A device and method for measuring the linear expansion coefficient of the interface transition zone of concrete

Abstract

The present application relates to the field of concrete material performance test analysis, and discloses a kind of concrete interface transition zone linear expansion coefficient measuring device and method, the device includes water circulation heating mechanism and measuring mechanism;Water circulation heating mechanism includes heating cylinder, water inlet pipe, water outlet pipe, test baffle and adjustable temperature cold and hot integrated circulating water machine, adjustable temperature cold and hot integrated circulating water machine is communicated with the heating cavity on heating cylinder by water inlet pipe and water outlet pipe;Test baffle is sealed in the opening of heating cylinder and is connected with measuring mechanism.The method is used for simulating temperature change in actual engineering by adjustable temperature cold and hot integrated circulating water machine regulation and control heating cylinder temperature, temperature cycle to cavity aggregate-cement mortar combination test piece, by multi-interface superposition amplification overall deformation effect, eliminate accidental error caused by single interface measurement, realize the accurate determination of interface transition zone linear expansion coefficient, provide key technical reference for concrete mesoscopic temperature cracking mechanism research and anti-cracking design.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of concrete material performance test analysis, in particular to a device and method for measuring the linear expansion coefficient of the interface transition zone of concrete. BACKGROUND

[0002] The interface transition zone (ITZ) is the core interface connecting the aggregate and mortar in the multiphase system of concrete, is also the "third phase" different from the aggregate and mortar, and is the key area determining the performance of concrete. At present, it is generally believed in the academic circle that it is mainly formed due to the boundary effect of coarse aggregate and the micro-zone water secretion effect. This special area not only directly affects the mechanical properties, mass and heat transfer properties of concrete, but also is the weakest link in the concrete matrix. Existing research shows that the interface transition zone plays an important role in the strength of concrete and the failure process of concrete. From the microstructure characteristics, the interface transition zone has the significant characteristics of high porosity and low strength, and the low-density calcium hydroxide (C-H) crystals are enriched in the interface transition zone. This structural characteristic directly leads to the initiation and widespread distribution of micro-cracks in the interface transition zone; at the same time, due to the large difference in the linear expansion coefficient between the interface transition zone and the aggregate, when the temperature gradient is formed in the concrete structure due to the internal and external temperature difference, the deformation of the interface transition zone and the aggregate will not be coordinated, which will lead to the constraint stress in the concrete. With the accumulation of constraint stress, the internal crack will continue to expand, and finally cause the macroscopic cracking of concrete. Therefore, the linear expansion coefficient of the interface transition zone is particularly important in the study of the micro-temperature cracking mechanism of concrete, and due to the special structure of the interface transition zone and the extremely small size, it cannot be obtained by direct measurement.

[0003] At present, there are technical bottlenecks in the direct measurement of the linear expansion coefficient of the interface transition zone (ITZ) of concrete, and the related research has long relied on empirical values, which directly restricts the research on the microstructure of concrete, the simulation accuracy of thermal stress of concrete structure, and the temperature cracking mechanism. Specifically, the ITZ is a weak area between the aggregate and the cement matrix, with a thickness of only microns, and a porous and non-uniform structure. However, the traditional thermal expansion test equipment is limited by the millimeter-level spatial resolution, and cannot realize accurate positioning and measurement of the local micro-zone, resulting in difficulty in directly obtaining the linear expansion coefficient.

