Light cement-based composite material formula design method applied to composite beam
By determining the target stacking curve and calculating the residuals, the raw material ratio of lightweight ultra-high performance cement matrix composites is solved, and the problem of relying on tests and field experience is achieved, achieving more stable performance and efficient production.
Patent Information
- Application Number
- CN202510190146.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-20
- Publication Date
- 2025-06-20
AI Technical Summary
The preparation technology of lightweight ultra-high performance cement-based composite materials mainly relies on tests and on-site experience, resulting in unstable performance and high volatility.
By determining the target stacking curve based on the particle size and density of the raw materials of the cement-based composite material, the residuals between the multiple actual stacking curves and the target stacking curve are obtained, and the raw material ratio range is determined based on the relationship between the residual and the residual threshold, thereby enhancing the scientific nature of the ratio design.
It improves the stability of lightweight ultra-high performance cement matrix composite materials, reduces performance volatility, makes production more efficient, and has more stable quality and performance.
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Abstract
Description
Technical Field
[0001] This application relates to the field of construction technology, and particularly to a method for designing the formula of a lightweight cement-based composite material applied to composite beams. Background Art
[0002] The UHPC material in the steel girder bridge deck pavement layer is composed of raw materials such as cement, quartz sand, mineral admixtures, steel fibers, and water reducers. After setting and hardening, it exhibits ultra-high mechanical properties, anti-deformation ability (toughness), and excellent durability, and can effectively cope with local stress concentration and large deformation of the steel bridge deck.
[0003] Ultra-high performance concrete has excellent fatigue resistance and ultra-high toughness, can extend the service life of the structure, and reduce the operation cost of the entire life cycle of the structure. The ultimate tensile strength of the UHPC layer is high. This composite bridge deck structure can not only improve the stiffness of the steel bridge deck, but also improve the anti-cracking and deformation-inhibiting ability of the pavement layer, and can significantly improve the performance of the bridge deck structure for overcoming the problems existing in traditional steel bridge deck pavements, and has great engineering application value. This technology has been successively applied to large highway and railway bridge projects such as Zhaoqing Mafang Bridge, Zhuzhou Fengxi Bridge, Dongting Lake Second Bridge, Hutong Yangtze River Bridge, and Chengdu-Kunming Railway Jinsha River Bridge.
[0004] Ultra-high performance concrete has a large amount of cementitious materials, and usually uses finer quartz sand combined with powders to obtain a denser structure and reduce the generation of pore defects and microcracks in the matrix. In contrast, lightweight ultra-high performance concrete has the characteristics of light weight, low shrinkage, and low cost, and is also an important extension of ultra-high performance concrete, and also has broad application space in the field of steel bridge deck pavement. However, the preparation technology of lightweight ultra-high performance concrete mainly relies on experiments and on-site experience, resulting in unstable performance and large fluctuations of the produced lightweight ultra-high performance concrete. Summary of the Invention
[0005] This application provides a method for designing the formula of a lightweight cement-based composite material applied to composite beams to improve the stability of the lightweight ultra-high performance cement-based composite material and reduce fluctuations.
[0006] In a first aspect, this application provides a method for designing the formula of a lightweight cement-based composite material applied to composite beams, including the following steps:
[0007] Determine the target packing curve of the raw materials of the cement-based composite material according to the particle size and density of the raw materials of the cement-based composite material;
[0008] Obtain the actual packing curves of the raw materials of the cement-based composite material under multiple ratios of the raw materials of the cement-based composite material;
[0009] Obtain the residuals between multiple actual packing curves and the target packing curve;
[0010] Determine the raw material ratio range of the cement-based composite material according to the relationship between the residuals and the residual threshold.
[0011] In this application, by obtaining the residuals between multiple actual packing curves and the target packing curve, and determining the raw material ratio range of the cement-based composite material according to the relationship between the residuals and the residual threshold, the scientific nature of the lightweight ultra-high performance cement-based composite material ratio design method can be enhanced, and a preparation technical route for lightweight ultra-high performance cement-based composite materials to determine the key preparation parameters based on the characteristics of raw materials is established, making the production of lightweight ultra-high performance cement-based composite materials more efficient, and the quality and performance more stable. This method is simple to calculate, can accurately obtain the reasonable proportion range of different components of lightweight ultra-high performance cement-based composite materials, and efficiently prepare lightweight ultra-high performance cement-based composite materials with excellent performance.
[0012] It should be noted that obtaining the residuals between multiple actual packing curves and the target packing curve, and determining the raw material ratio range of the cement-based composite material according to the relationship between the residuals and the residual threshold is to make the actual packing curve closer to the target packing curve, so that the actual packing state is consistent with the theoretical packing state.
