Concrete hydration heat analysis method

Abstract

The invention discloses a concrete hydration heat analysis method. The method comprises the following steps: preparing concrete and testing an adiabatic temperature rise curve and final hydration heat; concrete hydration parameters, hydration heat and hydration degrees corresponding to all the time points are calculated in sequence; the hydration heat value is adjusted according to the hydration degree increase and decrease condition; and completing concrete hydration heat analysis. According to the concrete hydration heat analysis method, the problem that a traditional hydration heat model cannot accurately calculate the initial temperature of concrete hydration can be solved, accurate calculation of the concrete hydration heat in the whole process is achieved, and a better foundation is provided for structural thermal coupling analysis.

Description

Technical Field

[0001] The invention relates to the technical field of concrete hydration heat analysis, in particular to a concrete hydration heat analysis method. Background Art

[0002] Early cracks in large-volume concrete structures have always been an important issue affecting their structural durability, especially for structures such as nuclear containment and LNG storage tanks that have strict crack control. One of the most important reasons for early cracks in large-volume concrete is the large amount of hydration heat generated rapidly inside the structure at the initial stage of hydration, which leads to a large temperature difference between the inside and outside of the structure, a large difference in cooling rate and shrinkage deformation, and thus cracks. Therefore, accurate analysis of the temperature during concrete pouring is a necessary means to effectively control early cracks in large-volume concrete structures.

[0003] The concrete hydration heat analysis model is a key factor affecting the accuracy of structural hydration heat temperature field analysis. There are three main forms of classic hydration heat models, including exponential, hyperbolic and composite exponential. On this basis, many scholars have proposed correction methods to improve the accuracy of fitting analysis. However, in reality, the existing models cannot reflect the characteristics of slow temperature rise due to low temperature and slow splash reaction in the early stage of hydration reaction, making it difficult to complete accurate structural hydration heat temperature field analysis. Summary of the invention

[0004] In view of this, the present application provides a concrete hydration heat analysis method, the main purpose of which is to solve the technical problem that the existing hydration heat curve deviates greatly from the actual situation in the early stage of concrete hydration, and mainly includes the following steps:

[0005] Step 101: prepare a concrete test block using the same mix ratio as the target structure, and test the adiabatic temperature rise curve T(t) and final hydration heat Q0 of the test block;

[0006] Step 102: Take time t1 = Δt, and calculate the concrete hydration parameter m corresponding to time t1 in sequence. b (t1), concrete hydration heat Q(t1) and hydration degree α(t1);

[0007] Step 103 takes n=2, 3, ..., m respectively, and takes time t n =nΔt, calculate t n The concrete hydration parameter mb(t n ), concrete hydration heat Q(t n ) and hydration degree α(t n );

[0008] Step 104 compares α(t n-1 ) and α(t n ), if α(t n-1)>α(t n ), then continue to calculate t n+1 The parameters corresponding to the moment; if α(t n-1 )>α(t n ), then take Q(t n )=Q(t n-1 ), and then continue to calculate t n+1 The parameters corresponding to the moment;

[0009] Step 105 calculates [t1, t2, ..., t m ] corresponding to the concrete hydration heat [Q(t1), Q(t2), ..., Q(t m )] to complete the concrete hydration heat analysis.

[0010] Furthermore, the size of the concrete test block in step 101 should be no less than 70.6 mm×70.6 mm×70.6 mm.

[0011] Furthermore, the concrete hydration parameter m in step 102 is b (t), concrete hydration heat Q(t), and hydration degree α(t) are parameters that change with time t, and the calculation method is as follows:

[0012]

[0013]

[0014]

[0015] Where t is time, Q(t) is the concrete hydration heat corresponding to time t, Q0 is the final concrete hydration heat obtained in step 101, and m b (t) is the concrete hydration parameter corresponding to time t, T(t) is the concrete adiabatic temperature rise curve obtained in step 101, and a and b are fitting parameters obtained by nonlinear fitting of the adiabatic temperature rise curve.

