CN116106200A - Method for evaluating ITZ permeability coefficient of concrete by aggregate type - Google Patents
Method for evaluating ITZ permeability coefficient of concrete by aggregate type Download PDFInfo
- Publication number
- CN116106200A CN116106200A CN202310258004.9A CN202310258004A CN116106200A CN 116106200 A CN116106200 A CN 116106200A CN 202310258004 A CN202310258004 A CN 202310258004A CN 116106200 A CN116106200 A CN 116106200A
- Authority
- CN
- China
- Prior art keywords
- aggregate
- itz
- test piece
- model
- concrete
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
- G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Abstract
The invention relates to a method for evaluating the permeability coefficient of concrete ITZ by aggregate type, which belongs to the field of permeability coefficient measurement and comprises the steps of selecting a mould and a model aggregate, bonding the model aggregate with the bottom of a concrete column-shaped mould, and calculating the average thickness of the concrete ITZ; calculating ITZ area and cement mortar area, and measuring D SU And D CE The method comprises the steps of carrying out a first treatment on the surface of the According to the invention, only the types of model aggregates are considered, complex three-dimensional infiltration calculation is simplified to two dimensions through a test means, the infiltration areas of ITZ and cement mortar on the cross section of a test piece are calculated, the concrete ITZ infiltration coefficient is calculated quantitatively, only the number of the model aggregates and the infiltration area of erosion media on the cross section are considered, the complexity of the concrete ITZ infiltration coefficient calculation is reduced, a quantitative research method for the infiltration coefficient is provided for concrete ITZ test research, scientific basis is provided for the application of different types of aggregates in engineering structures, and the method has important theoretical significance and practical value.
Description
Technical Field
The invention relates to a method for evaluating the ITZ permeability coefficient of concrete by aggregate type, belonging to the technical field of permeability coefficient measurement.
Background
The Interface Transition Zone (ITZ) is the weakest link in the concrete, has the characteristics of low density, high porosity, low hardness and the like, and the structure and the performance of the ITZ determine the overall performance of the cement concrete to a great extent. Because ITZ has very high porosity, under the coupling effect of load and environmental factors, cracks are generated and spread from the ITZ of concrete initially in the service process of the concrete structure, erosion media are transmitted faster in the ITZ, and the erosion media in the environment enter the ITZ to cause the change of the interior of the concrete, so the permeability of the ITZ directly determines the durability of the concrete. Particularly in reinforced concrete structures, the passivation film of the steel bar is easily eroded by an erosion medium to generate a soluble product, and the erosion of the passivation film causes the steel bar to be corroded, so that the durability of the concrete is reduced.
The thickness of the concrete ITZ is generally 20-50 mu m, the research means is relatively single, and the volume of the ITZ mainly depends on factors such as the surface area, the number, the grading, the length-diameter ratio, the curvature and the like of the aggregate. Because the aggregate type, the shape and the size are irregular, and the aggregate type has a critical influence on the ITZ of the concrete, the establishment of a test method for evaluating the ITZ permeability of the concrete by different types of aggregate is critical to the durability evaluation of the concrete.
Disclosure of Invention
Aiming at a series of problems that aggregate types are changeable in concrete ITZ permeability coefficient research, the permeability coefficient calculation process is complex, most of current concrete ITZ researches are based on numerical simulation, theoretical models and other means, verification of test data is lacking and the like, the invention provides a method for evaluating the concrete ITZ permeability coefficient by the aggregate types. According to the invention, columnar model aggregates with a plurality of specified shapes and sizes are used for manufacturing the ITZ in the concrete test piece simulation concrete, only the types of the model aggregates are changed, then the thickness of the concrete ITZ on the cross section is observed through microscopic experiments such as SEM after standard maintenance of the test piece is completed, and the complex three-dimensional infiltration calculation process is simplified to two dimensions.
