CN113486530A - Macro-microscopic model equivalent method for analyzing use state of reinforced concrete in chloride ion environment - Google Patents

Macro-microscopic model equivalent method for analyzing use state of reinforced concrete in chloride ion environment Download PDF

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CN113486530A
CN113486530A CN202110804156.5A CN202110804156A CN113486530A CN 113486530 A CN113486530 A CN 113486530A CN 202110804156 A CN202110804156 A CN 202110804156A CN 113486530 A CN113486530 A CN 113486530A
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concrete
itz
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aggregate
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张芹
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Nanjing Vocational University of Industry Technology NUIT
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Abstract

The invention discloses a macro-micro model equivalent method for analyzing the use state of reinforced concrete in a chloride ion environment, which relates to the technical field of building material analysis, and comprises the steps of S1, establishing the equivalence of mechanical properties of micro concrete and a macro concrete model, S2, establishing the equivalent diffusion coefficient of a single aggregate and ITZ
Figure DDA0003165743900000011
S3, obtaining the equivalent diffusion coefficient D of the aggregate and the ITZ according to the quantity ratio of the aggregates with different particle diameterseqS4, the mortar, the aggregate and the ITZ microscopic concrete are equivalent to a concrete macroscopic diffusion coefficient D, aiming at the complex maritime work environment, the calculation of an analysis main body can be effectively reduced while the requirement of analysis is met by the equivalent methodDimensionality, improved calculation efficiency, and further enrichment and development of a basic method for researching the durability of the reinforced concrete structure.

