CN117805156B - Method for testing hydration degree of interface transition zone between repair material and base material - Google Patents

Method for testing hydration degree of interface transition zone between repair material and base material Download PDF

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CN117805156B
CN117805156B CN202410212425.2A CN202410212425A CN117805156B CN 117805156 B CN117805156 B CN 117805156B CN 202410212425 A CN202410212425 A CN 202410212425A CN 117805156 B CN117805156 B CN 117805156B
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interface transition
granite
transition zone
interface
polishing
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赵翔
李翔宇
吴书豪
阎宇航
赵文斌
田力丹
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Taiyuan University of Technology
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    • G01N23/2206—Combination of two or more measurements, at least one measurement being that of secondary emission, e.g. combination of secondary electron [SE] measurement and back-scattered electron [BSE] measurement
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    • G01—MEASURING; TESTING
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    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
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Abstract

The invention relates to the technical field of repair work of original buildings, in particular to a method for testing hydration degree of an interface transition zone between a repair material and a base material; the method comprises the following steps: (1) BSE test block processing; (2) BSE image processing, namely observing the transition region by using a scanning electron microscope, and determining the range of the interface transition region through the change condition of the porosity; (3) extracting a test block in an interface transition zone; (4) Testing the hydration degree of the interface transition zone, performing a true density test, taking out the interface transition zone completely, and performing a thermogravimetric test to obtain the hydration degree; the invention designs a brand new method, the ITZ between the repair material and the base material is completely taken out, the hydration product is researched, and the repairability of the repair material can be more accurately determined by analyzing the hydration degree.

Description

Method for testing hydration degree of interface transition zone between repair material and base material
Technical Field
The invention relates to the technical field of repair work of original buildings, in particular to a method for testing hydration degree of an interface transition zone between a repair material and a base material.
Background
Concrete structures are prone to cracking, wear and fall under various loads and environmental influences. In addition, raw surface defects may occur due to improper construction operations. These defects can severely shorten the service life of the concrete structure and even affect its safety.
The appropriate repair can prolong the service life of the concrete structure, and has great benefits from the aspects of economy and environment. Because of aging problems with a large number of concrete structures, there is a growing need for concrete repair. According to one report of the american society of civil engineers (American Society of CIVIL ENGINEERS, ASCE) 2019, the united states and asian countries may spend 2.2 trillion dollars and 2 trillion dollars, respectively, in the maintenance and repair of concrete structures for the next five years. However, to date, the durability of concrete repairs seems to be unsatisfactory. One report published by Con Rep Net in 2004 indicates that in Europe, less than 10% of repairs can work for more than 25 years, with more than half of the repairs failing within 10 years. One of the most important reasons for failure of concrete repair is the weak interface with the substrate. According to the literature, the interface region between the repair material and the concrete substrate is distinctly discontinuous. Compared with the repairing material and the matrix, the Interface Transition Zone (ITZ) is used as a weak link of cement mortar, and in the repairing process, the ITZ can generate a large number of pores and microcracks in the forming process due to overlarge local water cement ratio caused by a thin water film around the matrix. These characteristics of the repair material and concrete substrate interface tend to cause stress concentration under load, ultimately inducing debonding at the interface. Accordingly, there is a great deal of research aimed at improving interfacial bonding properties in concrete repair. According to the literature, the bond strength between the repair material and the substrate can be enhanced by increasing the roughness of the substrate surface, changing the humidity conditions of the substrate, adding fibers or silica powder to the repair material, and using an interfacial agent. In addition, the prosthesis may be polymer modified to improve adhesion to the concrete substrate. However, repair mortars are often different from the substrate. Thus, the microstructure and properties between the prosthesis and the matrix are discontinuous. Such discontinuities can cause significant stress concentrations at the interface between the prosthesis and the substrate. In order to increase the interfacial bonding property between the repair mortar and the base material, it is necessary to increase the hydration degree between the repair material and the base material, and increase the hydration product, thereby increasing the bonding strength with the base material. The bonding between the repair material and the substrate can be further divided into: the bonding of the repair material to the old cement base material and the bonding of the repair material to the aggregate, it is therefore important to investigate the degree of hydration of the Interfacial Transition Zone (ITZ) between the repair material and the old cement base material and between the repair material and the aggregate.
