CN111505046B - Prediction method of concrete early-age thermal expansion coefficient multi-scale model - Google Patents
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- 239000004567 concrete Substances 0.000 title claims abstract description 99
- 238000000034 method Methods 0.000 title claims abstract description 59
- 239000004568 cement Substances 0.000 claims abstract description 34
- 239000000203 mixture Substances 0.000 claims abstract description 17
- 239000000378 calcium silicate Substances 0.000 claims description 40
- 229910052918 calcium silicate Inorganic materials 0.000 claims description 40
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 claims description 40
- 239000012071 phase Substances 0.000 claims description 28
- 238000012360 testing method Methods 0.000 claims description 24
- 238000000265 homogenisation Methods 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 239000011148 porous material Substances 0.000 claims description 13
- 239000007790 solid phase Substances 0.000 claims description 12
- 239000011083 cement mortar Substances 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 8
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims description 6
- 239000000920 calcium hydroxide Substances 0.000 claims description 6
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 5
- 239000004576 sand Substances 0.000 claims description 5
- 230000007613 environmental effect Effects 0.000 claims description 4
- 150000004645 aluminates Chemical class 0.000 claims description 3
- 229920006395 saturated elastomer Polymers 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims 1
- 239000000463 material Substances 0.000 description 10
- JLDKGEDPBONMDR-UHFFFAOYSA-N calcium;dioxido(oxo)silane;hydrate Chemical compound O.[Ca+2].[O-][Si]([O-])=O JLDKGEDPBONMDR-UHFFFAOYSA-N 0.000 description 5
- 238000004364 calculation method Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 239000011398 Portland cement Substances 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 239000003657 drainage water Substances 0.000 description 2
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- 230000000704 physical effect Effects 0.000 description 1
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Abstract
The invention discloses a method for predicting a multiscale model of a thermal expansion coefficient of concrete in an early age, which comprises the following steps of firstly carrying out multiscale division on the concrete; respectively calculating the relative volume content of each composition phase on different scales; from the minimum scale, homogenizing the elastic modulus parameters and the temperature stress coefficients of all scales gradually to the large scale; calculating the edge value of the thermal expansion coefficient of the maximum scale; and establishing a concrete thermal expansion coefficient prediction model in an early age stage by stages. According to the invention, a multi-scale prediction model of the early-age thermal expansion coefficient of the concrete is established according to the microstructure composition of the concrete and the elasticity and thermal properties of each composition phase, and the model considers the influence factors such as the mix proportion, the age, the cement, the coarse and fine aggregate types and properties, the temperature and the humidity, so that the prediction of the macroscopic property of the concrete based on the microstructure is realized, and the problem of numerous influence factors of the thermal expansion coefficient of the concrete is fundamentally solved.
Description
Technical Field
The invention belongs to the field of multi-scale calculation and analysis of cement-based materials, and particularly relates to a prediction method of a multi-scale model of a thermal expansion coefficient of concrete in an early age.
Background
The coefficient of thermal expansion is one of the main thermophysical parameters of concrete and is also an important parameter for characterizing the volume stability of concrete. The research on the thermal expansion coefficient of the concrete in the early age at home and abroad is mostly carried out by a macroscopic test method, and a prediction model is obtained based on the fitting of test results. Due to the reasons of raw materials, mixing ratio, environmental conditions, testing equipment, testing methods, operation techniques of testers and the like, the discreteness of the given thermal expansion coefficient is large, the model usually takes the age as a main parameter, the consideration factors are few, the thermal expansion mechanism cannot be revealed, and the model is limited in practical application; in addition, experimental studies require long continuous tests, which are time-consuming and energy-consuming.
The concrete is a non-uniform porous medium material, the distribution of the micro components of the concrete spans the scales of nanometer, micrometer, millimeter and the like, and the prediction of the physical and mechanical properties of the concrete can be essentially reduced into a plurality of scales. The multi-scale method can consider the structural characteristics of different scales of the material, and achieves the purpose of obtaining the macroscopic effectiveness performance based on the microstructure information. The multi-scale method is introduced into the research of the thermal expansion coefficient of the concrete, and has important significance for predicting and controlling the early temperature crack of the concrete structure and evaluating the early cracking risk.
