Manufacturing method of steam-cured steel fiber UHPC (Ultra High Performance Concrete) for prefabricating superposed beam

Abstract

The invention relates to the technical field of building materials, in particular to a manufacturing method of steam-cured steel fiber UHPC (Ultra High Performance Concrete) for prefabricating a superposed beam. The method comprises the following steps: S1, calculating by adopting an absolute volume method to obtain the mixing ratio dosage of each part of materials of UHPC; s2, adding the cement, the silica fume, the quartz sand, the cementing material and the additive into a stirrer according to the proportion, and stirring for 3 minutes; s3, adding the steel fibers in eight times, stirring for 30 seconds each time, and totally stirring for 4 minutes; s4, uniformly mixing the water and the water reducing agent, adding the mixture in three times, and stirring for 6 minutes; and S5, during pouring, a vibrating rod is adopted for following vibration until no bubbles are discharged. According to the manufacturing method of the steam-cured steel fiber UHPC for prefabricating the superposed beam, provided by the invention, the design key points based on an absolute volume method and a closest packing method are clearly pointed out by providing the design steps of the specific UHPC mix proportion, and a basis is provided for the design of the UHPC mix proportion.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly to a method for manufacturing steam-cured steel fiber UHPC for precast composite beams. Background Art

[0002] Ultra-High Performance Concrete (UHPC) configured based on the densest packing method (DSP) has been widely used in fields such as bridge engineering and prefabricated buildings due to its excellent mechanical properties (compressive strength > 120 MPa) and durability. In precast composite beam structures, UHPC as the main load-bearing layer can significantly improve the flexural stiffness and crack resistance of components. However, the traditional UHPC mix design and curing process still face the following technical bottlenecks when applied to the industrial production of precast components:

[0003] To improve the construction efficiency of precast composite beams, enhance the structural mechanical properties and durability, a construction method is adopted where a U-shaped permanent formwork is made of precast UHPC and ordinary concrete is poured inside. The precast UHPC permanent beam formwork is usually produced by steam curing in the factory. The maximum steam temperature in the precast factory can reach 70°C, and the difference from the laboratory environment will lead to differences in the workability and mechanical properties of UHPC, resulting in problems of different performance in design and construction.

[0004] The existing "Ultra-High Performance Concrete" (GB / T 31387-2025) puts forward the framework of "oriented by performance goals and determining the mix ratio through tests" for the relevant material property requirements of the raw materials (cementitious materials, aggregates, admixtures, fibers, mixing water) for UHPC production, but lacks specific design steps.

[0005] Therefore, a method for manufacturing steam-cured steel fiber UHPC for precast composite beams is designed to provide a technical solution for the above technical problems. Summary of the Invention

[0006] Based on this, it is necessary to provide a method for manufacturing steam-cured steel fiber UHPC for precast composite beams to solve the technical problems raised in the above background art.

[0007] To solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A method for manufacturing steam-cured steel fiber UHPC for precast composite beams comprises the following steps:

[0009] S1: Calculate the dosage of each part of the materials of UHPC by the absolute volume method;

[0010] S2: Add cement, silica fume, quartz sand, cementitious material and admixture into a mixer according to the ratio and stir for 3 min.

[0011] S3: Add steel fibers in eight portions, stir for 30 s each time for a total of 4 min.

[0012] S4: Mix water and water reducer evenly and add them in 3 portions and stir for 6 min.

[0013] S5: During pouring, use a vibrating rod to vibrate until no more bubbles are discharged.

[0014] As a preferred embodiment of the method for manufacturing steam-cured steel fiber UHPC for precast composite beams provided by the present invention, the materials of each part of the UHPC are respectively steel fibers, water, cementitious materials, admixtures, mineral admixtures, cement, and quartz sand.

[0015] As a preferred embodiment of the method for manufacturing steam-cured steel fiber UHPC for precast composite beams provided by the present invention, the mineral admixture is silica fume.