Common researches on ITZ are mostly to combine a Back Scattered Electron (BSE) graph and a picture gray level analysis method to obtain the porosity of ITZ, or to analyze the ITZ micromechanics of a cement-based material by utilizing a nanoindentation technology, or to establish a material model by adopting a method of combining nanoindentation test and mathematical analysis, so as to better describe the behavior of the cement-based material. There are few methods to study the hydration level by taking ITZ alone.
In view of this, it is necessary to design a completely new method for studying the degree of hydration of ITZ between the repair material and the aggregate in relation to the repair performance.
Disclosure of Invention
The invention overcomes the defects of the prior art and provides a method for testing the hydration degree of an interface transition zone between a repair material and a base material.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for testing hydration degree of an interface transition zone between a repair material and a base material comprises the following steps:
BSE block handling
A1. Cutting granite into cuboid with the thickness of 20 multiplied by 5mm by using the granite as a base aggregate for interface transition area study, placing the granite at the center of a 20 multiplied by 20mm die during molding, placing cement mortar at two ends of the granite, trowelling a cover film after vibrating, placing the granite into a curing box for curing, and demolding after 24 hours to obtain a test block;
A2. Cutting the test block from the middle, putting the cut workpiece into absolute ethyl alcohol for 24 hours, stopping hydration, coating the surface with low-viscosity epoxy resin, and carrying out vacuum impregnation to support a microstructure;
A3. Polishing the test block after the epoxy resin is solidified, wherein the polishing comprises two steps of rough grinding and polishing; firstly, using diamond sand paper to carry out coarse grinding, and then using alumina polishing solution to carry out grinding and polishing;
A4. After polishing, carrying out SEM-BSE to shoot an interface transition zone around the granite aggregate;
BSE image processing
B1. Obtaining 300 times magnified back scattering images, each BSE image comprising granite, a cement matrix and ITZ, taking 10 to 15 images in ITZ zone around granite aggregate;
B2. Manually capturing the boundary of the polymer using image pro image analysis software, drawing 10 continuous strips every 5 μm within 50 μm, and defining 5 continuous strips every 10 μm outside 50 μm according to a concentric expansion method using PS body functions along different distances from the surface of the aggregate to the bulk paste; then, the pore structure is segmented by metlab software, and each porosity is determined according to the determined pore threshold value, so that the ITZ range is determined, and the thickness H of the interface transition region is obtained;
C. Interface transition zone test block extraction
C1. Cutting granite into cuboid with the thickness of 40 multiplied by 20mm by using the granite as a base aggregate for interface transition area study, placing the granite at the center of a 40 multiplied by 160mm die during molding, placing cement mortar at two ends of the granite, vibrating and trowelling a cover film, placing the granite into a curing box for curing, and demolding after 24 hours;
C2. After maintenance, taking out the test strip, wiping the surface, measuring the interface strength by adopting a three-point bending-resistant method, taking the joint of granite and cement paste as a loading center, and expressing the bonding strength of the interface by using the bending strength;
C3. Taking the fracture part of the interface after fracture resistance, and putting the fracture part into alcohol for standby;
D. testing of hydration degree of interface transition zone
D1. Firstly taking 1g of powder from each peeling surface of the interface transition zone for measurement, and using the powder to approximate the density of the interface transition zone;
the mass m of the powder taken by each peeling surface of the interface transition zone is obtained according to the following formula (1)
（1）
Wherein ρ is the density, and the density of portland cement is used to approximate the density at ITZ; s is the surface area of the bonding site; h is the thickness of the interface transition area obtained in the step B2;
D2. then polishing all m-mass matrixes from fracture parts of the fracture-resistant interfaces by using diamond sand paper, and performing a true density test to obtain the accurate density of ITZ;
D3. And determining the quality of the accurate interface transition region according to the accurate density rho and the formula (1), thereby completely taking out the interface transition region, and performing thermogravimetric testing to obtain the hydration degree.
