A method for regulating the uniform distribution of fiber-reinforced self-compacting concrete based on mix design

Abstract

A method for regulating and controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix design belongs to the field of high-performance concrete optimization design. The present invention solves the problem of uncontrollable distribution of FR-SCC steel fibers. The present invention analyzes the settlement mechanism of steel fibers in freshly mixed FR-SCC slurry, adopts cross-sectional image analysis, quantitatively analyzes the distribution of steel fibers in FR-SCC specimens with different mix ratios, establishes the relationship between each raw material parameter and steel fiber distribution coefficient, and realizes the random and uniform distribution of steel fibers by regulating the raw material parameters. The present invention can be used to regulate and control the uniform distribution of steel fibers in fiber-reinforced self-compacting concrete.

Description

Technical Field

[0001] The invention belongs to the field of high-performance concrete optimization design, and specifically relates to a method for regulating and controlling the uniform distribution of fiber-reinforced self-compacting concrete. Background Art

[0002] As a cement-based composite material, fiber-reinforced self-compacting concrete (FR-SCC) is based on high fluidity and is known for its high strength and high density. It has the characteristics of self-compacting, high specific strength, low resource consumption, and high durability. It can not only meet the needs of ultra-long-distance pumping of large-scale projects such as high-rise and super-high-rise buildings and industrial plants in civil engineering in the 21st century, but also has broad application prospects in engineering facilities such as oil, nuclear power, ocean and military in highly corrosive environments. It is the main direction of future concrete technology development. One of the important means to comprehensively improve the performance of traditional self-compacting concrete (SCC) is to add steel fibers to the matrix to generate a new type of steel fiber reinforced FR-SCC. Since steel fibers can effectively bridge matrix cracks, limit crack expansion, enhance material ductility and crack resistance, and improve tensile and flexural strength, the overall performance of the material is improved. During the molding process, the uncontrollable spatial distribution of steel fibers (steel fiber sedimentation) caused by the high fluidity of FR-SCC has a significant impact on the material properties. In addition, the large amount of added steel fibers significantly increases the construction cost, seriously restricting its structural application.

[0003] Based on the current status of FR-SCC research, existing research is limited to ideal conditions in the laboratory. The mechanical properties of FR-SCC are evaluated based on the assumption that steel fibers are uniformly and randomly distributed in the FR-SCC matrix. There may be certain safety hazards in evaluating the bearing capacity and durability of FR-SCC structures based on this result. In fact, the density of steel fibers is more than three times that of concrete. Due to the high fluidity of FR-SCC, steel fibers have a tendency to settle downward in the fresh matrix, and the specific spatial distribution is closely related to its fresh performance. In many cases, steel fibers are not always evenly distributed in the FR-SCC matrix, and the specific fiber distribution state or settlement rate is difficult to determine by mix ratio. When the fiber is unevenly distributed in the matrix, its enhancement effect on the performance of concrete will be reduced or even disappear, resulting in more local defects. Changes in fiber distribution inside large-section components will greatly affect the bearing capacity and overall performance of the structure. Uniform fiber distribution reduces the maximum size of these defects and maximizes the beneficial role of fibers in the matrix.

[0004] In summary, solving the problem of uncontrollable steel fiber distribution in FR-SCC is very necessary to ensure material performance. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of uncontrollable distribution of steel fibers in FR-SCC, and propose a method for achieving random and uniform distribution of steel fibers in FR-SCC by establishing the relationship between the raw material mix ratio and the distribution of steel fibers in the fresh FR-SCC slurry.

[0006] The technical solution adopted by the present invention to solve the above technical problems is:

[0007] A method for regulating and controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix ratio design, the method specifically comprising the following steps:

[0008] Step 1: preparing FR-SCC slurry according to a preset raw material mass ratio, wherein the raw materials for preparing FR-SCC slurry include cement, slag powder, silica fume, fly ash, aggregate, water reducing agent, steel fiber and water;

[0009] Step 2: Using the FR-SCC slurry prepared in step 1, FR-SCC specimens are prepared by molding and curing;

[0010] The prepared specimen is then cut, and the cross section is processed after cutting to obtain the cross section of the FR-SCC specimen;

[0011] Step 3, obtain the cross-sectional image of the FR-SCC specimen, and process and analyze the obtained image to obtain the fiber area content at different depths of the specimen; and calculate the steel fiber distribution coefficient α from the casting surface to the bottom of the specimen according to the fiber area content at different depths of the specimen;

[0012] Step 4: Calculate the water-cement ratio equivalent parameter Ψ according to the preset water-cement ratio, calculate the cement ratio equivalent parameter Z according to the preset sand-gravel ratio and cement-sand ratio, and calculate the water-reducing agent equivalent dosage ω according to the preset water-reducing agent dosage. SP ;

[0013] The water-cement ratio refers to the ratio of the mass of water in the raw materials to the total mass of the cementitious materials, and the cementitious materials include cement, slag powder, silica fume and fly ash;

[0014] The mortar-sand ratio refers to the ratio of the total mass of cementitious materials in the raw materials to the mass of sand in the aggregate;