[0016] As a preferred embodiment of the method for manufacturing steam-cured steel fiber UHPC for precast composite beams provided by the present invention, in step S1, the mixing ratio dosages of the materials of each part of the UHPC are calculated by the absolute volume method, and the steps are as follows:

[0017] Calculate the masses of steel fibers, water, cementitious materials, admixtures, mineral admixtures, cement, and quartz sand per unit volume.

[0018] As a preferred embodiment of the method for manufacturing steam-cured steel fiber UHPC for precast composite beams provided by the present invention, calculate the mass of steel fibers per unit volume, and the expression is as follows:

[0019] m f0 =7850ρ f ;

[0020] where m f0 is the mass of steel fibers used in 1 m 3 of reactive powder concrete;

[0021] Calculate the mass of water per unit volume, and the expression is as follows:

[0022] m w0 =m′ w0 (1-β);

[0023] where: m w0 is the water consumption per cubic meter of concrete when meeting the actual slump requirement; m' w0The water consumption per cubic meter of concrete when no admixture is added and the actual slump requirement is met; β represents the water reduction rate of the admixture.

[0024] Calculate the mass of the cementitious materials, and the expression is as follows:

[0025]

[0026] Where: m b0 is the amount of cementitious materials in 1 m 3 of ultra-high performance concrete; W / B is the water-cement ratio.

[0027] Calculate the mass of the admixture per unit volume, and the expression is as follows:

[0028] m j0 = m b0 β b ;

[0029] Where: m j0 , m b0 are the masses of the admixture and the cementitious materials in 1 m 3 of ultra-high performance concrete respectively; β b is the dosage of the admixture.

[0030] Calculate the amount of mineral admixture, and the expression is as follows:

[0031] m a0 = m b0 β f ;

[0032] Where: β f is the dosage of the mineral admixture.

[0033] Calculate the amount of cement per unit volume, and the expression is as follows:

[0034] m c0 = m b0 - m a0 .

[0035] As a preferred embodiment of the method for manufacturing steam-cured steel fiber UHPC for precast composite beams provided by the present invention, determine the relative proportion of each particle size of quartz sand according to the closest packing method, and calculate the amount of each particle size of quartz sand by using the absolute volume method in combination with the apparent density and bulk density of quartz sand.

[0036] As a preferred embodiment of the method for manufacturing steam-cured steel fiber UHPC for precast composite beams provided by the present invention, the relative proportion of each particle size of quartz sand is coarse sand: medium sand: fine sand = 0.577: 0.277: 0.146.

[0037] It can be seen without doubt that through the above technical solutions of the present application, the technical problems to be solved by the present application can surely be solved.

[0038] Meanwhile, through the above technical solutions, the present invention has at least the following beneficial effects:

[0039] 1. The steam curing steel fiber UHPC manufacturing method for precast composite beams provided by the present invention, through the proposed specific design steps of the UHPC mix proportion, and considering the curing conditions of precast factories, proposes a manufacturing method for precast composite beams, thus clearly pointing out the design key points based on the absolute volume method and the most compact packing method, providing a basis for the UHPC mix proportion design.

[0040] 2. The design and manufacturing method for determining the UHPC mix proportion of the present invention provides a basis for the manufacturing of precast U-shaped UHPC permanent beam forms.

[0041] 3. The present invention, according to the provisions and calculation methods of T / CCPA35 "Code for Design of Ultra-High Performance Concrete Structures", GB / T 31387 "Ultra-High Performance Concrete", and JG / T 472 "Steel Fiber Reinforced Concrete", proposes a mix proportion design method for UHPC based on the absolute volume method. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0043] Figure 1 It is a schematic diagram of the steam curing steel fiber UHPC mix proportion design method for the precast composite beam of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] In order to enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in combination with the drawings.

[0046] It should be noted that, without conflict, the embodiments in the present invention and the features and technical solutions in the embodiments can be combined with each other.