Further, in step A3, the test pieces were polished with 150 mesh, 320 mesh, 600 mesh, 800 mesh and 1200 mesh diamond coated abrasive at 800rad for 15 minutes, respectively, with 3.5um and 1um sized alumina polishing solution for about 15 minutes, respectively, and after each step, the samples were cleaned with ultrasonic waves in alcohol to remove polishing debris.
Further, in step D2, the m-quality substrate was sanded with 1000 mesh diamond sand paper.
Further, in the step D1, the density of Portland cement ordinary cement is 3.0-3.15 g/cm 3, and 3.0g/cm 3 is calculated.
Compared with the prior art, the invention has the following beneficial effects:
The invention designs a brand new method, the ITZ between the repair material and the base material is completely taken out, the hydration product is researched, and the repairability of the repair material can be more accurately determined by analyzing the hydration degree.
The invention relates to the study of hydration products by preparing special test pieces and taking out ITZ completely in combination with Scanning Electron Microscopy (SEM) -Back Scattered Electrons (BSE), true density (gas displacement method) and thermogravimetric testing (TG-DTG). The result shows that the bonding strength between cement mortar and aggregate and the hydration degree of ITZ are positively correlated, and by applying the characteristic of obviously improving the hydration of ITZ, the hydration degree of ITZ can be used for representing the repair performance of the repair material.
Drawings
FIG. 1 is an interface transition zone test model.
FIG. 2 is a broken-away view of a test piece.
Fig. 3 is a SEM microscopic sample cut view.
Fig. 4 is an example of an original diagram of an interface transition region SEM-BSE of embodiment 1.
Fig. 5 is an example of an interface transition zone SEM-BSE boundary acquisition map of embodiment 1.
Fig. 6 is an example of an interface transition zone scan stripe description diagram of embodiment 1.
FIG. 7 is a schematic representation of the pore distribution at the transition zone of the interface of examples 1-3.
FIG. 8 is a thermogravimetric analysis at ITZ of examples 1-3.
FIG. 9 is a thermogravimetric analysis of the substrates of examples 1-3.
Fig. 10 is an SEM image of the interfacial transition zone spall surface of example 1.
Fig. 11 is an SEM image of the interfacial transition zone spall surface of example 2.
Fig. 12 is an SEM image of the interfacial transition zone spall surface of example 3.
Detailed Description
The invention is further illustrated below with reference to specific examples.
Example 1
1. The composite modified cement mortar is prepared from the following raw materials in parts by weight: 100 parts of cement, 200 parts of standard sand, 40 parts of water and 0.8 part of PC water reducer.
2. The preparation process of the composite modified cement mortar comprises the following steps of preparing the cement mortar by adopting a CTE7000 type high-speed shearing stirrer:
(1) The PC solution water reducer is weighed according to the mixing proportion, water is mixed, and ultrasonic treatment and dissolution are carried out by using a Scientz-750F ultrasonic instrument manufactured by Ningbo new Zhi Biotech Co.
(2) Weighing standard sand according to a mixing ratio, pouring the standard sand into a cement mortar stirring pot (before the standard sand is put into the pot, the stirring pot and stirring blades are required to be wetted by wet cotton cloth), pouring the solution obtained in the step (1) into the stirring pot filled with the standard sand, and stirring at a low speed (100 r/min) for 60s;
(3) Weighing a certain amount of cement according to the mixing proportion. Adding into a stirring pot, stirring at low speed (100 r/min) for 60s, stirring at high speed for 30s, and stopping;
(4) During the stopping period, the cement mortar attached to the stirring pot is scraped off, and the mortar is turned up and down by using a shovel, so that the slurry is fully mixed. And stopping the machine after stirring at a high speed for 90 seconds to obtain the cement mortar.
(5) And (3) placing the concrete mixture cement mortar into a mould for forming, removing the mould after one day, and curing under standard conditions.
