Low drying shrinkage ultra-high performance concrete and preparation method and curing method thereof

Abstract

The application relates to a low-drying-shrinkage ultra-high-performance concrete and a preparation method and a curing method thereof, and belongs to the technical field of building materials.The application aims to provide a low-drying-shrinkage ultra-high-performance concrete and a preparation method and a curing method thereof.The application adopts the technical scheme that the low-drying-shrinkage ultra-high-performance concrete comprises the following raw materials in parts by mass: 800-1200 parts of powder; 900-1300 parts of fine aggregate; 15-25 parts of water reducing agent; and 170-250 parts of water; the powder comprises Portland cement and mineral admixture, wherein the mass ratio of the mineral admixture to the powder is not higher than 0.15:1; the mineral admixture comprises silica fume and nano calcium carbonate powder; the average particle size of the Portland cement is less than 30 mu m, the ratio of the average particle size of the silica fume to the average particle size of the Portland cement is 0.1-0.7:1, and the average particle size of the nano calcium carbonate powder is less than 100 nm.

Description

TECHNICAL FIELD

[0001] The application relates to a low-drying-shrinkage ultra-high performance concrete and a preparation method and a curing method thereof. BACKGROUND

[0002] Ultra-high performance concrete (UHPC) has a compressive strength of not less than 120 MPa and an axial tensile strength of not less than 8 MPa, and is an ideal engineering material. However, UHPC has a severe early shrinkage after initial setting, which seriously affects the volume stability of a structure, or causes potential cracking risk when the structural resistance is low, so that the concrete after pouring is prone to durability problems and the performance advantages of the material are difficult to fully play.

[0003] The early shrinkage of concrete is generally divided into early self-shrinkage and early drying shrinkage. Research shows that due to the presence of a large amount of cementitious materials in the components, the hydration reaction in the UHPC is relatively severe, which causes a large self-shrinkage of the matrix. With the continuous progress of the hydration reaction, the concentrated hydration heat causes the water in the matrix to evaporate rapidly, or causes the UHPC to have a prominent early drying shrinkage, so that the early drying shrinkage is also an important factor affecting the volume stability of the UHPC.

[0004] At present, the evolution law of the early drying shrinkage of the UHPC and the structure cracking problem caused thereby have not been paid enough attention, and there are few effective measures to cope with the problem, so it is difficult to effectively guarantee the volume stability of the UHPC. SUMMARY

[0005] The technical problem to be solved by the application is to provide a low-drying-shrinkage ultra-high performance concrete, which adjusts the cement and mineral admixture gradation to improve the matrix resistance of the UHPC from the inside of the material, so as to better guarantee the volume stability of the UHPC at the early age stage.

[0006] The application also provides a preparation method of the low-drying-shrinkage ultra-high performance concrete.

[0007] The application also provides a curing method of the low-drying-shrinkage ultra-high performance concrete, which adapts to the hydration reaction and free water evaporation law in the UHPC to inhibit the drying shrinkage of the concrete to a certain extent.

[0008] The technical scheme adopted by the application is that the low-drying-shrinkage ultra-high performance concrete comprises the following raw materials in parts by mass:

[0009]

[0010] The powder material comprises Portland cement and mineral admixtures, wherein the mass ratio of mineral admixtures to powder material is not higher than 0.15:1;

[0011] The mineral admixtures comprise silica fume and nano calcium carbonate powder;

[0012] The average particle size of the Portland cement is less than 30 μm, the ratio of the average particle size of the silica fume to the average particle size of the Portland cement is between 0.1 and 0.7:1, and the average particle size of the nano calcium carbonate powder is less than 100 nm.

[0013] When the particle size ratio of the silica fume to the cement is between 0.1 and 0.3, the mass ratio of the mineral admixtures to the powder material is not more than 0.05:1, and the mass ratio of the calcium carbonate powder to the mineral admixtures is not more than 0.2:1;

[0014] When the particle size ratio of the silica fume to the cement is between 0.3 and 0.5, the mass ratio of the mineral admixtures to the powder material is not more than 0.1:1, and the mass ratio of the calcium carbonate powder to the mineral admixtures is not more than 0.1:1;

[0015] When the particle size ratio of the silica fume to the cement is between 0.5 and 0.7, the mass ratio of the mineral admixtures to the powder material is not more than 0.15:1, and the mass ratio of the calcium carbonate powder to the mineral admixtures is not more than 0.07:1.