[0047] It should be noted that similar reference numerals and letters indicate similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0048] Example 1

[0049] Refer to Figure 1 , a method for manufacturing steam-cured steel fiber UHPC for precast composite beams.

[0050] The mix proportion dosage of each part of the UHPC is calculated by the absolute volume method. The materials of each part of the UHPC are steel fiber, water, cementitious material, admixture, silica fume (the mineral admixture used in this example is silica fume), cement, and quartz sand respectively;

[0051] Add cement, silica fume, quartz sand, etc. into the mixer according to the ratio and stir;

[0052] Add the steel fiber in eight times, and stir evenly each time;

[0053] Then mix water and water reducer evenly and add them in 3 times and stir evenly;

[0054] During pouring, use a vibrating rod to follow and vibrate until no more bubbles are discharged to ensure the density.

[0055] Example 2

[0056] Disclosed on the basis of the above Example 1.

[0057] The mix proportion dosage of each part of the UHPC is calculated by the absolute volume method. The materials of each part of the UHPC are steel fiber, water, cementitious material, admixture, silica fume (the mineral admixture used in this example is silica fume), cement, and quartz sand respectively;

[0058] Add cement, silica fume, quartz sand, etc. into the mixer according to the ratio and stir for 3 min;

[0059] Add the steel fiber in eight times, stir for 30 s each time for a total of 4 min;

[0060] Then mix water and water reducer evenly and add them in 3 times and stir for 6 min.

[0061] During pouring, use a vibrating rod to follow and vibrate until no more bubbles are discharged to ensure the density.

[0062] The production method of the precast permanent formwork is as follows: The specimens are cast on the operation formwork. After a batch of UHPC reinforced formworks are cast, the entire operation formwork is adjusted to the vibrating table for centralized vibration to ensure that each batch of specimens is fully vibrated. Considering that the maximum temperature of the manufacturer's high-temperature steam curing equipment is 70°C, the formwork is removed after static curing for 24 hours and then placed in a high-temperature steam curing chamber for heating to 70°C and curing for 72 hours, and then natural curing is carried out until 28 days.

[0063] Referring to the provisions of the "Design Code for Ultra-High Performance Concrete Structures" (T / CCPA 35-2022), the water-binder ratio, steel fiber content, and binder content of UHPC all refer to the dosage range of "Ultra-High Performance Concrete" (GB / T 31387-2025), and the absolute volume method is used to calculate the material dosage, and the steps are as follows:

[0064] The first step: The masses of steel fiber, water, binder, admixture, mineral admixture, cement, and quartz sand per unit volume, and their corresponding calculation methods are as follows:

[0065] (1) Calculate the mass of steel fiber per unit volume, and the expression is as follows:

[0066] m f0 =7850ρ f (1)

[0067] Among them, m f0 is the mass (kg) of steel fiber used in 1 m 3 of reactive powder concrete;

[0068] (2) Calculate the mass of water per unit volume, and the expression is as follows:

[0069] m w0 =m' w0 (1-β) (2)

[0070] Among them: m w0 is the water consumption (kg / m 3 ) per cubic meter of concrete when meeting the actual slump requirement; m' w0 is the water consumption (kg / m 3 ) per cubic meter of concrete when meeting the actual slump requirement estimated without admixture; β represents the water reduction rate of the admixture.

[0071] (3) Calculate the binder mass, and the expression is as follows:

[0072]

[0073] Among them: m b0 is the binder dosage (kg / m 3 of ultra-high performance concrete 3);W / B is the water-binder ratio.

[0074] (4) Calculate the mass of admixture per unit volume, and the expression is as follows:

[0075] m j0 =m b0 β b (4)

[0076] Where: m j0 、m b0 are the masses of admixture and binder in 1 m 3 ultra-high performance concrete (kg / m 3 ) respectively; β b is the admixture dosage (%), which is determined according to tests specifically.

[0077] (5) Calculate the dosage of mineral admixture, and the expression is as follows:

[0078] m a0 =m b0 β f (5)

[0079] Where: β f is the dosage of mineral admixture (%);

[0080] (6) Calculate the cement dosage per unit volume, and the expression is as follows:

[0081] m c0 =m b0 -m a0 (6).