The invention adopts the following technical scheme:
a method for evaluating the ITZ permeability coefficient of concrete by aggregate type, comprising the following steps:
(1) Selecting a proper mold:
selecting a concrete column-shaped mould with a runway-shaped cross section, wherein the height of the concrete column-shaped mould is 50mm, the concrete column-shaped mould consists of two semicircular areas which are symmetrical and equal in size, a non-detachable baffle plate which is equal in height to the concrete column-shaped mould is arranged between the two semicircular areas, the two semicircular areas are respectively used for filling an ITZ area (containing model aggregate) and a cement mortar area (not containing model aggregate), the sum of the cross sectional areas of the two semicircular areas is recorded as A, and the bottom of the concrete column-shaped mould is a detachable wood plate;
(2) The method comprises the steps of selecting a cuboid with the side length of 100mm or a cylinder with the same diameter as a model aggregate (other shape aggregates can be selected if special requirements exist), selecting a model aggregate material which is consistent with a real aggregate, selecting a cylinder model aggregate when the actual roundness sigma of the aggregate is more than or equal to 0.75, and selecting a cuboid model aggregate when the actual roundness sigma of the aggregate is less than 0.75, wherein:
wherein: sigma is the aggregate solidThe inter-roundness; a is that 0 The projection area of coarse aggregate particles in the maximum outline image is; l (L) 0 Projecting the outline perimeter for coarse aggregate particles in the maximum outline image;
the roundness measuring instrument comprises a camera and an image processing device, wherein the camera can be used for photographing and image processing to obtain an outline image of aggregate, and the largest outline image is selected from the outline image;
(3) After the type and shape of the model aggregate are determined, placing a plurality of cut model aggregates with the height of 50mm in one semicircular area of the concrete columnar die prepared in the step (1), bonding the bottom of the model aggregate with the bottom of the concrete columnar die, in order to avoid superposition of ITZ around the model aggregate, uniformly distributing the model aggregates when placing, pouring cement mortar in the two semicircular areas of the concrete columnar die, uniformly distributing slurry in the areas at two sides of the die according to the test procedure of highway engineering cement and cement concrete (JTGE 30) when pouring the cement mortar, placing the slurry in a standard curing chamber for curing after pouring, removing a test piece until the curing reaches a specified age, and separating the concrete columnar die from the bottom of the test piece to obtain a test piece containing the model aggregate and a test piece containing the cement mortar respectively;
(4) Preparing a plurality of parallel test pieces (the parallel test pieces are test pieces with parameters such as mixing ratio, stirring time, maintenance method and the like which are completely the same as those of test pieces for experiments and can be regarded as one or more identical test pieces under the same conditions), and drying, cleaning the surfaces and polishing the surfaces according to the requirements of general rule of scanning electron microscope analysis method (JY/T0584-2020); the sample is sent into a sample chamber, then the amplification factor is selected, a scanning electron microscope is focused, parameters such as contrast, brightness and the like are regulated, the image is photographed and stored after being clear, the thickness value of the interface transition zone is determined according to the scale and the length in the screenshot, the thickness value of the concrete ITZ is observed and recorded through a scanning electron microscope, 4 corner and 1 center model aggregate are selected as representative, 20 times of thickness is recorded along the periphery of each model aggregate, the average value is taken, and the average thickness of the concrete ITZ is recorded as d;
(5) After determining the ITZ thickness as d, IT is calculated in the ITZ regionZ area A ITZ And cement mortar area A in ITZ zone CE ；
(6) The test piece containing the model aggregate and the cement mortar obtained in the step (4) are subjected to the test piece treatment according to erosion media (chloride ions, O 2 And CO 2 Etc.) penetration test, while determining the penetration coefficient D of a test piece containing a model aggregate SU Permeability coefficient D with cement mortar test piece CE ；
For the penetration test, in the test piece containing the model aggregate, the penetration coefficient of the test piece meets the following conditions:
the permeability coefficient D of the concrete Interface Transition Zone (ITZ) can be reversely deduced according to the above ITZ ：
Wherein: d (D) SU The permeability coefficient of the test piece containing the model aggregate is obtained by a permeability test of the test piece containing the model aggregate; d (D) CE The permeability coefficient of the test piece of the pure cement mortar is obtained by a pure cement mortar test piece permeability test; a is the total cross-sectional area of the two semicircular areas; a is that AGG 1 model aggregate cross-sectional area; d (D) ITZ Is the Interfacial Transition Zone (ITZ) permeability coefficient.
The permeability coefficient measuring device can be used for simultaneously measuring the permeability areas of the ITZ and the cement mortar on the cross section of the test piece and quantitatively calculating the permeability coefficient of the concrete ITZ.
Preferably, in the step (1), the radius of the semicircular area is 50mm, and the thickness of the baffle is 12mm.
Preferably, in the step (3), the number of the model aggregates is 10, and the number is proper, so that the model aggregates can be uniformly put down in the die, and a larger ITZ area is provided, so that measurement errors are reduced.
Preferably, the bottom of the model aggregate is bonded to the bottom of the concrete column-shaped mold by using an adhesive such as epoxy resin.