[0004] Therefore, there is an urgent need for a device and method for measuring the linear expansion coefficient of the interface transition zone of concrete to overcome the limitations of the prior art. SUMMARY

[0005] In order to overcome the problems in the prior art, the present application aims to provide a device and method for measuring the linear expansion coefficient of the interface transition zone of concrete, which realizes the measurement of the linear expansion coefficient of the interface transition zone of concrete.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] A method for measuring linear expansion coefficient of a concrete interface transition zone, comprising the following steps:

[0008] S1: preparing test pieces, including aggregate-cement mortar combined test pieces, aggregate test pieces and cement mortar test pieces;

[0009] S2: measuring the thickness of the interface transition zone of the aggregate-cement mortar combined test pieces and the length of each test piece;

[0010] S3: placing the test pieces in a heating cylinder and starting an adjustable temperature cold-hot integrated circulating water machine, adjusting the temperature of the heating cavity to make the test pieces deform, measuring the deformation of the test pieces by a vibrating wire strain gauge, keeping the temperature of the heating cavity unchanged, and obtaining stable measurement data when the reading of the vibrating wire strain gauge no longer changes;

[0011] S4: calculating the linear expansion coefficient of the interface transition zone according to the measured data in S2 and S3.

[0012] The application is further provided as follows: in step S2, a microhardness tester is used to measure the hardness change trend of the cement mortar and aggregate at the interface of the aggregate-cement mortar combined test pieces, and the interface transition zone boundary is determined by taking the hardness change of 20% as a threshold to obtain the thickness of the interface transition zone.

[0013] Based on the microhardness gradient method, the ITZ boundary is accurately defined by the hardness sudden change point at the mortar-aggregate interface, and the boundary blurring problem caused by interference in all directions in the traditional image method is solved.

[0014] The application is further provided as follows: in step S3, when the test pieces are placed in the heating cylinder, one end of the test pieces slightly exceeds the heating cylinder to ensure that the test baffle is in complete contact with the surface of the test pieces and avoids the test baffle contacting the shell and the heating cylinder. The part of the test pieces exceeding the heating cylinder is wrapped with heat preservation asbestos to keep the temperature of the test pieces consistent.

[0015] The application is further provided as follows: in step S4, the linear expansion coefficient is calculated by the following formula:

[0016] The formula for calculating the linear expansion coefficient of the test pieces is:

[0017]

[0018] In the formula: is the linear expansion coefficient of the test pieces, ; is the strain of the test pieces generated by heating, ; is the difference between the final temperature and the initial temperature of the test pieces, ; based on the formula, the linear expansion coefficient of the aggregate test pieces is calculated respectively The linear expansion coefficient of the cement mortar test piece ;

[0019] The deformation of the aggregate-cement mortar combination test piece

[0020]

[0021] Also has:

[0022]

[0023] According to the above, the linear expansion coefficient calculation formula of the interface transition zone of the aggregate-cement mortar combination test piece is derived as follows:

[0024] In the formula, is the deformation of the aggregate-cement mortar combination test piece, respectively, the deformation of the aggregate plate, the cement mortar and the interface transition zone in the aggregate-cement mortar combination test piece; respectively, the linear expansion coefficient of the aggregate plate, the cement mortar and the interface transition zone; respectively, the thickness of the interface transition zone, the aggregate plate and the cement mortar in the aggregate-cement mortar combination test piece; is the difference between the final temperature and the initial temperature of the aggregate-cement mortar combination test piece, is the total deformation of the aggregate-cement mortar combination test piece.

[0025] The present application further provides that the thickness of the cement mortar is calculated by the following formula:

[0026]

[0027] In the formula, is the length of the aggregate-cement mortar combination test piece.

[0028] The present application also relates to a concrete interface transition zone linear expansion coefficient measuring device, which is suitable for the above-mentioned concrete interface transition zone linear expansion coefficient measuring method, and comprises a water circulation heating mechanism and a measuring mechanism.

[0029] The water circulation heating mechanism comprises a heating cylinder, a water inlet pipe, a water outlet pipe and an adjustable temperature cold and hot integrated circulating water machine, the heating cylinder is provided with a heating cavity, and the adjustable temperature cold and hot integrated circulating water machine is connected with the heating cavity through the water inlet pipe and the water outlet pipe respectively.

[0030] The water circulation heating mechanism further comprises a test baffle, and the test baffle is arranged at the opening of the heating cylinder and connected with the measuring mechanism.