[0082] (7) Calculate the dosages of quartz sands of each particle size; according to the provisions of GB / T 31387, conduct sieve analysis on quartz sands, and determine the relative proportions of quartz sands of each particle size according to the most compact packing method. Specifically, coarse sand: medium sand: fine sand = 0.577: 0.277: 0.146.

[0083] Second step: According to JG / T 472-2015 "Steel Fiber Reinforced Concrete", the formula for calculating the material dosages of the mix proportion by the absolute volume method is:

[0084]

[0085] Where, m c0 、m a0 、m w0 、m s0 are the masses of cement, mineral admixture, water and quartz sand used in 1 m 3 ultra-high performance concrete (kg) respectively; ρ c 、ρ a 、ρ w 、ρ srespectively represent the density of cement, the density of mineral admixture, the density of water, and the density of quartz sand (kg / m 3 ), ρ f is the volume fraction of steel fiber; α is the air content percentage of steel fiber reinforced concrete, and when no air-entraining admixture is used, it is taken as 1;

[0086] According to m s0 calculated in formula (7), and according to the ratio of coarse sand: medium sand: fine sand = 0.577: 0.277: 0.146 determined by the closest packing method, calculate the masses of the three types of quartz sand, namely coarse, medium, and fine, respectively.

[0087] Example 3

[0088] Based on the above Example 1 and Example 2, the parameters of the precast composite beam are publicly obtained.

[0089] The precast part of the precast assembled composite beam uses ultra-high performance concrete material with a compressive strength above 120 MPa;

[0090] The mix proportion design of steel fiber UHPC is used in the fabrication of precast assembled composite beams. Considering the construction fluidity problem, measure the slump, spread, and cube compressive strength values of the mixture to determine the final optimized mix proportion;

[0091] According to the construction technical conditions of the factory precast UHPC permanent formwork, use cube specimens adapted with the same curing method.

[0092] Example 4

[0093] Based on the raw materials proposed in the above Example 1 and Example 2, provide the mix ratio and source of the corresponding raw materials.

[0094] I. Material Source

[0095] Silica fume: Select silica fume from a certain manufacturer in Shandong, with a SiO2 mass fraction of 94.33% and a specific surface area of 19 m 2 / g. The density is 2000 kg / m 3 .

[0096] Cement: Select Jidong brand P.O 42.5 portland cement from Jilin Jinyu Jidong Environmental Protection Technology Co., Ltd. The density is 3000 kg / m 3 .

[0097] Steel fiber: Use straight steel fiber (diameter: 0.2 mm, length: 13 mm).

[0098] Water reducing agent: It is a high-performance polycarboxylate water reducing agent produced by a certain manufacturer in Changchun. It is a light yellow oily liquid with a water reducing rate of 46% and a solid content of 37%.

[0099] Water: Tap water is used.

[0100] Quartz sand: Quartz sand produced by a certain manufacturer in Hebei is used, and the content of SiO2 is 98%.

[0101] According to the provisions of "Ultra-High Performance Concrete" (GB / T 31387-2025), sieve analysis of quartz sand is carried out, and the fineness modulus, moisture content, apparent density, and bulk density of quartz sand are measured as shown in Table 1:

[0102] Table 1: Performance indicators of quartz sand

[0103]

[0104]

[0105] II. Mix proportion according to the provided materials

[0106] The trial mix proportions are shown in Table 2, and a total of 12 groups of mix proportion tests are carried out. The slump, spread, and cube compressive strength values at 3, 7, and 28 days of the mixture are measured as shown in Table 3.