Disclosure of Invention
The invention aims to provide a method for predicting a multiscale model of thermal expansion coefficients of early-age concrete aiming at the defects of the prior art. According to the mixing proportion of the concrete, the type of the cement, the types of the coarse aggregate and the fine aggregate and performance parameters, the thermal expansion coefficient of the concrete can be determined by adopting a multi-scale method, so that accurate parameters are provided for controlling and evaluating the temperature cracks of the concrete in the early age.
The purpose of the invention is realized by the following technical scheme: a prediction method of a concrete early-age thermal expansion coefficient multi-scale model comprises the following steps:
(1) the concrete is divided into different scales according to the microstructure composition, and the different scales contain different phases.
(2) And (3) respectively obtaining the volume percentage of different phases in different scales divided by the step (1).
(3) Gradually adopting a homogenization method from the minimum scale to the upper part, and calculating the thermal expansion coefficient of the drainage water of each scale according to the volume percentage of different phases in different scales obtained in the step (2)
And coefficient of thermal expansion without drainage
Wherein f is φ Porosity, alpha, in the dimension X f,X Is the coefficient of thermal expansion, K, of pore water of dimension X f Is the bulk modulus of the pore water,
is the bulk modulus of the dimension X,
is the temperature stress coefficient of the dimension X,
is the Biot coefficient for the scale X,
the Biot modulus for the scale X,
thermal porosity coefficient of variation for scale X;
the equal parts are calculated according to the following formulas respectively:
wherein k is r 、f r Respectively, the bulk modulus, volume fraction, kappa, of the r-th phase of the dimension X r Temperature stress coefficient, k, of the r-th phase of dimension X 0 The bulk modulus of the reference medium is the dimension X,
shear modulus at the scale X;
calculated according to the following formula:
wherein, g r Shear modulus for the dimension X, the r < th > phase;
g 0 the shear modulus of the reference medium is dimension X; the volume modulus of the concrete is finally obtained
Thermal expansion coefficient without drainage
And coefficient of thermal expansion of drainage
(4) Obtaining the bulk modulus of the concrete at each early age according to the steps (2) to (3)
Coefficient of thermal expansion without drainage
And coefficient of thermal expansion of drainage
Calculating the thermal expansion coefficient alpha (t) of the concrete at the early age t:
wherein, t i Initial setting time, t f The final setting time; alpha is alpha a (t) is the additional thermal expansion coefficient at time t, calculated according to the following formula:
wherein S is the saturation coefficient of concrete, Delta T represents the change of temperature, K s Δ p is the change in capillary pressure p due to changes in temperature and relative humidity, which is the bulk modulus of the concrete solid phase framework.
Further, the step (1) is specifically: dividing concrete into six scales of a scale I, a scale II, a scale III, a scale IV, a scale V, a scale VI and the like from small to large according to the composition of a microstructure; the dimension I comprises basic blocks of hydrated calcium silicate and nanopores; the dimension II comprises a calcium silicate hydrate solid phase and a gel hole after the dimension I is homogenized; the scale III comprises high-density calcium silicate hydrate after being homogenized by the scale II and low-density calcium silicate hydrate after being homogenized by the scale II; the dimension IV comprises calcium silicate hydrate, calcium hydroxide, unhydrated cement particles, aluminate and capillary pores after the homogenization of the dimension III; the scale V comprises the cement paste and sand after the scale IV is homogenized; and the dimension VI comprises the cement mortar and the coarse aggregate after the homogenization of the dimension V.
Further, homogenizing the scale VI to obtain the concrete.
Further, the step (2) specifically comprises: the volume percentage contents of different phases on the scales I, II, III and IV are obtained by tests, or calculated by a Powers model, a Jennings-Tennis model or a CEMHYD3D model; the volume percentage content of different phases on the scales V and VI is obtained according to the mixing proportion of the concrete.
Further, the test is an environmental scanning electron microscope test.
Further, the homogenization method in the step (3) and the step (4) specifically comprises the following steps: calculating a homogenized calcium silicate hydrate solid phase on the scale I by adopting a Self-consistency method, wherein a reference medium is the calcium silicate hydrate solid phase; on the scale II, calculating homogenized high-density calcium silicate hydrate and low-density calcium silicate hydrate by adopting a Self-consistency method, wherein reference media are high-density calcium silicate hydrate and low-density calcium silicate hydrate; calculating homogenized calcium silicate hydrate on a scale III by adopting a Self-consistency method, wherein a reference medium is calcium silicate hydrate; calculating homogenized cement paste on the scale IV by adopting a Self-consistency method, wherein a reference medium is the cement paste; calculating homogenized cement mortar on the scale V by adopting a Mori-Tanaka method, wherein a reference medium is cement paste; and calculating homogenized concrete on the scale VI by adopting a Mori-Tanaka method, wherein the reference medium is cement mortar.
