Device and method for testing shrinkage cracking resistance toughness of pavement cementing material

Abstract

The invention belongs to a material evaluation method, and relates to a device and a method for testing shrinkage cracking resistance toughness of a pavement cementing material, and the testing method comprises the following steps: S1, manufacturing a test piece; s2, mounting a test piece; s3, anti-shrinkage cracking toughness test: adjusting the temperature and humidity of the test device, monitoring real-time data of the test piece in the shrinkage deformation process through a shrinkage monitoring assembly, and obtaining shrinkage load data Fi and shrinkage deformation quantity data li corresponding to the test piece during ith acquisition; and S4, calculating the shrinkage cracking toughness. The mechanical property of the material can be truly reflected through the shrinkage cracking toughness, accurate simulation of the shrinkage state of the pavement cementing material is realized, and the accuracy, scientificity and rationality of a test result are improved.

Description

Technical Field

[0001] The invention belongs to a material evaluation method and relates to a testing device and method for the shrinkage cracking toughness resistance of pavement cementing materials. Background Art

[0002] Asphalt mixture, cement concrete and other road cementing materials have been widely used in the surface and base layers of highways at all levels. When the road cementing base is completed, it shrinks and deforms due to temperature changes or water evaporation, forming internal stress inside the structure, causing microcracks, shrinkage cracks, and then destroying the overall structure of the road. Therefore, for road materials, accurately evaluating their toughness against shrinkage cracking is of great significance to ensure the durability of asphalt pavement and semi-rigid base structure.

[0003] At present, the evaluation of the shrinkage performance of pavement cementing materials is mainly based on the shrinkage test method of inorganic binder stabilized materials T0854-2024 in the "Test Code for Inorganic Binder Stabilized Materials for Highway Engineering" (JTG 3441-2024). This method mainly uses a displacement meter to test the change of the length of the beam-type specimen under a specific environment with the shrinkage time, and then obtains its shrinkage strain and shrinkage coefficient as the evaluation index for evaluating the shrinkage performance of inorganic binder stabilized materials. Although the existing specifications use displacement sensors and data acquisition systems to improve the measurement precision and accuracy, the existing test equipment and methods still have some drawbacks in shrinkage performance testing, and there is still room for improvement in its test accuracy. The main reasons are as follows:

[0004] (1) The shrinkage coefficient is used as the ratio of shrinkage strain to water loss rate. During the test, the test specimen must be frequently removed from the shrinkage instrument for weighing. The test specimen is frequently disturbed, which destroys its natural shrinkage state and affects the measurement precision and accuracy.

[0005] (2) The existing test method uses a beam-type specimen and only measures the shrinkage strain in the long axis direction. The actual shrinkage of pavement cementing materials is the result of the superposition of the longitudinal and transverse directions in the horizontal direction. Therefore, the existing test specimens and methods are difficult to reflect their actual usage conditions. In addition, since pavement stabilization materials such as cement are spatially discrete to a certain extent, there are certain differences in the performance of each specimen, and the shrinkage performance of each specimen will also be different. The applicability of the measurement method cannot be guaranteed by the parallel measurement method.

[0006] (3) The existing evaluation methods mainly use the shrinkage coefficient as the evaluation index of shrinkage performance, but this is a deformation index and cannot reflect the true mechanical properties of the material;

[0007] (4) In the existing test, the test specimen needs to be installed again after each weighing, which is time-consuming and labor-intensive. In addition, the installation error of the displacement sensor will also have a certain impact on the test results, making it difficult to ensure the accuracy of the final test results of the shrinkage coefficient.

[0008] In summary, there are major deficiencies in the existing testing methods and result evaluation of pavement bonding materials, which cannot reflect the true mechanical properties of the materials, resulting in reduced accuracy of shrinkage performance test results, and poor scientificity and rationality. Summary of the invention

[0009] In view of the technical problems described in the above background technology that there are major deficiencies in the testing methods and result evaluation of pavement bonding materials, which cannot reflect the true mechanical properties of the materials, resulting in reduced accuracy of shrinkage performance test results, and poor scientificity and rationality, the present invention provides a testing device and method for the shrinkage cracking toughness of pavement bonding materials.