[0031] ​In actual use, the test piece is placed in the heating cylinder and in contact with the test baffle, the set temperature of the temperature-adjustable cold and hot integrated circulating water machine is adjusted, the temperature-adjustable cold and hot integrated circulating water machine changes the temperature of the water in the heating cavity to adjust the temperature of the test piece, and the aggregate-cement mortar combined test piece is heated to simulate the temperature change in the actual project.

[0032] The application further provides that the water circulation heating mechanism further comprises a shell and a bearing platform, the shell is arranged on the bearing platform, and the heating cylinder is arranged in the shell.

[0033] The application further provides that heat insulation cotton is arranged between the shell and the heating cylinder.

[0034] The heat insulation cotton plays a heat preservation role and prevents the temperature of the heating cylinder from fluctuating.

[0035] The application further provides that the measuring mechanism comprises a test special cable, a frequency reading instrument and a vibrating wire strain gauge, the vibrating wire strain gauge is connected with the frequency reading instrument through the test special cable, one end of the vibrating wire strain gauge is fixed on the shell through a bolt, and the other end of the vibrating wire strain gauge is connected with the test baffle.

[0036] In summary, the beneficial effects of the above technical solutions of the application are as follows:

[0037] 1. The temperature of the heating cylinder is controlled through the temperature-adjustable cold and hot integrated circulating water machine, the aggregate-cement mortar combined test piece is heated to simulate the temperature change in the actual project. The device can be connected with multiple measuring devices, and the aggregate-cement mortar combined test piece, the cement mortar test piece and the aggregate test piece can be tested at the same time, so that the operation process is simplified and the test time is greatly shortened. Through the determination method, the interface transition zone linear expansion coefficient can be accurately determined, and reference is provided for the research on the concrete mesoscopic temperature cracking mechanism and the anti-cracking design in the actual project.

[0038] 2. The overall deformation effect of the multi-interface superposition amplification ITZ is effectively eliminated, the error problem caused by accidental factors in single-interface measurement is effectively eliminated, and the accuracy and objectivity of data and conclusions are ensured; based on the microhardness gradient method, the ITZ boundary is accurately defined through the hardness sudden change point at the mortar-aggregate interface, the boundary blurring problem caused by interference in the traditional image method is solved, and a foundation is laid for accurate calculation of the linear expansion coefficient. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed for the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0040] Figure 1 A concrete interface transition zone linear expansion coefficient measuring device;

[0041] Figure 2 A schematic diagram of an aggregate-cement mortar combined test piece;

[0042] Figure 3 A displacement cloud map of an analysis model in which the temperature changes from 20°C to 30°C in Example 1;

[0043] Figure 4 A displacement cloud map of an analysis model in which the temperature changes from 20°C to 40°C in Example 1.

[0044] In the drawings, the meanings of the reference numerals are as follows:

[0045] 1, test cable, 2, frequency reading instrument, 3, vibrating wire strain gauge, 4, fixing bolt, 5, thermal insulation cotton, 6, test baffle, 7, test piece, 8, water outlet pipe, 9, water inlet pipe, 10, adjustable temperature cold and hot integrated circulating water machine, 11, shell, 12, bearing platform, 13, heating cavity, 101, heating cylinder;

[0046] 100, aggregate plate, 200, cement mortar. DETAILED DESCRIPTION

[0047] In order for those skilled in the art to better understand the technical solutions of the present application, the technical solutions of the present application will be described clearly and completely below in combination with the drawings of the present application. Other similar embodiments obtained by those skilled in the art without creative labor on the basis of the embodiments in the present application shall all belong to the scope of protection of the present application.

[0048] The present application will be further described below in combination with the drawings and preferred embodiments.