3. The method for testing the hydration degree of the interface transition zone between the composite modified cement mortar serving as a repairing material and a base material comprises the following steps of:
BSE block handling
A1. Cutting granite into cuboid with the thickness of 20 multiplied by 5mm by using the granite as aggregate for interface transition area study, placing the granite at the right center of a 20 multiplied by 20mm die during molding, placing the composite modified cement mortar in the step (4) at two ends of the granite, trowelling a covering film after vibrating, placing the covering film into a curing box for curing, and demolding after 24 hours to obtain a test block;
A2. cutting the test block from the middle, putting the cut workpiece into absolute ethyl alcohol for 24 hours, stopping hydrating, coating the surface with low-viscosity epoxy resin, carrying out vacuum impregnation to support a microstructure, and polishing after the epoxy resin is solidified.
A3. In the sample preparation, the grinding and polishing method mainly comprises two steps of rough grinding and polishing. In order to meet the precision requirement of sample polishing, the gradient of the granularity of the grinding material is prevented from influencing the sample, the test is carried out by respectively carrying out rough grinding for 15 minutes under the condition of 800rpm by using 150-mesh, 320-mesh, 600-mesh, 800-mesh and 1200-mesh diamond sand paper, and respectively carrying out grinding and polishing for about 15 minutes by using alumina polishing liquid with the granularity of 3.5um and 1um, and after each step, the sample is cleaned in alcohol by using ultrasonic waves to remove polishing fragments.
A4. After polishing, SEM-BSE was performed to photograph the interfacial transition zone around the granite aggregate.
BSE image processing
B1. A 300-fold magnification back-scattered image was obtained. Each BSE image includes granite, cement matrix, and ITZ. 10 to 15 images were taken in the ITZ zone around the aggregate.
B2. The boundaries of the polymer were manually captured using image pro image analysis software. According to the concentric expansion method, 10 continuous strips are drawn every 5um within 50um and 5 continuous strips are delineated every 10um outside 50um at different distances from the aggregate surface to the bulk paste along the captured boundaries using the PS body function. And then dividing the pore structure by metlab software, and determining each porosity according to the determined pore threshold value, thereby determining the ITZ range and obtaining the thickness H of the interface transition region.
C. Interface transition zone test block extraction
C1. Cutting granite into cuboid with the thickness of 40 multiplied by 20mm by using the granite as aggregate for interface transition area study, placing the granite at the right center of a 40 multiplied by 160mm die during molding, placing the composite modified cement mortar in the step (4) at two ends of the granite, trowelling the cover film after vibrating, placing the cover film into a curing box for curing, and demolding after 24 hours;
C2. Curing the sample until a certain age, taking out the test strip, wiping the surface, measuring the interface strength by adopting a three-point bending-resistant method, taking the joint of granite and cement paste as a loading center, and expressing the bonding strength of the interface by using the bending strength.
C3. And after fracture resistance, taking the fracture part of the interface, and putting the interface into alcohol for standby.
D. testing of hydration degree of interface transition zone
D1. Firstly taking 1g of powder from each peeling surface of the interface transition zone for measurement, and using the powder to approximate the density of the interface transition zone;
the mass m of the powder taken by each peeling surface of the interface transition zone is obtained according to the following formula (1)
（1）
Wherein ρ is the density, the density of the Portland cement ordinary cement is similar to the density of ITZ, the density of the Portland cement ordinary cement is 3.0-3.15 g/cm 3, and 3.0g/cm 3 is calculated; s is the surface area of the bonding site; h is the thickness of the interface transition area obtained in the step B2;
D2. then polishing all m-mass matrixes from fracture parts of the fracture-resistant interfaces by using diamond sand paper, and performing a true density test to obtain the accurate density of ITZ;
D3. And determining the quality of the accurate interface transition region according to the accurate density rho and the formula (1), thereby completely taking out the interface transition region, and performing thermogravimetric testing to obtain the hydration degree.