[0013] It should be noted that compared with traditional cement-based composite materials, lightweight cement-based composite materials have a lower apparent density and the same or higher compressive strength. For example, the apparent density of traditional ultra-high performance cement-based composite materials is 2400 - 2500 kg / m 3 , and the compressive strength is 120 - 160 MPa, while the apparent density of lightweight ultra-high performance cement-based composite materials is 2050 - 2150 kg / m 3 , and the compressive strength is 110 - 140 MPa.
[0014] In some embodiments, the determining the raw material ratio of the cement-based composite material according to the relationship between the residuals and the residual threshold includes:
[0015] If the residuals meet the residual threshold, establish a first correspondence relationship between the compressive strength of the cement-based composite material specimen and the apparent density of the cement-based composite material specimen and the content of ceramic sand and the pre-wetting water amount of ceramic sand in the raw materials of the cement-based composite material;
[0016] Determine the content of ceramic sand and the pre-wetting water amount of ceramic sand in the raw materials of the cement-based composite material according to the first correspondence relationship.
[0017] Since the parameters most relevant to the strength of cement-based composites are the content of ceramic sand and the pre-wetting water amount of ceramic sand, and the apparent density is a significant characteristic of lightweight cement-based composites, by establishing a first correspondence relationship between the compressive strength of cement-based composite specimens, the apparent density of cement-based composite specimens, and the content of ceramic sand and the pre-wetting water amount of ceramic sand in the raw materials of cement-based composites, and determining the content of ceramic sand and the pre-wetting water amount of ceramic sand in the raw materials of cement-based composites according to the first correspondence relationship, it is possible to determine the content of ceramic sand and the pre-wetting water amount of ceramic sand in the raw materials of cement-based composites on the premise of meeting the maximum compressive strength and the minimum apparent density. If the residual satisfies the residual threshold, it means that the residuals between multiple actual packing curves and the target packing curve are within an acceptable range. For example, if the residual is ±10%, it is considered that the residual satisfies the residual threshold. The residual reflects the deviation degree between the actual packing curve and the preset target packing curve. The smaller the absolute value of the residual, the smaller the deviation, and the larger the absolute value of the residual, the larger the deviation.
[0018] It should be noted that the content of ceramic sand refers to the mass ratio of ceramic sand in the entire raw materials of cement-based composites, and the pre-wetting water amount of ceramic sand refers to the mass ratio of the water to be added to the ceramic sand to the weight of the ceramic sand before preparing the cement-based composites.
[0019] In some embodiments, after determining the content of ceramic sand and the pre-wetting water amount of ceramic sand in the raw materials of cement-based composites according to the correspondence relationship, it further includes:
[0020] Establishing a second correspondence relationship between the compressive strength of cement-based composite specimens, the apparent density of cement-based composite specimens, and the particle size ratio of ceramic sand in the raw materials of cement-based composites;
[0021] Determining the particle size ratio of ceramic sand in the raw materials of cement-based composites according to the second correspondence relationship.
[0022] The particle size ratio of ceramic sand also affects the apparent density and compressive strength of lightweight cement-based composites. By establishing a second correspondence relationship between the compressive strength of cement-based composite specimens, the apparent density of cement-based composite specimens, and the particle size ratio of ceramic sand in the raw materials of cement-based composites, and determining the particle size ratio of ceramic sand in the raw materials of cement-based composites according to the second correspondence relationship, the particle size of the ceramic sand used and the ratio between different particle sizes can be determined.
[0023] In some embodiments, after determining the particle size ratio of ceramic sand in the raw materials of cement-based composites according to the second correspondence relationship, it further includes:
[0024] Calculating the cost of the raw materials of cement-based composites within the particle size ratio of ceramic sand in the raw materials of cement-based composites;
[0025] Determining the raw material ratio of cement-based composites according to the cost.
[0026] Since there are multiple formulations within an acceptable range for the residual, when comprehensively considering the apparent density and compressive strength of the cement-based composite material, the dosage of ceramsite sand, the pre-wetting water amount, and the particle size ratio of ceramsite sand can be determined. However, there are still multiple groups of dosages for other raw material components of the cement-based composite material, all of which meet the original requirements for apparent density and compressive strength. At this time, by calculating the cost and based on the principle of minimum cost, the final formulation of the raw materials for the cement-based composite material is determined.
[0027] In some embodiments, the method for establishing the second correspondence relationship includes a statistical method. To establish the second correspondence relationship between the compressive strength of the cement-based composite material specimen, the apparent density of the cement-based composite material specimen, and the particle size ratio of ceramsite sand in the raw materials of the cement-based composite material, a physical statistics method can be used, which can more accurately reflect the relationship between the compressive strength of the cement-based composite material specimen, the apparent density of the cement-based composite material specimen, and the particle size ratio of ceramsite sand in the raw materials of the cement-based composite material.
