Low-drying-shrinkage ultra-high-performance concrete as well as preparation method and maintenance method thereof

Abstract

The invention relates to low-drying-shrinkage ultra-high-performance concrete as well as a preparation method and a curing method thereof. The invention is suitable for the technical field of building materials. The technical problem to be solved by the invention is to provide the low-drying-shrinkage ultra-high-performance concrete as well as the preparation method and the curing method of the low-drying-shrinkage ultra-high-performance concrete. The technical scheme adopted by the invention is as follows: the concrete with low drying shrinkage and ultra-high performance comprises the following raw materials in parts by mass: 800-1200 parts of powder; 900 to 1300 parts of fine aggregate; 15 to 25 parts of a water reducing agent; 170 to 250 parts of water; the powder material comprises Portland cement and a mineral admixture, and the mass ratio of the mineral admixture to the powder material 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 smaller than 30 microns, 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 smaller than 100 nm.

Description

Technical Field

[0001] The present invention relates to a low drying shrinkage ultra-high performance concrete and a preparation method and a curing method thereof, which are applicable to the technical field of building materials. Background Art

[0002] Ultra-high performance concrete (UHPC) is an ideal engineering material with a compressive strength of no less than 120MPa and an axial tensile strength of no less than 8MPa. However, UHPC shrinks rapidly after initial setting, which seriously affects the volume stability of the structure or brings potential cracking risks when the structural resistance is low, making the concrete prone to durability problems after pouring and making it difficult to fully exert the performance advantages of the material.

[0003] The early shrinkage of concrete is usually divided into early autogenous shrinkage and early shrinkage. Studies have shown that due to the presence of more cementitious materials in the components, the hydration reaction inside UHPC is more intense, causing the matrix to have a large autogenous shrinkage. As the hydration reaction continues, the concentrated hydration heat causes the water in the matrix to evaporate rapidly, or causes UHPC to have prominent early shrinkage. Therefore, early shrinkage is also an important factor affecting the volume stability of UHPC.

[0004] At present, the evolution law of early shrinkage of UHPC and the structural cracking problem caused by it have not received enough attention, and there are few relevant countermeasures, which makes it difficult to effectively ensure the volume stability of UHPC. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in view of the above-mentioned problems, a low drying shrinkage ultra-high performance concrete is provided, by adjusting the gradation of cement and mineral admixtures, the matrix resistance of UHPC is improved from the inside of the material, so as to better ensure the volume stability of UHPC at the early age stage.

[0006] In view of the above-mentioned problems, a method for preparing low drying shrinkage ultra-high performance concrete is also provided.

[0007] In view of the above-mentioned problems, a maintenance method for low drying shrinkage ultra-high performance concrete is provided, which adapts to the internal hydration reaction and free water evaporation law of UHPC to inhibit the drying shrinkage of concrete to a certain extent.

[0008] The technical solution adopted by the present invention is: a low drying shrinkage ultra-high performance concrete, characterized by comprising the following raw materials in parts by weight:

[0009]

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

[0011] The mineral admixture comprises silica fume and nano calcium carbonate powder;

[0012] 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.

[0013] 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;

[0014] 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;

[0015] 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.

[0016] The mass ratio of the powder to the fine aggregate is 0.8-1.2:1, the mass ratio of the water reducer 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.

[0017] A low drying shrinkage ultra-high performance concrete, comprising the following raw materials in parts by weight:

[0018] Raw material a: powder, including

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

[0020] a2. Mineral admixtures, including

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

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

[0023] Raw material b: fine aggregate, including

[0024] b1. 1130 parts of river sand;

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

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

[0027] A method for preparing the low drying shrinkage ultra-high performance concrete comprises:

[0028] Pour the powder and fine aggregate into the mixer and stir them to make the materials evenly mixed to obtain dry mixed materials;

[0029] Pour the water reducer into the water and stir thoroughly to form a homogeneous mixture. Take part of the mixture and add it to the dry mixed materials. After stirring at a low speed, add the remaining mixture. At the same time, control the mixer to rotate at a high speed and stir until the materials are mixed into a high-fluidity slurry.

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

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

[0032] 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.

[0033] The step of performing gradient moisture curing on concrete comprises:

[0034] The relative humidity of the environment in the first stage 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 environment in the third stage is 70%, and the curing time is 2-4h;

[0037] The three-stage maintenance is continuous maintenance, and the cumulative maintenance time shall not exceed 10 hours.

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

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

[0040] 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.

[0041] The step of performing gradient moisture curing on concrete comprises:

[0042] The relative humidity of the environment in the first stage 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 relative humidity of the environment in the third stage is 70%, and the curing time is 2-4h;

[0045] The three-stage maintenance is continuous maintenance, and the cumulative maintenance time shall not exceed 10 hours.

[0046] The beneficial effect of the present invention is that the present invention optimizes the grading among cement, silica fume and nano calcium carbonate powder, thereby improving the matrix resistance of UHPC from the inside of the material, thereby reducing the early shrinkage of ultra-high performance concrete and slightly improving the early strength.