[0015] The sand-to-gravel ratio refers to the ratio of the mass of sand in the aggregate to the mass of stone in the aggregate in the raw materials;

[0016] Step 5: continuously changing the preset raw material mass ratio, and repeating the process from step 1 to step 4 once for each set of raw material mass ratio;

[0017] According to the Ψ, Z, ω obtained each time SP and the preset steel fiber content ωf , the steel fiber distribution coefficient α obtained each time is fitted, and the steel fiber distribution coefficient fitting surface equation α=α(Ψ,Z,ω SP ,ω f );

[0018] Then, the initially obtained steel fiber distribution coefficient fitting surface equation is interpolated, and finally the fiber distribution coefficient fitting surface equation under different parameter variables is obtained;

[0019] Step 6. Obtain the corresponding steel fiber distribution coefficient according to the engineering requirements, and use the steel fiber distribution coefficient and the fitting surface equation to infer the water-cement ratio equivalent parameters, bone cement ratio equivalent parameters, water reducer equivalent dosage and steel fiber dosage, and then determine the corresponding water-cement ratio, mortar-sand ratio, sand-gravel ratio and water reducer dosage according to the inverted equivalent parameters and equivalent dosage, so as to obtain the raw material quality mix ratio that meets the engineering requirements.

[0020] The beneficial effects of the present invention are:

[0021] The present invention proposes a method for regulating and controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix ratio design. The present invention analyzes the settlement mechanism of steel fibers in fresh FR-SCC slurry, adopts a cross-sectional image analysis method, quantitatively analyzes the distribution of steel fibers in FR-SCC specimens with different mix ratios, establishes the relationship between various raw material parameters and steel fiber distribution coefficients, and realizes the random and uniform distribution of steel fibers regulated by the raw material parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of the method of the present invention;

[0023] Figure 2 Schematic diagram of cutting of the specimen;

[0024] In the figure, d is the diameter of the specimen, and L is the height of the specimen;

[0025] Figure 3 This is the processing flow chart of the specimen cross-section image. DETAILED DESCRIPTION

[0026] Specific implementation method 1. Combination Figure 1 The present embodiment is described in detail. The present embodiment describes a method for controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix ratio design, and the method specifically comprises the following steps:

[0027] Step 1: preparing a freshly mixed FR-SCC slurry according to a preset raw material mass ratio, wherein the raw materials for preparing the FR-SCC slurry include cement, slag powder, silica fume, fly ash, aggregate (including sand and stone), water reducing agent, steel fiber and water;

[0028] Step 2: Using the FR-SCC slurry prepared in step 1, FR-SCC specimens are prepared by molding and curing;

[0029] Then the prepared specimen is cut, and the cross section is processed after cutting to obtain a clean and smooth FR-SCC specimen cross section;

[0030] Step 3, obtain the cross-sectional image of the FR-SCC specimen, and process and analyze the obtained image to obtain the fiber area content at different depths of the specimen; and calculate the steel fiber distribution coefficient α from the casting surface to the bottom of the specimen according to the fiber area content at different depths of the specimen;

[0031] Step 4: Calculate the water-cement ratio equivalent parameter Ψ according to the preset water-cement ratio, calculate the cement ratio equivalent parameter Z according to the preset sand-gravel ratio and cement-sand ratio, and calculate the water-reducing agent equivalent dosage ω according to the preset water-reducing agent dosage (i.e. the ratio of the water-reducing agent mass to the cementitious material mass). SP ;

[0032] The water-cement ratio refers to the ratio of the mass of water in the raw materials to the total mass of the cementitious materials, and the cementitious materials include cement, slag powder, silica fume and fly ash;

[0033] The mortar-sand ratio refers to the ratio of the total mass of cementitious materials in the raw materials to the mass of sand in the aggregate;

[0034] The sand-to-gravel ratio refers to the ratio of the mass of sand in the aggregate to the mass of stone in the aggregate in the raw materials;

[0035] Step 5: continuously changing the preset raw material mass ratio, and repeating the process from step 1 to step 4 once for each set of raw material mass ratio;

[0036] According to the Ψ, Z, ω obtained each time SP and the preset steel fiber content ω f , the steel fiber distribution coefficient α obtained each time is fitted, and the steel fiber distribution coefficient fitting surface equation α=α(Ψ,Z,ω SP ,ω f );

[0037] Steel fiber content f is: the volume of steel fiber in the specimen as a percentage of the specimen volume;

[0038] Then, the initially obtained steel fiber distribution coefficient fitting surface equation is interpolated, and finally the fiber distribution coefficient fitting surface equation under different parameter variables is obtained;

[0039] Step 6. Obtain the corresponding steel fiber distribution coefficient according to the engineering requirements, and use the steel fiber distribution coefficient and fitting formula to infer the water-cement ratio equivalent parameters, bone cement ratio equivalent parameters, water reducer equivalent dosage and steel fiber dosage, and then determine the corresponding water-cement ratio, mortar-sand ratio, sand-gravel ratio and water reducer dosage according to the inverted equivalent parameters and equivalent dosage, so as to obtain the raw material quality mix ratio that meets the engineering requirements.