[0010] In the test, the present invention collects the load data F at each time point. i and shape variable data l i , the shrinkage cracking toughness of the test specimen is calculated, which is used as an evaluation index to characterize the anti-shrinkage cracking toughness of pavement bonding materials. It can truly reflect the mechanical properties of the material, realize the accurate simulation of the shrinkage state of pavement bonding materials, and improve the accuracy, scientificity and rationality of the test results.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] The present invention provides a method for testing the shrinkage cracking toughness of pavement cementing materials, comprising the following steps:

[0013] S1. Test specimen preparation

[0014] Forming and curing the pavement cementing materials to obtain test specimens;

[0015] S2. Test specimen installation

[0016] Coating an anti-friction coating on a fixed bottom plate of the test device, placing a test specimen on the anti-friction coating and installing and fixing it;

[0017] S3. Shrinkage cracking toughness test

[0018] Adjust the temperature and humidity of the test device, monitor the real-time data of the test specimen during the shrinkage deformation process through the shrinkage monitoring component, and collect real-time data signals every interval ΔT until the set time is reached; obtain the shrinkage load data F corresponding to the test specimen at the i-th collection i and shrinkage deformation data li ;

[0019] S4. Calculation of shrinkage cracking toughness

[0020] The shrinkage load data F collected above i and shrinkage deformation data l i , substitute into the following calculation formula to calculate the shrinkage cracking toughness SCT:

[0021]

[0022] Where:

[0023] SCT is shrinkage cracking toughness, J / cm 2 ;

[0024] N is the total number of times the shrinkage load data reaches the peak value during the shrinkage deformation process, times;

[0025] F i is the shrinkage load value of the test specimen at the i-th collection, N;

[0026] l i is the shrinkage deformation value of the test specimen during the i-th collection, mm;

[0027] l i-1 is the shrinkage deformation value of the test specimen during the i-1th collection, mm;

[0028] S is the cross-sectional area of ​​the test specimen, cm 2 .

[0029] It is further defined that in step S1, the specific process of preparing the test specimen is:

[0030] S1.1. Use a square plate body to shape the pavement cementing material to obtain a plate-type specimen;

[0031] S1.2. The plate specimens are cured for 7 days. In the last day of the curing period, the plate specimens are saturated with water for 24 hours. Finally, the saturated plate specimens are wiped dry to obtain test specimens.

[0032] It is further defined that in step S3, each time data is collected, the shrinkage load data and shrinkage deformation data in the transverse direction of the test specimen, and the shrinkage load data and shrinkage deformation data in the longitudinal direction are obtained respectively.

[0033] It is further defined that the specific method of step S4 is:

[0034] Substituting the shrinkage load data and shrinkage deformation data in the transverse direction into the shrinkage cracking toughness calculation formula, the shrinkage cracking toughness in the transverse direction is obtained;

[0035] The shrinkage load data and shrinkage deformation data in the longitudinal direction are used to obtain the shrinkage cracking toughness in the longitudinal direction;

[0036] Compare the shrinkage cracking toughness in the transverse direction with the shrinkage cracking toughness in the longitudinal direction, and take the smaller value as the calculation result of the shrinkage cracking toughness.

[0037] It is further defined that as the shrinkage cracking toughness SCT value increases, the toughness of the pavement bonding material increases.

[0038] A testing device for implementing the testing method of the shrinkage cracking toughness of pavement cementing materials, the testing device comprising:

[0039] Test box: used to place the fixed base plate, shrinkage monitoring components, temperature control equipment, humidity control equipment, environmental controller and test specimens;

[0040] Fixed bottom plate: used to fix the test specimen;

[0041] Temperature control device: used to adjust and control the temperature inside the test box 1;

[0042] Humidity control device: used to adjust and control the temperature in the test box 1;

[0043] Environmental controller: connected to the temperature control device and the humidity control device respectively, used to control the working status of the temperature control device and the humidity control device respectively until the temperature and humidity in the test chamber reach the target set values;

[0044] Temperature sensor: placed in the test box and connected to the temperature control device, and transmits the collected temperature data to the central computer;

[0045] Humidity sensor: connected to the humidity control device placed in the test box, and transmits the collected humidity data to the central computer;

[0046] Shrinkage monitoring component: placed on the fixed base plate and connected to the test specimen, used to test the test specimen against shrinkage cracking toughness and obtain shrinkage load data and shrinkage deformation data; used to transmit the shrinkage load data and shrinkage deformation data to the central computer;

[0047] and

[0048] Central computer: connected to the temperature sensor, humidity sensor, environmental controller and shrinkage monitoring component respectively, used to receive temperature, humidity, shrinkage load data and shrinkage deformation data, and process the collected data to calculate the shrinkage cracking toughness SCT.

[0049] It is further defined that the contraction monitoring assembly includes a transverse contraction monitoring assembly and a longitudinal contraction monitoring assembly respectively connected to the central computer;

[0050] The transverse shrinkage monitoring assembly is placed in the transverse direction of the test specimen, and is used to monitor the shrinkage load data and shrinkage deformation data in the transverse direction of the test specimen;

[0051] The longitudinal shrinkage monitoring assembly is placed in the longitudinal direction of the test specimen and is used to monitor the shrinkage load data and shrinkage deformation data in the longitudinal direction of the test specimen.