[0016] The mass ratio of the powder material to fine aggregate is 0.8-1.2:1, the mass ratio of the water reducing agent to the powder material is 0.01-0.03:1, and the mass ratio of the mixing water to the powder material is 0.16-0.25:1.

[0017] A low-drying-shrinkage ultra-high-performance concrete comprises the following raw materials in mass parts:

[0018] Raw material a: powder material, comprising

[0019] a1, Portland cement with an average particle size of about 15.2 μm, 916 parts;

[0020] a2, mineral admixtures, comprising

[0021] a21, silica fume with an average particle size of about 6.2 μm, 91 parts;

[0022] a22, nano calcium carbonate powder with an average particle size of about 60 nm, 10 parts;

[0023] Raw material b: fine aggregate, comprising

[0024] b1, river sand, 1130 parts;

[0025] Raw material c: water reducing agent, 20 parts;

[0026] Raw material d: water, 203 parts.

[0027] A preparation method of the low-drying shrinkage ultra-high performance concrete, comprising:

[0028] Pour the powder material and fine aggregate into a mixer, and stir to make the materials uniformly mixed to obtain dry mixed materials;

[0029] Pour the water reducing agent into water and stir to obtain a homogeneous mixture, take part of the mixture and add to the dry mixed materials, stir at low speed, then add the remaining mixture, and control the mixer to rotate at high speed, and stir until the materials are mixed into a high-fluidity slurry.

[0030] A curing method of the low-drying shrinkage ultra-high performance concrete, comprising:

[0031] Pour the slurry of the low-drying shrinkage ultra-high performance concrete into a concrete component mold, and regularly measure the penetration resistance value of the slurry;

[0032] When the penetration resistance strength reaches the initial setting strength of the slurry defined by the specification, record the initial setting time and perform gradient humidity curing on the concrete.

[0033] The gradient humidity curing on the concrete comprises:

[0034] The relative humidity of the first stage environment is 90%, and the curing time is 4-6h;

[0035] The relative humidity of the second stage environment is 80%, and the curing time is 2-4h;

[0036] The relative humidity of the third stage environment is 70%, and the curing time is 2-4h;

[0037] The three-stage curing is continuous curing, and the cumulative curing time is not more than 10 hours.

[0038] A curing method of the concrete prepared by the preparation method, comprising:

[0039] Pour the slurry of the low-drying shrinkage ultra-high performance concrete into a concrete component mold, and regularly measure the penetration resistance value of the slurry;

[0040] When the penetration resistance strength reaches the initial setting strength of the slurry defined by the specification, record the initial setting time and perform gradient humidity curing on the concrete.

[0041] The gradient humidity curing on the concrete comprises:

[0042] The relative humidity of the first stage environment is 90%, and the curing time is 4-6h;

[0043] The relative humidity of the second stage environment is 80%, and the curing time is 2-4h;

[0044] The third stage environment relative humidity is 70%, and the curing time is 2-4h.

[0045] The three-stage curing is continuous curing, and the cumulative curing time is not more than 10 hours.

[0046] The application has the beneficial effects that: the application realizes the improvement of the matrix resistance of UHPC from the inside of the material by optimizing the gradation among cement, silica fume and nano calcium carbonate powder, thereby reducing the early dry shrinkage of the ultra-high performance concrete, and slightly improving the early strength.

[0047] The application adopts gradient humidity curing, and determines the humidity and time of each stage curing based on the internal hydration reaction and free water evaporation law of UHPC, realizes the reduction of matrix water loss, and thereby inhibits the dry shrinkage to a certain extent. The gradient humidity curing of the application reduces the curing time, but still can obtain good shrinkage reduction effect, and greatly reduces the early dry shrinkage of the ultra-high performance concrete.

[0048] The application improves the matrix resistance of UHPC from the inside of the material by optimizing and adjusting the gradation of the concrete; the gradient humidity curing is adopted to influence the water evaporation rate from the outside, and the internal gradation and external curing are combined, so that the early dry shrinkage of the ultra-high performance concrete is greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 It is an early dry shrinkage diagram of the ultra-high performance concrete under different curing systems.

[0050] Figure 2 It is an early dry shrinkage diagram of the ultra-high performance concrete under different admixture gradations.

[0051] Figure 3 It is an early dry shrinkage diagram of the application examples 2-6.