In the research of the prior cement-based material microscopic test, the microscopic sample is usually cut by a macroscopic test piece, but as the cement-based material is mostly a brittle material and an interface transition area is fragile, the microscopic sample is extremely fragile when being cut for multiple times by using a diamond cutter, the accuracy of analysis on microscopic characteristics of the microscopic sample is greatly influenced, meanwhile, the bonding force of granite aggregate and cement mortar is weaker, the granite and a matrix are extremely easy to break when being cut for multiple times by using the diamond cutter, and the yield of the obtained microscopic sample is lower. Therefore, in the test, the manufacture of the microscopic sample is independently designed, the size of the sample is required to be ensured to be small enough on the premise of avoiding the size effect, so that the cutting times are reduced, and finally, a cube mould with the length, width and height of 20mm is selected for manufacturing the sample, so that the thickness of the interface transition zone is measured.
In order to obtain accurate interface transition region density, the method adopts true density to measure the density. The minimum mass required for the true density is 1g which is far greater than the mass of an interface transition zone on an exfoliation surface, so that 1/m (m is the mass of the interface transition zone on the exfoliation surface), and the powder of the interface transition zone with the mass greater than 1g is obtained by polishing 1/m (rounding upwards) of the exfoliation surface, and the true density test is carried out, so that the quality of the interface transition zone is obtained more accurately.
Example 2
1. The composite modified cement mortar is prepared from the following raw materials in parts by weight: 85 parts of cement, 200 parts of standard sand, 40 parts of water, 15 parts of coal-series metakaolin and 3.1 parts of high-efficiency PC water reducer.
2. The preparation process of the composite cement mortar is as follows, and adopts CTE7000 type high-speed shearing stirring machine to prepare cement mortar:
(1) The PC water reducing agent is weighed according to the mixing proportion and mixed with water, and is subjected to ultrasonic treatment and dissolution by using Scientz-750F ultrasonic instrument manufactured by Ningbo new Zhi Biotech Co.
(2) Weighing standard sand according to a mixing ratio, pouring the standard sand into a cement mortar stirring pot (before the standard sand is put into the stirring pot, the stirring pot and stirring blades are required to be wetted by wet cotton cloth), pouring the solution obtained in the step (1) into the stirring pot filled with the standard sand, and stirring at a low speed (100 r/min) for 60s;
(3) Weighing a certain amount of cement and coal-series metakaolin according to the mixing proportion. Adding into a stirring pot, stirring at low speed (100 r/min) for 60s, stirring at high speed for 30s, and stopping;
(4) During the stopping period, the cement mortar attached to the stirring pot is scraped off, and the mortar is turned up and down by using a shovel, so that the slurry is fully mixed. And stopping the machine after stirring at a high speed for 90 seconds to obtain the cement mortar.
(5) And (3) placing the concrete mixture cement mortar into a mould for forming, removing the mould after one day, and curing under standard conditions.
3. The method for testing the hydration degree of the interface transition zone between the repair material and the base material by using the composite modified concrete is the same as that of the example 1.
Example 3
1. The composite modified cement mortar is prepared from the following raw materials in parts by weight: 85 parts of cement, 200 parts of standard sand, 40 parts of water, 15 parts of coal-series metakaolin, 0.06 part of graphene oxide and 4.1 parts of high-efficiency PC water reducer.
2. The preparation process of the composite modified cement mortar comprises the following steps of preparing the cement mortar by adopting a CTE7000 type high-speed shearing stirrer:
(1) And (3) placing the graphene oxide, the water reducer and water into an ultrasonic system, performing ultrasonic treatment under the condition of ice-water bath for 10min to prepare graphene oxide modifier dispersion liquid, and performing ultrasonic treatment, dissolution and dispersion by using a Scientz-750F ultrasonic instrument manufactured by Ningbo new ganoderma biotechnology Co.
(2) Weighing standard sand according to a mixing ratio, pouring the standard sand into a cement mortar stirring pot (before the standard sand is put into the stirring pot, the stirring pot and stirring blades are required to be wetted by wet cotton cloth), pouring the solution obtained in the step (1) into the stirring pot filled with the standard sand, and stirring at a low speed (100 r/min) for 60s;
(3) Weighing a certain amount of cement and coal-series metakaolin according to the mixing proportion. Adding into a stirring pot, stirring at low speed (100 r/min) for 60s, stirring at high speed for 30s, and stopping;
(4) During the stopping period, the cement mortar attached to the stirring pot is scraped off, and the mortar is turned up and down by using a shovel, so that the slurry is fully mixed. And stopping the machine after stirring at a high speed for 90 seconds to obtain the cement mortar.