[0028] In some embodiments, the method for establishing the first correspondence relationship includes a regression method. Using the regression method can quickly determine the dosage of ceramsite sand and the pre-wetting water amount within the formulation range that meets the residual threshold, reduce the amount of experiments, and improve efficiency.
[0029] In some embodiments, the raw materials for the cement-based composite material include cement, metal fibers, ceramsite sand, admixtures, and water reducers. Metal fibers are usually added to high-strength cement-based composite materials to improve the strength of lightweight cement-based composite materials. The metal fibers include but are not limited to steel fibers, and the admixtures include but are not limited to silica fume, microspheres, etc. It should be noted that when preparing the cement-based composite material, an appropriate amount of water also needs to be added to form a slurry, and usually the addition amount of water is 6% - 10% of the total mass of the cement-based composite material.
[0030] In some embodiments, in determining the target packing curve of the raw materials for the cement-based composite material according to the particle size and density of the raw materials for the cement-based composite material: the method for determining the target packing curve of the raw materials for the cement-based composite material includes the close packing theory mathematical model method. Using the close packing theory mathematical model can quickly establish the target packing curve, reduce the amount of experiments, and improve efficiency.
[0031] In some embodiments, the method for obtaining the actual packing curves of the raw materials for the cement-based composite material under multiple formulations of the raw materials for the cement-based composite material includes the sieving method. The actual packing curve is more accurate using the sieving method.
[0032] In some embodiments, the method for obtaining the residuals between multiple actual packing curves and the target packing curve includes the least squares method. Using the least squares method can quickly determine the residuals between the actual packing curve and the target packing curve, and improve efficiency. Description of the Drawings
[0033] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.
[0034] Figure 1 It is a flowchart of the formulation design method of the lightweight cement-based composite material according to an embodiment of the present application.
[0035] Figure 2 It is a flowchart of the formulation design method of the lightweight cement-based composite material according to an embodiment of the present application.
[0036] Figure 3 It is a flowchart of the formulation design method of the lightweight cement-based composite material according to an embodiment of the present application.
[0037] Figure 4 It is a flowchart of the formulation design method of the lightweight cement-based composite material according to an embodiment of the present application.
[0038] Figure 5 It is the residual normal probability distribution diagram of the apparent density and compressive strength of the lightweight cement-based composite material in Embodiment 1 of the present application.
[0039] Figure 6 It is the 3D response surface diagram and contour diagram of the apparent density and compressive strength of the lightweight cement-based composite material in Embodiment 1 of the present application.
[0040] Figure 7 It is the contour diagram of the optimization results of the apparent density and compressive strength of the lightweight cement-based composite material in Embodiment 1 of the present application.
[0041] Figure 8 It is the relationship diagram of the ceramsite sand particle size ratio and the slump flow, apparent density, compressive strength, flexural strength and elastic modulus of the lightweight cement-based composite material in Embodiment 1 of the present application. Detailed implementation manners
[0042] To make the objectives, technical solutions and advantages of the present application clearer, the following will clearly and completely describe the technical solutions of the present application in combination with the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present application.
[0043] The UHPC material in the steel girder bridge deck pavement is composed of raw materials such as cement, quartz sand, mineral admixture, steel fiber and water reducer. After setting and hardening, it exhibits ultra-high mechanical properties, anti-deformation ability (toughness) and excellent durability, and can effectively cope with the local stress concentration and large deformation of the steel bridge deck.
[0044] Ultra-high performance cementitious composites have excellent fatigue resistance and ultra-high toughness, can extend the service life of the structure, and reduce the operation cost of the whole life cycle of the structure. The UHPC layer has a high ultimate tensile strength. This combined bridge deck structure can not only improve the stiffness of the steel bridge deck, but also improve the anti-cracking and deformation inhibition ability of the pavement layer, and can significantly improve the bridge deck structure performance for overcoming the problems existing in the traditional steel bridge deck pavement, and has great engineering application value. This technology has been successively applied to large highway and railway bridge projects such as Zhaoqing Mafang Bridge, Zhuzhou Fengxi Bridge, Dongting Lake Second Bridge, Hutong Yangtze River Bridge, and Chengdu-Kunming Railway Jinsha River Bridge.
[0045] Ultra-high performance concrete has a large amount of cementitious materials, and usually uses finer quartz sand combined with powder to obtain a denser structure, reduce the pore defects and microcracks in the matrix. In contrast, lightweight ultra-high performance concrete has the characteristics of light weight, low shrinkage and low cost, and is also an important extension of ultra-high performance concrete, and also has broad application space in the field of steel bridge deck pavement. However, the preparation technology of lightweight ultra-high performance concrete mainly relies on experiments and on-site experience, resulting in unstable performance and large fluctuations of the produced lightweight ultra-high performance concrete.