[0052] Figure 4 It is an early dry shrinkage diagram of the application comparative examples 1-3. DETAILED DESCRIPTION

[0053] In order to better understand the technical scheme of the present application, the embodiments of the present application will be described in detail below with reference to the drawings.

[0054] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0055] In the embodiments of the present application, the specific conditions not marked are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The mixing raw materials, admixtures and the like not marked with the manufacturer are all conventional products that can be obtained by market purchase.

[0056] The gradual change rule of drying shrinkage is closely related to the distribution state of pore water under evaporation effect. When the water loss of the matrix increases and the internal humidity decreases, the vapor pressure in the pore decreases and the shrinkage stress acting on the pore wall increases, so that the concrete appears continuous drying shrinkage deformation to meet the demand of stress balance. Therefore, limiting the water loss of the pore and delaying the evolution process of the meniscus from the large pore to the small pore is the core idea of restraining the drying shrinkage of the concrete.

[0057] The smaller the curvature radius of the meniscus is, the greater the capillary pressure is. The curvature radius of the meniscus in the small pore is small, and the capillary pressure generated is greater, resulting in greater shrinkage stress. With the evaporation of water, the meniscus gradually migrates from the large pore to the small pore, and the shrinkage stress gradually increases. By delaying the migration of the meniscus from the large pore to the small pore, the growth rate of the capillary pressure can be reduced, thereby reducing the drying shrinkage stress.

[0058] Due to the large content of cement and the intense hydration reaction, concentrated hydration heat is easily generated in the ultra-high performance concrete at the early age stage, which leads to large early evaporation of the matrix, rapid reduction of the size of the pore meniscus, sharp increase of the shrinkage stress, and further causes serious early drying shrinkage of the concrete. Therefore, it is necessary to develop the preparation and curing methods of the ultra-high performance concrete in combination with the powder grading, early hydration, evaporation rule and shrinkage mechanism, so as to effectively inhibit the early drying shrinkage of the matrix while ensuring the mechanical properties of the material.

[0059] Example 1: This example is a kind of low drying shrinkage ultra-high performance concrete, which comprises the following raw materials by mass: 800-1200 parts of powder, 900-1300 parts of fine aggregate, 15-25 parts of water reducing agent and 170-250 parts of water.

[0060] The powder in this example comprises Portland cement and mineral admixtures, wherein the mineral admixtures comprise silica fume and nano calcium carbonate powder.

[0061] In this example, the mass ratio of the mineral admixtures to the powder is not higher than 0.15:1; the average particle size of the Portland cement is less than 30 μm, the ratio of the average particle size of the silica fume to the average particle size of the Portland cement is between 0.1-0.7:1, and the average particle size of the nano calcium carbonate powder is less than 100 nm. If the mass ratio of the mineral admixtures to the powder is higher, the particle size of the cement is larger, and the particle size ratio of the silica fume to the cement is not appropriate, it is difficult to effectively optimize the grading of the ultra-high performance concrete, and improve the matrix density and early drying shrinkage resistance.

[0062] In the example, when the particle size ratio of silica fume to cement is between 0.1 and 0.3, the mass ratio of mineral admixture to powder is not more than 0.05:1, and the mass ratio of calcium carbonate powder to mineral admixture is not more than 0.2:1; when the particle size ratio of silica fume to cement is between 0.3 and 0.5, the mass ratio of mineral admixture to powder is not more than 0.1:1, and the mass ratio of calcium carbonate powder to mineral admixture is not more than 0.1:1; when the particle size ratio of silica fume to cement is between 0.5 and 0.7, the mass ratio of mineral admixture to powder is not more than 0.15:1, and the mass ratio of calcium carbonate powder to mineral admixture is not more than 0.07:1. The mass ratio of mineral admixture to powder is determined according to the particle size ratio of silica fume to cement, so as to reduce the voids between the stacked particles and further optimize the gradation of the powder, so as to control the cement dosage, efficiently suppress the dry shrinkage of the matrix, and improve the strength of the concrete. The nano calcium carbonate powder can effectively improve the compactness of the matrix, but has a large specific surface area and a strong water adsorption capacity, so the amount of the nano powder is limited to avoid affecting the fluidity and preparation quality of the concrete.

