamer is a polyether defoamer with a pH value of 5.0~8.0 and a viscosity of 100~700 mPa·s.

7. The low-shrinkage, high-bondage ultra-high performance concrete according to claim 1, characterized in that, The steel fiber is a copper-plated microfiber steel fiber, which is straight, with an average diameter of 0.20~0.22mm, a length of 12~14mm, and a tensile strength ≥2450MPa.

8. The method for preparing low-shrinkage, high-bondage, ultra-high performance concrete according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Weigh out cement, fly ash, silica fume, ultrafine zeolite powder, CaO-MgO composite expansion agent and graphene oxide powder according to the proportions, put them into the mixer and mix evenly. S2. The fine aggregate is first subjected to pre-wetting and water absorption treatment to obtain pre-wetted aggregate; S3. Add water, composite additives (mixed with defoamer and shrinkage-reducing composite water-reducing agent), and pre-wetted aggregates according to the proportion, and stir until the powder material is completely fluidized into a plastic state. S4. Add steel fibers in proportion and mix to obtain ultra-high performance concrete mixture, pour and mold it, and cure it according to standard to obtain the low-shrinkage, high-bonding ultra-high performance concrete.

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