Preferably, in step (5):
(1) when the model aggregate is square aggregate, the side length of the model aggregate is recorded as l, A ITZ ＝n×(πd 2 +4dl) (the peripheral ITZ area on each side of the square aggregate was dl, and the peripheral ITZ shape on each corner of the square aggregate was 1/4 circle, the area was pi d 2 /4)，
(2) When the model aggregate is circular aggregate, the radius is r and A ITZ ＝n×π[(r+d) 2 -r 2 ]，
Wherein: a is the total cross-sectional area of two semicircular areas in mm 2 The method comprises the steps of carrying out a first treatment on the surface of the n is the number of model aggregates, and 10 is taken; a is that ITZ ITZ area in mm on cross section of test piece containing model aggregate 2 ；A CE The area of the cement mortar area in mm in the cross section of the test piece containing the model aggregate 2 The method comprises the steps of carrying out a first treatment on the surface of the d is the ITZ thickness in mm; l is the side length of the square model aggregate, and the length is 10mm; r is the radius of the round model aggregate, and 5mm is taken.
Preferably, in the step (6), the device for the penetration test comprises four sealing grooves, wherein two sealing grooves are penetration medium sealing grooves, two sealing grooves are common medium sealing grooves, a model aggregate-containing test piece and a cement mortar test piece which are subjected to maintenance in the step (3) are placed between the four sealing grooves, and the model aggregate-containing test piece and the cement mortar test piece jointly form a cylinder with the radius of 50mm and the height of 50 mm.
Preferably, the test piece containing the model aggregate and the cement mortar test piece are coated with epoxy resin or the like on the side edges before being placed in the four sealing grooves so as to prevent permeation of the permeation medium from the side edges.
Preferably, in the step (6), a communication port with a semicircular cross section area is arranged between the permeable medium sealing groove and the common medium sealing groove, one end of the test piece is arranged in the permeable medium sealing groove through the communication port, and the other end of the test piece is arranged in the common medium sealing groove;
a fixed net is arranged between the communication port and the test piece, the fixed net is a semicircular copper net with the radius of 50mm and the thickness of 1mm, a plurality of through holes which are uniformly distributed are arranged in the middle of the fixed net, so that chloride ions can freely permeate between the solution, the copper net and the test piece, and the round edge of the fixed net is provided with a thin iron sheet with the height of 10mm;
the rubber ring is arranged in the test area between the permeable medium sealing groove and the common medium sealing groove, the height of the rubber ring is 50mm, the cross section of the rubber ring is in a runway shape, two semi-cylindrical test pieces, namely a test piece containing model aggregate and a cement mortar test piece, can be put down simultaneously, the radius of the rubber ring is slightly smaller than that of the test piece, the rubber ring is made of high-temperature-resistant and ageing-resistant butyl rubber, can be freely stretched and tightly wrapped on the test piece, the device can prevent permeation media from permeating from the side edges of the test pieces, so that experimental results are more accurate, a soft rubber baffle plate with the thickness of 5mm is arranged in the middle of the rubber ring and is used for separating the two test pieces, and pipe hoops for fixing the test pieces are arranged at two ends of the rubber ring and are used for hooping the test pieces, the rubber ring and thin iron sheets on a fixed net.
The present invention is not limited to the details of the prior art.
The beneficial effects of the invention are as follows:
the method of the invention uses model aggregates with specified shapes and sizes to manufacture the ITZ in the concrete test piece to simulate concrete, only considers the types of the model aggregates, simplifies complex three-dimensional permeation calculation into two dimensions by a test means, calculates the permeation area of ITZ and cement mortar on the cross section of the test piece, quantitatively calculates the ITZ permeation coefficient of the concrete, only considers the quantity of the model aggregates and the permeation area of erosion media on the cross section, reduces the complexity of calculating the ITZ permeation coefficient of the concrete, provides a quantitative research method of the permeation coefficient for the ITZ test research of the concrete, provides scientific basis for the application of different types of aggregates in engineering structures, and has important theoretical significance and practical value.
Drawings
FIG. 1 is a schematic view of a concrete columnar mold of the present invention;
FIG. 2 is a schematic distribution diagram of a model aggregate, wherein (a) is a cuboid, and (b) is a cylinder;
FIG. 3 is a schematic view of the apparatus structure of the permeation test;
FIG. 4 is a schematic structural view of a rubber ring;
FIG. 5 is a schematic illustration of the manner in which the pipe clamp is secured;
wherein, 1-baffle, 2-infiltration medium seal groove, 3-ordinary medium seal groove, 4-thin iron sheet, 5-ferrule, 6-rubber ring, 7-support.