[0107] Table 2: UHPC mix proportion list (kg / m 3 )

[0108]

[0109] Table 3: Test results of UHPC mix proportion

[0110]

[0111]

[0112] According to the test results in Table 3, the UHPC mix proportion dosage obtained by the proposed calculation method, according to the requirements of "Technical Specification for Concrete Pumping Construction" (JGJ / T 10-2011), when the maximum pumping height is 400m, the slump is 230 - 260mm, and the spread is 450 - 590mm. Referring to this regulation and the cube compressive strength value, a suitable UHPC mix proportion is selected as shown in Table 4.

[0113] Table 4: UHPC mix proportion (kg / m 3 )

[0114]

[0115] It can be seen from Table 3 that the UHPC obtained by the mix proportion design method proposed in the present invention has a compressive strength of 136 MPa, a slump of 244 mm, and a spread of 370 mm. While meeting the fluidity requirements for precast component construction, it has high compressive strength, providing greater guarantee for the mechanical properties of the structure.

[0116] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the present invention to the specific embodiments described. Obviously, according to the content of this specification, many modifications and variations can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for preparing steam-cured steel fiber UHPC for prefabricated composite beams, characterized in that: Here are the steps: S1: The absolute volume method is used to calculate the proportion of each part of the UHPC material; S2: Add cement, silica fume, quartz sand, cementitious materials and admixtures into a mixer according to the proportion and stir for 3 minutes; S3: Add the steel fiber in eight batches, stirring for 30 seconds each time for a total of 4 minutes; S4: Mix water and water reducer evenly and add in three times and stir for 6 minutes; S5: Use a vibrating rod to vibrate during pouring until no more bubbles are discharged.

2. The method for preparing steam-cured steel fiber UHPC for prefabricated composite beams according to claim 1, characterized in that: The various materials of the UHPC are steel fiber, water, cementitious material, admixture, mineral admixture, cement and quartz sand.

3. The method for preparing steam-cured steel fiber UHPC for prefabricated composite beams according to claim 2, characterized in that: The mineral admixture is silica fume.

4. The method for preparing steam-cured steel fiber UHPC for prefabricated composite beams according to claim 1, characterized in that: In step S1, the absolute volume method is used to calculate the proportion of each part of the UHPC material, and the steps are as follows: Calculate the mass of steel fiber, water, cementitious materials, admixtures, mineral admixtures, cement and quartz sand per unit volume.

5. The method for preparing steam-cured steel fiber UHPC for prefabricated composite beams according to claim 4, characterized in that: Calculate the mass of steel fiber per unit volume, the expression is as follows: m f0 =7850r f ; Among them, m f0 1m 3 The quality of steel fibers used in reactive powder concrete; Calculate the mass of water per unit volume using the following expression: m w0 =m′ w0 (1-b); Where: m w0 m' is the water consumption per cubic meter of concrete when the actual slump requirement is met; w0 It is the water consumption per cubic meter of concrete when no admixture is added to meet the actual slump requirement; β represents the water reduction rate of the admixture; Calculate the mass of cementitious materials using the following expression: Where: m b0 1m 3 The amount of cementitious materials used in ultra-high performance concrete; W / B is the water-cement ratio; Calculate the mass of admixture per unit volume, the expression is as follows: m j0 =m b0 b b ; Where: m j0 、m b0 1m respectively 3 Quality of admixtures and cementitious materials in ultra-high performance concrete; b is the dosage of admixture; Calculate the amount of mineral admixture, the expression is as follows: m a0 =m b0 b f ; Where: β f is the amount of mineral admixture; Calculate the amount of cement per unit volume, the expression is as follows: m c0 =m b0 -m a0 。 6. The method for preparing steam-cured steel fiber UHPC for prefabricated composite beams according to claim 4, characterized in that: The relative proportion of each particle size of quartz sand is determined according to the most compact packing method, and the amount of quartz sand of each particle size is calculated by combining the apparent density and bulk density of quartz sand with the absolute volume method.

7. The method for producing steam-cured steel fiber UHPC for prefabricated composite beams according to claim 6, characterized in that: The relative proportions of each particle size of quartz sand are coarse sand: medium sand: fine sand = 0.577:0.277:0.146.

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