Description

Macro-microscopic model equivalent method for analyzing use state of reinforced concrete in chloride ion environment
Technical Field
The invention belongs to the technical field of building material analysis, and particularly relates to a macro-micro model equivalent method for analyzing the use state of reinforced concrete in a chloride ion environment.
Background
With the high-speed development of economy in China, some important cross-sea bridges, submarine tunnels and other infrastructures supported by means of top technology are put into construction or use. As a material used for a large amount of infrastructure, concrete is increasingly highlighted in safety and durability in construction and use, and higher requirements are put on design. Therefore, the proposal and application of the basic method in the durability research of the reinforced concrete structure are focused.
Concrete is a composite material, which consists of coarse aggregate, mortar and a bonding interface between the coarse aggregate and the mortar. In numerical simulation, the state of use of a concrete structure is generally analyzed by a multi-scale method. However, in the marine environment, corrosion of concrete by chloride ions can cause corrosion of steel bars, and the concrete protective layer can crack due to corrosion volume expansion of the steel bars, so that the transportation channel of chloride ions in the concrete can be obviously changed, and the corrosion damage process of the steel bars is aggravated. The above processes are coupled so that the analysis of the use state of the reinforced concrete structure becomes relatively complicated. The analysis precision and the calculation efficiency are balanced, a reasonable macroscopic and microscopic equivalent simulation method is provided for a large or complex reinforced concrete structure, and the research of applying the method to the gradual reinforced process coupling of chloride ion erosion and reinforcing steel corrosion expansion is relatively less.
Disclosure of Invention
In order to develop a basic method for researching the durability of a large reinforced concrete structure in a complex environment, the invention aims to provide a macroscopic and microscopic model equivalent method for analyzing the use state of concrete in a chloride ion environment.
In order to achieve the purpose, the invention adopts the following technical scheme:
the concrete mesoscopic analysis model is shown in fig. 4, and the equivalent macroscopic model of the mesoscopic analysis model is shown in fig. 5.
A macro and microscopic model equivalent method for analyzing the use state of reinforced concrete in a chloride ion environment comprises the following steps:
s1, simplifying the concrete microscopic model into a concrete macroscopic model with equal size according to the randomly generated concrete microscopic model, obtaining a stress-strain curve of the microscopic concrete by applying axial tension to the microscopic model, thereby obtaining equivalent mechanical parameters of the macroscopic concrete, and establishing the equivalence of the mechanical properties of the microscopic concrete and the macroscopic concrete model;
s2, establishing equivalent diffusion coefficient of single aggregate and ITZ
Figure RE-GDA0003201677540000021
ITZ refers to the interfacial transition zone, and its equivalent formula is as follows:
Figure RE-GDA0003201677540000022
wherein R is the radius of a single aggregate,
Figure RE-GDA0003201677540000023
the ITZ diffusion coefficient outside the single aggregate of the ith particle size,
Figure RE-GDA0003201677540000024
is the i-th aggregate diffusion coefficient, δ is the thickness of the ITZ;
s3, obtaining the equivalent diffusion coefficient D of the aggregate and the ITZ according to the quantity ratio of the aggregates with different particle diameterseqThe formula is as follows:
Figure RE-GDA0003201677540000025
in the formula, N(i)Is the total number of aggregates of the i-th class particle size;
s4, equating mortar, aggregate and ITZ microscopic concrete to be a concrete macroscopic diffusion coefficient D, wherein the formula is as follows:
Ditz＝αDcp
Figure RE-GDA0003201677540000026
in the formula, DitzIs the diffusion coefficient of ITZ, alpha is the diffusion ratio of ITZ to mortar, fcpIs the ratio of the total area occupied by the mortar, faggThe ratio of the aggregate to the total area, DcpIs the diffusion coefficient of chloride ions in the mortar, fitzIs ITZ of total areaThe ratio of the products.
Preferably, the penetration ability of the aggregate is neglected in the step S1, i.e., the step S
Figure RE-GDA0003201677540000027
The method can be applied to the durability research of the large reinforced concrete structure in the complex environment.
The invention has the advantages that: the concrete microscopic and macroscopic equivalent method provided by the invention has clear design thought and simple operation process, and the calculated concrete macroscopic diffusion coefficient D can effectively realize the analysis of the problems related to the durability of the concrete structure in the chloride ion environment, thereby providing an efficient analysis means for the design of the marine reinforced concrete structure and the analysis of the degradation problems in the use process.
Drawings
FIG. 1 is a stress-strain curve of a macro concrete under uniaxial tension;
FIG. 2 is a macroscopic and microscopic simulated contrast of chloride ion as a function of depth;
FIG. 3 is a graph showing the concrete damage caused by chlorine ions.
Fig. 4 is a concrete microscopic analysis model.
Fig. 5 is an equivalent macroscopic model of the mesoscopic model in fig. 4.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.
And S1, realizing the equivalence of concrete mesoscopic and macroscopic models in terms of mechanical properties. According to the material parameters of the concrete mesoscopic model (see table 1), the aging process of uniaxial tension of the mesoscopic concrete is analyzed to obtain a stress-strain curve (figure 1) of the concrete, so that equivalent material parameters of the concrete macroscopic model under the same size are obtained, the tensile strength of the concrete macroscopic model is about 0.95MPa, and the elastic modulus is about 39.5 GPa.
TABLE 1 mechanical parameters of concrete components
Material Modulus of elasticity (MPa) Poisson ratio Tensile strength (MPa)
Cement mortar 30×103 0.2 1.43
Aggregate material 70×103 0.16 -
ITZ 25×103 0.22 1.2
S2, analytical example, only one side of the concrete was exposed to an analytical environment having a chloride ion concentration of 1.5%, D is knowncp＝3.04×10-12m2A, a is 3, neglecting the penetration ability of the aggregate, i.e. the
Figure RE-GDA0003201677540000032
Randomly putting aggregates according to a Fuller curve, and calculating to obtain f in the example model through a related programagg＝0.4526，fitz＝0.1190，fcp0.4284, and according to S2-S3 in the summary of the invention section, D is calculatedeq＝2.45×10-12m2S, substituted into the following equation:
Ditz＝αDcp
Figure RE-GDA0003201677540000031
s3, obtaining D through the concrete microscopic and macroscopic equivalent method provided by the patentitz＝9.12× 10-12m2S, the final D is 2.69 × 10-12m2/s。
S4, the macroscopic diffusion coefficient D of the concrete obtained according to the method is brought into a relevant program, and the concentration distribution of the chloride ions in the concrete is respectively calculated based on the microscopic model and the macroscopic model, so that distribution curves (figure 2) of the chloride ion concentrations of the two models changing along with the depth after 20 years are obtained. It can be obviously seen that the change curve of the concentration of the chlorine ions in the equivalent macroscopic concrete along with the diffusion depth is basically consistent with that obtained by the simulation of the microscopic concrete on the premise of allowing the calculation precision, and the adoption of the equivalent method provided by the patent is reasonable.
And S5, considering the coupling of chloride ion diffusion and reinforcement rust expansion under the marine environment to cause the concrete cracking process, and taking the material parameters of the macro concrete obtained by using the S2-S4 equivalent method into a related analysis program to obtain the damage distribution condition in the concrete. As can be seen from FIG. 3, according to the macro and micro model equivalent method provided by the patent, the concrete damage cracking process caused by reinforcement corrosion and expansion under the chloride ion environment can be better simulated by the macro concrete model.
It will be appreciated by those skilled in the art that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed above are therefore to be considered in all respects as illustrative and not restrictive. All changes which come within the scope of or equivalence to the invention are intended to be embraced therein.