[0049] Example 1

[0050] As shown in the drawings, a concrete interface transition zone linear expansion coefficient measuring method according to a preferred embodiment of the present application is measured by using a concrete interface transition zone linear expansion coefficient measuring device, and includes the following steps: Figures 1-4 S1: making a test piece 7, the test piece 7 including an aggregate-cement mortar combined test piece, an aggregate test piece, and a cement mortar test piece;

[0051] The aggregate-cement mortar combined test piece making method is to polish the aggregate plate 100 around with 800-mesh fine sandpaper to be flat, then place it vertically to the bottom surface in a mold, then pour the cement mortar 200 in the mold to obtain the aggregate-cement mortar combined test piece, and the structure of the aggregate-cement mortar combined test piece is as shown in the drawings.

[0052] Figure 2 ​​

[0053] The size of the aggregate plate 100 in the aggregate-cement mortar combination specimen is 20 mm in length and width and 5 mm in thickness, and the number of aggregate plates is 10, with a placement interval of more than 2 mm. The size of the aggregate-cement mortar combination specimen is 20 mm in length and width and 100 mm in height.

[0054] A cement mortar specimen and an aggregate specimen of the same size as the aggregate-cement mortar combination specimen are prepared. The cement mortar of the cement mortar specimen is consistent with the cement mortar of the aggregate-cement mortar combination specimen, and the aggregate plate 100 of the aggregate specimen is consistent with the aggregate plate 100 of the aggregate-cement mortar combination specimen. Before testing, the surfaces of the specimens are polished flat.

[0055] S2: Measure the interface transition zone thickness of the aggregate-cement mortar combination specimen and the length of each specimen 7;

[0056] The hardness change trend at the junction of the cement mortar 200 and the aggregate plate 100 of the aggregate-cement mortar combination specimen is measured using a microhardness tester, and the interface transition zone boundary is determined by taking the hardness change of 20% as the threshold to obtain the interface transition zone thickness. The instrument used for interface transition zone thickness testing is an HV-1000 microhardness tester.

[0057] According to the current relevant research, the interface transition zone thickness and strength are mainly related to the type of aggregate and the water-cement ratio of the cement mortar 200, and the interface thickness is usually 40-100 At the same time, the strength of the interface is significantly lower than that of the aggregate and the mortar part, so the microhardness at the junction of the cement mortar 200 and the aggregate plate 100 of the aggregate-cement mortar combination specimen is measured using a microhardness tester. A diamond indenter with a face angle of 136° of an inverted pyramid four-prism is used for testing, and the test load is 0.098 N. The length of the diagonal line of the test indentation is usually 10-20 During the test, the first point is punched at the joint, and then every 5 points are punched along the vertical aggregate direction, and the cement mortar 200 and the aggregate plate 100 are tested on the mortar side 100 within the range during testing, and the position of the rapid change in hardness is recorded as the boundary of the interface transition zone, and the length of this interval is the thickness of the interface transition zone.

[0058] In order to accurately obtain the interface transition zone thickness of the aggregate-cement mortar combination specimen, three places where the mortar and the aggregate meet are selected, and the interface transition zone thickness of the four surfaces of the specimen is tested using a microhardness tester. Five points are selected for measurement at the same interval on each surface, and the measurement results are averaged to obtain the interface transition zone thickness.

[0059] At the same time, high-precision vernier caliper is also needed to accurately measure the length of the aggregate specimen, cement mortar specimen and aggregate-cement mortar combined specimen and record the length.

[0060] The Vickers microhardness tester testing principle is as follows: the Vickers hardness test is to press a 136° regular diamond indenter into the surface of the tested object with a specified test force, after a specified holding test force time, the test force is removed, the indentation diagonal of the specimen surface is measured by a micrometer eyepiece, the average pressure of the indentation conical surface area is calculated, that is, the Vickers hardness value, and the calculation formula is:

[0061]

[0062] In the formula, is the Vickers hardness, is the experimental force, is the average value of the lengths of two diagonals of the indentation. The indentation depth and the diagonal are related as follows:

[0063]

[0064] In the formula, is the indentation depth, is the average value of the lengths of two diagonals of the indentation.