[0046] In view of this, the present application provides a method for designing the formula of lightweight cementitious composites for composite beams to improve the stability of lightweight ultra-high performance cementitious composites and reduce fluctuations.
[0047] In the first aspect, as Figure 1 shown, the present application provides a method for designing the formula of lightweight cementitious composites, including the following steps:
[0048] S100. Determine the target packing curve of the raw materials of the cementitious composites according to the particle size and density of the raw materials of the cementitious composites;
[0049] S200. Obtain the actual packing curves of the raw materials of the cementitious composites under multiple raw material ratios of the cementitious composites;
[0050] S300. Obtain the residuals between multiple actual packing curves and the target packing curve;
[0051] S400. Determine the raw material ratio range of the cementitious composites according to the relationship between the residuals and the residual threshold.
[0052] By obtaining the residuals between multiple actual packing curves and the target packing curve, and determining the raw material ratio range of the cement-based composite material according to the relationship between the residuals and the residual threshold, the scientific nature of the mixing ratio design method of the lightweight ultra-high performance cement-based composite material can be enhanced, and a preparation technical route of the lightweight ultra-high performance cement-based composite material for determining the key preparation parameters based on the characteristics of the raw materials is established, making the production of the lightweight ultra-high performance cement-based composite material more efficient, and the quality and performance more stable. This method is simple to calculate and can accurately obtain the reasonable ratio range of different components of the lightweight ultra-high performance cement-based composite material, and efficiently prepare the lightweight ultra-high performance cement-based composite material with excellent performance.
[0053] It should be noted that obtaining the residuals between multiple actual packing curves and the target packing curve, and determining the raw material ratio range of the cement-based composite material according to the relationship between the residuals and the residual threshold is to make the actual packing curve closer to the target packing curve, so that the actual packing state is consistent with the theoretical packing state.
[0054] It should be noted that compared with traditional cement-based composite materials, lightweight cement-based composite materials have a lower apparent density and the same or higher compressive strength. For example, the apparent density of traditional ultra-high performance cement-based composite materials is 2400 - 2500 kg / m 3 , and the compressive strength is 120 - 160 MPa, while the apparent density of lightweight ultra-high performance cement-based composite materials is 2050 - 2150 kg / m 3 , and the compressive strength is 110 - 140 MPa.
[0055] Combined with the first aspect, in some embodiments provided in the present application, as Figure 2 shown, the determining of the raw material ratio of the cement-based composite material according to the relationship between the residuals and the residual threshold includes:
[0056] S401. If the residual meets the residual threshold, establish a first correspondence relationship between the compressive strength of the cement-based composite material specimen and the apparent density of the cement-based composite material specimen and the content of ceramsite sand and the pre-wetted water amount of ceramsite sand in the raw materials of the cement-based composite material;
[0057] S402. Determine the content of ceramsite sand and the pre-wetted water amount of ceramsite sand in the raw materials of the cement-based composite material according to the first correspondence relationship.
[0058] Since the parameters most relevant to the strength of cement-based composites are the content of ceramic sand and the pre-wetting water amount of ceramic sand, and the apparent density is a significant characteristic of lightweight cement-based composites, by establishing a first correspondence relationship between the compressive strength of cement-based composite specimens, the apparent density of cement-based composite specimens, and the content of ceramic sand and the pre-wetting water amount of ceramic sand in the raw materials of cement-based composites, and determining the content of ceramic sand and the pre-wetting water amount of ceramic sand in the raw materials of cement-based composites according to the first correspondence relationship, it is possible to determine the content of ceramic sand and the pre-wetting water amount of ceramic sand in the raw materials of cement-based composites on the premise of meeting the maximum compressive strength and the minimum apparent density. If the residual satisfies the residual threshold, it means that the residuals between multiple actual packing curves and the target packing curve are within an acceptable range. For example, if the residual is ±10%, it is considered that the residual satisfies the residual threshold. The residual reflects the deviation degree between the actual packing curve and the preset target packing curve. The smaller the absolute value of the residual, the smaller the deviation, and the larger the absolute value of the residual, the larger the deviation.
[0059] It should be noted that the content of ceramic sand refers to the mass ratio of ceramic sand in the entire raw materials of cement-based composites, and the pre-wetting water amount of ceramic sand refers to the mass ratio of the water added to ceramic sand before preparing cement-based composites to the weight of ceramic sand.