Detailed Description
In order to make the technical problems, technical solutions and advantages to be solved by the present invention more apparent, the following detailed description will be given with reference to the accompanying drawings and specific embodiments, but not limited thereto, and the present invention is not fully described and is according to the conventional technology in the art.
Example 1:
a method for evaluating the ITZ permeability coefficient of concrete by aggregate type, comprising the following steps:
(1) Selecting a proper mold:
selecting a concrete columnar mould with a runway-shaped cross section, wherein the height of the concrete columnar mould is 50mm, the concrete columnar mould consists of two semicircular areas which are symmetrical and equal in size, a non-detachable baffle plate 1 which is equal in height to the concrete columnar mould is arranged between the two semicircular areas, the two semicircular areas are respectively used for filling an ITZ area (containing model aggregate) and a cement mortar area (not containing model aggregate), the sum of the cross sections of the two semicircular areas is recorded as A, and the bottom of the concrete columnar mould is a detachable wood plate;
(2) The method comprises the steps of selecting a cuboid with the side length of 100mm or a cylinder with the same diameter as a model aggregate (other shape aggregates can be selected if special requirements exist), selecting a model aggregate material which is consistent with a real aggregate, selecting a cylinder model aggregate when the actual roundness sigma of the aggregate is more than or equal to 0.75, and selecting a cuboid model aggregate when the actual roundness sigma of the aggregate is less than 0.75, wherein:
wherein: sigma is the actual roundness of the aggregate; a is that 0 The projection area of coarse aggregate particles in the maximum outline image is; l (L) 0 Projecting the outline perimeter for coarse aggregate particles in the maximum outline image;
the roundness measuring instrument comprises a camera and an image processing device, wherein the camera can be used for photographing and image processing to obtain an outline image of aggregate, and the largest outline image is selected from the outline image;
(3) After the type and shape of the model aggregate are determined, placing a plurality of cut model aggregates with the height of 50mm in one semicircular area of the concrete columnar die prepared in the step (1), bonding the bottom of the model aggregate with the bottom of the concrete columnar die, in order to avoid superposition of ITZ around the model aggregate, uniformly distributing the model aggregates when placing, pouring cement mortar in the two semicircular areas of the concrete columnar die, uniformly distributing slurry in the areas at two sides of the die according to the test procedure of highway engineering cement and cement concrete (JTGE 30) when pouring the cement mortar, placing the slurry in a standard curing chamber for curing after pouring, removing a test piece until the curing reaches a specified age, and separating the concrete columnar die from the bottom of the test piece to obtain a test piece containing the model aggregate and a test piece containing the cement mortar respectively;
(4) Preparing a plurality of parallel test pieces (the parallel test pieces are test pieces with parameters such as mixing ratio, stirring time, maintenance method and the like which are completely the same as those of test pieces for experiments and can be regarded as one or more identical test pieces under the same conditions), and drying, cleaning the surfaces and polishing the surfaces according to the requirements of general rule of scanning electron microscope analysis method (JY/T0584-2020); the sample is sent into a sample chamber, then the amplification factor is selected, a scanning electron microscope is focused, parameters such as contrast, brightness and the like are regulated, the image is photographed and stored after being clear, the thickness value of the interface transition zone is determined according to the scale and the length in the screenshot, the thickness value of the concrete ITZ is observed and recorded through a scanning electron microscope, 4 corner and 1 center model aggregate are selected as representative, 20 times of thickness is recorded along the periphery of each model aggregate, the average value is taken, and the average thickness of the concrete ITZ is recorded as d;
(5) After determining the ITZ thickness d, the ITZ area A in the ITZ region is calculated ITZ And cement mortar area A in ITZ zone CE ；
(6) The test piece containing the model aggregate and the cement mortar obtained in the step (4) are subjected to the test piece treatment according to erosion media (chloride ions, O 2 And CO 2 Etc.) penetration test, while determining the penetration coefficient D of a test piece containing a model aggregate SU Permeability coefficient D with cement mortar test piece CE ；
For the penetration test, in the test piece containing the model aggregate, the penetration coefficient of the test piece meets the following conditions:
the permeability coefficient D of the concrete Interface Transition Zone (ITZ) can be reversely deduced according to the above ITZ ：
Wherein: d (D) SU The permeability coefficient of the test piece containing the model aggregate is obtained by a permeability test of the test piece containing the model aggregate; d (D) CE The permeability coefficient of the test piece of the pure cement mortar was obtained by a test of the permeability of the test piece of the pure cement mortar (D SU 、D CE Can also be measured using existing specifications and techniques); a is the total cross-sectional area of the two semicircular areas; a is that AGG 1 model aggregate cross-sectional area; d (D) ITZ Is the Interfacial Transition Zone (ITZ) permeability coefficient.