[0065] S3: The specimen 7 is placed in the heating cylinder 101, and the temperature-adjustable cold and hot integrated circulating water machine 10 is turned on, the temperature of the heating cavity 13 is adjusted to deform the specimen 7, the deformation amount of the specimen 7 is measured by the vibrating wire strain gauge 3, the temperature of the heating cavity is kept unchanged, and stable measurement data is obtained when the vibrating wire strain gauge reading no longer changes.

[0066] Specifically, the heat-conducting grease is applied on the surface of the specimen 7, then the specimen 7 is placed in the heating cylinder 101, the temperature-adjustable cold and hot integrated circulating water machine 10 is turned on, the initial temperature of the specimen is 20℃, the hot water flows in the heating cavity 13, and the deformation amount of the specimen 7 is measured by the vibrating wire strain gauge 3 after the temperature is stable. When the specimen 7 is placed in the heating cylinder 101, one end of the specimen 7 slightly exceeds the heating cylinder 101, so as to ensure that the test baffle 6 is in full contact with the surface of the specimen 7 and avoid that the test baffle 6 contacts the shell 11 and the heating cylinder 101, which affects the result. The part of the specimen exceeding the heating cylinder is wrapped with heat preservation asbestos, so that the temperature of the specimen is kept consistent.

[0067] After the reading of the frequency reading instrument 2 is stable, the zero is set, the set temperature of the temperature-adjustable cold and hot integrated circulating water machine 10 is adjusted to 30℃, the set temperature of 30℃ is kept unchanged, the reading change of the frequency reading instrument 2 is continuously observed, and the reading of the frequency reading instrument 2 is recorded after the reading is stable.

[0068] S4: Calculate the linear expansion coefficient of the interface transition zone according to the data measured in S2 and S3.

[0069] The linear expansion coefficient of the test piece is calculated by the following formula:

[0070]

[0071] In the formula, is the linear expansion coefficient of the test piece, ; is the strain of the test piece generated by heating, ; is the difference between the final temperature and the initial temperature of the test piece, ; Based on the formula, the linear expansion coefficient of the aggregate test piece , the linear expansion coefficient of the cement mortar test piece ;

[0072] For the aggregate-cement mortar combined test piece, the deformation is:

[0073]

[0074] Also:

[0075]

[0076] Accordingly, the linear expansion coefficient calculation formula of the interface transition zone of the aggregate-cement mortar combined test piece is:

[0077]

[0078] In the formula, is the deformation of the aggregate-cement mortar combined test piece, are the deformations of the aggregate plate 100, the cement mortar 200, and the interface transition zone in the aggregate-cement mortar combined test piece, respectively; are the linear expansion coefficients of the aggregate plate 100, the cement mortar 200, and the interface transition zone, respectively; are the thicknesses of the interface transition zone, the aggregate plate 100, and the cement mortar 200 in the aggregate-cement mortar combined test piece, respectively; is the difference between the final temperature and the initial temperature of the aggregate-cement mortar combined test piece, is the total deformation of the aggregate-cement mortar combined test piece.

[0079] The thickness of the cement mortar 200 is calculated by the following formula:

[0080]

[0081] In the formula, Length of the aggregate-cement mortar combined test piece.

[0082] The method and device for accurately measuring the linear expansion coefficient of the interface transition zone of concrete provided by the application are used to test the aggregate-cement mortar combined test piece with a water-cement ratio of 0.5, the cement mortar test piece and the aggregate test piece, wherein the aggregate material is limestone, and the aggregate-cement mortar combined test piece is cast according to the casting method described in the application. The interface thickness is measured according to the method for measuring the interface transition zone thickness described in the application, and the interface transition zone thickness is obtained by averaging multiple measurements, which is 84.37 μm. The measurement data are shown in Table 1. The linear expansion coefficient of the interface transition zone is measured by the method without calculating the linear expansion coefficient of the aggregate-cement mortar combined test piece, and thus the linear expansion coefficient of the aggregate-cement mortar combined test piece is not calculated.

