Design method of composite cementitious material composition of fast hardening and early strength concrete

Abstract

This application discloses a design method for the composite cementitious material composition of rapid-hardening, early-strength concrete. By selecting the molar ratios of chemical components to meet specific conditions, and using the compressive strength of the cement paste as the response variable, a polynomial regression model is performed on the experimental data to obtain a mathematical model for the composite cementitious material composition design. By setting target content ranges and target compressive strengths for desired components, regression calculations are performed on the mathematical model. Finally, after evaluation combining mathematical methods and the system's packing state, a design mix proportion that meets the requirements for the composite cementitious material composition is obtained. This application's design method, based on its inherent mechanism, can formulate rapid-hardening, early-strength concrete that meets different functional requirements and is suitable for various operating conditions, providing a design basis for rapid-hardening, early-strength concrete materials based on composite cementitious material systems.

Description

Technical Field

[0001] This application belongs to the field of building materials technology, specifically relating to a design method for the composition of composite cementitious materials in fast-hardening, early-strength concrete. Background Technology

[0002] With the construction of highway bridges, the increasing tonnage and traffic volume of vehicles, as well as the rise in overloading and exceeding weight limits, makes road maintenance and repair of highway bridges even more crucial. A comprehensive analysis and investigation of highway bridge defects has revealed that concrete components such as bridge expansion joints, hollow slabs, and abutment slabs have become the most vulnerable parts of highway bridge structures. Due to the repeated impacts of vehicle tonnage, traffic volume, and the loads on highway bridges, coupled with environmental erosion, the service life of concrete components such as bridge expansion joints, hollow slabs, and abutment slabs is far shorter than the design life of highway bridges.

[0003] Currently, steel fiber reinforced concrete is the most commonly used type of concrete for bridge expansion joint transition zones in engineering projects. Steel fiber reinforced concrete is a new type of composite material formed by incorporating randomly distributed short steel fibers into ordinary concrete. The randomly distributed steel fibers can effectively inhibit the propagation of micro-cracks and the formation of macro-cracks in concrete, significantly improving the tensile, flexural, impact, and fatigue resistance of the concrete. Although steel fiber reinforced concrete has become the mainstream choice for bridge expansion joint transition zone concrete due to its superior tensile, flexural, impact, and fatigue resistance properties, and has the widest application range and the largest application ratio, its early performance deficiencies can lead to a waste of traffic resources and negatively impact the effectiveness of repair and maintenance of the expansion joint transition zone concrete.

[0004] Therefore, in the repair and maintenance of highway bridges, concrete should ideally possess the characteristics of rapid hardening and early strength to minimize the waste of traffic resources and the adverse effects of repair and maintenance. In recent years, some scholars have proposed a type of rapid-hardening, early-strength concrete for repair, such as the invention described in patent announcement CN 103360001 B, which uses 525 early-strength silicate cement as a base and introduces liquid KDSP-1 type composite admixtures to prepare a rapid-hardening, early-strength concrete for repair. However, this invention uses a single type of cement, which cannot be well-suited for formulation design based on actual working conditions, and it is only applicable to cement concrete pavements, lacking widespread applicability.

[0005] Rapid-hardening, early-strength concrete using a single cement system typically has limitations. Silicate cement is currently the main cementitious material in concrete production, but its production consumes significant resources and energy, causing severe environmental pollution. The continuous rise in cement prices has also led to a significant increase in concrete costs. From the perspectives of energy conservation, environmental protection, and cost savings, there is an urgent need to find more suitable cementitious materials. Sulfoaluminate cement, as a low-energy-consumption cement, not only has low carbon dioxide emissions during production but also possesses advantages such as high early strength, rapid strength development, and erosion resistance, attracting widespread attention in the industry. In recent years, some scholars have proposed a composite cementitious material based on sulfoaluminate cement and silicate cement. For example, the composite cementitious material used in authorization announcement number CN 105884239 A is based on sulfoaluminate cement, with the introduction of an appropriate amount of silicate cement. Furthermore, for the sulfoaluminate cement-silicate cement composite system, a pre-prepared admixture is introduced to modify it, thereby achieving a sulfoaluminate cement-silicate cement-based rapid-hardening, early-strength concrete. This invention does not provide a composition design method for composite cementitious materials, and its focus is on proposing an admixture for a sulfoaluminate cement-silicate cement composite system to achieve rapid-hardening and early-strength concrete. Therefore, this invention does not have promotional value.