Further, in the step (4), the saturation coefficient S ═ V of the concrete ew /V p (ii) a Wherein, V ew Is the volume content of evaporable water per unit volume of set cement, V p Water-saturated porosity.
Further, in the step (4), the capillary pressure
Wherein RH is relative humidity, R is an ideal gas constant, T is absolute temperature, and v' is the molar volume of water.
The invention has the beneficial effects that: the invention establishes a multi-scale prediction method of the concrete early-age thermal expansion coefficient based on the common rule that the concrete thermal expansion coefficient changes along with the age and the essential attributes that the composition and the characteristics of the concrete microstructure evolve along with the age, establishes the relation between the concrete microstructure and the macroscopic thermal expansion performance, and fundamentally solves the problems of a plurality of influence factors on the macroscopic performance of the cement-based material and large dispersion of test data. By the method, the thermal expansion coefficient of the concrete at any age moment can be conveniently obtained, a set of testing device is not needed for real-time monitoring, and the precision level reaches the nanoscale; the method can predict the thermal expansion coefficient of the concrete at each age in the early age, can also predict the thermal expansion coefficients of the concrete at other ages after the early age, and has wide applicability.
Drawings
FIG. 1 is a schematic diagram of a concrete multiphase multi-scale composite process;
FIG. 2 is a graph comparing the test value and the predicted value of the thermal expansion coefficient of concrete.
Detailed Description
The technical scheme of the invention is explained in detail in the following with the accompanying drawings:
the method is based on the evolution rule of the concrete microstructure along with the age and the influence mechanism on the thermal expansion coefficient, establishes a multi-scale prediction model of the thermal expansion coefficient of the concrete in the early age according to the composition phase and the essential attributes of each phase of the concrete microstructure, and accurately predicts the development rule of the thermal expansion coefficient of the concrete in the early age according to the model.
Concrete is a heterogeneous material whose composition is related to multiple scales, such as high and low density hydrated calcium silicate on the nanometer scale, hydrated products such as calcium hydroxide, unhydrated cement particles, large capillary pores on the micrometer scale, cement paste, aggregate on the millimeter scale. The multi-scale method can consider the cross-scale and cross-level material mechanics characteristics of space and time, and is an important method for predicting material performance. The homogenization theory is an effective multi-scale calculation method, has the advantages of strict theory and easiness in numerical value realization of macroscopic equivalent performance of the material, and is an important method for designing the composite material, predicting the performance and optimizing the structure. On the scales of high-density calcium silicate hydrate, low-density calcium silicate hydrate, calcium hydroxide, unhydrated cement particles, coarse aggregate and fine aggregate, the thermal expansion coefficients of the composition phases on different scales are the inherent properties of the phases, and are not related to conditions such as water-cement ratio, age and the like, and the distribution and the content of the basic phases are changed only, so that the thermal expansion coefficients of the concrete scales and the like are changed along with the age. By adopting a multi-scale method and combining the evolution of the microstructure of the concrete in the early age, the development and the change of the thermal expansion coefficient of the concrete in the early age can be essentially predicted.
The invention discloses a multiscale prediction method for early-age thermal expansion coefficient of concrete, which specifically comprises the following steps:
step 1, dividing concrete into six scales from small to large according to microstructure composition: a scale I, a scale II, a scale III, a scale IV, a scale V and a scale VI;
the multi-scale division of the concrete can be flexibly carried out according to actual conditions, the minimum scale is divided into the nanometer scale, the minimum scale is determined based on the current research level at home and abroad and can reflect the thermal expansion mechanism of the cement-based material from the nanometer scale, the maximum scale is the concrete, and the following division method is preferably adopted from the perspective of the thermal expansion coefficient:
the dimension I comprises basic blocks of hydrated calcium silicate (C-S-H basic building block) and nanopores (nanoporosity); the dimension II comprises a calcium silicate hydrate solid phase (C-S-H solid) and a gel pore (gel porosity) after the homogenization of the dimension I; the scale III comprises high-density calcium silicate hydrate (HD C-S-H) after the homogenization of the scale II and low-density calcium silicate hydrate (LD C-S-H) after the homogenization of the scale II; the dimension IV comprises calcium silicate hydrate (C-S-H), Calcium Hydroxide (CH), unhydrated cement particles, aluminate and capillary pores after the homogenization of the dimension III; the dimension V comprises the cement paste and sand after the dimension IV is homogenized; the dimension VI comprises the cement mortar and the coarse aggregate after the homogenization of the dimension V; and homogenizing the scale VI to obtain the concrete. The minimum dimension of the invention is dimension I, and the characteristic dimension of the invention is in nanometer dimension.