[0040] The movement of steel fibers in the fresh FR-SCC matrix is ​​essentially related to the fresh fluidity of the matrix and the stress of the fibers in the matrix. Steel fibers are simultaneously subjected to the combined effects of gravity, buoyancy, viscous resistance and other external forces in the fresh matrix. The composition of FR-SCC raw materials has a direct impact on the flowability of the fresh slurry, which in turn affects the distribution of fibers in the fresh slurry. This embodiment obtains the numerical relationship between the water-cement ratio, mortar-sand ratio, sand-stone ratio, water-reducing agent dosage, steel fiber dosage and steel fiber distribution coefficient through preliminary tests to guide the subsequent FR-SCC preparation process and mix design; by calculating and integrating equivalent parameters, they are converted into a normalized form to facilitate the engineering application of the method.

[0041] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the specific process of step 1 is as follows:

[0042] Step 11: Weigh the cement, slag powder, silica fume, fly ash, aggregate (including sand and stone), water reducer, steel fiber and water of the preset mass mix ratio respectively, and pour the cement, slag powder, silica fume, fly ash and aggregate into the mixing pot after weighing;

[0043] Step 1 and 2: After the water reducer and water are evenly mixed, the mixture is added into a stirring pot and stirred at a low speed for 2 minutes. During the low-speed stirring process, steel fibers are gradually and evenly added into the stirring pot. After all the steel fibers are added, high-speed stirring is continued for 2 minutes to obtain a FR-SCC slurry.

[0044] In this embodiment, low speed and high speed are relative concepts, and stirring is first performed at a relatively low speed, and then at a relatively high speed. This embodiment ensures that all raw materials are fully mixed, eliminating experimental errors caused by insufficient mixing in the subsequent preparation process.

[0045] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that the rate of the low-speed stirring is 80 to 120 rpm, and the rate of the high-speed stirring is 180 to 220 rpm.

[0046] The other steps and parameters are the same as those in the first or second embodiment.

[0047] Specific implementation method 4: This implementation method is different from the specific implementation methods 1 to 3 in that the specific process of step 2 is as follows:

[0048] Step 2: Prepare the mold in advance, pour the FR-SCC slurry prepared in step 1 into the mold at one time until the slurry is 1-2mm higher than the test mold opening. While pouring the slurry into the mold, use a spatula to tamp the slurry along the side wall of the mold.

[0049] Step 22: Keep the mold processed in step 21 vertical and move it to a horizontal ground. Use a plastic film to seal the upper mouth of the mold as soon as possible to ensure air isolation and slow down water loss, and obtain a test mold;

[0050] Step 23: Curing the specimen obtained in step 22:

[0051] Place the test mold at room temperature above 20°C (e.g. 25°C) and let it stand for 24 hours, then remove the plastic film and demould. After demoulding, continue to cure for more than 7 days;

[0052] Step 24: After the test piece obtained in step 23 is formed, the test piece is cut by a cutting machine;

[0053] The schematic diagram of the cutting process is as follows Figure 2 As shown, the cutting direction is parallel to the casting direction of the specimen, and the casting direction is from top to bottom;

[0054] Step 25: Select the middle part of the specimen from the specimen cut in step 24, and perform rough grinding, fine grinding and polishing on the cross section of the selected specimen to obtain a smooth and clean FR-SCC specimen cross section.

[0055] The processing method of step 25 can increase the color contrast between the steel fiber and the cement matrix, which is beneficial to the subsequent image analysis.

[0056] The other steps and parameters are the same as those in Specific Embodiments 1 to 3.

[0057] Specific implementation method five: Combination Figure 3 This embodiment is different from the first to fourth embodiments in that the specific process of step three is as follows:

[0058] Step 3: Due to the limitation of the lens, a super-depth-of-field camera is used to collect images of different positions on the same section of the specimen, and the collected images are stitched to generate the entire section image;

[0059] During the entire image acquisition process, the shooting area is always kept under high light irradiation, so that the local fibers are reflected and illuminated, thereby increasing the color contrast between the steel fibers and the FR-SCC matrix;

[0060] Step 32: input the image generated in step 31 into image processing software for size correction to obtain a size-corrected image;

[0061] Remove the redundant borders beyond the specimen section on the stitched image through size correction;

[0062] Step 33: converting the size-corrected image obtained in step 32 into a grayscale image, and performing contrast enhancement on the grayscale image to obtain a contrast-enhanced image;

[0063] Make steel fibers more prominent in the image through contrast enhancement;

[0064] Step 34: convert the contrast-enhanced image obtained in step 33 into a binary image with only black and white colors, and set size and shape filtering thresholds to remove noise in the binary image to obtain a denoised image;

[0065] Step 35: divide the denoised image obtained in step 34 into equal-height regions (i.e., the dividing line between adjacent regions after division is perpendicular to the pouring direction to ensure that pixels of the same height are divided into the same region, but one region can contain pixels of different heights), and divide the denoised image into n parts;

[0066] During the segmentation process, the influence of the wall effect on the analysis should be avoided and the edge area of ​​the image should be removed;

[0067] Step 36: Based on the image obtained in step 35, calculate the steel fiber distribution coefficient α from the casting surface to the bottom of the specimen. The calculation method is as follows:

[0068]

[0069] Among them, S i is the steel fiber area content of the i-th part of the specimen section, It is the average fiber area content of each part divided by the specimen cross section, and n is the number of parts divided into the specimen cross section.