[0063] The preparation method of the low-dry-shrinkage ultra-high-performance concrete in the example includes the following steps:

[0064] 1) Material preparation: the powder, fine aggregate, water reducing agent, and water are weighed according to the concrete proportion and target amount;

[0065] 2) Dry mixing of materials: the cement, silica fume, nano calcium carbonate powder, and fine aggregate with different particle sizes are sequentially poured into a mixer, and then low-speed stirring is performed for 2 min, so as to uniformly mix the materials, and dry mixed materials are obtained;

[0066] 3) Wet mixing of materials: the water reducing agent is poured into water and fully stirred to obtain a homogeneous mixture, 1 / 2 of the mass of the mixture is added to the dry mixed materials, low-speed stirring is performed for 2 min, then the remaining mixture is added, and at the same time, the mixer is set to high-speed rotation, and the stirring time is not less than 6 min, until the materials are mixed into a high-fluidity slurry.

[0067] The curing method of the low-dry-shrinkage ultra-high-performance concrete in the example includes the following steps:

[0068] ①, the slurry prepared in the example is poured into a concrete component mold, a setting test sample is prepared, then a film is coated on the surface of the slurry and the test piece is left to stand, and then the penetration resistance value of the slurry is measured before the estimated initial setting time, and the measurement time interval is 15 min.

[0069] ②, when the penetration resistance strength reaches the initial setting strength of the slurry defined in the specification, the initial setting time is recorded, and the concrete is subjected to gradient humidity curing.

[0070] The gradient humidity curing of the concrete in the embodiment includes a first stage, a second stage and a third stage in sequence, wherein the relative humidity of the first stage environment is 90%, the curing time is 4-6h; the relative humidity of the second stage environment is 80%, the curing time is 2-4h; the relative humidity of the third stage environment is 70%, the curing time is 2-4h; the three-stage curing is continuous curing, and the cumulative curing time is not more than 10 hours.

[0071] In some specific embodiments, the mass ratio of the powder to the fine aggregate is 0.8-1.2:1, the mass ratio of the water reducing agent to the powder is 0.01-0.03:1, and the mass ratio of the mixing water to the powder is 0.16-0.25:1.

[0072] The embodiment optimizes the gradation among cement, silica fume and nano calcium carbonate powder, refines the pores, reduces the number of small pores, improves the matrix resistance of UHPC from the inside of the material, efficiently slows down the evaporation rate of water under the premise of controlling the curing time through gradient humidity curing, delays the evolution of the meniscus, and combines internal gradation with external curing, thereby greatly reducing the early drying shrinkage of ultra-high performance concrete.

[0073] Embodiment 2: The embodiment is a low drying shrinkage ultra-high performance concrete, and the raw materials of the concrete include a powder, a fine aggregate, a water reducing agent and water, wherein the powder contains Portland cement and mineral admixtures, and the mineral admixtures contain silica fume and nano calcium carbonate powder.

[0074] The raw materials of the concrete in the embodiment include, in parts by mass, 916 parts of Portland cement with an average particle size of about 15.2 μm, 91 parts of silica fume with an average particle size of about 6.2 μm, 10 parts of calcium carbonate powder with an average particle size of about 60 nm, 1130 parts of river sand, 20 parts of water reducing agent and 203 parts of water.

[0075] In the example, the particle size ratio of the silica fume to the cement is about 0.4:1, the mass ratio of the mineral admixtures to the powder is about 0.1:1, the mass ratio of the nano calcium carbonate powder to the mineral admixtures is about 0.1:1, the mass ratio of the powder to the river sand is 0.9:1, and the mass ratio of the mixing water to the powder is about 0.2.

[0076] The preparation method of the low drying shrinkage ultra-high performance concrete in the embodiment includes the following steps:

[0077] 1) Material preparation: 916 parts of cement, 91 parts of silica fume, 10 parts of nano calcium carbonate powder, 1130 parts of river sand, 20 parts of water reducing agent and 203 parts of mixing water are weighed according to the concrete proportion;

[0078] 2) Dry mixing of materials: the cement, silica fume, nano calcium carbonate powder and fine aggregate with different particle sizes are sequentially poured into a mixer, and then low-speed stirring is performed for 2 min to uniformly mix the materials;

[0079] 3) Material wet mixing: pour water reducing agent into water and stir well into a homogeneous mixture, take 1 / 2 mass of the mixture and add it to the dry mixed material, stir at low speed for 2 min, then add the remaining mixture while controlling the mixer to rotate at high speed, set the stirring time to no less than 6 min, until the material is mixed into a high fluidity slurry.