Step 2, respectively calculating the relative volume contents of the composition phases of different scales at different times of each age, wherein the relative volume contents are expressed by volume percentages as follows:
the Volume fractions of the different phases on the scales I, II, III, IV can be obtained by experiments (environmental scanning electron microscope experiments) or by the Powers model (Powers T.C., Brown yard T.L.Studies of the Physical Properties of the Hardened Portland and center Paste, part5.Studies of the Hardened Paste by Means of the spectral-Volume measures [ J ] Journal of the American Concrete Institute,1947,18(6): MH669-; the volume fractions of the phases on the scales V and VI are obtained according to the mix proportion of the concrete;
step 3, starting from the minimum size, upwards and gradually adopting a homogenization method; the homogenization method employs the Self-consistency method (see [ Eshelby J.D. the Determination of the Elastic Field of an Elastic introduction and Related schemes [ C ]. Proceedings of the Royal Society of London Series A,1957 ]) on the dimensions I, II, III, IV, with the reference medium corresponding to each dimension being itself; the method of Mori-Tanaka is adopted on the scales V and VI (see [ Mori T., Tannaka K. Average Stress in Matrix and Average Elastic Energy of Materials with Misfit incorporation [ J ]. Acta Metallurgica,1973,21(5):571 574 ]), and the reference medium corresponding to each scale is cement paste and cement mortar, and specifically:
calculating a homogenized calcium silicate hydrate solid phase on the scale I by adopting a Self-consistency method, wherein a reference medium is the calcium silicate hydrate solid phase; on the scale II, a Self-consistency method is adopted to calculate homogenized high-density and low-density calcium silicate hydrate, and a reference medium is the high-density and low-density calcium silicate hydrate; calculating homogenized calcium silicate hydrate on a scale III by adopting a Self-consistency method, wherein a reference medium is the calcium silicate hydrate; calculating homogenized cement paste on a scale IV by adopting a Self-consistency method, wherein reference media are the cement paste per se; adopting a Mori-Tanaka method to calculate homogenized cement mortar on the scale V, wherein the reference medium is cement paste, and sand is inclusion; and (3) calculating homogenized concrete on a scale VI by adopting a Mori-Tanaka method, wherein a reference medium is cement mortar, and coarse aggregate is mixed.
The coefficient of thermal expansion for each dimension is calculated according to the following formula:
in which the upper index hom represents the homogenized, and the lower index X represents the dimension X;
is the coefficient of thermal expansion of the drainage water in this dimension,
coefficient of thermal expansion for non-drainage of this scale, f φ Porosity of this scale, α f,X Is the coefficient of thermal expansion, K, of pore water of this scale f Is the bulk modulus of pore water;
is the bulk modulus of this scale and,
is the temperature stress coefficient of this scale and,
for a porous elastic Biot coefficient of this scale,
the porous elastic Biot modulus of this scale,
is the rulerThe coefficient of thermal porosity change of the pores,
respectively according to the following formulas:
in the formula, k r 、f r The volume modulus, volume fraction, kappa, of the r-th phase of the scale r Temperature stress coefficient, k, of the r-th phase of the scale 0 Referencing the bulk modulus of the medium for the scale;
the shear modulus for this scale is calculated according to the following formula:
wherein, g r Shear modulus, α, of the r-th phase of this scale 0 Calculated according to the following formula:
in the formula, g 0 The shear modulus of the medium is referenced for this scale.
