Method for determining high fly ash concrete adiabatic temperature rise
By combining experimental and simulation methods, the adiabatic temperature rise parameters of high fly ash concrete were obtained, which solved the problem of large simulation error in the existing technology and realized the accurate simulation of temperature change of high fly ash concrete.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA INST OF WATER RESOURCES & HYDROPOWER RES
- Filing Date
- 2022-11-01
- Publication Date
- 2026-06-26
AI Technical Summary
Existing technologies are insufficient to accurately simulate the heating process of high fly ash concrete at various stages, especially the later heating caused by fly ash hydration, which leads to significant errors in simulation analysis.
The thermal conductivity, thermal conductivity, density, specific heat, linear expansion coefficient, and Poisson's ratio of high fly ash concrete were obtained through experiments. Combined with simulation calculations and measured temperature data, regression analysis was used to obtain the adiabatic temperature rise parameters of the latter half of the model, and a complete temperature rise formula was derived for accurately simulating concrete temperature changes.
It achieves an accurate reflection of temperature changes in concrete with high fly ash content, taking into account both early and late stages, thus improving simulation accuracy and reducing errors.
Smart Images
Figure CN115828516B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of concrete research, and in particular relates to a method for determining the adiabatic temperature rise of concrete with high fly ash content. Background Technology
[0002] In the construction of concrete dams, temperature load is a major factor affecting the safety of the dam body. During the construction and operation phases, the dam often experiences significant tensile stress due to temperature changes within the dam structure, leading to cracks. With the development of concrete technology, new varieties and processes of concrete materials are constantly emerging. In hydropower projects, the application of high-fly ash concrete will become more widespread. Its hydration heat characteristics and temperature deformation directly affect the dam structure, temperature control, and joint grouting effect.
[0003] Current concrete adiabatic temperature rise parameters are fitted using 28-day experimental results, which often differ from actual adiabatic temperature rise parameters in engineering projects. Therefore, it is necessary to use simulation analysis programs to perform inverse analysis of the concrete adiabatic temperature rise using measured temperatures at multiple measuring points on the dam. This will minimize the error between the temperature distribution calculated in the forward analysis and the measured temperature distribution at the selected measuring points. Only then can the obtained concrete adiabatic temperature rise parameters be used for concrete temperature stress calculation and analysis.
[0004] However, for concrete with high fly ash content or concrete with slow heat generation, the hydration of fly ash depends on the hydration products of cement and is slow. Current adiabatic temperature rise testing equipment cannot fully reflect the heat of hydration of fly ash in the later stages. Commonly used adiabatic temperature rise models in simulation analysis, whether exponential, logarithmic, or maturity-based, cannot accurately reflect the later-stage heat generation of concrete caused by the delayed hydration of fly ash. If the early-age period is considered, the later-stage error is large; if the later-stage error is reduced, the early-stage error becomes significant. Therefore, it is impossible to accurately simulate the heat generation of concrete with high fly ash content at various stages, especially the later-stage heat generation caused by fly ash hydration. Summary of the Invention
[0005] To overcome the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a method for determining the adiabatic temperature rise of high fly ash concrete, which can accurately reflect the temperature change of high fly ash concrete, take into account both early and late stages, and simulate the actual hydration heat process of high fly ash concrete more flexibly and accurately.
[0006] The technical solution of this invention is: a method for determining the adiabatic temperature rise of concrete with high fly ash content, comprising the following steps:
[0007] (1) Through experiments, the thermal conductivity, thermal conductivity, density, specific heat, linear expansion coefficient, and Poisson's ratio of high fly ash concrete were obtained; then, the initial adiabatic temperature rise parameters of high fly ash concrete were obtained through adiabatic temperature rise tests.
[0008] (2) According to the model First, the first part of the model is determined. Using measured data of the dam body and combined with simulation calculations, the first part of the model is obtained:
[0009] (3) Using thermometers pre-embedded in the structure, the temperature rise of the concrete after reaching the minimum temperature in actual engineering was measured. Based on the relationship between this data and the curing age, the second half of the model was analyzed. Regression analysis was performed to obtain the adiabatic temperature rise parameters of the formula in the latter part of the model: Q2, α2, β2;
[0010] (4) The complete formula is derived: The temperature field of the concrete is then calculated based on this formula.
[0011] This invention first determines the first part of the model. Using measured data of the dam body and combined with simulation calculations, the first part of the model is obtained. Using thermometers pre-embedded in the structure, the temperature rise of concrete after reaching the minimum temperature in actual engineering is measured. Based on the relationship between this data and the age, regression analysis is performed on the second half of the model to obtain the adiabatic temperature rise parameters of the formula for the second half of the model, thus obtaining a complete formula. Based on this formula, the concrete temperature field is calculated. Therefore, it can accurately reflect the temperature change of high fly ash concrete, taking into account both early and late ages, and more flexibly and accurately simulate the actual hydration heat process of high fly ash concrete. Attached Figure Description
[0012] Figure 1 This is a schematic diagram of the three-dimensional calculation model of the power plant dam section.