(5) And (3) placing the concrete mixture cement mortar into a mould for forming, removing the mould after one day, and curing under standard conditions.
3. The method for testing the hydration degree of the interface transition zone between the repair material and the base material by using the composite modified concrete is the same as that of the example 1.
The test results for examples 1-3 are as follows: the compressive strength of the cement mortar is measured according to a test method specified in a standard GB/T50081-2002, and the quick chloride ion permeability coefficient of the cement mortar is measured according to a test method for long-term durability and durability of the GB/T50082-2009 ordinary concrete.
Table performance index of different test groups
From the first table, along with the composite modification of the coal-series metakaolin and the graphene oxide, the compressive strength of the cement mortar is increased, the chloride ion permeability coefficient is reduced, and the improvement range is larger, and the two properties are greatly related to the interface transition region, so that the interface transition region is improved. As can be seen from the bond strength of the interfacial transition, the composite modification increases the bond strength of the interfacial transition.
Fig. 7 is a schematic diagram showing the pore distribution of the interface transition region in examples 1-3, and it can be seen from the scanning image of SEM-BSE of the test block that the range of the interface transition region is reduced by the composite improving effect, and the pores of the interface transition region are also reduced, so that it is proved that the porosity of the interface transition region between the cement-based material and the aggregate can be improved by the composite improving effect, thereby strengthening the performance of the composite cement mortar.
From the scanned pictures of the interface transition zone, the composite improvement effect enables the interface transition zone to be more compact, and the fact that the composite improvement effect can improve the interface transition zone between the cement-based material and the aggregate is proved.
Examples 1-3 the true densities of the sample interface transition regions are as follows
Table two example one ITZ single point true density
Table three example two ITZ single point true density
ITZ single point true density for Table four example three
Knowing the range of the interface transition region and the density of the interface transition region, the mass of the interface transition region can be obtained by a density formula as shown in Table five, by polishing the calculated mass at the fracture, polishing the corresponding mass according to the calculated mass, and taking out the ITZ completely. And performing thermogravimetric analysis on the obtained mass.
Quality of Table five ITZ
FIG. 8 is a thermogravimetric analysis at ITZ for examples 1-3 and FIG. 9 is a thermogravimetric analysis at the substrate for examples 1-3. Comparison of the interfacial transition with the thermogravimetric analysis of the matrix of example 1 shows that the peaks of ettringite Ett and calcium silicate hydrate C-S-H, both in the matrix and in ITZ, are example 3> example 2> example 1, and that the peaks of calcium hydroxide CH and calcium carbonate CaCO 3 are example 1> example 2> example 3. When the bonding strength of the repairing material and the base material is increased, the hydration degree of ITZ between the repairing material and the base material is also better, and the fact that the repairing performance of the material can be better judged by analyzing the hydration degree of the interface transition zone of the cement base material is proved.
Looking at the spall surface shown in fig. 2, fig. 10, 11 and 12 show SEM images of the spall surface of the interface transition regions of example 1, example 2 and example 3. As can be seen from the figure, the microstructure of the cement mortar with CMK added is denser than that of the cement mortar with M added. While the high levels of Al 2O3 and SiO 2 in CMK consume silicate and CH in the cement matrix, resulting in increased rates of formation and formation of C-S-H and C-A-S-H. Furthermore, the denser microstructure may be due to more consumption of CH, while CMK has finer particles as filler, filling voids, forming a denser microstructure compared to the control sample. Meanwhile, compared with the image, the hydration product is more uniform and compact after the graphene oxide is added, and different hydration products are combined together. The method has the advantages that due to the combined action of CMK and graphene oxide, the dispersion of the graphene oxide is promoted, more nucleation sites are provided for hydration products, the conclusion is consistent with the conclusion obtained by thermogravimetry, and further, the analysis of the hydration degree of the interface transition region between the cement-based material and the aggregate by the method is better proved, so that the repair performance of the material is better judged.