Step 4, repeating the steps 2 to 3 for each early age moment to obtain the thermal expansion coefficient of the concrete at each early age moment, including the thermal expansion coefficient without water drainage
And coefficient of thermal expansion of drainage
And can further draw the change curve of the thermal expansion coefficient of the concrete along with the age, which is specifically as follows:
the thermal expansion coefficient of the concrete at initial setting is changed from the thermal expansion coefficient without water drainage
Determining and reflecting the influence of the concrete raw material and the pores on the thermal expansion coefficient; the thermal expansion coefficient of the concrete at final setting is determined by the thermal expansion coefficient of the drainage
Determining; the thermal expansion coefficient of the concrete is determined by a linear interpolation method of the thermal expansion coefficients during initial setting and final setting between the initial setting and the final setting; the thermal expansion coefficient of the finally set concrete consists of a drainage thermal expansion coefficient and an additional thermal expansion coefficient, and the influence of the factors such as the type and the performance of the raw materials of the concrete, the mixing proportion, the age, the temperature, the humidity and the like on the thermal expansion coefficient is quantitatively reflected; the common law that the thermal expansion coefficient of common concrete develops along with the age is as follows: after mixing, the mixture reaches the maximum value during initial setting, then is rapidly reduced, reaches the minimum value during final setting, and then gradually increases or tends to be stable along with the age; calculating the thermal expansion coefficient of the concrete at the early age t by using the following formula:
wherein t is age, t i Initial setting time, t f For final setting time, α a (t) is the additional thermal expansion coefficient at the age t, and is calculated according to the following formula:
wherein S is the saturation coefficient of concrete, and S is-V ew /V p Calculation of where V ew Is the volume content of evaporable water per unit volume of set cement, V p Water-saturated porosity; Δ T represents a change in temperature;
bulk modulus of homogenized concrete; k s The volume modulus of the concrete solid-phase framework; Δ p is the change in capillary pressure p due to changes in temperature and relative humidity, calculated according to the Kelvin-Laplace equation:
in the formula, RH is relative humidity, R is an ideal gas constant, T is absolute temperature, and v' is the molar volume of water.
The invention does not need to be monitored by a set of testing device, and can adopt MATLAB and the like to compile computer software according to the steps to carry out rapid solution. And (4) adopting concrete with different mixing ratios, different types of cement and different types of coarse and fine aggregates, and repeating the steps 2 to 4 to obtain the change curve of the thermal expansion coefficients of the corresponding different concrete along with the age.
In order to verify the prediction effect of the method of the invention, the following tests were carried out:
the method of the invention is used for predicting the thermal expansion coefficient of the concrete which adopts the ordinary portland cement, has the water cement ratio of 0.45, the river sand as the fine aggregate and the limestone as the coarse aggregate in the early age, and carries out comparative analysis with the test value. The test contents are as follows:
1. overview
1.1 test stock
The cement is ordinary portland cement, and the chemical composition of the cement is shown in table 1.
Table 1: the main chemical component content of the cement
1.2 protocol
The size of the test piece is 100mm multiplied by 500mm, the test piece is placed into an oven for testing after pouring, and a thermal expansion coefficient testing system is adopted to test the thermal expansion coefficient.
1.3 coefficient of thermal expansion of the principal phase
Table 2: coefficient of thermal expansion of each component
2. Model validation and evaluation
The experimental values of the coefficient of thermal expansion of concrete in the early stage and the predicted values of the present invention are shown in FIG. 2. It can be seen that the predicted value is well matched with the test value, which shows that the model can better predict the precision.
The invention adopts a multi-scale method, establishes the relation between the microstructure and the macroscopic performance of the concrete, and can predict the thermal expansion coefficient of the early-age concrete according to the cement components, the mixing proportion of the concrete, the types of coarse and fine aggregates, which is difficult to realize by the prior art.