[0060] Combined with the first aspect, in some embodiments provided by the present application, as Figure 3 shown, after determining the content of ceramic sand and the pre-wetting water amount of ceramic sand in the raw materials of cement-based composites according to the correspondence relationship, it further includes:
[0061] S403. Establish a second correspondence relationship between the compressive strength of cement-based composite specimens, the apparent density of cement-based composite specimens, and the particle size ratio of ceramic sand in the raw materials of cement-based composites;
[0062] S404. Determine the particle size ratio of ceramic sand in the raw materials of cement-based composites according to the second correspondence relationship.
[0063] The particle size ratio of ceramic sand will also affect the apparent density and compressive strength of lightweight cement-based composites. By establishing a second correspondence relationship between the compressive strength of cement-based composite specimens, the apparent density of cement-based composite specimens, and the particle size ratio of ceramic sand in the raw materials of cement-based composites, and determining the particle size ratio of ceramic sand in the raw materials of cement-based composites according to the second correspondence relationship, it is possible to determine the particle size of ceramic sand used and the ratio between different particle sizes.
[0064] Combined with the first aspect, in some embodiments provided by the present application, as Figure 4 shown, after determining the particle size ratio of ceramic sand in the raw materials of cement-based composites according to the second correspondence relationship, it further includes:
[0065] S405. Calculate the cost of the raw materials of the cement-based composite material within the particle size ratio of the ceramic sand in the raw materials of the cement-based composite material;
[0066] S406. Determine the raw material ratio of the cement-based composite material according to the cost.
[0067] Since there are multiple formulations within an acceptable range of residuals, when comprehensively considering the apparent density and compressive strength of the cement-based composite material, the dosage of the ceramic sand, the pre-wetting water amount, and the particle size ratio of the ceramic sand can be determined. However, there are still multiple groups of dosages for other components of the raw materials of the cement-based composite material, all of which meet the original requirements of the apparent density and compressive strength. At this time, by calculating the cost and according to the principle of the minimum cost, the final ratio of the raw materials of the cement-based composite material is determined.
[0068] Combined with the first aspect, in some embodiments provided by the present application, the method for establishing the second corresponding relationship includes the statistical method. The method of establishing the second corresponding relationship between the compressive strength of the cement-based composite material specimen, the apparent density of the cement-based composite material specimen, and the particle size ratio of the ceramic sand in the raw materials of the cement-based composite material can adopt the physical statistics method, which can more accurately reflect the relationship between the compressive strength of the cement-based composite material specimen, the apparent density of the cement-based composite material specimen, and the particle size ratio of the ceramic sand in the raw materials of the cement-based composite material.
[0069] Combined with the first aspect, in some embodiments provided by the present application, the method for establishing the first corresponding relationship includes the regression method. Using the regression method can quickly determine the dosage of the ceramic sand and the pre-wetting water amount within the formulation range that meets the residual threshold, reduce the test amount, and improve the efficiency.
[0070] Combined with the first aspect, in some embodiments provided by the present application, the raw materials of the cement-based composite material include cement, metal fibers, ceramic sand, admixtures, and water reducers. Metal fibers are usually added to high-strength cement-based composite materials to improve the strength of lightweight cement-based composite materials. The metal fibers include but are not limited to steel fibers, and the admixtures include but are not limited to silica fume, microspheres, etc. It should be noted that when preparing the cement-based composite material, an appropriate amount of water also needs to be added to form a slurry. Usually, the addition amount of water is 6-10% of the total mass of the cement-based composite material. The water reducers include but are not limited to polycarboxylic high-performance water reducers.
[0071] Combined with the first aspect, in some embodiments provided by the present application, in determining the target packing curve of the raw materials of the cement-based composite material according to the particle size and density of the raw materials of the cement-based composite material: The method for determining the target packing curve of the raw materials of the cement-based composite material includes the close packing theory mathematical model method. Using the close packing theory mathematical model can quickly establish the target packing curve, reduce the experimental amount, and improve the efficiency.
[0072] In combination with the first aspect, in some embodiments provided by the present application, the method for obtaining the actual packing curve of the raw materials of cement-based composites under multiple raw material ratios of cement-based composites includes the sieving method, and the actual packing curve is more accurate using the sieving method.
[0073] In combination with the first aspect, in some embodiments provided by the present application, the method for obtaining the residuals between multiple actual packing curves and a target packing curve includes the least squares method. Using the least squares method can quickly determine the residuals between the actual packing curve and the target packing curve, improving efficiency.
[0074] The technical solutions provided by the present application will be described in detail below in conjunction with embodiments.