[0013] Figure 2 This is a schematic diagram showing the material zoning of the factory dam section model.
[0014] Figure 3 This is a graph showing the temperature rise value and curve fitting of roller-compacted concrete.
[0015] Figures 4-9 Comparison curves of measured temperature and simulation calculation results of the dam body in the powerhouse dam section.
[0016] Figure 10 The flowchart is a method for determining the adiabatic temperature rise of concrete with high fly ash content according to the present invention. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0018] To make the description of this disclosure more detailed and complete, illustrative descriptions of embodiments and specific examples of the present invention are provided below; however, these are not the only forms of implementing or utilizing the specific examples of the present invention. The embodiments cover features of multiple specific examples and methods and steps for constructing and operating these specific examples, and their order. However, other specific examples may also be used to achieve the same or equivalent functions and order of steps.
[0019] like Figure 10 As shown, this method for determining the adiabatic temperature rise of high fly ash concrete includes the following steps:
[0020] (1) Through experiments, the thermal conductivity, thermal conductivity, density, specific heat, linear expansion coefficient, and Poisson's ratio of high fly ash concrete were obtained; then, the initial adiabatic temperature rise parameters of high fly ash concrete were obtained through adiabatic temperature rise tests.
[0021] (2) According to the model First, the first part of the model is determined. Using measured data of the dam body and combined with simulation calculations, the first part of the model is obtained:
[0022] (3) Using thermometers pre-embedded in the structure, the temperature rise of the concrete after reaching the minimum temperature in actual engineering was measured. Based on the relationship between this data and the curing age, the second half of the model was analyzed. Regression analysis was performed to obtain the adiabatic temperature rise parameters of the formula in the latter part of the model: Q2, α2, β2;
[0023] (4) The complete formula is derived: The temperature field of the concrete is then calculated based on this formula.
[0024] This invention first determines the first part of the model. Using measured data of the dam body and combined with simulation calculations, the first part of the model is obtained. Using thermometers pre-embedded in the structure, the temperature rise of concrete after reaching the minimum temperature in actual engineering is measured. Based on the relationship between this data and the age, regression analysis is performed on the second half of the model to obtain the adiabatic temperature rise parameters of the formula for the second half of the model, thus obtaining a complete formula. Based on this formula, the concrete temperature field is calculated. Therefore, it can accurately reflect the temperature change of high fly ash concrete, taking into account both early and late ages, and more flexibly and accurately simulate the actual hydration heat process of high fly ash concrete.
[0025] Preferably, in step (1), the initial thermodynamic parameters and initial adiabatic temperature rise parameters of the concrete are obtained through a 28-day concrete test. The initial concrete temperature field is calculated using these parameters. Based on this, the parameters are continuously optimized, and the square of the error between the maximum temperature and the measured maximum temperature, as well as the adiabatic temperature rise per hour, are calculated as inversion parameters.
[0026] Preferably, in step (2), the adiabatic temperature rise model of the first stage of the high fly ash concrete in this project is fitted based on the measured temperature value and the simulation calculation results:
[0027] θn=26.5τ / (3+τ) (1)
[0028] Where θn is the adiabatic temperature rise of the concrete; τ is the age, in days;
[0029] Substituting θn=26.5τ / (3+τ) into As the first segment of the model, after substitution, it becomes
[0030] Preferably, in step (3), after obtaining the first segment of the model, based on the measured temperature value of the concrete after reaching a stable temperature and the calculated data, the exponential temperature rise parameters of the roller-compacted concrete are fitted by regression analysis as follows: Q0=6, α2=0.0024, β2=0.80.
[0031] Preferably, in step (3), based on the expression (1) for fitting the adiabatic temperature rise design value and the temperature rise parameters in the second part of the regression analysis, the hydration heat temperature rise function model for fly ash-compacted and normal high-strength concrete is obtained as follows:
[0032]
[0033] Preferably, in step (4), the dam body temperature process line obtained according to the new hydration heat temperature rise function model is compared with the measured data.
[0034] The following is an example of a method for determining the adiabatic temperature rise of high-fly ash concrete, using a dam section of a certain engineering plant as an example. The method includes the following steps:
[0035] 1. Through a 28-day concrete test, the initial thermodynamic parameters and initial adiabatic temperature rise parameters of the concrete were obtained. The initial concrete temperature field was calculated using these parameters. Based on this, the parameters were continuously optimized, and the squared error between the maximum temperature and the measured maximum temperature, as well as the hourly adiabatic temperature rise, were used as inversion parameters. The adiabatic temperature rise parameters and initial thermal parameters of the concrete are listed in Tables 1 and 2.