[0006] With the rapid development of transportation and the surge in traffic volume, bridges are not only prone to damage to expansion joint devices, but also experience varying degrees of wear and tear on their expansion joint anchorage zones, approach slabs, piers, and concrete crash barriers. Therefore, it is necessary to develop a design method for a universal composition of composite cementitious materials based on a composite cement system—specifically, rapid-hardening, early-strength concrete—that can be used not only in the transition zone of bridge expansion joints to meet relevant design requirements, but also for general concrete components of bridges. Summary of the Invention

[0007] The purpose of this application is to overcome the shortcomings of the prior art and provide a design method for the composition of composite cementitious materials for fast-hardening and early-strength concrete. This addresses the technical problem that existing fast-hardening and early-strength concrete composite cementitious materials have limited applicable working conditions and lack a universal design method for the composition of composite cementitious materials based on composite cement systems that can adapt to different working conditions and meet different functional requirements.

[0008] To achieve the aforementioned objectives, this application provides a design method for the composition of composite cementitious materials in fast-setting, high-strength concrete, comprising the following steps:

[0009] The components of the composite cementitious material for rapid-hardening and early-strength concrete are selected, and the molar contents of SiO2, Al2O3, CaO and SO3 in the composite cementitious material satisfy the following relationship: SiO2:Al2O3:CaO:SO3=0.57~0.83 :0.07~0.17 :0.52~0.72 :0~0.02;

[0010] Using the content of each selected component as the independent variable, the proportion of each component in each group of experiments was designed based on the D-optimal design principle. Response surface methodology was adopted, with the compressive strength Y1 on day T1 and the compressive strength Y2 on day T2 of the cementitious paste made from the composite cementitious material as the dependent variables. Mathematical relationships between Y1 and the content of each component, and between Y2 and the content of each component were established for each group of experimental data. Polynomial fitting regression was performed to obtain a mathematical model for the composition design of the composite cementitious material, and a mathematical evaluation was conducted to ensure the accuracy and reliability of the mathematical model.

[0011] The target content range of each component, as well as the target compressive strength Y1 and target compressive strength Y2, are set. The content of each component that meets the requirements is solved using the mathematical model that satisfies the mathematical evaluation conditions. The packing state of the system is evaluated to avoid internal defects caused by poor packing state, which would affect the performance of the composite cementitious material.

[0012] The multi-evaluation system for the composite cementitious material composition design consists of a mathematical evaluation of the model before solving and an evaluation of the system packing state of the solution results after solving.

[0013] Furthermore, each of the components includes cement component A, cement component B, silica fume, fly ash microspheres, and mineral powder.

[0014] Furthermore, the cement component A includes at least one of the following: P.II 52.5 strength grade silicate cement, PO 52.5 ordinary silicate cement, slag silicate cement, pozzolanic silicate cement, fly ash silicate cement, and composite silicate cement.

[0015] Furthermore, the cement component B includes at least one of sulfoaluminate cement, aluminate cement, and ferroaluminate cement of strength grade 42.5.

[0016] Furthermore, the silica fume has a SiO2 mass content of not less than 98% and a specific surface area of ​​not less than 15500 m². 2 / kg, with an activity index of not less than 100% after 28 days.

[0017] Furthermore, the fly ash microspheres have a loss on ignition of no more than 5%, a water requirement ratio of no more than 90%, and a spherical particle volume fraction of no less than 95%.

[0018] Furthermore, the mineral powder is of grade S105 or higher, and has a specific surface area of ​​not less than 500 m². 2 / kg, with an activity index of not less than 95% at 7 days and not less than 105% at 28 days.

[0019] Furthermore, cement component A is P.II 52.5 strength grade silicate cement; cement component B is 42.5 strength grade sulfoaluminate cement; the silica fume has a SiO2 mass content of not less than 98% and a specific surface area of ​​not less than 15500 m². 2 / kg, with a 28-day activity index of not less than 100%; the fly ash microspheres have a loss on ignition of not more than 5%, a water requirement ratio of not more than 90%, and a spherical particle volume fraction of not less than 95%; the mineral powder is of S140 grade, with a 28-day activity index of not less than 140%.