Claims (8)
1. A prediction method of a concrete early-age thermal expansion coefficient multi-scale model is characterized by comprising the following steps:
(1) dividing concrete into different scales according to microstructure composition, wherein the different scales comprise different phases;
(2) respectively obtaining the volume percentage contents of different phases in different scales divided in the step (1);
(3) gradually adopting a homogenization method from the minimum scale to the upper part, and calculating the thermal expansion coefficient of drainage of each scale according to the volume percentage content of different phases in different scales obtained in the step (2)
And coefficient of thermal expansion without drainage
：
Wherein,
is a porosity of the scale X and,
is the coefficient of thermal expansion of pore water in the dimension X,
is the bulk modulus of the pore water,
is the bulk modulus of the dimension X,
is the temperature stress coefficient of the dimension X,
is the Biot coefficient for the scale X,
biot model at dimension XThe amount of the compound (A) is,
thermal porosity coefficient of variation for scale X;
respectively according to the following formula:
wherein,
respectively is the volume modulus and volume fraction of the r th phase of the dimension X,
the temperature stress coefficient of the r-th phase of dimension X,
the bulk modulus of the reference medium is the dimension X,
shear modulus at the scale X;
calculated according to the following formula:
wherein,
shear modulus of the r < th > phase at dimension X;
，
the shear modulus of the reference medium is dimension X; the volume modulus of the concrete is finally obtained
Thermal expansion coefficient without drainage
And coefficient of thermal expansion of drainage
；
(4) Obtaining the volume modulus of the concrete at each early age according to the steps (2) to (3)
Thermal expansion coefficient without drainage
And coefficient of thermal expansion of drainage
Calculating the thermal expansion coefficient of the concrete at the early age t moment
：
Wherein,
in order to set the time for the initial setting,
the final setting time;
the additional thermal expansion coefficient at the time t is calculated according to the following formula:
wherein,
is the saturation factor of the concrete and is,
which is indicative of a change in temperature of the,
is the volume modulus of the concrete solid-phase framework,
is capillary pressure caused by temperature and relative humidity change
The change is that the number of the first and second,
is the bulk modulus of the homogenized concrete.
2. The method for predicting the multiscale model of early-age thermal expansion coefficients of concrete according to claim 1, wherein the step (1) is specifically as follows: dividing concrete into a scale I, a scale II, a scale III, a scale IV, a scale V and a scale VI from small to large according to the composition of a microstructure; the dimension I comprises basic blocks of hydrated calcium silicate and nanopores; the dimension II comprises a calcium silicate hydrate solid phase and a gel hole after the dimension I is homogenized; the scale III comprises high-density calcium silicate hydrate after being homogenized by the scale II and low-density calcium silicate hydrate after being homogenized by the scale II; the dimension IV comprises calcium silicate hydrate, calcium hydroxide, unhydrated cement particles, aluminate and capillary pores after the homogenization of the dimension III; the scale V comprises the cement paste and sand after the scale IV is homogenized; and the dimension VI comprises the cement mortar and the coarse aggregate after the homogenization of the dimension V.
3. The method for predicting the multiscale model of early-age thermal expansion coefficients of concrete according to claim 2, wherein the concrete is obtained after the scale VI is homogenized.
4. The method for predicting the multiscale model of early-age thermal expansion coefficients of concrete according to claim 3, wherein the step (2) is specifically as follows: the volume percentage contents of different phases on the scales I, II, III and IV are obtained by tests, or calculated by a Powers model, a Jennings-Tennis model or a CEMHYD3D model; the volume percentage content of different phases on the scales V and VI is obtained according to the mixing proportion of the concrete.
5. The method for predicting the multiscale model of early-age thermal expansion coefficients of concrete according to claim 4, wherein the test is an environmental scanning electron microscope test.
6. The method for predicting the multiscale model of the early-age thermal expansion coefficient of concrete according to claim 3, wherein the homogenization method is specifically as follows: calculating a homogenized calcium silicate hydrate solid phase on the scale I by adopting a Self-consistency method, wherein a reference medium is the calcium silicate hydrate solid phase; on the scale II, the homogenized high-density calcium silicate hydrate and low-density calcium silicate hydrate are calculated by adopting a Self-consistency method, and reference media are high-density calcium silicate hydrate and low-density calcium silicate hydrate; calculating homogenized calcium silicate hydrate on a scale III by adopting a Self-consistency method, wherein a reference medium is calcium silicate hydrate; calculating homogenized cement paste on a scale IV by adopting a Self-consistency method, wherein a reference medium is the cement paste; calculating homogenized cement mortar on a scale V by adopting a Mori-Tanaka method, wherein a reference medium is cement paste; and calculating homogenized concrete in a scale VI by adopting a Mori-Tanaka method, wherein the reference medium is cement mortar.
7. The method for predicting the multiscale model of early-age thermal expansion coefficients of concrete according to claim 1, wherein in the step (4), the saturation coefficient of the concrete
(ii) a Wherein,
is the volume content of evaporable water per unit volume of set cement,
water-saturated porosity.
8. The method for predicting the multiscale model of early-age thermal expansion coefficients of concrete according to claim 1, wherein in the step (4), the capillary pressure is measured
(ii) a Wherein,
is the relative humidity of the air or the air,
the gas constant is an ideal gas constant,
in the case of an absolute temperature,
is the molar volume of water.
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