[0070] The more uniform the fiber distribution in the specimen section, the closer α is to 1; the more uneven the fiber distribution in the specimen section or the more obvious the sedimentation, the closer α is to 0;

[0071] This implementation method is divided into three parts: image acquisition, image processing and image analysis. The image processing part accurately identifies the fibers and FR-SCC matrix in the cross section according to the color contrast of the image, and gives a series of parameters related to the quantitative cross-sectional fiber distribution; the image analysis part obtains the fiber distribution coefficient of each part of the specimen along the casting depth, laying an experimental foundation for establishing the relationship between the subsequent rheological parameters and the fiber distribution coefficient.

[0072] The other steps and parameters are the same as those in Specific Embodiments 1 to 4.

[0073] Specific implementation method 6: This implementation method is different from the specific implementation methods 1 to 5 in that the specific process of step 4 is as follows:

[0074] Step 41: normalize the preset water-binder ratio of the test to obtain the water-binder ratio equivalent parameter Ψ;

[0075] Step 42: Integrate the preset mortar-sand ratio and sand-stone ratio to obtain the bone-cement ratio equivalent parameter Z:

[0076]

[0077] Among them, e is the base of natural logarithm, Z1 is the mortar-sand ratio, and Z2 is the sand-gravel ratio;

[0078] When Z2=∞, Z=Z1; when Z2=0, Z=1.25Z1;

[0079] Step 4. Normalize the preset water reducer dosage to obtain the equivalent water reducer dosage ω SP :

[0080] Considering that the water reduction rate of water reducers commonly used in the preparation of FR-SCC is generally in the range of 20%-40%, the equivalent dosage of water reducer ω SP The expression is:

[0081]

[0082] This implementation method processes several parameters such as water-cement ratio, bone-cement ratio, and water-reducing agent dosage according to the mix ratio designed in the preliminary test, and calculates the equivalent parameters of the water-cement ratio, the equivalent parameters of the bone-cement ratio, and the equivalent dosage of the water-reducing agent to facilitate the evaluation of the steel fiber distribution coefficient under different test mix ratios.

[0083] The other steps and parameters are the same as those in Specific Implementation Methods 1 to 5.

[0084] Specific implementation method 7: This implementation method is different from specific implementation methods 1 to 6 in that the specific process of step 41 is as follows:

[0085] Step S1: Generate a vector M1=[m 水泥 ,m 矿渣 ,m 粉煤灰 ,m 硅灰 ], where m 水泥 is the mass of cement in FR-SCC paste, m 矿渣 is the mass of slag powder in FR-SCC paste, m 粉煤灰 is the mass of fly ash in FR-SCC paste, m 硅灰 is the mass of silica fume in FR-SCC slurry;

[0086] Step S2: Generate water-binder ratio equivalent matrix Wherein, diag() represents a diagonal matrix. The dimension of the matrix is ​​the number of values ​​in brackets. The values ​​on the main diagonal from the upper left to the lower side are the values ​​in brackets. Each value represents the conversion coefficient of the corresponding raw material relative to cement.

[0087] Step S3, the calculation formula of the water-binder ratio equivalent parameter Ψ is:

[0088]

[0089] Here, ||·||1 represents the 1-norm.

[0090] Assume that M = [m1,…m n ],but

[0091]

[0092] In this embodiment, the processing method of the water-binder ratio designed in the preliminary test is specifically explained, and the water-binder ratio equivalent parameter calculation formula related to the cement, slag, fly ash, and silica fume dosage is given. When the raw materials involved change, it is necessary to adjust the vector in step S1 and the conversion coefficient in the equivalent matrix in step S2. The introduction of the water-binder ratio equivalent parameter facilitates the evaluation of the fiber distribution coefficient under different test water-binder ratios.

[0093] The other steps and parameters are the same as those in Specific Embodiments 1 to 6.