[0036] Table 1. Temperature rise parameters of concrete adiabatic insulation
[0037]
[0038] Table 2 Initial thermodynamic parameters of concrete
[0039]
[0040] 2: Based on the measured temperature values and simulation calculation results, the adiabatic temperature rise model of the first section of the high fly ash concrete in this project was fitted: (The location of the monitoring equipment is shown in Table 3, and the comparison between the measured maximum temperature and the simulation calculation results is shown in Table 4).
[0041] θn=26.5τ / (3+τ) (1)
[0042] The simulation calculation model and model material partitions are shown below. Figure 1 , 2 The dam base elevation is 203m, and the dam crest elevation is 384m. The toothed groove is made of roller-compacted concrete, and the dam body is made of normal concrete. The boundary conditions for the temperature field calculation are: the bedrock is adiabatic on all sides, bottom, and surface, while other surfaces are heat exchange boundaries.
[0043] In the formula: θn is the adiabatic temperature rise of concrete; τ is the curing time, d.
[0044] Table 3. Numbering and Location of Thermometers in the Plant Dam Section
[0045]
[0046]
[0047] Table 4 Comparison of Measured Maximum Temperature of Dam Body and Simulation Calculation Results
[0048]
[0049]
[0050] 3: Substitute θn=26.5τ / (3+τ) into As the first segment of the model, after substitution, it becomes
[0051] 4. After obtaining the first segment of the model, based on the measured temperature rise of concrete after reaching a stable temperature and the calculated data, regression analysis was used to fit the exponential temperature rise parameters of roller-compacted concrete as follows: Q0=6, α2=0.0024, β2=0.80.
[0052] The temperature rise value and curve fitting graph are shown below. Figure 3 .
[0053] 5: Based on the fitted expression (1) for the adiabatic temperature rise design value and the temperature rise parameters in the second part of the regression analysis, the hydration heat temperature rise function model for fly ash-mixed compacted and normal high-strength concrete is as follows:
[0054]
[0055] 6: Compare the dam body temperature process curve obtained based on the new hydration heat temperature rise function model with the measured data, see... Figures 4-9 .
[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.
Claims
1. A method for determining the adiabatic temperature rise of high-fly ash concrete, characterized in that: It includes the following steps: (1) Through experiments, the thermal conductivity, thermal conductivity coefficient, bulk density, specific heat, coefficient of linear expansion, and Poisson's ratio of concrete with high fly ash content were obtained; Then, the initial adiabatic temperature rise parameters of the high fly ash concrete were obtained through adiabatic temperature rise tests. (2) According to the model First, the first part of the model is determined. Using measured data of the dam body and combined with simulation calculations, the first part of the model is obtained: ; (3) Using the thermometers pre-embedded in the structure, measure the temperature rise of the concrete after reaching the minimum temperature in actual engineering. Based on the relationship between the temperature rise and the age, analyze the second half of the model. Regression analysis was performed to obtain the adiabatic temperature rise parameters of the formula in the latter part of the model: Q2, α2, β2; (4) The complete formula is obtained: Then, the temperature field of the concrete is calculated based on this formula. In step (2), the adiabatic temperature rise model of the first stage of the high fly ash concrete in this project is fitted based on the measured temperature value and the simulation calculation results: （1） Where θn is the adiabatic temperature rise of the concrete; Age, in days; The formula Substitution As the first segment of the model, after substitution, it becomes ; In step (3), after obtaining the first segment of the model, based on the measured temperature value of the concrete after reaching a stable temperature and the calculated data, the exponential temperature rise parameters of the roller-compacted concrete are fitted by regression analysis as follows: Q2=6, α2=0.0024, β2=0.80; Based on the fitted expression (1) for the adiabatic temperature rise design value and the temperature rise parameters in the second part of the regression analysis, the hydration heat temperature rise function model for fly ash-compacted and normal high-strength concrete is as follows: （2）。 2. The method for determining the adiabatic temperature rise of high-fly ash concrete according to claim 1, characterized in that: In step (1), the initial thermodynamic parameters and initial adiabatic temperature rise parameters of concrete are obtained through a 28-day concrete test. The initial concrete temperature field is calculated using the initial thermodynamic parameters and initial adiabatic temperature rise parameters. Based on this, the system is continuously optimized, and the square of the error between the highest temperature and the measured highest temperature, as well as the adiabatic temperature rise per hour, are calculated as inversion parameters.
3. The method for determining the adiabatic temperature rise of high-fly ash concrete according to claim 2, characterized in that: Step (4) also includes comparing the dam body temperature process line obtained based on the new hydration heat temperature rise function model with the measured data.