The permeability coefficient measuring device can be used for simultaneously measuring the permeability areas of the ITZ and the cement mortar on the cross section of the test piece and quantitatively calculating the permeability coefficient of the concrete ITZ.
Example 2:
a method for evaluating the ITZ permeability coefficient of concrete by aggregate type, as described in example 1, except that the radius of the semicircular area was 50mm and the thickness of the baffle was 12mm.
Example 3:
a method for evaluating the ITZ permeability coefficient of concrete by aggregate type is disclosed in example 2, except that the number of model aggregates is 10, and the number is proper, so that the model aggregates can be uniformly put down in a mould, and the model aggregates have larger ITZ area, so that the measurement error is reduced.
Example 4:
a method for evaluating the ITZ permeability coefficient of concrete by aggregate type is as described in example 3, except that the bottom of the model aggregate is bonded to the bottom of the concrete column-shaped mold by using a bonding agent such as epoxy resin.
Example 5:
a method for evaluating the ITZ permeability coefficient of concrete by aggregate type as described in example 4, except that in step (5):
(1) when the aggregate is square, as shown in FIG. 2 (a), the side length is l, A ITZ ＝n×(πd 2 +4dl) (the peripheral ITZ area on each side of the square aggregate was dl, and the peripheral ITZ shape on each corner of the square aggregate was 1/4 circle, the area was pi d 2 /4)，
/>
(2) When the aggregate is a round aggregate, the radius is r, A as shown in FIG. 2 (b) ITZ ＝n×π[(r+d) 2 -r 2 ]，
Wherein: a is the total cross-sectional area of two semicircular areas in mm 2 The method comprises the steps of carrying out a first treatment on the surface of the n is the number of model aggregates, and 10 is taken; a is that ITZ ITZ area in mm on cross section of test piece containing model aggregate 2 ；A CE The area of the cement mortar area in mm in the cross section of the test piece containing the model aggregate 2 The method comprises the steps of carrying out a first treatment on the surface of the d is the ITZ thickness in mm; l is the side length of the square model aggregate, and the length is 10mm; r is the radius of the round model aggregate, and 5mm is taken.
Example 6:
in the method for evaluating the ITZ permeability coefficient of concrete according to the aggregate type, as shown in the embodiment 5, the difference is that in the step (6), as shown in fig. 3, the device for the permeability test comprises four sealing grooves, two of which are the permeable medium sealing grooves 2 and two of which are the common medium sealing grooves 3, a model aggregate-containing test piece and a cement mortar test piece which are cured in the step (3) are placed between the four sealing grooves, and the model aggregate-containing test piece and the cement mortar test piece jointly form a cylinder with the radius of 50mm and the height of 50 mm.
The test piece containing the model aggregate and the cement mortar test piece are coated with epoxy resin and the like on the side edges before being placed in the four sealing grooves so as to prevent permeation of a permeation medium from the side edges.
In the step (6), a communication port with a semicircular cross section area is arranged between the permeable medium sealing groove 2 and the common medium sealing groove 3, one end of a test piece is arranged in the permeable medium sealing groove 2 through the communication port, and the other end of the test piece is arranged in the common medium sealing groove 3;
a fixed net is arranged between the communication port and the test piece, the fixed net is a semicircular copper net with the radius of 50mm and the thickness of 1mm, the fixed net is fixed on the communication port, a plurality of evenly distributed through holes are arranged in the middle of the fixed net, free penetration of chloride ions between the solution, the copper net and the test piece is ensured, and the round edge of the fixed net is provided with a thin iron sheet 4 with the height of 10mm;
the test area in the middle of the osmotic medium closed 2 groove and the common medium closed groove 3 is provided with a rubber ring, the height of the rubber ring is 50mm, the cross section of the rubber ring is in a runway shape, two semi-cylindrical test pieces can be put down simultaneously, as shown in fig. 4, namely, a model aggregate test piece and a cement mortar test piece are contained, the radius of the rubber ring is slightly smaller than that of the test piece, high-temperature-resistant and ageing-resistant butyl rubber is selected as a material, the test piece can be tightly wrapped by free expansion, the osmotic medium can be prevented from permeating from the side edge of the test piece, the experimental result is more accurate, the middle part of the rubber ring is provided with a soft rubber baffle with the thickness of 5mm, and the two ends of the rubber ring are respectively provided with a pipe hoop 5 for fixing the test pieces, the rubber ring 6 and a thin iron piece 4 on the fixed network are hooped, and the osmotic coefficient of the two semi-cylindrical test pieces can be measured simultaneously.