Claims (3)

1. A macro and microscopic model equivalent method for analyzing the use state of reinforced concrete in a chloride ion environment is characterized by comprising the following steps:
s1, simplifying the concrete microscopic model into a concrete macroscopic model with equal size according to the randomly generated concrete microscopic model, obtaining a stress-strain curve of the microscopic concrete by applying axial tension to the microscopic model, thereby obtaining equivalent mechanical parameters of the macroscopic concrete, and establishing the equivalence of the mechanical properties of the microscopic concrete and the macroscopic concrete model;
s2, establishing equivalent diffusion coefficient of single aggregate and ITZ
Figure FDA0003165743870000011
The equivalent formula is as follows:
Figure FDA0003165743870000012
wherein R is the radius of a single aggregate,
Figure FDA0003165743870000013
the ITZ diffusion coefficient outside the single aggregate of the ith particle size,
Figure FDA0003165743870000014
the diffusion coefficient of the ith aggregate is delta, and the ITZ thickness is delta;
s3, obtaining the equivalent diffusion coefficient D of the aggregate and the ITZ according to the quantity ratio of the aggregates with different particle diameterseqThe formula is as follows:
Figure FDA0003165743870000015
in the formula, N(i)Is the total number of aggregates of the i-th class particle size;
s4, equating mortar, aggregate and ITZ microscopic concrete to be a concrete macroscopic diffusion coefficient D, wherein the formula is as follows:
Ditz＝αDcp
Figure FDA0003165743870000016
in the formula, DitzIs the diffusion coefficient of ITZ chloride ions, alpha is the diffusion ratio of ITZ to mortar, fcpIs the ratio of the total area occupied by the mortar, faggThe ratio of the aggregate to the total area, DcpIs the diffusion coefficient of chloride ions in the mortar, fitzIs the ratio of ITZ to total area.
2. The macro and microscopic model equivalent method for analyzing the using state of the reinforced concrete in the chloride ion environment according to claim 1, characterized in that: the step S1 ignores the penetration ability of the aggregate, that is, the step
Figure FDA0003165743870000017
3. The macro-microscopic model equivalent method for analyzing the using state of the reinforced concrete in the chloride ion environment according to claim 1 or 2, wherein the equivalent method can be applied to the durability research of the large reinforced concrete structure in the complex environment.
CN202110804156.5A 2021-07-16 2021-07-16 Macro-microscopic model equivalent method for analyzing use state of reinforced concrete in chloride ion environment Withdrawn CN113486530A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115205486A (en) * 2022-07-14 2022-10-18 重庆交通大学 Concrete three-dimensional microscopic numerical model construction method and chloride ion transmission simulation system
CN117077501A (en) * 2023-10-17 2023-11-17 中南大学 Heterogeneous steel slag concrete permeability coefficient calculation method

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115205486A (en) * 2022-07-14 2022-10-18 重庆交通大学 Concrete three-dimensional microscopic numerical model construction method and chloride ion transmission simulation system
CN117077501A (en) * 2023-10-17 2023-11-17 中南大学 Heterogeneous steel slag concrete permeability coefficient calculation method
CN117077501B (en) * 2023-10-17 2024-01-09 中南大学 Heterogeneous steel slag concrete permeability coefficient calculation method

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