[0020] Furthermore, the D-optimal design principle is as follows:

[0021] Construct an information matrix M, M=F T F(x) is obtained by maximizing the determinant of the information matrix M, thus satisfying the condition.

[0022] Where F(x) = ;

[0023] In the formula, x1, x2, ..., x N These represent the first, second, ..., Nth groups of trials, respectively, f m (x N ) represents the content of the m-th component in the composite cementitious material in the N-th group of tests.

[0024] Further, the composite cementitious material contains the following components in the following mass ratios: cement component A 0.2-0.7, cement component B 0-0.3, silica fume 0.1-0.2, fly ash microspheres 0.1-0.2, mineral powder 0.03-0.2, and the total mass ratio of cement component A to cement component B is 0.5-0.7;

[0025] The mathematical model is as follows:

[0026] Y1=7.32449A-130.985B-432.351C+753.024D-211.931E+337.515AB+658.449AC-1066. 3AD+201.289AE+1036.36BC-966.881BD+361.133BE-623.808CD+1027.07CE-578.778DE;

[0027] Y2=198.088A-81.8649B+1345.02C+1020.64D+106.583E+293.373AB-2083.06AC-1440.7 5AD-147.007AE-1838.27BC-1242.74BD+93.6159BE-2774.53CD-1297.46CE-1314.97DE;

[0028] In the formula, A is the mass percentage of cement component A, B is the mass percentage of cement component B, C is the mass percentage of silica fume, D is the mass percentage of fly ash microspheres, E is the mass percentage of mineral powder, Y1 is the compressive strength on day 1, and Y2 is the compressive strength on day 28.

[0029] Furthermore, the paste is prepared by the following method:

[0030] Weigh each of the components according to the D-optimal design ratio;

[0031] The components are dry-mixed.

[0032] Add a water-reducing agent to the dry-mixed mixture and then perform wet mixing;

[0033] After the wet-mixed slurry is placed in a mold, vibrated, cured in a thin film, and then demolded, it is finally cured according to standard or steam curing until the specified age to obtain the composite cementitious slurry.

[0034] Furthermore, the water-reducing agent is a polycarboxylate high-efficiency water-reducing agent with a water reduction rate of 25-30%.

[0035] Furthermore, the response surface methodology is aided by one of the following software programs: Design-Expert, Minitab, or JMP.

[0036] Compared with the prior art, this application has the following technical effects:

[0037] This application discloses a design method for the composition of a composite cementitious material in rapid-hardening, early-strength concrete. The method utilizes a cement-blended system to prepare rapid-hardening, early-strength concrete without adding rapid-hardening, early-strength admixtures. Rapid hardening and early strength are effectively achieved from the cementitious material system itself. The method selects each component of the composite cementitious material by determining the molar ratio of chemical components to meet specific conditions. Using the compressive strength of the cement paste as the response variable, a polynomial regression model is performed on the experimental data to obtain a mathematical model for the composite cementitious material composition design. This model is then mathematically evaluated to ensure its accuracy and reliability. By setting target content ranges and target compressive strengths for desired components, regression calculations are performed on the mathematical model to obtain the design ratio of the composite cementitious material composition that meets the requirements. The system's packing state is evaluated to avoid internal defects caused by poor packing state, which could affect the performance of the composite cementitious material.

[0038] The design method of this application selects the components of the composite cementitious material by adjusting the molar ratio of chemical components, thereby controlling its hydration products within a certain range. This limits the range of constituent components from the perspective of hydration mechanism, and thus limits the f in the D-optimal design principle. m (x N By defining the content range represented by [missing information], the linear algebraic calculations of its information matrix M are simplified, reducing computational threads and optimizing the experimental design calculation process, thus enabling more precise preparation of fast-hardening, early-strength concrete that meets specific design requirements. Simultaneously, by combining mathematical and system packing state multiple evaluations, multi-dimensional control methods are used to formulate composite cementitious materials that can meet different functional requirements and are suitable for different service conditions. This provides a design basis for fast-hardening, early-strength concrete materials based on composite cementitious material systems, and is of great significance for their promotion and application. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 A flowchart illustrating a design method for the composition of composite cementitious materials in a fast-hardening, early-strength concrete, as provided in an embodiment of this application.