[0075] Example 1
[0076] Composition of raw materials for lightweight ultra-high performance cement-based composites: Cement (particle size 10 - 30um, density 3 - 3.15 g / cm 3 ), microfilament copper-plated steel fiber (length 13 - 16mm, density 77850 kg / m 3 , diameter 0.15 - 0.25mm), silica fume (particle size 0.1 - 0.2μm, density 2.2 - 2.3 g / cm 3 ), composite admixture formed by fly ash microspheres (particle size 20 - 150μm, density 0.1 - 0.6 g / cm 3 ), porous shale ceramsite (particle size 0 - 4.75mm, density 1489 kg / m 3 ), water reducing agent (polycarboxylate superplasticizer).
[0077] The target packing curve particle close packing theoretical model of the proportion of each raw material component is determined, and the mathematical formula of the model is:
[0078]
[0079] Where D i is the particle size, P(D i ) refers to the cumulative fraction (%) of particles smaller than D i , D max is the maximum particle size, D min is the minimum particle size, and q is the packing coefficient. The q value is selected as 0.23 in the experimental design.
[0080] The actual packing curve is measured through a sieve mesh. The specific test method can be obtained by on-site sieving with sieve meshes of different particle sizes. The raw material compositions of cement-based composites with multiple formulations are measured.
[0081] The residuals between the actual packing curves and the target packing curves of multiple cement-based composite material formulations are determined by the least squares method. The mathematical formula of the model is as follows:
[0082]
[0083] Among them, D i i+1 represents a certain grading range of particles; n represents the number of selected particles; P mix and P tar represent the actual packing curve and the target curve between particles respectively; RSS represents the sum of squared residuals.
[0084] Select the cement-based composite material raw material formulations with residuals satisfying ±10% as the candidate formulations. Specifically, as shown in Table 1:
[0085] Table 1 Candidate Formulations of Cement-Based Composite Materials
[0086] <![CDATA[Cement (kg / m 3 )]]> <![CDATA[Composite admixture (kg / m 3 )]]> <![CDATA[Ceramic sand (kg / m 3 )]]> Steel fiber (%) Water-binder ratio <![CDATA[Water reducing agent (kg / m 3 )]]> 790～850 390～430 595～655 1.5～2.5 0.16～0.2 20～30
[0087] Based on the candidate formulations, through the central composite point experimental design method of two factors and two levels, the experimental groups for the influence of the pre-wetting water amount of ceramsite sand and the ceramsite sand content on the apparent density and compressive strength are set as shown in Table 2:
[0088] Table 2 Experimental Groups for the Influence of the Pre-Wetting Water Amount of Ceramsite Sand and the Ceramsite Sand Content on the Apparent Density and Compressive Strength
[0089] Group <![CDATA[Content of pottery sand (kg / m 3 )]]> Pre-wetting water amount of ceramsite sand (%) 1 625 8 2 640 12 3 595 8 4 610 10 5 625 4 6 640 11 7 655 8 8 610 6 9 640 6
[0090] Substitute different pre-wetting water amounts of ceramsite sand and ceramsite sand contents into the dense packing mathematical model, calculate a total of 9 different ratios, and test the apparent density and 28-day test block compressive strength values of the 9 ratios. Specifically, as shown in Table 3:
[0091] Table 3 9 Different Raw Material Ratios of Cement-Based Composite Materials
[0092]
[0093] According to the results of the ratio test, establish the regression equations between the initial apparent density M, the 28-day specimen compressive strength N and the ceramsite sand content (x1, kg / m 3 ), and the pre-wetting water amount of ceramsite sand (x2, %). The obtained functional relationship is as follows:
[0094] M = 12.808x1 + 139.167x2 - 0.200x1x2 - 0.010x1 2 - 0.453x2 2 - 2200.799;
[0095] N=2.138x1-10.667x2+0.024x1x2-0.002x1 2 -0.158x2 2 -467.785;
[0096] The correlation coefficient R2 in the model of apparent density M and compressive strength N reached 85.15% and 88.08% respectively, and the fitting models of the two response values had high accuracy. In addition, when the signal-to-noise ratio is greater than 4, it is appropriate. In this paper, the signal-to-noise ratios of apparent density M and compressive strength N are 4.86 and 5.02 respectively, and the signals are sufficient, so the model can be used to guide the design space.
[0097] The applicability of the model can be evaluated through residual diagnosis. Figure 5 (1) Apparent density and Figure 5 The normal probability distribution diagram of compressive strength in (2) is a graphical expression to verify the two response parameter models. Almost every point is located near the straight line and is roughly distributed in an "S" shape, which shows that the residual data is consistent with the law of normal distribution. The residuals are evenly distributed within the data range of the model, indicating that the model is very stable when it is established and no large drift occurs.