[0052] It is further defined that the lateral shrinkage monitoring assembly includes a deformation testing unit and a boundary fixing unit, and the deformation testing unit and the boundary fixing unit are respectively arranged on opposite side walls in the lateral direction of the test specimen; the longitudinal shrinkage monitoring assembly has the same structure as the lateral shrinkage monitoring assembly.

[0053] It is further defined that the test specimen is obtained by curing a plate specimen, the plate specimen is composed of a pavement bonding material sample and an anchoring side wall, and an anchoring side wall is respectively arranged on the four side walls of the pavement bonding material sample; the deformation test unit includes a first connecting screw, a strain gauge sensor and a second connecting screw connected in sequence, the first connecting screw is connected to the anchoring side wall, and the second connecting screw is hinged to a fixed column arranged on a fixed base plate; the strain gauge sensor is electrically connected to a central computer.

[0054] The beneficial effects of the present invention are:

[0055] 1. The test and evaluation method provided by the present invention proposes shrinkage cracking toughness SCT as a characterization index of shrinkage cracking toughness, which not only reflects the shrinkage deformation factor, but also takes into account the influence of shrinkage stress. It can intuitively reflect the damage limit of shrinkage cracking of cementitious materials, realize the scientific characterization of the shrinkage cracking resistance of pavement cementitious materials, and enable the research on shrinkage cracking toughness to better serve the design and performance testing of pavement cementitious materials.

[0056] 2. The present invention simulates the actual service environment of pavement cementing materials through an intelligently controlled test box, ensuring that the shrinkage effect is scientific and reasonable, and improving the accuracy of the test results of anti-shrinkage cracking toughness; based on the shrinkage monitoring component, continuous and uninterrupted observation of the shrinkage process of the test specimen is achieved, avoiding test errors caused by frequent disassembly and disturbance of the specimen, and ensuring the accuracy of the test results.

[0057] 3. The present invention discloses a testing device and method for the shrinkage cracking toughness of pavement bonding materials, which can be used to simulate the shrinkage cracking process of pavement bonding materials, realize the shrinkage cracking performance test of pavement bonding materials, and further realize the quantitative evaluation of the shrinkage cracking performance of pavement bonding materials.

[0058] 4. The present invention adopts a square test specimen, and two sets of valid data can be obtained through one test, which not only improves the test efficiency, but also takes into account the directionality of material shrinkage deformation. By defining the most unfavorable situation, the test evaluation results are safer and more reliable.

[0059] 5. The testing device of the present invention has a simple structure, is scientific and reasonable, is easy to implement, and can be used in standardized production. Its promotion and application has extremely important engineering significance for studying the shrinkage cracking resistance of pavement cementing materials and structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A schematic plan view of a testing device provided by the present invention;

[0061] Figure 2 A schematic diagram of a test box provided by the present invention;

[0062] Figure 3 It is a schematic diagram of a plate-type test piece of the present invention;

[0063] Figure 4 Schematic diagram of anchoring side wall;

[0064] Figure 5 Schematic diagram of the plate-type test piece forming of the present invention; wherein: a is a plate-type test piece forming diagram; b is a schematic diagram of the forming test mold;

[0065] Figure 6 It is a schematic diagram of a plate-type specimen deformation test unit of the present invention;

[0066] Figure 7 It is a schematic diagram of a plate-type specimen boundary fixing unit of the present invention;

[0067] Figure 8 is a typical shrinkage load-deformation curve of the present invention;

[0068] In the figure:

[0069] 1-test box; 11-temperature control device; 12-humidity control device; 13-environmental controller; 14, temperature sensor; 15-humidity sensor; 16-top cover; 17-slide; 2-fixed bottom plate; 21-fixed column; 22-ring; 23-ball joint; 3-contraction monitoring component; 31-amplifier; 32-deformation test unit; 321-strain gauge sensor; 322-first connecting screw; 323-second connecting screw; 33-boundary fixing unit; 331-third connecting screw; 4-plate specimen; 41-pavement bonding material specimen; 42-anchoring side wall; 421-convex base plate; 422-end enlarged anchor rod; 43-molding test mold; 431-card slot; 5-central computer; 51-connecting line. DETAILED DESCRIPTION

[0070] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0071] The test and evaluation method and device provided by the present invention are described in detail below with reference to specific embodiments.