[0016] Furthermore, the concrete hydration parameter m in step 102 is b (t) The following conditions should be met: b (t h ) = t h , where t h It is the number of days after concrete pouring when the hydration heat reaches half.

[0017] Furthermore, the values ​​of the two parameters Δt and m in step 102, step 103, step 104, and step 105 are not limited, and the staff needs to determine the specific values ​​of each parameter according to the actual accuracy requirements of the thermal coupling analysis.

[0018] The beneficial technical effects of the present invention are:

[0019] The concrete hydration heat analysis method proposed in the present invention can better reflect the characteristic of slow temperature rise in the initial stage of concrete hydration reaction, solves the problem that traditional hydration heat model cannot accurately calculate the initial temperature of concrete hydration, realizes accurate calculation of the whole process of concrete hydration heat, and provides a better basis for structural thermal coupling analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 A schematic diagram showing a flow chart of a concrete hydration heat analysis method provided by the present invention

[0022] Figure 2 The actual measured adiabatic temperature rise curve of concrete in an embodiment of a concrete hydration heat analysis method provided by the present invention is shown.

[0023] Figure 3 A comparison diagram of the calculated results and measured data in an embodiment of a concrete hydration heat analysis method provided by the present invention is shown. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0025] When simulating the temperature changes of structures at early ages, the traditional concrete hydration thermal analysis model cannot reflect the slow temperature rise caused by low temperature and slow splash reaction in the early stage of hydration reaction. As a result, a good fitting effect cannot be obtained within the first two days of the hydration reaction, and it is difficult to provide an accurate temperature field basis for subsequent structural thermal coupling analysis.

[0026] In view of the above problems, the present invention provides a concrete hydration heat analysis method, such as Figure 1 As shown, the following steps are included:

[0027] Step 101: prepare a concrete test block using the same mix ratio as the target structure, and test the adiabatic temperature rise curve T(t) and the final hydration heat Q0 of the test block, wherein the size of the test block should be no less than 70.6 mm×70.6 mm×70.6 mm;

[0028] Step 102: Take time t1 = Δt, and calculate the concrete hydration parameter m corresponding to time t1 in sequence. b(t1), concrete hydration heat Q(t1) and hydration degree α(t1). Δt is the incremental step size of the analysis, and its specific value is not limited and is determined by the staff according to the actual accuracy requirements of the thermal-mechanical coupling analysis; Q, m b , α are parameters related to time t, and their calculation methods are as follows:

[0029]

[0030]

[0031]

[0032] Wherein, t is time; Q(t) is the concrete hydration heat corresponding to time t; Q0 is the final concrete hydration heat obtained in step 101; m b (t) is the concrete hydration parameter corresponding to time t, which should satisfy m b (t h ) = t h , where t h is the number of days after concrete pouring when the hydration heat reaches half; T(t) is the concrete adiabatic temperature rise curve obtained in step 101; a and b are fitting parameters obtained by nonlinear fitting of the adiabatic temperature rise curve;

[0033] Step 103 takes n=2, 3, ..., m respectively, and takes time t n =nΔt, calculate t n The concrete hydration parameter m corresponding to the time b (t n ), concrete hydration heat Q(t n ) and hydration degree α(t n ), where m is the maximum incremental number of analysis steps, and its specific value is not limited and is determined by the staff according to the actual accuracy requirements and total time of thermal coupling analysis;

[0034] Step 104 compares α(t n-1 ) and α(t n ), if α(t n-1 )>α(t n ), then continue to calculate t n+1 The parameters corresponding to the moment; if α(t n-1 )>α(t n ), then take Q(t n )=Q(t n-1 ), and then continue to calculate t n+1 The parameters corresponding to the time; the adjusted hydration heat calculation results can ensure that the hydration degree increases monotonically with time in the actual hydration process, avoiding data deviation;

[0035] Step 105 calculates [t1, t2, ..., t m ] corresponding to the concrete hydration heat [Q(t1), Q(t2), ..., Q(t m )] to complete the concrete hydration heat analysis.