As shown in fig. 5, the thin iron sheet 4 is a part of the penetration test device extending out, and the test piece and the rubber ring 6 are inserted into the thin iron sheet, and then clamped by the external pipe clamp 5, so that the penetration device is connected with the test piece and the tightness of the penetration device is maintained.
The device is also provided with a bracket 7 for fixing the medium slot of the osmotic medium slot and the medium slot of the common medium slot.
In this embodiment, a soft rubber baffle with a thickness of 5mm is arranged in the middle of the rubber ring 6 and used for separating two test pieces, two permeable medium closed grooves 2, or a gap between two common medium closed grooves 3 is also 5mm, so that the rubber ring and the test pieces of the runway type can be just fixed.
In this example, the permeability coefficient D of the test piece containing the model aggregate was measured by using a device for a permeability test SU Permeability coefficient D with cement mortar test piece CE In this case, several common methods for measuring permeability coefficient can be input in the control procedure of fig. 3, and the rapid permeation of chloride ions is illustrated as an example, and the ASTM C1202 method is used to measure the diffusion coefficient of chloride ions, and two equal parts of the treated (vacuum water retention, etc.) test pieces are placed between four electrolytic cells (i.e., between 2 permeable medium seal grooves and 2 common medium seal grooves). Placing 5% NaCl solution at the cathode, placing 0.3mol/L NaOH solution at the anode, applying 22V voltage by control program, and measuring chloride ion concentration in the anode solution every six hours by rapid chloride ion test (RCT), when the cumulative chloride ion concentration and time linear regression coefficient are greater than 0.9 to reach steady state, automatically stopping the system and according to the formula input in the control program
And calculating the chloride ion permeability coefficient, which is a unified expression.
Where R is the gas constant (r=8.31J/mol/K), T is the experimental temperature (t=293K), L is the specimen thickness (l=0.05m), V is the anode cell volume (v=2.1l), Z is the absolute value of chloride ion charge (z=1), and F is the faraday constant (f=96.49×10) 3 C/mol), E is the applied voltage (e=22v), γ is the activity coefficient (γ=1), C 0 Is the concentration of chloride ions (c) in the cathode cell 0 =52.6 g/L); a is the effective cross-sectional area of the test piece (a= 0.006362m 2 )；
Is the slope of the cumulative concentration of chloride ions over time.
While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the present invention.
Claims (7)
1. A method for evaluating the ITZ permeability coefficient of concrete by aggregate type, which is characterized by comprising the following steps:
(1) Selecting a proper mold:
selecting a concrete column-shaped mould with a runway-shaped cross section, wherein the height of the concrete column-shaped mould is 50mm, the concrete column-shaped mould consists of two semicircular areas which are symmetrical and equal in size, a non-detachable baffle plate which is equal in height to the concrete column-shaped mould is arranged between the two semicircular areas, the two semicircular areas are respectively used for filling an ITZ area and a cement mortar area, the sum of the cross sections of the two semicircular areas is recorded as A, and the bottom of the concrete column-shaped mould is a detachable wood plate;
(2) The method comprises the steps of selecting a cuboid with the side length of 100mm or a cylinder with the same diameter as a model aggregate, selecting a model aggregate material which is consistent with a real aggregate, selecting a cylinder model aggregate when the actual roundness sigma of the aggregate is more than or equal to 0.75, and selecting a cuboid model aggregate when the actual roundness sigma of the aggregate is less than 0.75, wherein:
wherein: sigma is the actual roundness of the aggregate; a is that 0 The projection area of coarse aggregate particles in the maximum outline image is; l (L) 0 Projecting the outline perimeter for coarse aggregate particles in the maximum outline image;