[0080] The curing method of the low drying shrinkage ultra-high performance concrete in this embodiment includes the following steps:

[0081] ①, pour the ultra-high performance concrete slurry prepared in this embodiment into a concrete component mold, at the same time prepare setting test samples according to the "Standard Test Methods for Basic Properties of Building Mortar" JGJ / T70-2009, then cover the surface of the slurry with a film and place the test piece, then measure the penetration resistance value of the slurry before the estimated initial setting time, the measurement time interval is 15 min.

[0082] ②, when the penetration resistance value reaches 0.3 MPa, record the initial setting time and perform gradient humidity curing on the concrete, the relative humidity of the first stage environment is 90%, the curing time is 6 h; the relative humidity of the second stage environment is 80%, the curing time is 2 h; the relative humidity of the third stage environment is 70%, the curing time is 2 h.

[0083] Example 3: The material ratio and concrete preparation method in this example are the same as those in Example 2, the difference is the gradient humidity curing mode of the concrete, the first stage curing time is adjusted to 4 h; the second and third stage curing times remain unchanged, still 2 h.

[0084] Example 4: The material ratio and concrete preparation method in this example are the same as those in Example 3, the difference is the gradient humidity curing mode of the concrete, the first and third stage curing times remain unchanged, 4 h and 2 h respectively; the second stage curing time is adjusted to 4 h.

[0085] Example 5: The curing method in this example is the same as that in Example 2, the difference is the concrete ratio, in Example 2, 916 parts of Portland cement with an average particle size of about 15.2 μm, 91 parts of silica fume with an average particle size of about 6.2 μm, and 10 parts of calcium carbonate powder with an average particle size of about 60 nm are adjusted to 967 parts of Portland cement with an average particle size of about 15.2 μm, 40 parts of silica fume with an average particle size of about 3.2 μm, and 10 parts of calcium carbonate powder with an average particle size of about 60 nm.

[0086] In this embodiment, the particle size ratio of silica fume to cement is about 0.2:1, the mass ratio of mineral admixture to powder is about 0.05:1, and the mass ratio of nano calcium carbonate powder to mineral admixture is 0.2:1.

[0087] Example 6: The curing method in this example is the same as that in Example 2, except that the concrete mix is adjusted, i.e., 916 parts of Portland cement with an average particle size of about 15.2 μm, 91 parts of silica fume with an average particle size of about 6.2 μm, and 10 parts of calcium carbonate powder with an average particle size of about 60 nm in Example 2 are adjusted to 865 parts of Portland cement with an average particle size of about 15.2 μm, 142 parts of silica fume with an average particle size of about 9.3 μm, and 10 parts of calcium carbonate powder with an average particle size of about 60 nm.

[0088] In this example, the ratio of the particle sizes of the silica fume and the cement is about 0.6:1, the mass ratio of the mineral admixture to the powder is about 0.15:1, and the mass ratio of the nano calcium carbonate powder to the mineral admixture is about 0.07:1.

[0089] Comparative Example 1: This example differs from Example 2 in both the concrete mix and the curing method. In this example, the powder is 1017 parts of cement, and no silica fume or nano calcium carbonate is added, i.e., the powder gradation is not considered, and no curing is performed.

[0090] Comparative Example 2: The curing method in this example is the same as that in Example 3, except that the concrete mix is different. In this example, the powder is 1017 parts of cement, and no silica fume or nano calcium carbonate is added, i.e., the powder gradation is not considered.

[0091] Comparative Example 3: The concrete mix in this example is the same as that in Example 5, except that the curing method is different. In this example, the concrete is not cured.

[0092] Table 1. Concrete mix, curing method, and test results

[0093]

[0094] The early drying shrinkage and the early strength of the ultra-high performance concrete in Examples 2-6 and Comparative Examples 1-3 are shown in Table 1 and Figures 1-4 With the cement and the admixture gradation optimization and the gradient humidity curing method, the early drying shrinkage of the ultra-high performance concrete is reduced by 63.2% to 93.4%, and the volume stability, the mechanical properties, and the durability of the material are improved.