[0036] The following is described by specific embodiments:

[0037] Step 101: Prepare concrete using the mix ratio shown in Table 1, and obtain its final hydration heat Q0=223 J / g through testing. The adiabatic temperature rise curve is as follows: Figure 2 shown.

[0038] Table 1 Example concrete mix ratio

[0039]

[0040] In step 102, t1 = Δt = 1h is taken, and nonlinear fitting is performed on the adiabatic temperature rise curve to obtain a = 2.04 and b = 0.19, from which we can obtain

[0041] Step 103 takes n=2, 3, ..., 200 respectively, and takes time t n =nΔt, calculate t n The concrete hydration parameter m corresponding to the time b (t n ), concrete hydration heat Q(t n ) and hydration degree α(t n );

[0042] Step 104 compares α(t n-1 ) and α(t n ), if α(t n-1 )>α(t n ), then continue to calculate t n+1 The parameters corresponding to the moment; if α(t n-1 )>α(t n ), then take Q(t n )=Q(t n-1 ), and then continue to calculate t n+1 The parameters corresponding to the moment;

[0043] Step 105 calculates [t1, t2, ..., t m ] corresponding to the concrete hydration heat [Q(t1), Q(t2), ..., Q(t m )], input the data into the UMATHT subroutine in the finite element software ABAQUS and perform structural thermal-mechanical coupling analysis to obtain the curve of structural temperature variation with time, such as Figure 3 As shown. Figure 3Comparison between the calculated results and the measured data shows that the concrete hydration heat analysis method provided by the present invention has good accuracy, can accurately calculate the hydration heat of the entire concrete hydration process, and lays a good foundation for structural thermal coupling analysis.

[0044] The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art can make equivalent substitutions or changes based on the technical solutions and inventive concepts disclosed by the present invention, and the obtained technical solutions should be included in the protection scope of the present invention.

Claims

1. A concrete hydration heat analysis method comprising the following steps: Step 101: prepare a concrete test block using the same mix ratio as the target structure, and test the adiabatic temperature rise curve T(t) and final hydration heat Q0 of the test block; Step 102: Take time t1 = Δt, and calculate the concrete hydration parameter m corresponding to time t1 in sequence. b (t1), concrete hydration heat Q(t1) and hydration degree α(t1); Step 103 takes n=2, 3, ..., m respectively, and takes time t n =nΔt, calculate t n The concrete hydration parameter m corresponding to the time b (t n ), concrete hydration heat Q(t n ) and degree of hydration α(t n ); Step 104 compares α(t n-1 ) and α(t n ), if α(t n-1 )>α(t n ), then continue to calculate t n+1 The parameters corresponding to the moment; if α(t n-1 )>α(t n ), then take Q(t n )=Q(t n-1 ), and then continue to calculate t n+1 The parameters corresponding to the moment; Step 105 calculates [t1, t2, ..., t m ] the concrete hydration heat corresponding to the moment [Q(t1), Q(t2), ..., Q(t m )] to complete the concrete hydration heat analysis.

2. A concrete hydration heat analysis method as claimed in claim 1, characterized in that: In step 102, the concrete hydration parameter m b (t), concrete hydration heat Q(t), and hydration degree α(t) are parameters that change with time t, and the calculation method is as follows: Wherein, t is time, Q0 is the final hydration heat of cement obtained in step 101, T(t) is the adiabatic temperature rise curve of concrete obtained in step 101, and a and b are fitting parameters obtained by nonlinear fitting of the adiabatic temperature rise curve.

3. A concrete hydration heat analysis method as claimed in claim 1, characterized in that: In step 102, the concrete hydration parameter m b (t) should satisfy m b (t h ) = t h , where t h It is the number of days after concrete pouring when the hydration heat reaches half.

4. A concrete hydration heat analysis method as claimed in claim 1, characterized in that: The size of the concrete test block in step 101 should be no less than 70.6 mm×70.6 mm×70.6 mm.

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