[0098] Figure 6 (1) is the 3D response surface diagram of the apparent density, Figure 6 (2) is the 3D response surface diagram of compressive strength, Figure 6 (3) is the contour map of apparent density, Figure 6 (4) is the contour map of compressive strength, which clearly shows the influence of the input variables: clay sand content and clay sand pre-wetting water volume on the two response parameters. The response surface has a certain curvature and the color transition is smooth, which shows that the clay sand content and clay sand pre-wetting water volume have a significant effect on the two response parameters, but the significance of the clay sand pre-wetting water volume on the response parameters of apparent density and compressive strength is greater than that of the clay sand content, because both surfaces are steep relative to the clay sand pre-wetting water volume, but gentle relative to the clay sand content. The shape of the contour lines reflects the strength of the interaction between the input variables. The contour lines are all elliptical, indicating that the interaction between the clay sand content and the clay sand pre-wetting water volume has a significant effect on the fracture parameters.
[0099] The clay sand dosage, clay sand pre-wetting water volume, compressive strength and apparent density are jointly solved to meet the following requirements:
[0100] M=12.808x1+139.167x2-0.200x1x2-0.010x1 2 -0.453x2 2 -2200.799;
[0101] N=2.138x1-10.667x2+0.024x1x2-0.002x12 -0.158x2 2 -467.785;
[0102] M ≥ 115;
[0103] N ≤ 2150;
[0104] 595 ≤ x1 ≤ 655;
[0105] 6 ≤ x2 ≤ 12.
[0106] The obtained x1 is 640 kg / m 3 and x2 is 11%, that is, the content of ceramic sand is 640 kg / m 3 and the pre-wetted water amount of ceramic sand is 11%. The optimization results are as Figure 7 shown. The raw material formula of the cement-based composite material that meets the requirements is shown in Table 4:
[0107] Table 4 Raw material formula of the cement-based composite material that meets the requirements
[0108]
[0109] A continuous gradation of aggregates with reasonable matching of different sizes of particles can obtain the minimum aggregate void ratio and achieve the effect of dense packing. To further optimize the mix ratio of lightweight ultra-high performance cement-based composites, the gradation ratios of coarse and fine ceramic sand aggregates are adjusted. Based on Group 1 of the optimized mix ratio in Table 4, a mix ratio system under different ceramic sand gradations is prepared, with a total of five groups. The slump flow, apparent density, compressive strength, elastic modulus, and flexural strength of the lightweight ultra-high performance cement-based composites with different ceramic sand gradation mix ratios are obtained. The test results are as Figure 8 (1) and Figure 8 (2) shown.
[0110] For lightweight ultra-high performance cementitious composites with different fine aggregate gradations, both the slump flow and apparent density increase with the increase in the proportion of fine sand, while the compressive strength, flexural strength, and elastic modulus first increase and then decrease with the increase in the proportion of fine sand. Increasing the content of fine sand can improve the workability of the LUHPC mixture to a certain extent. In addition, the higher the proportion of fine sand in the particle size gradation, the better the mechanical properties. This is because after the fine sand is crushed into smaller particles, there are fewer internal defects, but the apparent density also increases. Mixing coarse sand and fine sand can optimize the gradation and make the packing degree inside the LUHPC more dense. Lightweight aggregate cementitious composites are prone to problems such as insufficient flexural strength and elastic modulus. Although the fine sand with a smaller particle size reduces its own pores after crushing and its strength is improved to a certain extent, the low elastic modulus of the fine sand itself has not changed significantly. In contrast, the slump flows of the fine aggregate gradations (coarse:fine) of 25:75 and 0:100 are 595 mm and 608 mm respectively, and the 28-day compressive strengths are 136.3 Mpa and 134.7 Mpa respectively. In order to achieve better results for lightweight ultra-high performance cementitious composites and meet the design requirements for mechanical properties, the fine aggregate gradation (coarse:fine) of 25:75 is preferably selected as the particle size ratio of the fine sand, where the coarse grade refers to the particle size range of 2 - 4.75 mm, and the fine grade refers to the particle size range of 0.01 - 2 mm.
[0111] Based on the optimized mix ratios in Table 4, the pre-wetting water content of the lightweight aggregates, and the particle size ratios, the costs of different mix ratios are calculated, as shown in Table 5:
[0112] Table 5 Costs of Different Formulations
[0113] Group Cost (yuan / ton) 1 5517.22 2 5483.57 3 5896.49
[0114] Based on the costs in Table 5, the final formulation of the lightweight cementitious composite is shown in Table 6:
[0115] Table 6 Optimal Formulation of Lightweight Cementitious Composite
[0116]
[0117] Among them, the pre-wetting water content of the fine sand is 11%.