[0047] The present invention adopts gradient humidity curing, and determines the humidity and time of each stage of curing based on the internal hydration reaction of UHPC and the law of free water evaporation, so as to reduce the moisture loss of the matrix, thereby inhibiting drying shrinkage to a certain extent. The gradient humidity curing of the present invention reduces the curing time, but still can obtain a good shrinkage reduction effect, greatly reducing the early shrinkage of ultra-high performance concrete.

[0048] The present invention improves the matrix resistance of UHPC from the inside of the material by optimizing and adjusting the concrete gradation; affects the water evaporation rate from the outside through gradient humidity curing, and combines internal gradation with external curing to significantly reduce the early shrinkage of ultra-high performance concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 Illustration of early shrinkage of ultra-high performance concrete under different curing systems.

[0050] Figure 2 This is a diagram showing the early shrinkage of ultra-high performance concrete with different admixture gradations.

[0051] Figure 3 This is a diagram illustrating early shrinkage of Examples 2-6 of the present invention.

[0052] Figure 4 It is a diagram showing the early shrinkage of comparative examples 1-3 of the present invention. DETAILED DESCRIPTION

[0053] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying 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 ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0055] If no specific conditions are specified in the examples of the present invention, the conventional conditions or the conditions recommended by the manufacturer are used. The mixing raw materials, admixtures, etc., whose manufacturers are not specified, are all conventional products that can be purchased from the market.

[0056] The gradual change of drying shrinkage is closely related to the distribution state of pore water under evaporation. When the water loss of the matrix increases and the internal humidity decreases, the vapor pressure in the pores decreases and the shrinkage stress acting on the pore wall increases, causing the concrete to undergo continuous shrinkage deformation to meet the stress balance requirements. Therefore, limiting the loss of pore water and delaying the evolution of the meniscus from large pores to small pores is the core idea of ​​restricting concrete shrinkage.

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

[0058] Due to the high cement content and violent hydration reaction, concentrated hydration heat is prone to occur inside the ultra-high performance concrete at the early stage, resulting in large early evaporation of the matrix, rapid reduction of the pore meniscus size, and sharp increase in shrinkage stress, which in turn causes serious early shrinkage of concrete. Therefore, it is necessary to formulate ultra-high performance concrete preparation and maintenance methods based on powder grading, early hydration, evaporation law and shrinkage mechanism, so as to effectively inhibit the early shrinkage of the matrix while ensuring the mechanical properties of the material.

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

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

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

[0062] In this 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 does not exceed 0.05:1, and 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, and 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, and the mass ratio of calcium carbonate powder to mineral admixture does not exceed 0.07:1. The mass ratio of mineral admixture to powder is formulated according to the particle size ratio of silica fume to cement to reduce the gaps between the stacked particles, further optimize the powder gradation, and achieve the control of cement dosage, effectively inhibit the shrinkage of the matrix, and improve the strength of concrete. Among them, nano calcium carbonate powder can effectively improve the density of the matrix, but its specific surface area is large and its ability to adsorb water is strong. Therefore, the amount of nano powder is limited to avoid affecting the fluidity and preparation quality of concrete.

[0063] The method for preparing low drying shrinkage ultra-high performance concrete in this embodiment comprises the following steps:

[0064] 1) Material preparation: weigh powder, fine aggregate, water reducer and water according to the concrete mix ratio and target dosage;

[0065] 2) Dry mixing of materials: Pour cement, silica fume, nano calcium carbonate powder and fine aggregates of different particle sizes into the mixer in sequence, and then stir at a low speed for 2 minutes to mix the materials evenly to obtain dry mixed materials;

[0066] 3) Wet mixing of materials: Pour the water reducer into water and stir thoroughly to form a homogeneous mixture. Take 1 / 2 of the mixture and add it to the dry mixed materials. Stir at a low speed for 2 minutes and then add the remaining mixture. At the same time, control the mixer to rotate at a high speed and set the stirring time to be no less than 6 minutes, until the materials are mixed into a high-fluidity slurry.

[0067] The curing method of low drying shrinkage ultra-high performance concrete in this embodiment comprises the following steps:

[0068] ①. Pour the slurry prepared in this embodiment into a concrete component mold, prepare a setting test specimen at the same time, then coat the surface of the slurry and let the specimen stand, and then measure the penetration resistance value of the slurry before the estimated initial setting time, with a measurement time interval of 15 minutes.

[0069] ② When the penetration resistance strength reaches the initial setting strength of the slurry defined in the specification, record the initial setting time and carry out gradient humidity curing on the concrete.

[0070] In this embodiment, the gradient humidity curing of concrete includes a first stage, a second stage and a third stage which are performed in sequence, wherein the relative humidity of the environment in the first stage is 90%, and the curing time is 4-6 hours; the relative humidity of the environment in the second stage is 80%, and the curing time is 2-4 hours; the relative humidity of the environment in the third stage is 70%, and the curing time is 2-4 hours; the three-stage curing is continuous curing, and the cumulative curing time does not exceed 10 hours.