[0072] Example 1

[0073] The present invention also provides a testing device, comprising:

[0074] Test box 1: used to place the fixed base plate 2, the shrinkage monitoring component 3, the temperature control device 11, the humidity control device 12, the environmental controller 13 and the test specimen;

[0075] Fixed bottom plate 2: used to fix the test specimen;

[0076] Temperature control device 11: used to adjust and control the temperature in the test box 1;

[0077] Humidity control device 12: used to adjust and control the temperature in the test box 1;

[0078] Environmental controller 13: connected to the temperature control device 11 and the humidity control device 12 respectively, and used to control the working states of the temperature control device 11 and the humidity control device 12 respectively until the temperature and humidity in the test box 1 reach the target set values;

[0079] Temperature sensor: placed in the test box and connected to the temperature control device, and transmits the collected temperature data to the central computer;

[0080] Humidity sensor: connected to the humidity control device placed in the test box, and transmits the collected humidity data to the central computer;

[0081] Shrinkage monitoring component 3: placed on the fixed base plate 2 and connected to the test specimen, used to perform shrinkage crack toughness test on the test specimen and obtain shrinkage load data and shrinkage deformation data; used to transmit the shrinkage load data and shrinkage deformation data to the central computer 5;

[0082] Central computer 5: connected to temperature control device 11, humidity control device 12, environment controller 13 and shrinkage monitoring component 3 respectively, for receiving temperature, humidity, shrinkage load data and shrinkage deformation data, and processing the collected data to calculate shrinkage cracking toughness SCT.

[0083] See also Figure 1The testing device for the shrinkage cracking toughness of pavement cementing materials provided in this embodiment includes a testing box 1, a fixed base plate 2, a shrinkage monitoring component 3, a plate specimen 4 and a central computer 5.

[0084] See also Figure 2 In this embodiment, the test box 1 is a rectangular box, and a top cover 16 is provided on the top of the test box 1. The top cover 16 is provided with left and right parts, and the top cover 16 is closed by a slide 17 on the upper edge of the test box.

[0085] In this embodiment, the fixed bottom plate 2 is located in the test box 1, and the shrinkage monitoring component 3 is connected to the fixed bottom plate 2 and the plate test piece 4 respectively, and is used to fix the plate test piece 4 and measure the shrinkage deformation and shrinkage stress of the plate test piece 4. The shrinkage deformation and shrinkage stress measurement signals are processed by the amplifier 31 and transmitted to the central computer 5 through the connecting line 51 for storage.

[0086] In this embodiment, a temperature control device 11 and a humidity control device 12 are installed in the test box 1. The temperature control device 11 and the humidity control device 12 are respectively connected to an environmental controller 13 placed outside the test box 1. A temperature sensor 14 and a humidity sensor 15 are also provided in the test box 1. The environmental controller 13, the temperature sensor 14, and the humidity sensor 15 are all connected to the central computer 5.

[0087] Specifically, the temperature sensor 14 collects temperature condition data in the test box 1, and the humidity sensor 15 collects humidity condition data in the test box 1. After being processed and analyzed by the central computer 5, the instructions are transmitted to the environmental controller 13. The environmental controller 13 controls the working status of the temperature control device 11 and the humidity control device 12 until the temperature and humidity conditions in the test box 1 reach the target set values.

[0088] See also Figure 3 In this embodiment, the plate specimen 4 is composed of a pavement bonding material specimen 41 and an anchoring side wall 42. The pavement bonding material specimen 41 is a square specimen, and the anchoring side walls 42 are correspondingly arranged on the four side walls of the pavement bonding material specimen 41.

[0089] It is particularly noted that the length of the anchoring side wall 42 is smaller than the side length of the pavement bonding material sample 41 to prevent adjacent anchoring side walls 42 from colliding with each other during the shrinkage of the pavement bonding material sample 41 and affecting the natural shrinkage deformation process of the pavement bonding material sample 41.

[0090] See also Figure 4Preferably, the anchoring side wall 42 is composed of a convex substrate 421 and an end-enlarged anchor rod 422. The convex substrate 421 is located on the surrounding side walls of the pavement cementing material sample 41 and is embedded in the edge of the pavement cementing material sample 41 through the end-enlarged anchor rod 422. Preferably, the convex substrate 421 is a metal plate with a convex cross-section.

[0091] In this embodiment, the fixed bottom plate 2 is located at the bottom of the test box 1. Four fixed columns 21 are provided on the fixed bottom plate 2. Rings 22 are installed on the fixed columns 21. The rings 22 can slide freely up and down along the axis of the fixed columns 21. A ball joint 23 is provided on the rings 22.