[0118] The construction technical process for on-site production of lightweight ultra-high performance cement-based composites is as follows: 1) Premix cement, composite admixture, steel fiber, and water reducer in advance to form a dry mix, and store it in a ton bag for moisture-proof; 2) Conduct pre-wetting treatment on ceramsite sand two hours before mixing, precisely control the amount of pre-wetting water in combination with a water pipe and a flow meter, store the pre-wetted ceramsite sand in a customized tooling bucket, and pay attention to preventing the evaporation of pre-wetting water; 3) Clean the mixing system before LUHPC mixing, use a crane to put the dry mix into the main machine, immediately use a special feeding fixture to lift the tooling bucket to a specified height, pour out the pre-wetted ceramsite sand and put it into the main machine, stir the dry mix and ceramsite sand for one minute, then weigh the required water agent and stir for 4 - 5 minutes. After observing that the mixture reaches an appropriate flow state, subsequent discharging and pouring construction can be carried out.
[0119] In the description of this specification, the description with reference to terms such as "an embodiment / way", "some embodiments / ways", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment / way or example are included in at least one embodiment / way or example of this application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment / way or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments / ways or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments / ways or examples described in this specification and the features of different embodiments / ways or examples.
[0120] It should be noted that in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including", or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article, or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article, or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article, or device including the said element. In this application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.
[0121] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A method for designing a lightweight cement-based composite material formula for composite beams, characterized in that: The following steps are involved: Determine the target stacking curve of the raw materials of cement-based composite materials according to the particle size and density of the raw materials of cement-based composite materials; Obtaining actual accumulation curves of cement-based composite material raw materials under multiple cement-based composite material raw material ratios; Obtaining residuals between a plurality of actual stacking curves and a target stacking curve; According to the relationship between the residual and the residual threshold, the raw material ratio range of cement-based composite materials is determined.
2. The method for designing a formula of a lightweight cement-based composite material for composite beams according to claim 1, characterized in that: Determining the raw material ratio of the cement-based composite material according to the relationship between the residual and the residual threshold comprises: If the residual meets the residual threshold, the first corresponding relationship between the compressive strength of the cement-based composite material specimen and the apparent density of the cement-based composite material specimen and the amount of ceramic sand added in the raw materials of the cement-based composite material and the amount of pre-wetting water of the ceramic sand is established; The amount of ceramic sand added in the raw materials of the cement-based composite material and the amount of pre-wetting water for the ceramic sand are determined according to the first corresponding relationship.
3. The method for designing a formula of a lightweight cement-based composite material for composite beams according to claim 2, characterized in that: After determining the amount of ceramic sand added and the amount of pre-wetting water for the ceramic sand in the raw materials of the cement-based composite material according to the corresponding relationship, the following steps are further included: Establishing the second corresponding relationship between the compressive strength of cement-based composite material specimens and the apparent density of cement-based composite material specimens and the proportion of the ceramic sand particle size in the raw materials of cement-based composite materials; The particle size ratio of ceramic sand in the raw materials of the cement-based composite material is determined according to the second corresponding relationship.
4. The method for designing a formula of a lightweight cement-based composite material for composite beams according to claim 3, characterized in that: After determining the proportion of the ceramic sand particle size in the raw material of the cement-based composite material according to the second corresponding relationship, the method further includes: Calculate the cost of cement-based composite materials within the ceramic sand particle size ratio in the cement-based composite materials raw materials; Determine the raw material ratio of cement-based composite materials based on cost.
5. The method for designing a formula of a lightweight cement-based composite material for composite beams according to claim 3, characterized in that: The method for establishing the second corresponding relationship includes a statistical method.
6. The method for designing a formula of a lightweight cement-based composite material for composite beams according to claim 2, characterized in that: The method for establishing the first corresponding relationship includes a regression method.
7. The method for designing a formula of a lightweight cement-based composite material for composite beams according to claim 1, characterized in that: The raw materials of the cement-based composite material include cement, metal fiber, ceramic sand, admixture and water reducing agent.
8. The method for designing a formula of a lightweight cement-based composite material for composite beams according to claim 1, characterized in that: In the method of determining the target stacking curve of the cement-based composite material raw material according to the particle size and density of the cement-based composite material raw material: the method of determining the target stacking curve of the cement-based composite material raw material includes a close packing theory mathematical model method.
9. The method for designing a formula of a lightweight cement-based composite material for composite beams according to claim 1, characterized in that: The method for obtaining actual stacking curves of cement-based composite material raw materials under multiple cement-based composite material raw material ratios includes a screening method.
10. The method for designing a formula of a lightweight cement-based composite material for composite beams according to claim 1, characterized in that: The method for obtaining residuals between a plurality of actual stacking curves and a target stacking curve comprises a least square method.