Claims (4)

1. The method for testing the hydration degree of the interface transition zone between the repair material and the base material is characterized by comprising the following steps of:
BSE block handling
A1. Cutting granite into cuboid with the thickness of 20 multiplied by 5mm by using the granite as a base aggregate for interface transition area study, placing the granite at the center of a 20 multiplied by 20mm die during molding, placing cement mortar at two ends of the granite, trowelling a cover film after vibrating, placing the granite into a curing box for curing, and demolding after 24 hours to obtain a test block;
A2. Cutting the test block from the middle, putting the cut workpiece into absolute ethyl alcohol for 24 hours, stopping hydration, coating the surface with low-viscosity epoxy resin, and carrying out vacuum impregnation to support a microstructure;
A3. Polishing the test block after the epoxy resin is solidified, wherein the polishing comprises two steps of rough grinding and polishing; firstly, using diamond sand paper to carry out coarse grinding, and then using alumina polishing solution to carry out grinding and polishing;
A4. After polishing, carrying out SEM-BSE to shoot an interface transition zone around the granite aggregate;
BSE image processing
B1. Obtaining 300 times magnified back scattering images, each BSE image comprising granite, a cement matrix and ITZ, taking 10 to 15 images in ITZ zone around granite aggregate;
B2. Manually capturing the boundary of the polymer using image pro image analysis software, drawing 10 continuous strips every 5 μm within 50 μm, and defining 5 continuous strips every 10 μm outside 50 μm according to a concentric expansion method using PS body functions along different distances from the surface of the aggregate to the bulk paste; then, the pore structure is segmented by metlab software, and each porosity is determined according to the determined pore threshold value, so that the ITZ range is determined, and the thickness H of the interface transition region is obtained;
C. Interface transition zone test block extraction
C1. Cutting granite into cuboid with the thickness of 40 multiplied by 20mm by using the granite as a base aggregate for interface transition area study, placing the granite at the center of a 40 multiplied by 160mm die during molding, placing cement mortar at two ends of the granite, vibrating and trowelling a cover film, placing the granite into a curing box for curing, and demolding after 24 hours;
C2. After maintenance, taking out the test strip, wiping the surface, measuring the interface strength by adopting a three-point bending-resistant method, taking the joint of granite and cement paste as a loading center, and expressing the bonding strength of the interface by using the bending strength;
C3. Taking the fracture part of the interface after fracture resistance, and putting the fracture part into alcohol for standby;
D. testing of hydration degree of interface transition zone
D1. Firstly taking 1g of powder from each peeling surface of the interface transition zone for measurement, and using the powder to approximate the density of the interface transition zone;
the mass m of the powder taken by each peeling surface of the interface transition zone is obtained according to the following formula (1)
（1）
Wherein ρ is the density, and the density of portland cement is used to approximate the density at ITZ; s is the surface area of the bonding site; h is the thickness of the interface transition area obtained in the step B2;
D2. then polishing all m-mass matrixes from fracture parts of the fracture-resistant interfaces by using diamond sand paper, and performing a true density test to obtain the accurate density of ITZ;
D3. And determining the quality of the accurate interface transition region according to the accurate density rho and the formula (1), thereby completely taking out the interface transition region, and performing thermogravimetric testing to obtain the hydration degree.
2. The method according to claim 1, wherein the test pieces are sequentially polished with 150 mesh, 320 mesh, 600 mesh, 800 mesh and 1200 mesh coated abrasive at 800rpm for 15 minutes in step A3, respectively, with 3.5um and 1um sized alumina polishing solution for 15 minutes, and after each step, the sample is cleaned with ultrasonic waves in alcohol to remove polishing debris.
3. The method of claim 1, wherein the step D2 is performed by polishing the m-mass substrate with 1000 mesh diamond sand paper.
4. The method for testing the hydration level of an interface transition zone between a repair material and a base material according to claim 1, wherein the Portland cement portland cement in the step D1 has a density of 3.0-3.15 g/cm 3 and 3.0g/cm 3.
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