(3) After the type and shape of the model aggregate are determined, placing a plurality of cut model aggregates with the height of 50mm in one semicircular area of the concrete columnar mould prepared in the step (1), bonding the bottom of the model aggregate with the bottom of the concrete columnar mould, in order to avoid superposition of ITZ around the model aggregate, uniformly distributing the model aggregates when placing, pouring cement mortar in the two semicircular areas of the concrete columnar mould, placing the model aggregates in a standard curing room for curing after pouring is finished, removing a test piece until the curing reaches a specified age, and separating the concrete columnar mould from the bottom of the test piece to obtain a test piece containing the model aggregate and a test piece containing the cement mortar respectively;
(4) Preparing a plurality of parallel test pieces containing model aggregate test pieces, observing and recording the ITZ thickness values of the concrete by a scanning electron microscope, selecting 4 model aggregates at corners and 1 model aggregate at the center as representative, recording 20 times of thickness along the periphery of each model aggregate, taking an average value, and recording the ITZ average thickness of the concrete as d;
(5) After determining the ITZ thickness d, the ITZ area A in the ITZ region is calculated ITZ And cement mortar area A in ITZ zone CE ；
(6) Simultaneously measuring the permeability coefficient D of the test piece containing the model aggregate according to the penetration test of the erosion medium of the test piece containing the model aggregate and the cement mortar obtained in the step (4) SU Permeability coefficient D with cement mortar test piece CE ；
For the penetration test, in the test piece containing the model aggregate, the penetration coefficient of the test piece meets the following conditions:
the permeability coefficient D of the transition zone of the concrete interface can be reversely deduced according to the method ITZ ：
Wherein: d (D) SU The permeability coefficient of the test piece containing the model aggregate is obtained by a permeability test of the test piece containing the model aggregate; d (D) CE The permeability coefficient of the test piece of the pure cement mortar is obtained by a pure cement mortar test piece permeability test; a is the total cross-sectional area of the two semicircular areas; a is that AGG 1 model aggregate cross-sectional area; d (D) ITZ Is the permeability coefficient of the interface transition zone.
2. The method for evaluating the ITZ penetration coefficient of concrete according to claim 1, wherein in the step (1), the radius of the semicircular area is 50mm, and the thickness of the baffle is 12mm.
3. The method for evaluating the ITZ penetration coefficient of concrete according to claim 2, wherein in the step (3), the number of the model aggregates is 10, and the bottom of the model aggregates is bonded to the bottom of the concrete column-shaped mold by using an epoxy resin adhesive.
4. A method for evaluating the ITZ penetration coefficient of concrete according to claim 3, wherein in step (5):
(1) when the model aggregate is square aggregate, the side length of the model aggregate is recorded as l, A ITZ ＝n×(πd 2 +4dl)，
(2) When the model aggregate is circular aggregate, the radius is r and A ITZ ＝n×π[(r+d) 2 -r 2 ]，
Wherein: a is the total cross-sectional area of two semicircular areas in mm 2 The method comprises the steps of carrying out a first treatment on the surface of the n is the number of model aggregates, and 10 is taken; a is that ITZ ITZ area in mm on cross section of test piece containing model aggregate 2 ；A CE The area of the cement mortar area in mm in the cross section of the test piece containing the model aggregate 2 The method comprises the steps of carrying out a first treatment on the surface of the d is the ITZ thickness in mm; l is the side length of the square model aggregate, and the length is 10mm; r is the radius of the round model aggregate, and 5mm is taken.
5. The method for evaluating the ITZ permeability coefficient of concrete according to claim 4, wherein in the step (6), the device for the permeability test comprises four sealing grooves, two of the sealing grooves are permeable medium sealing grooves, two of the sealing grooves are common medium sealing grooves, the model-containing aggregate test piece and the cement mortar test piece which are cured in the step (3) are placed between the four sealing grooves, and the model-containing aggregate test piece and the cement mortar test piece form a cylinder with the radius of 50mm and the height of 50 mm.
6. The method for evaluating the ITZ permeability coefficient of concrete according to claim 5, wherein the model-containing aggregate test piece and the cement mortar test piece are coated with epoxy resin or the like on the sides to prevent permeation of the medium from the sides before being placed in the four sealing grooves.