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

[0072] This embodiment optimizes the grading of cement, silica fume, and nano-calcium carbonate powder, refines the pores, reduces the number of small pores, and improves the matrix resistance of UHPC from the inside of the material; through gradient humidity curing, the evaporation rate of water is effectively slowed down while controlling the curing time, and the evolution of the meniscus is delayed. The internal grading is combined with the external curing, thereby greatly reducing the early shrinkage of ultra-high performance concrete.

[0073] Example 2: This example is a low drying shrinkage ultra-high performance concrete, the raw materials of which include powder, fine aggregate, water reducer and water, wherein the powder includes silicate cement and mineral admixtures, and the mineral admixtures include silica fume and nano calcium carbonate powder.

[0074] The raw materials of the concrete in this embodiment include, by mass, 916 parts of silicate 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 reducer and 203 parts of water.

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

[0076] The method for preparing low drying shrinkage ultra-high performance concrete in this embodiment comprises the following steps:

[0077] 1) Material preparation: according to the concrete mix ratio, weigh 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 reducer and 203 parts of mixing water;

[0078] 2) Dry mixing of materials: Pour cement, silica fume, nano calcium carbonate powder and fine aggregates of different particle sizes into the mixer in sequence, and then stir at a low speed for 2 minutes to mix the materials evenly;

[0079] 3) Wet mixing of materials: Pour the water reducer into water and stir thoroughly to form a homogeneous mixture. Take 1 / 2 of the mixture and add it to the dry mixed materials. Stir at a low speed for 2 minutes and then add the remaining mixture. At the same time, control the mixer to rotate at a high speed and set the stirring time to be no less than 6 minutes, until the materials are mixed into a high-fluidity slurry.

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

[0081] ①. Pour the ultra-high performance concrete slurry prepared in this embodiment into a concrete component mold, and prepare a setting test specimen according to the "Standard for Test Methods for Basic Performance of Building Mortar" JGJ / T70-2009, and then coat the surface of the slurry and let the specimen stand. After that, measure the penetration resistance value of the slurry before the estimated initial setting time, and the measurement time interval is 15 minutes.

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

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

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

[0085] Example 5: The curing method in this example is the same as that in Example 2, except that the concrete mix ratio is adjusted from 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 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 ratio is adjusted from 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 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 embodiment, the particle size ratio of silica fume to cement is about 0.6:1, the mass ratio of mineral admixture to powder is about 0.15:1, and the mass ratio of nano calcium carbonate powder to mineral admixture is about 0.07:1.

[0089] Comparative Example 1: This example differs from Example 2 in both concrete mix proportion and curing method. The difference is that the powder in this example is 1017 parts of cement, without adding silica fume and nano-calcium carbonate, that is, the powder grading 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 for the concrete mix ratio. The powder in this example is 1017 parts of cement, without adding silica fume and nano-calcium carbonate, that is, the powder gradation is not considered.

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

[0092] Table 1 Ultra-high performance concrete mix proportion, curing system and test results

[0093]

[0094] The early shrinkage and early strength of the ultra-high performance concrete in Examples 2-6 and Comparative Examples 1-3 are shown in Table 1 and Figure 1-4 As shown in the figure, combined with the optimization of cement and admixture grading and the gradient humidity curing method, the early shrinkage of ultra-high performance concrete was reduced by 63.2% to 93.4%, which greatly improved the volume stability, mechanical properties and durability of the material.

Claims

1. A low drying shrinkage ultra-high performance concrete, characterized in that: The invention comprises the following raw materials in parts by weight: The powder comprises silicate cement and mineral admixtures, 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 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 reducer 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.

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

5. A method for preparing the 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 stir them to make the materials evenly mixed to obtain dry mixed materials; Pour the water reducer into the water and stir thoroughly to form a homogeneous mixture. Take part of the mixture and add it to the dry mixed materials. After stirring at a low speed, add the remaining mixture. At the same time, control the mixer to rotate at a high speed and stir until the materials are mixed into a high-fluidity 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: Pour the paste of low drying shrinkage ultra-high performance concrete into the concrete component mold and regularly measure the penetration resistance value of the paste; 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.

7. The curing method according to claim 6, characterized in that: The step of performing gradient moisture curing on concrete comprises: The relative humidity of the environment in the first stage is 90%, and the curing time is 4-6h; The relative humidity of the second stage environment is 80%, and the curing time is 2-4h; The relative humidity of the environment in the third stage is 70%, and the curing time is 2-4h; The three-stage maintenance is continuous maintenance, and the cumulative maintenance time shall not exceed 10 hours.

8. A method for curing concrete prepared by the preparation method according to claim 5, characterized in that: include: Pour the paste of low drying shrinkage ultra-high performance concrete into the concrete component mold and regularly measure the penetration resistance value of the paste; 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.

9. The curing method according to claim 8, characterized in that: The step of performing gradient moisture curing on concrete comprises: The relative humidity of the environment in the first stage is 90%, and the curing time is 4-6h; The relative humidity of the second stage environment is 80%, and the curing time is 2-4h; The relative humidity of the environment in the third stage is 70%, and the curing time is 2-4h; The three-stage maintenance is continuous maintenance, and the cumulative maintenance time shall not exceed 10 hours.

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