[0041] Figure 2 A flowchart illustrating the preparation of a neat paste from a composite cementitious material, as provided in this application embodiment;

[0042] Figure 3Internal scanning electron microscope (SEM) micrograph of the paste prepared in test group 17 after 28 days of hardening and molding, as provided in the embodiments of this application;

[0043] Figure 4 This is a comparison chart showing the predicted and actual values ​​of the mechanical properties of cementitious paste in 25 experimental groups, based on the design method for the composition of composite cementitious materials in a fast-hardening, early-strength concrete according to an embodiment of this application. Detailed Implementation

[0044] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0045] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0046] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0047] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0048] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0049] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a well-known unit of mass in the chemical industry, such as µg, mg, g, or kg.

[0050] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0051] This application provides a design method for the composition of composite cementitious materials in rapid-hardening, early-strength concrete. The overall process is as follows: Figure 1 As shown, it includes the following steps:

[0052] (1) Select the components of the composite cementitious material for rapid-hardening and early-strength concrete. The molar contents of SiO2, Al2O3, CaO and SO3 in the composite cementitious material of rapid-hardening and early-strength concrete should satisfy the following relationship: SiO2:Al2O3:CaO:SO3=0.57~0.83 : 0.07~0.17 : 0.52~0.72 : 0~0.02. That is, the molar contents of SiO2, Al2O3, CaO and SO3 in the composite cementitious material composed of each component need to satisfy the above relationship. By controlling the content relationship of each compound in the composite cementitious material as a whole, the hydration reaction of each component in the composite cementitious material during the subsequent mixing process can be controlled, thereby controlling the type and content of the hydration products generated. Limit the range of components from the perspective of hydration mechanism, thereby limiting the f in the D-optimal design principle. m (x N By defining the content range represented by ), the linear algebraic calculations of its information matrix M are simplified, the number of computational threads is reduced, and the calculation process of experimental design is optimized, so as to more accurately prepare fast-hardening and early-strength concrete that meets specific design requirements.

[0053] In this embodiment, the selected components include cement component A, cement component B, silica fume, fly ash, and mineral powder. Specifically, cement component A can be at least one of the following: P.II 52.5 strength grade silicate cement, PO 52.5 ordinary silicate cement, slag silicate cement, pozzolanic silicate cement, fly ash silicate cement, and composite silicate cement; cement component B can be at least one of the following: 42.5 strength grade sulfoaluminate cement, aluminate cement, and ferroaluminate cement; the silica fume has a SiO2 mass content of not less than 98% and a specific surface area of ​​not less than 15500 m². 2 / kg, 28-day activity index not less than 100%; fly ash microspheres loss on ignition not greater than 5%, water requirement ratio not greater than 90%, spherical particle volume fraction not less than 95%; mineral powder not lower than S105 grade, specific surface area not less than 500 m² 2 / kg, with an activity index of not less than 95% at 7 days and not less than 105% at 28 days.

[0054] (2) Using the content of each selected component as the independent variable, the proportion of each component in each group of experiments is designed based on the D-optimal design principle. The response surface design method is adopted. Specifically, one of the software, Design-Expert, Minitab, or JMP, can be used for auxiliary design. The compressive strength Y1 on day T1 and the compressive strength Y2 on day T2 of the cementitious paste made of composite cementitious material are used as dependent variables (i.e. response variables). The mathematical relationship between Y1 and the content of each component, and the mathematical relationship between Y2 and the content of each component are established for each group of experimental data. Polynomial fitting regression is performed to obtain the mathematical model for the composition design of composite cementitious material.

[0055] In the embodiments of this application, the selected components are: P.II 52.5 strength grade silicate cement A; 42.5 strength grade sulfoaluminate cement B; SiO2 mass content not less than 98%, specific surface area not less than 15500 m². 2 / kg, silica fume C with an activity index of not less than 100% after 28 days; fly ash D with a fly ash microsphere loss on ignition of not more than 5%, a water requirement ratio of not more than 90%, and a spherical particle volume fraction of not less than 95%; mineral powder E with S140 grade and an activity index of not less than 140% after 28 days.