[0094] Specific implementation eight: This implementation differs from one of the specific implementations one to seven in that the Ψ, Z, ω obtained each time are SP and the preset steel fiber content ω f , the steel fiber distribution coefficient α obtained each time is fitted; the specific process is:

[0095] Step C1, fix the steel fiber content ω f and the cement ratio equivalent parameter Z, the water-cement ratio equivalent parameter Ψ and the water reducing agent equivalent dosage ω obtained each time SP As a variable, the steel fiber distribution coefficient α is fitted to obtain the fitting formula α1=α1(Ψ,ω SP ), and record the fitting formula form;

[0096] Step C2: Fix the steel fiber content ω f , water-binder ratio equivalent parameter Ψ and water reducer equivalent dosage ω SP , using the bone glue ratio equivalent parameter Z obtained each time as a variable, fitting the steel fiber distribution coefficient α, obtaining the fitting formula α2=α2(Z), and recording the fitting formula form;

[0097] Step C3, fixing the bone glue ratio equivalent parameter Z, the water-binder ratio equivalent parameter Ψ and the water reducing agent equivalent parameter ω SP , with the preset steel fiber dosage ω f As a variable, the fiber distribution coefficient α is fitted to obtain the fitting formula α3=α3(ω f ), and record the fitting formula form;

[0098] Step C4: According to the fitting formula form obtained from step C1 to step C3, three fitting formulas are weighted, and four-parameter fitting is performed based on the test data. The fitting result obtained is:

[0099] α=μ1α1(Ψ,ω SP )+μ2α2(Z)+μ3α3(ω f ) (6)

[0100] Among them, μ1, μ2, and μ3 are weighting coefficients.

[0101] The value of the weighted coefficient is determined by experimental data, and the size relationship should be consistent with the influence of the four equivalent parameters on the fiber distribution coefficient α. Generally, under the actual application of the mix ratio conditions, the order of the influence of the four equivalent parameters on the fiber distribution coefficient α from large to small is: water-binder ratio equivalent parameter Ψ, water reducer equivalent parameter ω SP , Steel fiber contentω f , bone glue ratio equivalent parameter Z.

[0102] In addition, formula (6) should also satisfy several limit conditions:

[0103] (1)Ψ→∞,α→0; (2)ω SP →∞,α→0(3)ω f →∞,α→1;(4)Z→∞,α→1.

[0104] Through the analysis of the distribution coefficient of steel fiber reinforced concrete, the fitting relationship between the distribution coefficient α and the steel fiber content and the water reducer content is mainly expressed in the form of an exponential function. Considering the limiting conditions, the fitting form recommended by the present invention is:

[0105]

[0106] in, is the coefficient, σ2 is the fitting coefficient, and exp[] is the exponential function. Formula (7) is the function form obtained by combining similar terms in formula (6).

[0107] In this embodiment, the process of obtaining the four-parameter fiber distribution coefficient fitting equation is specifically explained. Since the fitting process of the four parameter variables requires a huge amount of calculation, it is necessary to split each parameter, first obtain the fitting function form separately, and then establish the relationship between each form; by controlling the variables and the weighting process, the calculation amount of the fitting process is reduced and the fitting accuracy can be improved.

[0108] The other steps and parameters are the same as those in Specific Embodiments 1 to 7.

[0109] Specific implementation method 9: This implementation method is different from specific implementation methods 1 to 8 in that the specific process of step 6 is as follows:

[0110] Step 6: 1. According to the engineering requirements, give a rough estimate of the steel fiber distribution coefficient;

[0111] For situations where uniform distribution of steel fibers is required, the fiber distribution coefficient α can be controlled above 0.8;

[0112] Step 62: taking at least one of the water-cement ratio equivalent parameter, the bone cement ratio equivalent parameter, the water reducing agent equivalent dosage and the steel fiber dosage as a constant, and satisfying the number of constants k<4;

[0113] According to the raw materials provided by the actual project, control some variables in water-cement ratio, sand-gravel ratio, cement-sand ratio, water-reducing agent dosage, and steel fiber dosage to obtain at least one constant equivalent or constant variable, that is, at least one of the water-cement ratio equivalent parameter, cement ratio equivalent parameter, water-reducing agent equivalent dosage, and steel fiber dosage is a constant. Assume that k (k<4) constant variables / equivalents are known;

[0114] Step 6. Substitute k constants into the fitting surface equation α=α(Ψ,Z,ω SP ,ω f ), we get the functional form of 4-k variables;

[0115] Step 64: According to the steel fiber distribution coefficient range given in step 61 and the functional form of the 4-k variables obtained in step 63, the corresponding values ​​of the 4-k variables are obtained.

[0116] Find the surface portion of the function obtained in step 63 within the range given in step 61, and obtain the values ​​that the other (4-k) variables can take, among which the achievable value of the independent variable is the required mix ratio.

[0117] In particular, an example of solving the mix ratio for obtaining a concrete material with uniform fiber distribution, i.e., one with α approaching 1, is given.

[0118] Assuming that the water-binder ratio equivalent Ψ is limited to a constant Ψ0, substitute Ψ0 into the formula α=α(Ψ,Z,ω SP ,ωf ) into a formula containing only three variables:

[0119] α=α(Ψ0,Z,ω SP ,ω f ) (8)

[0120] For the three variables Z,ω in the above formula SP ,ω f Take the derivatives separately and get 3 derivative functions:

[0121]

[0122] By making the above three functions equal to 0, we can obtain the independent variable values ​​corresponding to multiple maximum values ​​{Z m},{ω SP,m},{ω f,m}, the variable value corresponding to the larger and achievable fiber distribution coefficient α is: Z0,ω SP,0 ,ω f,0 .

[0123] According to the result of the formula Z0,ω SP,0 ,ω f,0 , and the known Ψ0, can produce materials with uniform fiber distribution.