[0083]

[0084] The data in the above table are substituted into the formula for calculating the linear expansion coefficient of the interface transition zone to calculate that the linear expansion coefficient of the interface transition zone is at 20-30℃, and at 30-40℃. In order to verify the accuracy of the measurement results, a three-phase linear expansion model considering the cement mortar, the interface transition zone and the concrete is established by using a large-scale finite element analysis software Abaqus. Since only the deformation of the test piece in one direction needs to be considered, and all interface properties are the same in the finite element analysis, the aggregate-cement mortar combined test piece with the same height as the test piece described in the application is established, and the cement mortar, the interface transition zone and the aggregate are arranged from top to bottom. The measured parameters are imported into the software to verify the accuracy of the method proposed in the application.

[0085] The model adopts 4-node quadrilateral elements, a total of 45225 nodes and 44800 elements, and the minimum element size is half of the interface thickness. The boundary conditions of the model are the same as those of the measurement device, and the constraints along the z-axis and the x-axis are respectively applied to the bottom surface and the side surface of the model. Finally, the displacement nephogram of the model is analyzed, as shown in Figure 3 , Figure 4 .

[0086] The results show that the maximum displacement of the model appears on the upper surface. The strain can be calculated by , which is 94.93 and 189.1 , respectively. The error of the strain measured by the vibrating wire strain gauge is not more than 10%, which indicates that the measurement results obtained by the method described in the application are accurate, and the method and device for accurately measuring the linear expansion coefficient of the interface transition zone of concrete provided by the application can accurately measure the linear expansion coefficient of the interface transition zone.

[0087] Embodiment 2

[0088] As Figure 1 shown in the figure, a concrete interface transition zone linear expansion coefficient measuring device is suitable for the concrete interface transition zone linear expansion coefficient measuring method described in Embodiment 1, and comprises a water circulation heating mechanism and a measuring mechanism.

[0089] The water circulation heating mechanism comprises a heating cylinder 101, a water inlet pipe 9, a water outlet pipe 8, and an adjustable temperature cold and hot integrated circulating water machine 10. The heating cylinder 101 is provided with a heating cavity 13. The adjustable temperature cold and hot integrated circulating water machine 10 is connected with the heating cavity 13 through the water inlet pipe 9 and the water outlet pipe 8 respectively.

[0090] The water circulation heating mechanism further comprises a test baffle 6, which is arranged at the opening of the heating cylinder 101. The test baffle 6 is connected with the measuring mechanism.

[0091] In actual use, the test piece 7 is placed in the heating cylinder 101 and in contact with the test baffle 6. The set temperature of the adjustable temperature cold and hot integrated circulating water machine 10 is adjusted. The adjustable temperature cold and hot integrated circulating water machine 10 changes the temperature of the water in the heating cavity 13 to adjust the temperature of the test piece 7. The aggregate-cement mortar combined test piece is heated to simulate the temperature change in actual engineering.

[0092] In this embodiment, the adjustable temperature cold and hot integrated circulating water machine 10 is a QX-6A-HC cold and hot integrated circulating water machine.

[0093] The water circulation heating mechanism further comprises a housing 11 and a bearing platform 12. The housing 11 is arranged on the bearing platform 12, and the heating cylinder 101 is arranged in the housing 11. The housing 11 is made of metal, and the housing 11 supports the heating cylinder 101.

[0094] Heat insulation cotton 5 is arranged between the housing 11 and the heating cylinder 101. The heat insulation cotton 5 plays a heat preservation role and prevents the temperature of the heating cylinder 101 from fluctuating.

[0095] The measuring mechanism comprises a test special cable 1, a frequency reading instrument 2, and a vibrating wire strain gauge 3. The vibrating wire strain gauge 3 is connected with the frequency reading instrument 2 through the test special cable 1. One end of the vibrating wire strain gauge 3 is fixed on the housing 11 through a fixing bolt 4, and the other end is connected with the test baffle 6.