[0056] The molar contents of SiO2, Al2O3, CaO, and SO3 in the composite cementitious material of rapid-hardening and early-strength concrete are set to meet the following relationship: SiO2:Al2O3:CaO:SO3=0.57~0.83 : 0.07~0.17 : 0.52~0.72 : 0~0.02. The content (mass ratio) ranges of the five selected components A, B, C, D, and E are set as shown in Table 1 below.

[0057] Table 1

[0058]

[0059] In Table 1 above, the content range of silicate cement A is 0.2-0.7%, the content range of sulfoaluminate cement B is 0-0.3%, the content range of silica fume C is 0.1-0.2%, the content range of fly ash microspheres D is 0.1-0.2%, and the content range of mineral powder E is 0.03-0.2%. The total content of silicate cement A and sulfoaluminate cement B ranges from 0.5-0.7%. The total content of the composite cementitious material (i.e., A+B+C+D+E) is set to 1, and the contents of each independent variable are mutually constrained.

[0060] The D-optimal design principle of this application embodiment is:

[0061] Construct an information matrix M, M=F T F(x) is a matrix that maximizes the determinant of the information matrix M, thus yielding a F(x) that satisfies the condition.

[0062] Where F(x) = ;

[0063] In the formula, x1, x2, ..., x N These represent the first, second, ..., Nth groups of trials, respectively, f m (x N ) represents the content of the m-th component in the composite cementitious material in the N-th group of tests.

[0064] Specifically, the embodiments of this application designed a total of 1, 2, ..., 25 sets of tests. The composite cementitious material contains five components: A, B, C, D, and E. f1(x1) can represent the content of the first component (A) in the first set of tests, f2(x1) can represent the content of the second component (B) in the first set of tests, and so on.

[0065] The content ratios of each component in the 25 groups of experiments designed based on the D-optimal design principle are shown in Table 2 below.

[0066] Table 2

[0067]

[0068] In order to obtain a composite cementitious material system for rapid-hardening and early-strength concrete, T1 in this application embodiment is set to 1, that is, the compressive strength Y1 of the cement paste prepared by the composite cementitious material is tested on the first day. In order to obtain a rapid-hardening and early-strength concrete with durable performance, T2 in this application embodiment is set to 28, that is, the compressive strength Y2 of the cement paste prepared by the composite cementitious material is tested on the 28th day. It should be noted that T1 and T2 can also be other values, depending on the design requirements, and are not limited to the embodiments of this application.

[0069] The paste used in this application embodiment is prepared by the following method, and the overall preparation process is as follows: Figure 2 As shown:

[0070] (a) Weigh the components of each weight portion according to the 25 formulations designed by D-optimal above;

[0071] (b) Dry mix the weighed components of each group. Specifically, pour each component of each group into a planetary paste mixer and mix slowly for 2 minutes.

[0072] (c) Add an appropriate amount of water and water-reducing agent to the dry-mixed mixture and perform wet mixing. Specifically, dissolve the water-reducing agent in water and make it fully dissolved and mixed. Then pour about half of the amount into a planetary paste mixer and stir slowly for 3 minutes. Then add the remaining amount into the planetary paste mixer and stir slowly for 3 minutes.

[0073] (d) After wet mixing, the slurry is placed in a mold, vibrated, cured in a film, and then demolded. Finally, it is cured in a standard manner or steamed until the specified age to obtain the neat slurry.

[0074] The compressive strength Y1 test was conducted on the mortar prepared in the above 25 test groups on day 1 and day 28 respectively. Two mortar test blocks of 40×40×160 mm prepared in each test group were used as test samples for Y1 and Y2 respectively. The compressive strength test was conducted in accordance with the "Test Method for Strength of Cement Mortar" (GB / T 17671-2021). The test results are shown in Table 3 below.

[0075] Table 3

[0076]

[0077] As shown in Table 3 above, the neat cement paste without sulfoaluminate cement B had no 1-day compressive strength (i.e., Y1=0), indicating that sulfoaluminate cement B is one of the important contributors to the rapid hardening and early strength characteristics of composite cementitious materials. When the neat cement paste (test group 17) reached a 28-day compressive strength of 57.70 MPa, most of the fly ash particles had already hydrated, and the surface CSH gel layer was relatively thick. Under the action of Ca(OH)2 and gypsum, the fly ash particles continuously deagglomerated, releasing [SiO4]. 4- [AlO4] 5- Plasma groups and Ca 2+ SO4 4- This process forms gelling hydration products such as CSH gel, CSH gel, and AFt. By controlling the Ca / Si ratio, a CSH gel with an even lower Ca / Si ratio is generated, and a large amount of Al is dissolved in it. 3+ and Fe 3+ Mg 2+ Plasma is used to achieve a dense structure. CSH gel forms on the surface of fly ash particles and binds various microparticles in the system together, while ettringite fills the pores, making the structure dense.