[0124] This embodiment specifically explains the FR-SCC steel fiber distribution homogenization control process based on mix design. In actual engineering design, variables such as water-cement ratio, sand-stone ratio, mortar-sand ratio, water-reducing agent dosage, and steel fiber dosage generally have certain common values ​​or fixed values, which reduces the number of variables in the fitting function and reduces the amount of calculation in the control process. Even if the above variables are not known, the required fiber distribution can be obtained by solving the independent variable value of the fitting function within the specified fiber distribution coefficient range.

[0125] The other steps and parameters are the same as those in Specific Embodiments 1 to 8.

[0126] Embodiment 1

[0127] The method of the present invention is further described by way of example:

[0128] The present embodiment provides a method for controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix ratio design, and the method is implemented by the following steps:

[0129] Step 1: Prepare FR-SCC slurry according to the preset raw material mass ratio, wherein 3The finished concrete requires 191kg of raw materials cement, 50kg of slag powder, 50kg of silica fume, 217kg of fly ash, 1542kg of aggregate (874kg of sand, 668kg of stone), 6.46kg of water reducer (water reduction rate 25%), 70kg of steel fiber, and 190kg of water.

[0130] Step 2: Using the FR-SCC slurry prepared in step 1, FR-SCC specimens are prepared by molding and curing;

[0131] The prepared specimen is then cut, and the cross section is processed after cutting to obtain the cross section of the FR-SCC specimen;

[0132] Step 3, obtain the cross-sectional image of the FR-SCC specimen, and process and analyze the obtained image to obtain the fiber area content at different depths of the specimen; and calculate the steel fiber distribution coefficient α from the casting surface to the bottom of the specimen according to the fiber area content at different depths of the specimen;

[0133] Step 4: Calculate the water-cement ratio equivalent parameter Ψ according to the preset water-cement ratio, calculate the cement ratio equivalent parameter Z according to the preset sand-gravel ratio and cement-sand ratio, and calculate the water-reducing agent equivalent dosage ω according to the preset water-reducing agent dosage. SP ;

[0134] The water-cement ratio refers to the ratio of the mass of water in the raw materials to the total mass of the cementitious materials, and the cementitious materials include cement, slag powder, silica fume and fly ash;

[0135] The mortar-sand ratio refers to the ratio of the total mass of cementitious materials in the raw materials to the mass of sand in the aggregate;

[0136] The sand-gravel ratio refers to the ratio of the sand content in the aggregate to the stone content in the aggregate in the raw materials;

[0137] Step 5: continuously changing the preset raw material mass ratio, and repeating the process from step 1 to step 4 once for each set of raw material mass ratio;

[0138] According to the Ψ, Z, ω obtained each time SP and the preset steel fiber content ω f , the steel fiber distribution coefficient α obtained each time is fitted, and the steel fiber distribution coefficient fitting surface equation α=α(Ψ,Z,ω SP ,ω f );

[0139] ①Fixed steel fiber contentω f and the cement ratio equivalent parameter Z to obtain the water-cement ratio equivalent parameter Ψ and the water reducing agent equivalent dosage ω SPThe corresponding steel fiber distribution coefficient α;

[0140] Make the water-binder ratio equivalent parameter Ψ in the range of 0.25-0.45, with a step length of 0.02; water reducer equivalent dosage ω SP , the recommended range is 0.5%-1.5%, and the step size is 0.1%;

[0141] ②Fixed steel fiber contentω f , water-binder ratio equivalent parameter Ψ and water reducer equivalent dosage ω SP , to obtain the steel fiber distribution coefficient α corresponding to each bone glue ratio equivalent parameter Z;

[0142] The bone glue ratio equivalent parameter Z is in the range of 2.5-3.5, with a step size of 0.1;

[0143] ③Fixed cement ratio equivalent parameter Z, water-cement ratio equivalent parameter Ψ and water reducing agent equivalent parameter ω SP , to obtain the steel fiber dosage ω of each time f The corresponding steel fiber distribution coefficient α;

[0144] Steel fiber content f In the range of 0.5%-2.0% (volume percentage of finished concrete);

[0145] Steel fiber distribution coefficient α fitting:

[0146] Fixed steel fiber contentω f and the cement ratio equivalent parameter Z, the water-cement ratio equivalent parameter Ψ and the water reducing agent equivalent dosage ω obtained each time SP As a variable, the steel fiber distribution coefficient α is fitted to obtain the fitting formula α1=α1(Ψ,ω SP );

[0147] Fixed steel fiber contentω f , water-binder ratio equivalent parameter Ψ and water reducer equivalent dosage ω SP , using the bone glue ratio equivalent parameter Z obtained each time as a variable, the steel fiber distribution coefficient α is fitted to obtain the fitting formula α2=α2(Z);

[0148] Fixed cement ratio equivalent parameter Z, water-cement ratio equivalent parameter Ψ and water reducing agent equivalent parameter ω SP , with the preset steel fiber dosage ω f As a variable, the fiber distribution coefficient α is fitted to obtain the fitting formula α3=α3(ω f );