Claims

1. A low-drying-shrinkage ultra-high-performance concrete, characterized in that, The raw materials include the following parts by weight: 800-1200 parts of powder; 900-1300 parts of fine aggregate; 15-25 parts water-reducing agent; 170-250 parts water; The powder comprises silicate cement and mineral admixtures, wherein the mass ratio of mineral admixtures to powder is not higher than 0.15:1; The mineral admixture comprises silica fume and nano-calcium carbonate powder; The average particle size of the silicate cement is less than 30 μm, the ratio of the average particle size of the silica fume to the average particle size of the silicate cement is between 0.1 and 0.7:1, and the average particle size of the nano-calcium carbonate powder is less than 100 nm.

2. The low-drying-shrinkage ultra-high-performance concrete according to claim 1, characterized in that: When the particle size ratio of silica fume to cement is between 0.1 and 0.3, the mass ratio of mineral admixture to powder does not exceed 0.05:1, wherein the mass ratio of calcium carbonate powder to mineral admixture does not exceed 0.2:

1. When the particle size ratio of silica fume to cement is between 0.3 and 0.5, the mass ratio of mineral admixture to powder does not exceed 0.1:1, wherein the mass ratio of calcium carbonate powder to mineral admixture does not exceed 0.1:

1. When the particle size ratio of silica fume to cement is between 0.5 and 0.7, the mass ratio of mineral admixture to powder does not exceed 0.15:1, wherein the mass ratio of calcium carbonate powder to mineral admixture does not exceed 0.07:

1.

3. The low-drying-shrinkage ultra-high-performance concrete according to claim 1 or 2, characterized in that: The mass ratio of the powder to the fine aggregate is 0.8-1.2:1, the mass ratio of the water-reducing agent to the powder is 0.01-0.03:1, and the mass ratio of the water to the powder is 0.16-0.25:

1.

4. A low-drying-shrinkage ultra-high-performance concrete, characterized in that, The raw materials include the following parts by weight: Raw material A: Powder, containing a1. 916 parts of silicate cement with an average particle size of 15.2 μm; a2. Mineral admixtures, including a21, 91 parts of silica fume with an average particle size of 6.2 μm; a22. 10 parts of nano-calcium carbonate powder with an average particle size of 60nm; Raw material b: Fine aggregate, including b1. 1130 portions of river sand; Raw material c: 20 parts water-reducing agent; Raw material d: 203 parts water.

5. A method for preparing low-drying-shrinkage ultra-high-performance concrete according to any one of claims 1 to 4, characterized in that, include: Pour the powder and fine aggregate into the mixer and mix them until the materials are evenly combined to obtain the dry-mixed material. Pour the water-reducing agent into the water and stir thoroughly to form a homogeneous mixture. Take a portion of the mixture and add it to the dry-mixed materials. Stir at low speed and then add the remaining mixture. At the same time, control the mixer to rotate at high speed and stir until the materials are mixed into a highly fluid slurry.

6. A curing method for low-drying-shrinkage ultra-high-performance concrete according to any one of claims 1 to 4, characterized in that, include: The slurry of low drying shrinkage ultra-high performance concrete is poured into the mold of the concrete component, and the penetration resistance value of the slurry is measured periodically. Once the penetration resistance strength reaches the initial setting strength of the grout as defined in the specifications, record the initial setting time and perform gradient humidity curing on the concrete.

7. The maintenance method according to claim 6, characterized in that, The gradient humidity curing of concrete includes: The first stage requires a relative humidity of 90% and a curing time of 4-6 hours. The second stage involves an environment with a relative humidity of 80% and a curing time of 2-4 hours. The third stage requires an ambient relative humidity of 70% and a curing time of 2-4 hours. The third stage of maintenance is continuous, with a cumulative maintenance time not exceeding 10 hours.

8. A method for curing concrete prepared by the method of claim 5, characterized in that, include: The slurry of low drying shrinkage ultra-high performance concrete is poured into the mold of the concrete component, and the penetration resistance value of the slurry is measured periodically. Once the penetration resistance strength reaches the initial setting strength of the grout as defined in the specifications, record the initial setting time and perform gradient humidity curing on the concrete.

9. The maintenance method according to claim 8, characterized in that, The gradient humidity curing of concrete includes: The first stage requires a relative humidity of 90% and a curing time of 4-6 hours. The second stage involves an environment with a relative humidity of 80% and a curing time of 2-4 hours. The third stage requires an ambient relative humidity of 70% and a curing time of 2-4 hours. The third stage of maintenance is continuous, with a cumulative maintenance time not exceeding 10 hours.

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