[0078] Scanning electron microscopy (SEM) was performed on the paste sample (on day 28) prepared in test group 17 above, and its microscopic images are shown below. Figure 3 As shown, Figure 3 The study observed that a large amount of CSH gel was found in the microstructure of the concrete paste in the later stages, while ettringite was less abundant in the early stages, mainly generated by the pozzolanic reaction of later mineral admixtures. The internal pores were effectively filled by the highly alkaline hydrated calcium silicate gel and ettringite generated by the later pozzolanic reaction, resulting in improved matrix density and providing a foundation for mechanical strength.

[0079] For each group of experimental data, mathematical relationships were established between Y1 and the content of each component, and between Y2 and the content of each component. Design-Expert software was used to perform polynomial fitting regression on the experimental data to obtain a mathematical model for the composition design of the composite cementitious material.

[0080] Y1=7.32449A-130.985B-432.351C+753.024D-211.931E+337.515AB+658.449AC-1066. 3AD+201.289AE+1036.36BC-966.881BD+361.133BE-623.808CD+1027.07CE-578.778DE;

[0081] Y2=198.088A-81.8649B+1345.02C+1020.64D+106.583E+293.373AB-2083.06AC-1440.7 5AD-147.007AE-1838.27BC-1242.74BD+93.6159BE-2774.53CD-1297.46CE-1314.97DE;

[0082] In the formula, A is the mass percentage of silicate cement, B is the mass percentage of sulfoaluminate cement, C is the mass percentage of silica fume, D is the mass percentage of fly ash, E is the mass percentage of mineral powder, Y1 is the compressive strength on day 1, and Y2 is the compressive strength on day 28.

[0083] The mathematical model obtained above is subjected to multiple evaluations of mathematical modeling and system packing state, using R... 2 Adj-R 2 The evaluation was conducted using multiple evaluation indicators, including F-value, P-value, and signal-to-noise ratio. The evaluation results are shown in Table 4 below.

[0084] Table 4

[0085]

[0086] As shown in Table 4 above, the mathematical model for the composite cementitious material composition design has the lowest F-value (8.82) and all P-values ​​are less than 0.01%, indicating that the mathematical model is highly significant and that the independent variables can effectively predict changes in the response variable; the coefficient of determination R0 2 and the corrected coefficient of determination Adj-R 2 The values ​​are as high as 0.9348 and 0.8436 respectively, indicating that the model has a good fit and good reliability and prediction accuracy; and the signal-to-noise ratio of the compressive strength model is the lowest at 8.9102. Both are greater than 4, indicating that the mathematical model has good applicability.

[0087] Figure 4 This is a comparison chart showing the predicted and actual values ​​of the mechanical properties of neat cement paste in 25 experimental groups, based on the design method for the composition of composite cementitious materials in a fast-hardening, early-strength concrete according to an embodiment of this application. Figure 4 In the graph, the horizontal axis represents the measured strength value of the experimental group (MPa), and the vertical axis represents the predicted value (MPa) calculated using the mathematical model described above. Each point in the graph represents an experimental group. When a point is located on the diagonal of the graph, it indicates that the measured strength value of that experimental group equals the value calculated by the mathematical model. Figure 4 The distribution of each point along the diagonal can be observed and analyzed. Figure 4 This indicates that the mathematical model obtained from the embodiments of this application has a high degree of reliability in its calculation and prediction.

[0088] The target content ranges of each component, as well as the target compressive strengths Y1 and Y2, are set as shown in Table 5 below. For the composition design of the composite cementitious material that meets specific requirements, the above mathematical model is used to solve the multi-objective constraints and obtain the design content (proportion) of each component that meets specific requirements, as shown in Table 6 below.