[0096] In this embodiment, the vibrating wire strain gauge 3 is a YD-YBJ vibrating wire concrete surface strain gauge, and the measurement accuracy is 0.1 .

[0097] Finally, it should be noted that the above is only to illustrate the technical solutions of the present application, and is not a limitation on the scope of protection of the present application, and simple modifications or equivalent replacements of the technical solutions of the present application by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A method of determining the linear expansion coefficient of the interface transition zone of concrete, characterized in that, Comprising the following steps: S1: making test pieces, the test pieces comprising aggregate-cement mortar combination test pieces, aggregate test pieces and cement mortar test pieces; S2: measuring the interface transition zone thickness of the aggregate-cement mortar combination test pieces and the lengths of the test pieces; wherein the hardness change trend of the cement mortar and the aggregate interface of the aggregate-cement mortar combination test pieces is measured by using a microhardness tester, the interface transition zone boundary is judged to obtain the interface transition zone thickness; S3: heating the test pieces until the test pieces no longer deform, and recording the deformation amount of the test pieces; S4: calculating the linear expansion coefficient of the interface transition zone according to the measured data in S2 and S3; The linear expansion coefficient calculation formula of the test piece is: In the formula: is the linear expansion coefficient of the test piece, ; is the strain generated by heating of the test piece, ; is the difference between the final temperature and the initial temperature of the test piece, ; Based on the formula, the linear expansion coefficient of the aggregate sample is calculated , the linear expansion coefficient of the cement mortar sample ; For the aggregate-cement mortar composite specimen, the deformation thereof is: : Meanwhile, there is: Accordingly, the linear expansion coefficient calculation formula of the interface transition zone of the aggregate-cement mortar combination test piece is derived as: In the formula, is the deformation of the aggregate-cement mortar composite specimen, is the deformation of the aggregate-cement mortar composite specimen, is the linear expansion coefficient of the aggregate-cement mortar composite specimen, is the thickness of the aggregate-cement mortar composite specimen, is the difference between the final temperature and the initial temperature of the aggregate-cement mortar composite specimen, is the total deformation of the aggregate-cement mortar composite specimen.

2. The method of claim 1, wherein The thickness of the cement mortar is calculated by the following formula: In the formula, L is the length of the aggregate-cement mortar composite test piece.

3. A concrete interfacial transition zone linear expansion coefficient measuring apparatus adapted to the concrete interfacial transition zone linear expansion coefficient measuring method according to any one of claims 1 to 2, characterized by, The water circulation heating mechanism comprises a heating cylinder, a water inlet pipe, a water outlet pipe and an adjustable temperature cold and hot integrated circulating water machine, the heating cylinder is provided with a heating cavity, and the adjustable temperature cold and hot integrated circulating water machine is connected with the heating cavity through the water inlet pipe and the water outlet pipe respectively. The water circulation heating mechanism further comprises a test baffle, the test baffle is arranged at the opening of the heating cylinder, and the test baffle is connected with the measuring mechanism. The water circulation heating mechanism further comprises a shell and a bearing platform, the shell is arranged on the bearing platform, and the heating cylinder is arranged in the shell.

4. The apparatus for measuring the linear expansion coefficient of a concrete interface transition zone according to claim 3, wherein Heat insulation cotton is arranged between the shell and the heating cylinder.

5. The apparatus for measuring the linear expansion coefficient of a concrete interface transition zone according to claim 4, wherein The measuring mechanism comprises a test special cable, a frequency reading instrument and a vibrating wire strain gauge, the vibrating wire strain gauge is connected with the frequency reading instrument through the test special cable; one end of the vibrating wire strain gauge is fixed on the shell through a bolt, and the other end is connected with the test baffle.

6. The apparatus for measuring the linear expansion coefficient of a concrete interface transition zone according to claim 5, wherein ​

Images