[0149] The three fitting formulas are weighted and the fitting results are:

[0150] α=μ1α1(Ψ,ω SP)+μ2α2(Z)+μ3α3(ω f )

[0151] Then, the initially obtained steel fiber distribution coefficient fitting surface equation is interpolated, and finally the fiber distribution coefficient fitting surface equation under different parameter variables is obtained;

[0152] Step 6. Obtain the corresponding steel fiber distribution coefficient according to the engineering requirements, and use the steel fiber distribution coefficient and fitting formula to infer the water-cement ratio equivalent parameters, bone cement ratio equivalent parameters, water reducer equivalent dosage and steel fiber dosage, and then determine the corresponding water-cement ratio, mortar-sand ratio, sand-gravel ratio and water reducer dosage according to the inverted equivalent parameters and equivalent dosage, so as to obtain the raw material quality mix ratio that meets the engineering requirements.

[0153] The above calculation examples of the present invention are only used to explain the calculation model and calculation process of the present invention in detail, and are not intended to limit the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for regulating and controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix design, characterized in that: The method specifically comprises the following steps: Step 1: preparing FR-SCC slurry according to a preset raw material mass ratio, wherein the raw materials for preparing FR-SCC slurry include cement, slag powder, silica fume, fly ash, aggregate, water reducing agent, steel fiber and water; Step 2: Using the FR-SCC slurry prepared in step 1, FR-SCC specimens are prepared by molding and curing; The prepared specimen is then cut, and the cross section is processed after cutting to obtain the cross section of the FR-SCC specimen; Step 3, obtain the cross-sectional image of the FR-SCC specimen, and process and analyze the obtained image to obtain the fiber area content at different depths of the specimen; and calculate the steel fiber distribution coefficient α from the casting surface to the bottom of the specimen according to the fiber area content at different depths of the specimen; Step 4: Calculate the water-cement ratio equivalent parameter Ψ according to the preset water-cement ratio, calculate the cement ratio equivalent parameter Z according to the preset sand-gravel ratio and cement-sand ratio, and calculate the water-reducing agent equivalent dosage ω according to the preset water-reducing agent dosage. SP ; The water-cement ratio refers to the ratio of the mass of water in the raw materials to the total mass of the cementitious materials, and the cementitious materials include cement, slag powder, silica fume and fly ash; The mortar-sand ratio refers to the ratio of the total mass of cementitious materials in the raw materials to the mass of sand in the aggregate; The sand-to-gravel ratio refers to the ratio of the mass of sand in the aggregate to the mass of stone in the aggregate in the raw materials; Step 5: continuously changing the preset raw material mass ratio, and repeating the process from step 1 to step 4 once for each set of raw material mass ratio; According to the Ψ, Z, ω obtained each time SP and the preset steel fiber content ω f , the steel fiber distribution coefficient α obtained each time is fitted, and the steel fiber distribution coefficient fitting surface equation α=α(Ψ,Z,ω SP ,ω f ); The process of fitting the steel fiber distribution coefficient α obtained each time is as follows: Step C1, fix the steel fiber content ω f and the cement ratio equivalent parameter Z, the water-cement ratio equivalent parameter Ψ and the water reducing agent equivalent dosage ω obtained each time SP As a variable, the steel fiber distribution coefficient α is fitted to obtain the fitting formula α1=α1(Ψ,ω SP ), and record the fitting formula form; Step C2: Fix the steel fiber content ω f , water-binder ratio equivalent parameter Ψ and water reducer equivalent dosage ω SP , using the bone glue ratio equivalent parameter Z obtained each time as a variable, fitting the steel fiber distribution coefficient α, obtaining the fitting formula α2=α2(Z), and recording the fitting formula form; Step C3, fix the bone glue ratio equivalent parameter Z, the water-binder ratio equivalent parameter Ψ and the water reducing agent equivalent parameter ω SP , with the preset steel fiber dosage ω f As a variable, the steel fiber distribution coefficient α is fitted to obtain the fitting formula α3=α3(ω f ), and record the fitting formula form; Step C4: weight the three fitting formulas according to the fitting formulas obtained from Step C1 to Step C3, and obtain the fitting result as follows: α=μ1α1(Ψ,ω SP )+μ2α2(Z)+μ3α3(ω f ) (6) Among them, μ1, μ2, and μ3 are weighting coefficients; Then, the initially obtained steel fiber distribution coefficient fitting surface equation is interpolated, and finally the steel fiber distribution coefficient fitting surface equation under different parameter variables is obtained; Step 6. Obtain the corresponding steel fiber distribution coefficient according to the engineering requirements, and use the steel fiber distribution coefficient and the fitting surface equation to infer the water-cement ratio equivalent parameters, bone cement ratio equivalent parameters, water reducer equivalent dosage and steel fiber dosage, and then determine the corresponding water-cement ratio, mortar-sand ratio, sand-gravel ratio and water reducer dosage according to the inverted equivalent parameters and equivalent dosage, so as to obtain the raw material quality mix ratio that meets the engineering requirements.