[0089] Table 5

[0090]

[0091] Table 6

[0092]

[0093] Table 6 above lists the content ratios of each component in three groups of composite cementitious materials that meet specific requirements. Among them, the composite cementitious material designed in Group 1 (expected value = 1) has the best performance that meets or is closest to the specific requirements.

[0094] The MAA model was used to evaluate the packing status of the three groups of composite cementitious materials that meet the specific requirements. The calculation results are shown in Table 7 below.

[0095] MAA model: ;

[0096] In the formula, P(D) represents the cumulative percentage of residue on the sieve when the particle size is D, and D... max For the maximum particle size, D min Let q be the minimum particle size and q be the distribution modulus (taken as 0.23).

[0097] Table 7

[0098]

[0099] Table 7 shows that the packing ratio of the desired composite cementitious material (meeting specific requirements) has a total mean square of 338.331 with the MAA model, an F-value of 0.189, and a probability greater than F of 0.904, indicating that at the 0.05 level, the overall values ​​are not significantly different and exhibit good consistency. Multiple comparison analyses of groups 1, 2, and 3 with the MAA model show a high probability of 0.946, indicating a high fit. The homogeneity of variance test has a total mean square of 11.972, an F-value of 0.056, and a probability greater than F of 0.983, further demonstrating that the overall values ​​are not significantly different and exhibit good consistency. The packing ratio of the desired composite cementitious material exhibits excellent compact packing. Therefore, the packing ratio of the desired composite cementitious material is consistent with the design ratio of the target composite cementitious material.

[0100] Table 8

[0101]

[0102] The experiment was conducted according to the expected mix proportions in Group 1 of Table 6, and the measured 1-day compressive strength Y1 and 28-day compressive strength Y2 were obtained, as shown in Table 8. The data in Table 8 show that the measured values ​​fully meet the expected predicted values, demonstrating that the performance of the composite cementitious material designed in Group 1 (expected value = 1) does indeed meet the specific requirements.

[0103] This application discloses a method for designing the composition of a composite cementitious material for rapid-hardening, early-strength concrete. This method utilizes a cement-blended system to prepare rapid-hardening, early-strength concrete without adding any rapid-hardening, early-strength admixtures. Rapid hardening and early strength are effectively achieved from the cementitious material system itself. The method selects each component of the composite cementitious material by determining the molar ratio of chemical components to meet specific conditions. Using the compressive strength of the cement paste as the response variable, a polynomial regression model is performed on the experimental data to obtain a mathematical model for the composite cementitious material composition design. This model is then mathematically evaluated to ensure its accuracy and reliability. By setting the target content range of the desired components and the desired current compressive strength, regression calculations are performed on the mathematical model to obtain the design ratio of the composite cementitious material composition that meets the requirements. The packing state of the system is evaluated to avoid internal defects caused by poor packing state, which could affect the performance of the composite cementitious material.

[0104] The design method of this application selects composite cementitious material components by adjusting the molar ratio of chemical components, thereby controlling their hydration products within a certain range. It utilizes multi-dimensional control methods, combining the hydration mechanism itself with mathematical analysis and system packing state evaluation, to formulate composite cementitious materials that meet different functional requirements and are suitable for various operating conditions, producing fast-setting, early-strength concrete. This provides a design basis for fast-setting, early-strength concrete materials based on composite cementitious material systems, and is of great significance for their widespread application.

[0105] The design method of this application provides a mathematical methodology for the design of composite cementitious materials, enabling rapid hardening and early strength of concrete, improving its performance, and reducing carbon emissions. It is applicable to the rapid repair and replacement of bridge expansion joint transition zones and other concrete components, and has good prospects for widespread application.