7. The method for evaluating the ITZ permeability coefficient of concrete according to the aggregate type of claim 5, wherein in the step (6), a communication port with a semicircular cross section area is arranged between the permeable medium sealing groove and the common medium sealing groove, and the test piece is arranged at one end of the permeable medium sealing groove through the communication port, and the other end of the test piece is arranged at the common medium sealing groove;
a fixed net is arranged between the communication port and the test piece, the fixed net is a semicircular copper net with the radius of 50mm and the thickness of 1mm, a plurality of through holes which are uniformly distributed are arranged in the middle of the fixed net, so that chloride ions can freely permeate between the solution, the copper net and the test piece, and the round edge of the fixed net is provided with a thin iron sheet with the height of 10mm;
the test area in the middle of osmotic medium closed tank and ordinary medium closed tank is provided with the rubber ring, and the height of rubber ring is 50mm, and its cross section is the runway shape, can put down two semi-cylindrical test pieces simultaneously, contains model aggregate test piece and cement mortar test piece promptly, and the radius ratio test piece of rubber ring is little, and the material selects the butyl rubber of high temperature resistant and ageing resistance, and flexible can tightly wrap up the test piece freely, the rubber ring middle part is provided with 5mm thick flexible glue baffle and is used for separating two test pieces, and the rubber ring both ends all are equipped with the ferrule of fixed test piece for the thin iron sheet on test piece, rubber ring, the fixed net is hooped tightly.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310258004.9A CN116106200A (en) | 2023-03-14 | 2023-03-14 | Method for evaluating ITZ permeability coefficient of concrete by aggregate type |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310258004.9A CN116106200A (en) | 2023-03-14 | 2023-03-14 | Method for evaluating ITZ permeability coefficient of concrete by aggregate type |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116106200A true CN116106200A (en) | 2023-05-12 |
Family
ID=86263967
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310258004.9A Pending CN116106200A (en) | 2023-03-14 | 2023-03-14 | Method for evaluating ITZ permeability coefficient of concrete by aggregate type |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116106200A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116952995A (en) * | 2023-07-25 | 2023-10-27 | 水利部交通运输部国家能源局南京水利科学研究院 | Porosity-based nondestructive identification method for thickness of interface region between repair material and concrete |
-
2023
- 2023-03-14 CN CN202310258004.9A patent/CN116106200A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116952995A (en) * | 2023-07-25 | 2023-10-27 | 水利部交通运输部国家能源局南京水利科学研究院 | Porosity-based nondestructive identification method for thickness of interface region between repair material and concrete |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109813643B (en) | Concrete and gas permeability measuring method of surface coating material thereof | |
| CN116106200A (en) | Method for evaluating ITZ permeability coefficient of concrete by aggregate type | |
| CN107322763B (en) | Permeable concrete compressive strength test piece forming device and forming method | |
| CN109959773B (en) | Test device and method for reinforcing silt through demoulding microorganism grouting | |
| Nossoni et al. | Electrochemical-mechanistic model for concrete cover cracking due to corrosion initiated by chloride diffusion | |
| CN217738939U (en) | A device for testing concrete joint part waterproof material water-proof effects | |
| CN109557017B (en) | Corrosion resistance experiment method for steel bar for tropical marine atmospheric environment concrete structure | |
| Gupta et al. | Innovative test technique to evaluate “self-sealing” of concrete | |
| CN111650026A (en) | Nondestructive preservation process for granular soil sample | |
| Castel et al. | Influence of pre‐existing oxides layer and interface condition with carbonated concrete on active reinforcing steel corrosion | |
| Cabrera et al. | An assessment of concrete curing efficiency using gas permeability | |
| CN116754587A (en) | Quantitative characterization method for distribution of residual mortar layer on surface of recycled aggregate in three-dimensional layer | |
| CN114414344B (en) | Method for testing performance of concrete structural surface in water environment | |
| CN107345892B9 (en) | Method and device for measuring oxygen diffusion coefficients of cement-based materials in different exposure environments | |
| Van Mullem et al. | Preliminary Analysis of Non-destructive Test Methods to Evaluate the Self-healing Efficiency on the Construction Site | |
| CN205374240U (en) | Loading concrete pore structure evolution normal position monitoring devices | |
| Tu et al. | Corrosion resistance of concrete strengthened with fibre-reinforced polymer sheets | |
| CN106524979A (en) | Laboratory determination method of sulfate erosion depth in concrete | |
| CN113125551A (en) | Built-in magnetic sensor with double magnetic circuits and four measuring points and testing method thereof | |
| Alzyoud | Effect of reinforcement spacers on concrete microstructure and durability | |
| Ramezanianpour et al. | Evaluation of two automated methods for air-void analysis of hardened concrete | |
| CN217006896U (en) | Concrete corrosion experimental device under salt solution freeze-thaw cycle and load coupling action | |
| CN209911194U (en) | Indoor penetration test device for hydraulic asphalt concrete | |
| CN112884726B (en) | Concrete section identification and performance prediction feedback method and system | |
| CN117373581B (en) | Cement stone geometric tortuosity prediction method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |