CN108875282B - Method for measuring and calculating hydration reaction activation energy of concrete doped with magnesium oxide and application - Google Patents
Method for measuring and calculating hydration reaction activation energy of concrete doped with magnesium oxide and application Download PDFInfo
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- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 title claims abstract description 257
- 239000000395 magnesium oxide Substances 0.000 title claims abstract description 193
- 239000004567 concrete Substances 0.000 title claims abstract description 140
- 238000006703 hydration reaction Methods 0.000 title claims abstract description 135
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 title claims abstract description 132
- 230000004913 activation Effects 0.000 title claims abstract description 70
- 238000000034 method Methods 0.000 title claims abstract description 59
- 230000036571 hydration Effects 0.000 claims abstract description 54
- 239000004568 cement Substances 0.000 claims abstract description 19
- 238000006243 chemical reaction Methods 0.000 claims abstract description 17
- 238000013178 mathematical model Methods 0.000 claims abstract description 16
- 238000012360 testing method Methods 0.000 claims abstract description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 10
- 235000012245 magnesium oxide Nutrition 0.000 claims description 180
- 239000003795 chemical substances by application Substances 0.000 claims description 13
- 238000001354 calcination Methods 0.000 claims description 8
- 239000002994 raw material Substances 0.000 claims description 7
- 235000019738 Limestone Nutrition 0.000 claims description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 3
- 239000012615 aggregate Substances 0.000 claims description 3
- 239000003638 chemical reducing agent Substances 0.000 claims description 3
- 239000010459 dolomite Substances 0.000 claims description 3
- 229910000514 dolomite Inorganic materials 0.000 claims description 3
- 239000010881 fly ash Substances 0.000 claims description 3
- 239000006028 limestone Substances 0.000 claims description 3
- 239000011777 magnesium Substances 0.000 claims description 3
- 229910052749 magnesium Inorganic materials 0.000 claims description 3
- 239000001095 magnesium carbonate Substances 0.000 claims description 3
- 235000014380 magnesium carbonate Nutrition 0.000 claims description 3
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 claims description 3
- 229910000021 magnesium carbonate Inorganic materials 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 3
- 238000012933 kinetic analysis Methods 0.000 abstract description 4
- 238000004422 calculation algorithm Methods 0.000 abstract description 2
- 238000004088 simulation Methods 0.000 abstract description 2
- 238000011160 research Methods 0.000 description 11
- 239000000463 material Substances 0.000 description 5
- 238000013461 design Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 3
- 238000009795 derivation Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000005511 kinetic theory Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- -1 magnesia hydrates Chemical class 0.000 description 1
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 1
- 239000000347 magnesium hydroxide Substances 0.000 description 1
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 1
- 235000012054 meals Nutrition 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
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- G—PHYSICS
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- G06F—ELECTRIC DIGITAL DATA PROCESSING
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Abstract
The invention belongs to the technical field of concrete structure simulation, and relates to a method for measuring and calculating hydration reaction activation energy of externally-doped magnesium oxide concrete and application thereof. The method comprises the following steps: establishing the relationship between the hydration reaction rate and temperature of the magnesium oxide, the hydration degree of the magnesium oxide and the activation energy of the hydration reaction according to an Arrhenius formula; establishing a mathematical model for calculating the hydration reaction activation energy of the magnesium oxide in the concrete by combining the relationship between the hydration degree of the magnesium oxide and the expansion amount of the concrete; and calculating the hydration reaction activation energy of the magnesium oxide in the magnesium oxide concrete by using the established mathematical model and combining the test data of the autogenous volume deformation of the magnesium oxide concrete. The algorithm is deduced by a mathematical equation, is strict theoretically, and can be directly solved by means of the data of the autogenous volume deformation of the magnesia concrete; compared with the method that the reaction of the magnesium oxide with water or the hydration kinetic analysis of the cement containing the magnesium oxide is directly adopted, the reaction condition of the magnesium oxide in the concrete can be reflected more truly, and the method is simple and convenient to operate.
Description
Technical Field
The invention belongs to the technical field of concrete structure simulation, and particularly relates to a method for measuring and calculating hydration reaction activation energy of concrete doped with magnesium oxide and application of the method.
Background
The addition of magnesium oxide in concrete is one of the very effective anti-cracking technologies: by utilizing the micro-expansibility of the hydration of the magnesium oxide, the tensile stress and the volume shrinkage of the concrete generated in the cooling process can be compensated, thereby achieving the purpose of preventing the structure from cracking. The research on the compensation shrinkage of the magnesium oxide concrete has important significance for more effectively utilizing the shrinkage compensation function of the magnesium oxide concrete in the research and design process of actual engineering. The hydration dynamics of the periclase is the theoretical basis of the expansion of the magnesia concrete, has important significance for knowing the expansion performance of the magnesia and predicting the expansion deformation of the magnesia, and also has guiding effect on the stability evaluation of the magnesia in the cement.
The hydration speed of periclase determines the expansion performance of magnesia concrete, and the hydration speed of periclase has great relation with the formation condition of periclase (external environment temperature, humidity, etc.). The study on the hydration kinetics of the light calcined magnesia is carried out by the scholars at present, and the results of the related study show that the hydration of the light calcined magnesia in pure water has obvious difference with the hydration kinetic equation of the light calcined magnesia in cement clinker, and the difference is related to the properties of periclase and the test method. The situation is more complicated in cement concrete than when magnesium oxide is reacted directly with pure water. In some researches, periclase contained in cement clinker is adopted, the periclase has high generation temperature and low hydration activity and can be partially wrapped by cement minerals, and the hydration of the periclase is influenced by the hydration of cement. The method is used for testing, and the hydration of magnesium oxide contained in the cement is directly reflected.
However, the light burned magnesia doped with the additive has lower calcination temperature and higher activity of periclase compared with magnesia contained in cement, and simultaneously, the light burned magnesia doped with the additive and the cement are simply mixed together and do not wrap each other. Therefore, whether the hydration kinetics of periclase obtained from the existing research results are consistent with the hydration kinetics of the externally-doped magnesia in cement and even concrete is still to be further researched. Therefore, the research on the hydration reaction kinetic characteristics of the externally-doped magnesium oxide in the concrete has great significance.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a method for measuring and calculating hydration reaction activation energy of concrete doped with magnesium oxide, which can overcome the problems or at least partially solve the technical problems, and provides a method for measuring and calculating hydration reaction activation energy as a key parameter in the internal hydration kinetic analysis of the concrete doped with magnesium oxide.
The invention also aims to provide application of the method for measuring and calculating the hydration reaction activation energy of the concrete doped with the magnesium oxide in the dynamics research of the concrete containing the magnesium oxide.
In order to realize the purpose, the invention adopts the technical scheme that:
according to one aspect of the invention, the invention provides a method for measuring and calculating hydration reaction activation energy of concrete doped with magnesium oxide, which comprises the following steps:
establishing the relationship between the hydration reaction rate and temperature of the magnesium oxide, the hydration degree of the magnesium oxide and the activation energy of the hydration reaction according to an Arrhenius formula;
establishing a mathematical model for calculating the hydration reaction activation energy of the magnesium oxide in the concrete by combining the relationship between the hydration degree of the magnesium oxide and the expansion amount of the concrete;
and calculating the hydration reaction activation energy of the magnesium oxide in the magnesium oxide concrete by using the established mathematical model and combining the test data of the autogenous volume deformation of the magnesium oxide concrete.
As a further preferred technical solution, according to the arrhenius formula, the relationship between the hydration reaction rate of magnesium oxide at time t and the temperature, the hydration degree of magnesium oxide and the activation energy of hydration reaction can be expressed as:
wherein, zeta is the hydration degree of magnesium oxide;
is chemical reaction affinity; e m The unit is the activation energy of hydration reaction and kJ/mol; r is a molar gas constant with a unit kJ/mol.K; t is the thermodynamic temperature in K.
As a further preferable technical solution, the relationship between the hydration degree of magnesium oxide and the expansion amount of concrete can be expressed as:
ε au ＝f(ζ)；
wherein epsilon au The autogenous volume deformation of the magnesia concrete is shown; f (. zeta.) is a function of the degree of hydration of the magnesium oxide inside the concrete.
As a further preferred technical solution, the mathematical model of the hydration reaction activation energy of magnesium oxide in concrete can be expressed as:
wherein E is m The unit is the activation energy of hydration reaction and kJ/mol; r is a molar gas constant with a unit kJ/mol.K; t is t 1 And t 2 First age and second age, respectively, in units day; t is a unit of 1 And T 2 First and second thermodynamic temperatures, respectively, in K.
As a further preferred technical scheme, the established mathematical model of the hydration reaction activation energy of the magnesium oxide in the concrete is utilized, the test data of the autogenous volume deformation of the magnesium oxide concrete are combined, the autogenous volume deformation data of the concrete under two different temperature conditions are analyzed, and the hydration reaction activation energy of the magnesium oxide in the concrete can be calculated by selecting the age with the same or similar autogenous volume deformation.
As a further preferable technical scheme, the test data of the autogenous volume deformation of the magnesia concrete comprises the autogenous volume deformation amount, the temperature and the age of the concrete.
As a further preferred technical scheme, the externally-doped magnesia concrete comprises coarse aggregates, fine aggregates, cement, fly ash, a water reducing agent, an air entraining agent, water and a light-burned magnesia expanding agent;
preferably, the content of the light-burned magnesia expanding agent is 0.1-5.0 wt%, preferably 0.3-3.5 wt%.
As a further preferable technical scheme, the calcination temperature of the light-calcined magnesia expanding agent is 850-1200 ℃, and the calcination heat preservation time is 0.5-2 h.
In a more preferred embodiment, the magnesium oxide is derived from at least one of magnesium-containing periclase, limestone, dolomite, or magnesite as a raw material in the raw material.
According to another aspect of the invention, the invention provides application of the method for measuring and calculating the hydration reaction activation energy of the externally-doped magnesium oxide concrete in the kinetic study of the concrete containing magnesium oxide.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention provides a new method for analyzing the hydration reaction kinetics of magnesium oxide in concrete, which is particularly suitable for the hydration kinetics research of externally-doped magnesium oxide in concrete which is rarely researched at present, fills the blank of the research in the field, and provides powerful guidance for the performance and application research of magnesium oxide concrete.
2. According to the method for measuring and calculating the hydration reaction activation energy of the magnesium oxide in the magnesium oxide concrete, an Arrhenius formula, the relation between the hydration degree of the magnesium oxide and the concrete expansion amount, the test data of the autogenous volume deformation of the magnesium oxide concrete and the like are utilized, the hydration reaction activation energy of the magnesium oxide in the magnesium oxide concrete can be calculated, namely the hydration reaction activation energy of the magnesium oxide is calculated in a mode of combining mathematical equation derivation and the test data, and compared with the method of directly adopting the hydration reaction activation energy of the magnesium oxide contained in the cement, the method is tighter, more accurate and reliable, simple, easy to implement and good in application prospect.
3. The method is beneficial to promoting the development of the hydration kinetic theory of the magnesia concrete, thereby providing a certain theoretical basis for the material design of the magnesia-doped concrete.
4. The method can reflect the reaction condition of the magnesium oxide in the concrete more truly, has definite theoretical basis, and has the characteristics of simple, flexible, easy operation, strong operability, good result reliability, easy application in practice and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a graph showing the relationship between the age of concrete and its deformation of self-generated volume under different temperature conditions, and t in the present invention 1 And t 2 Schematic illustration of (a).
Detailed Description
Embodiments of the present invention will be described in detail below with reference to embodiments and examples, but those skilled in the art will understand that the following embodiments and examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. Those who do not specify the specific conditions are performed according to the conventional conditions or the conditions recommended by the manufacturer.
In a first aspect, in at least one embodiment, a method for measuring and calculating hydration reaction activation energy of externally-doped magnesium oxide concrete is provided, which comprises the following steps:
establishing the relationship between the hydration reaction rate and temperature of the magnesium oxide, the hydration degree of the magnesium oxide and the activation energy of the hydration reaction according to an Arrhenius formula;
establishing a mathematical model for calculating the hydration reaction activation energy of the magnesium oxide in the concrete by combining the relationship between the hydration degree of the magnesium oxide and the expansion amount of the concrete;
and calculating the hydration reaction activation energy of the magnesium oxide in the magnesium oxide concrete by using the established mathematical model and combining the test data of the autogenous volume deformation of the magnesium oxide concrete.
The invention provides a method for measuring and calculating hydration reaction activation energy as a key parameter in the internal hydration kinetic analysis of magnesium oxide doped concrete. The method adopts a conventional autogenous volume deformation test and a theoretical derivation method: in the process of solving the hydration reaction activation energy of the magnesium oxide, describing the relationship between the hydration reaction rate and the temperature of the magnesium oxide by adopting an Arrhenius formula, and establishing a mathematical model for calculating the hydration reaction activation energy of the magnesium oxide in the concrete by combining the relationship between the hydration reaction degree of the magnesium oxide and the expansion amount of the concrete; finally, combining the test result of the conventional autogenous volume deformation, the hydration reaction activation energy of the magnesium oxide in the concrete can be obtained.
The method fills the blank of the hydration dynamics research of the externally-doped magnesium oxide in the concrete, and provides powerful guidance for the performance and application research of the magnesium oxide concrete. Compared with the method of directly adopting hydration reaction activation energy of magnesium oxide contained in cement, the method of the invention is tighter, more accurate and more reliable, has simple method, is easy to realize and has good application prospect.
The invention is beneficial to promoting the development of the hydration dynamics theory of the magnesia concrete, thereby providing a certain theoretical basis for the material design of the magnesia-doped concrete. The method can reflect the reaction condition of the magnesium oxide in the concrete more truly, has definite theoretical basis, and has the characteristics of simple, flexible, easy operation, strong operability, good result reliability, easy application in practice and the like.
In a preferred embodiment, the method comprises the steps of:
(a) expansion rate of magnesium oxide concrete:
and establishing the relationship between the hydration reaction rate and temperature of the magnesium oxide, the hydration degree of the magnesium oxide and the activation energy of the hydration reaction according to an Arrhenius formula.
The expansion of magnesia concrete is essentially the process by which magnesia hydrates to magnesium hydroxide. Therefore, the process also follows the general rule of chemical reaction, the temperature and concentration are main influencing factors, the higher the temperature is, the faster the reaction is, the faster the hydration rate of magnesium oxide is, and the corresponding expansion increment is also larger; meanwhile, the swelling rate is proportional to the content of magnesium oxide participating in the reaction (which can be understood as the concentration in the liquid chemical reaction), and conforms to the chemical reaction kinetics equation-Arrhenius equation.
Thus, the hydration rate of magnesium oxide at time t can be expressed as a function of the chemical reaction affinity and temperature, and the hydration activity at that time, and is given by the formula (1):
wherein, zeta is the hydration degree of magnesium oxide;
is chemical reaction affinity; e m The unit is activation energy of hydration reaction and kJ/mol; r is a molar gas constant with a unit kJ/mol.K; t is the thermodynamic temperature in K.
(b) The autogenous volume deformation of the magnesia concrete:
the autogenous volume deformation of the magnesia concrete is mainly caused by the hydration of magnesia, so that the autogenous volume deformation of the magnesia concrete can be simulated by adopting a function of the hydration degree of the magnesia concrete. That is, the relationship between the hydration degree of magnesium oxide and the amount of concrete expansion can be expressed by the formula (2):
ε au ＝f(ζ) (2)
wherein epsilon au The autogenous volume deformation of the magnesia concrete is shown; f (. zeta.) is a function of the degree of hydration of the magnesium oxide inside the concrete.
It is considered that the same hydration degree of the magnesium oxide in the concrete samples having the same composition is obtained when the autogenous volume deformation of the concrete is the same.
(c) Activation energy of hydration reaction of magnesium oxide:
establishing a mathematical model for calculating the hydration reaction activation energy of the magnesium oxide in the concrete by combining the relationship between the hydration degree of the magnesium oxide and the expansion amount of the concrete;
according to equation (1), the expansion rate of concrete is only temperature dependent for any degree of hydration of magnesium oxide (ζ). Thus, under two different conditions of constant concrete curing temperature, the ratio of the hydration reaction rate (expansion rate) is a function of temperature:
the time required to reach the same degree of hydration therefore also correlates with the temperature of the concrete. Formula (1) can be rewritten as:
integrating the two sides of equation (5) simultaneously can obtain:
thus, the time required to reach a certain fixed hydration level under different temperature conditions can be expressed as:
further, combining the above formula, the activation energy E of hydration reaction of magnesium oxide in concrete m The mathematical model of (a) can be expressed as:
wherein E is m The unit is the activation energy of hydration reaction and kJ/mol; r is molar gasVolume constant, unit kJ/mol.K; t is t 1 And t 2 First age and second age, respectively, in units day; t is 1 And T 2 First and second thermodynamic temperatures, respectively, in K.
According to the equation (11), the hydration reaction activation energy of the magnesium oxide can be calculated by combining the autogenous volume deformation experimental data of the magnesium oxide concrete, only by analyzing the autogenous volume deformation data of the concrete under two different temperature conditions and selecting the age with the same or similar autogenous volume deformation.
From the above analysis, the hydration reaction activation energy of magnesium oxide in concrete can be indirectly determined by testing the autogenous volume deformation.
The concrete solving method of the method for measuring and calculating the hydration reaction activation energy of the externally-doped magnesia concrete is simple to operate and easy to realize.
In a preferred embodiment, the externally-doped magnesia concrete comprises coarse aggregates, fine aggregates, cement, fly ash, a water reducing agent, an air entraining agent, water and a light-burned magnesia expanding agent;
preferably, the mixing amount of the light-burned magnesia expanding agent is 0.1-5.0 wt%, preferably 0.3-3.5 wt%;
preferably, the water-cement ratio of the externally-doped magnesia concrete is 0.45-0.65, and preferably 0.56-0.59.
It is understood that the concrete composition of the magnesia concrete is not particularly limited, and the amount of each raw material is not particularly limited, and the magnesia concrete is prepared by using concrete raw materials and proportions commonly used or well known in the art and adding a certain amount of magnesia according to actual design and application requirements. The method has the characteristics of good adaptability, strong practicability and the like.
In a preferred embodiment, the calcination temperature of the light calcined magnesia expanding agent is 850-1200 ℃, and the calcination heat preservation time is 0.5-2 h.
In a preferred embodiment, the magnesium oxide is derived from the raw material in the raw meal from at least one of magnesium-containing periclase, limestone, dolomite or magnesite.
It should be understood that the source of magnesium oxide, the calcining temperature, and other treatment methods and conditions are not particularly limited in the present invention, and magnesium oxide materials commonly used or suitable in the art can be selected according to actual conditions and added to concrete after treatment.
In a second aspect, in at least one embodiment, there is provided a use of the method for measuring and calculating hydration reaction activation energy of the externally-doped magnesium oxide concrete in kinetic study of the concrete containing magnesium oxide.
The invention is further described below with reference to specific embodiments and the accompanying drawings.
Examples
FIG. 1 shows the relationship between concrete age and its autogenous volume deformation under different temperature conditions, provided by an embodiment of the present invention, and t in the present invention 1 And t 2 A schematic diagram of (a); referring to fig. 1, a method for measuring and calculating hydration reaction activation energy of concrete doped with magnesium oxide is realized by theoretical derivation: in the process of solving the hydration reaction activation energy of the magnesium oxide in the magnesium oxide concrete, firstly, the relationship between the chemical reaction activation energy and the age and the temperature is worked out according to an Arrhenius formula obeyed by the chemical reaction rate; then, by selecting two different fixed temperatures T 1 And T 2 And calculating the relation between the ratio of the time required for reaching the same hydration degree and the temperature, and establishing a mathematical model for calculating the hydration reaction activation energy of the magnesium oxide in the concrete.
Then, the age corresponding to the same autogenous volume deformation (hydration degree) can be selected according to the mathematical model of the hydration reaction activation energy of the magnesium oxide in the concrete and the autogenous volume deformation test data of the concrete, and then the solution can be carried out.
The application of the invention will now be described by taking a certain hydroelectric project which adopts externally-doped magnesia concrete as a dam filling material.
A certain hydropower station project is located in a gorge area in the western part of the Yunobi plateau, and the reservoir dam adopts externally-doped magnesia concrete as a filling material to achieve the purposes of reducing temperature control measures, shortening construction period and saving investment. By combining with design requirements and through a series of tests, the mix proportion of dam concrete is determined, and is shown in table 1:
table 1 dam concrete each component table
The autogenous volume deformation data of concrete at different temperatures for each age are shown in table 2.
TABLE 2 autogenous volume deformation of magnesia concrete of different water-cement ratio at different temperatures for different ages
The hydration reaction activation energy of the externally-doped magnesium oxide concrete with two water-to-gel ratios is calculated by applying the method for measuring and calculating the hydration reaction activation energy of the externally-doped magnesium oxide concrete.
(1) Magnesium oxide concrete with w/b equal to 0.56
Two values with the most approximate autogenous volume deformation are selected: 53.422(30 ℃, 28d age), 51.544(40 ℃, 14d age), applying equation (11), we can get:
wherein R is a molar gas constant of 8.314 kJ/mol.K, and the hydration reaction activation energy E of the magnesium oxide can be further obtained m It was 54.7 kJ/mol.
(2) Magnesium oxide concrete with w/b equal to 0.59
Two values with the most approximate autogenous volume deformation are selected: 13.378(20 ℃, 7d age), 11.826(40 ℃, 3d age), applying equation (11), we can get:
wherein R is a molar gas constant of 8.314 kJ/mol.K, and the hydration reaction activation energy E of the magnesium oxide can be further obtained m It was 32.5 kJ/mol.
As can be seen from the above calculation examples, the hydration reaction activation energies of magnesium oxide in different concretes are different.
In addition, as can be understood by those skilled in the art, in practice, the data points can be encrypted by increasing the number of measurements to find out multiple sets of data points with the same self-generated volume deformation value for calculation, and the calculation accuracy can be improved by using a multiple-set averaging method. Of course, the method is noted here as a matter of caution in practical application, but does not affect the theoretical rigor of the method.