[0106] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A design method for the composition of composite cementitious materials in rapid-hardening, high-strength concrete, characterized in that, Includes the following steps: The composite cementitious material for rapid-hardening, early-strength concrete is selected, and each component includes cement component A, cement component B, silica fume, fly ash microspheres, and mineral powder; cement component A is silicate cement of strength grade P.II 52.5; cement component B is sulfoaluminate cement of strength grade 42.5; the composite cementitious material contains the following mass proportions: cement component A 0.2-0.7; cement component B 0-0.3, and not 0; the total mass ratio of cement component A to cement component B is 0.5-0.7; The molar contents of SiO2, Al2O3, CaO, and SO3 in the composite cementitious material satisfy the following ratio: SiO2:Al2O3:CaO:SO3 = 0.57~0.83 : 0.07~0.17 : 0.52~0.72 : 0~0.02; Using the content of each selected component as the independent variable, the proportion of each component in each group of experiments was designed based on the D-optimal design principle. Response surface methodology was adopted, with the compressive strength Y1 on day 1 and the compressive strength Y2 on day 28 of the cementitious paste made from the composite cementitious material as the dependent variables. Mathematical relationships between Y1 and the content of each component, and between Y2 and the content of each component were established for each group of experimental data. Polynomial fitting regression was performed to obtain a mathematical model for the composition design of the composite cementitious material, and the mathematical model was mathematically evaluated. The D-optimal design principle is as follows: Construct an information matrix M, M=F T F(x) is obtained by maximizing the determinant of the information matrix M, thus satisfying the condition. Where F(x) = ; In the formula, x1, x2, ..., x N These represent the first, second, ..., Nth groups of trials, respectively, f m (x N ) represents the content of the m-th component in the composite cementitious material described in the N-th group of tests; Target content ranges for each component, as well as target compressive strengths Y1 and Y2, are set. The content of each component that meets the requirements is calculated using the mathematical model that satisfies the mathematical evaluation conditions. The packing state of the system that meets the requirements is then evaluated. The specific evaluation model is the MAA model, and the expression of the MAA model is: ； In the formula, P(D) represents the cumulative percentage of residue on the sieve when the particle size is D, and D... max For the maximum particle size, D min Let q be the minimum particle size and q be the distribution modulus, with a value of 0.

23.

2. The design method for the composite cementitious material composition of rapid-hardening, early-strength concrete as described in claim 1, characterized in that, The mineral powder is of grade no lower than S105, with a specific surface area of ​​no less than 500 m². 2 / kg, with an activity index of not less than 95% at 7 days and not less than 105% at 28 days.

3. The design method for the composite cementitious material composition of rapid-hardening, early-strength concrete as described in claim 2, characterized in that, The silica fume has a SiO2 content of not less than 98% and a specific surface area of ​​not less than 15,500 m². 2 / kg, with a 28-day activity index of not less than 100%; the fly ash microspheres have a loss on ignition of not more than 5%, a water requirement ratio of not more than 90%, and a spherical particle volume fraction of not less than 95%; the mineral powder is of S140 grade, with a 28-day activity index of not less than 140%.

4. The design method for the composite cementitious material composition of rapid-hardening, early-strength concrete as described in claim 1, characterized in that, The composite cementitious material also contains the following components in the indicated mass ratios: 0.1-0.2% silica fume, 0.1-0.2% fly ash microspheres, and 0.03-0.2% mineral powder; The mathematical model is as follows: Y1=7.32449A-130.985B-432.351C+753.024D-211.931E+337.515AB+658.449AC-1066. 3AD+201.289AE+1036.36BC-966.881BD+361.133BE-623.808CD+1027.07CE-578.778DE; Y2=198.088A-81.8649B+1345.02C+1020.64D+106.583E+293.373AB-2083.06AC-1440.7 5AD-147.007AE-1838.27BC-1242.74BD+93.6159BE-2774.53CD-1297.46CE-1314.97DE; In the formula, A is the mass percentage of cement component A, B is the mass percentage of cement component B, C is the mass percentage of silica fume, D is the mass percentage of fly ash microspheres, E is the mass percentage of mineral powder, Y1 is the compressive strength on day 1, and Y2 is the compressive strength on day 28.

5. The design method for the composite cementitious material composition of rapid-hardening, early-strength concrete as described in claim 1, characterized in that, The paste is prepared according to the following method: Weigh each of the components according to the D-optimal design principle; The components are dry-mixed. Add water and a water-reducing agent to the dry-mixed mixture and perform wet mixing; After the wet-mixed slurry is placed in a mold, vibrated, cured in a thin film, and then removed from the mold, it is finally cured according to standard or steam curing until the specified age to obtain the neat slurry.

6. The design method for the composite cementitious material composition of rapid-hardening, early-strength concrete as described in any one of claims 1-5, characterized in that, The response surface methodology can be assisted by any one of the following software: Design-Expert, Minitab, or JMP.

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