2. The method for controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix design according to claim 1, characterized in that: The specific process of step one is: Step 11: Weigh cement, slag powder, silica fume, fly ash, aggregate, water reducing agent, steel fiber and water of preset mass mix ratio respectively, and pour cement, slag powder, silica fume, fly ash and aggregate into a mixing pot after weighing; Step 1 and 2: After the water reducer and water are evenly mixed, the mixture is added into a stirring pot and stirred at a low speed for 2 minutes. During the low-speed stirring process, steel fibers are gradually and evenly added into the stirring pot. After all the steel fibers are added, high-speed stirring is continued for 2 minutes to obtain a FR-SCC slurry.

3. The method for controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix design according to claim 2, characterized in that: The low-speed stirring rate is 80-120 rpm, and the high-speed stirring rate is 180-220 rpm.

4. The method for controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix design according to claim 3, characterized in that: The specific process of step 2 is as follows: Step 2: Pour the FR-SCC slurry prepared in step 1 into the mold at one time until the slurry is 1-2 mm higher than the test mold opening. While pouring the slurry into the mold, use a spatula to tamp the slurry along the side wall of the mold. Step 22: Keep the mold processed in step 21 vertically and move it to a horizontal ground, and seal the upper opening of the mold with a plastic film to obtain a test mold; Step 23: Curing the specimen obtained in step 22: Place the test mold at room temperature above 20°C and let it stand for 24 hours, then remove the plastic film and demould. After demoulding, continue to cure for more than 7 days; Step 24: After the test piece obtained in step 23 is formed, the test piece is cut by a cutting machine; Step 25: Select the middle part of the specimen from the specimen cut in step 24, perform rough grinding, fine grinding and polishing on the cross section of the selected specimen to obtain the processed FR-SCC specimen cross section.

5. The method for controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix design according to claim 4, characterized in that: The specific process of step three is: Step 3: Use a super-depth-of-field camera to collect images of different positions on the same section of the test piece, and stitch the collected images to generate an image of the entire section; Step 32: input the image generated in step 31 into image processing software for size correction to obtain a size-corrected image; Step 33: converting the size-corrected image obtained in step 32 into a grayscale image, and performing contrast enhancement on the grayscale image to obtain a contrast-enhanced image; Step 34: convert the contrast-enhanced image obtained in step 33 into a binary image with only black and white colors, and set size and shape filtering thresholds to remove noise in the binary image to obtain a denoised image; Step 35: perform equal height area division on the denoised image obtained in step 34, and divide the denoised image into n parts; Step 36: Based on the image obtained in step 35, calculate the steel fiber distribution coefficient α from the casting surface to the bottom of the specimen. The calculation method is as follows: Among them, S i is the steel fiber area content of the i-th part of the specimen section, It is the average steel fiber area content of each part of the specimen cross section, and n is the number of parts of the specimen cross section.

6. The method for controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix design according to claim 5, characterized in that: The specific process of step 4 is as follows: Step 41: normalize the preset water-binder ratio to obtain a water-binder ratio equivalent parameter Ψ; Step 42: Integrate the preset mortar-sand ratio and sand-stone ratio to obtain the bone-cement ratio equivalent parameter Z: Among them, e is the base of natural logarithm, Z1 is the mortar-sand ratio, and Z2 is the sand-gravel ratio; Step 4. Normalize the preset water reducer dosage to obtain the equivalent water reducer dosage ω SP : Water reducing agent equivalent dosage ω SP The expression is:

7. The method for controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix design according to claim 6, characterized in that: The specific process of step 41 is: Step S1: Generate a vector M1=[m 水泥 ,m 矿渣 ,m 粉煤灰 ,m 硅灰 ], where m 水泥 is the mass of cement in FR-SCC paste, m 矿渣 is the mass of slag powder in FR-SCC paste, m 粉煤灰 is the mass of fly ash in FR-SCC paste, m 硅灰 is the mass of silica fume in FR-SCC slurry; Step S2: Generate water-binder ratio equivalent matrix D Ψ =diag(1,1.05,0.95,1.2), where diag() represents a diagonal matrix; Step S3, the calculation formula of the water-binder ratio equivalent parameter Ψ is: Here, ||·||1 represents the 1-norm.

8. The method for controlling the uniform distribution of fiber-reinforced self-compacting concrete based on mix design according to claim 1, characterized in that: The specific process of step six is ​​as follows: Step 6:

1. According to the engineering requirements, give a rough estimate of the steel fiber distribution coefficient; Step 62: taking at least one of the water-cement ratio equivalent parameter, the bone-cement ratio equivalent parameter, the water-reducing agent equivalent dosage and the steel fiber dosage as a constant, and satisfying the number of constants k<4; Step 6. Substitute k constants into the fitting surface equation α=α(Ψ,Z,ω SP ,ω f ), we get the functional form of 4-k variables; Step 64: According to the steel fiber distribution coefficient range given in step 61 and the functional form of the 4-k variables obtained in step 63, the corresponding values ​​of the 4-k variables are obtained.

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