The algorithm of the invention is derived from mathematical equations, is rigorous and reliable theoretically, and can be directly solved by means of the data of the autogenous volume deformation of the magnesia concrete; compared with the method that the reaction of the magnesium oxide and the water is directly adopted or the hydration kinetic analysis is carried out on the cement containing the magnesium oxide, the indirect solving method is not only convenient, but also can reflect the reaction condition of the magnesium oxide in the concrete more truly. In addition, the invention combines the practical engineering practice to give a specific example of the method, and the method is easy to be applied in practice.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and these modifications or substitutions do not depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. A method for measuring and calculating hydration reaction activation energy of externally-doped magnesia concrete is characterized by comprising the following steps:
establishing the relationship between the hydration reaction rate and temperature of the magnesium oxide, the hydration degree of the magnesium oxide and the activation energy of the hydration reaction according to an Arrhenius formula;
establishing a mathematical model for calculating the hydration reaction activation energy of the magnesium oxide in the concrete; the mathematical model may be represented as:
wherein E is m The unit is the activation energy of hydration reaction and kJ/mol; r is a molar gas constant with a unit kJ/mol.K; t is t 1 And t 2 First age and second age, respectively, in units day; t is 1 And T 2 A first thermodynamic temperature and a second thermodynamic temperature, respectively, in units of K;
by utilizing the established mathematical model of the hydration reaction activation energy of the magnesium oxide in the concrete and combining the relationship between the hydration degree of the magnesium oxide and the expansion amount of the concrete and the test data of the autogenous volume deformation of the magnesium oxide concrete, the method can carry out the treatment on the magnesium oxide concrete at two different temperatures T 1 And T 2 And (3) analyzing the data of the concrete autogenous volume deformation under the condition, and calculating the hydration reaction activation energy of the magnesium oxide in the concrete by selecting the age with the same or similar autogenous volume deformation.
2. The method for measuring and calculating the hydration reaction activation energy of the concrete doped with the magnesium oxide as claimed in claim 1, wherein the relationship between the hydration reaction rate and the temperature, the hydration degree of the magnesium oxide and the hydration reaction activation energy of the magnesium oxide at the time t can be expressed as follows according to the Arrhenius formula:
wherein,
is the hydration degree of magnesium oxide;
is chemical reaction affinity; e m The unit is the activation energy of hydration reaction and kJ/mol; r is a molar gas constant with a unit kJ/mol.K; t is the thermodynamic temperature in K.
3. The method for measuring and calculating the hydration reaction activation energy of the concrete doped with the magnesium oxide according to claim 1, wherein the relationship between the hydration degree of the magnesium oxide and the expansion amount of the concrete is expressed as follows:
wherein epsilon au The autogenous volume deformation of the magnesia concrete is shown; f (. zeta.) is a function of the degree of hydration of the magnesium oxide inside the concrete.
4. The method for measuring and calculating the hydration reaction activation energy of the externally-doped magnesia concrete according to claim 1, wherein the test data of the autogenous volume deformation of the magnesia concrete comprises the autogenous volume deformation amount, the temperature and the age of the magnesia concrete.
5. The method for measuring and calculating the hydration reaction activation energy of the externally-doped magnesia concrete according to any one of claims 1 to 4, wherein the externally-doped magnesia concrete comprises coarse aggregates, fine aggregates, cement, fly ash, a water reducing agent, an air entraining agent, water and a light-burned magnesia expanding agent.
6. The method for measuring and calculating the hydration reaction activation energy of the concrete doped with the magnesium oxide externally, according to claim 5, wherein the doping amount of the light-burned magnesium oxide expanding agent is 0.1-5.0 wt%.
7. The method for measuring and calculating the hydration reaction activation energy of the concrete doped with the magnesium oxide externally, according to claim 5, wherein the doping amount of the light-burned magnesium oxide expanding agent is 0.3-3.5 wt%.
8. The method for measuring and calculating the hydration reaction activation energy of the externally-doped magnesia concrete according to claim 5, wherein the calcination temperature of the lightly-calcined magnesia expansive agent is 850-1200 ℃, and the calcination heat preservation time is 0.5-2 h.
9. The method for measuring and calculating the hydration reaction activation energy of the externally-doped magnesia concrete according to any one of claims 1 to 4, wherein the magnesia is derived from at least one of raw materials of magnesium-containing periclase, limestone, dolomite or magnesite in raw materials.
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