[0092] See also Figure 1 In this embodiment, the shrinkage monitoring assembly 3 includes a deformation testing unit 32 and a boundary fixing unit 33, and the deformation testing unit 32 and the boundary fixing unit 33 are arranged on opposite side walls of the plate specimen 4 in a facing manner.

[0093] See also Figure 6 Specifically, the deformation test unit 32 includes a strain gauge sensor 321, a first connecting screw 322, and a second connecting screw 323. The two ends of the first connecting screw 322 are respectively connected to the strain gauge sensor 321 and the convex base plate 421, and the two ends of the second connecting screw 323 are respectively connected to the strain gauge sensor 321 and the ball joint 23. The first connecting screw 322, the strain gauge sensor 321, and the second connecting screw 323 are connected in sequence. When the pavement cementing material sample 41 undergoes shrinkage deformation, the convex base plate 421 of the anchoring side wall 42 is driven to move. Due to the limiting effect of the fixed column 21, the first connecting screw 322 and the second connecting screw 323 reversely stretch the strain gauge sensor 321. The strain gauge sensor 321 generates deformation and load data signals, which are processed by the amplifier 31 and transmitted to the central computer 5 through the connecting line 51.

[0094] See also Figure 7 In this embodiment, the boundary fixing unit 33 is used to limit the movement of the plate-type specimen 4. The boundary fixing unit 33 is provided with a third connecting screw 331. The two ends of the third connecting screw 331 are respectively connected to the convex base plate 421 and the ball joint 23.

[0095] In this embodiment, in order to improve the measurement accuracy, it is necessary to measure the shrinkage deformation and shrinkage load in two directions of the plate specimen 4. Therefore, the shrinkage monitoring assembly 3 is divided into two, namely, a transverse shrinkage monitoring assembly and a longitudinal shrinkage monitoring assembly respectively connected to the central computer 5.

[0096] The transverse shrinkage monitoring component is placed in the transverse direction of the plate specimen 4, and is used to monitor the shrinkage load data and shrinkage deformation data of the plate specimen 4 in the transverse direction; the longitudinal shrinkage monitoring component is placed in the longitudinal direction of the plate specimen 4, and is used to monitor the shrinkage load data and shrinkage deformation data of the plate specimen 4 in the longitudinal direction.

[0097] In the transverse shrinkage monitoring assembly, the deformation testing unit 32 and the boundary fixing unit 33 are respectively arranged on opposite side walls of the plate-type specimen 4 in the transverse direction.

[0098] In the longitudinal shrinkage monitoring assembly, the deformation testing unit 32 and the boundary fixing unit 33 are respectively arranged on opposite side walls of the plate specimen 4 in the longitudinal direction.

[0099] See also Figure 5 In this embodiment, the plate-type specimen 4 is prepared in a molding test mold 43, and a slot 431 is left on the four side walls of the molding test mold 43, and the cross-sectional shape of the slot 431 matches the convex substrate 421. In particular, during the molding process of the plate-type specimen 4, the four convex substrates 421 are first placed in the slots 431 on the four side walls of the molding test mold 43, and then the road surface cementing material is filled in the molding test mold 43, and the asphalt mixture wheel roller molding machine is used to perform rolling molding according to the set compaction work.

[0100] It is particularly noted that the molding thickness and side length of the plate specimen 4 can be selected according to the needs of the project. During the molding process of the plate specimen 4, the pavement bonding material is first configured according to the designed ratio, and its maximum dry density is determined according to the compaction test method of inorganic binder stabilized materials T0804-1994 in the "Test Code for Inorganic Binder Stabilized Materials for Highway Engineering" (JTG 3441-2024). Then, the maximum dry density and the volume of the molding test mold 43 are used to calculate the mass required for molding the pavement bonding material sample 41, which is weighed and placed in the molding test mold 43 for rolling.

[0101] It is particularly noted that in order to allow the plate-type specimen 4 to be better removed from the molding mold 43 after molding, the molding mold 43 containing the plate-type specimen 4 can be inverted on a flat plate, and then the bottom of the molding mold 43 can be knocked to allow the plate-type specimen 4 to be separated from the molding mold 43 to ensure the integrity of the plate-type specimen 4.

[0102] It is particularly noted that the temperature control device 11 and the humidity control device 12 can not only realize the regulation of temperature and humidity in the test box 1, but can also be used to simulate various actual use environments such as plateaus, severe cold, and extreme heat, to achieve an accurate assessment of the shrinkage cracking toughness of pavement cementing materials.

[0103] It is particularly noted that the top cover 16 is preferably made of double-layer tempered glass to achieve transparency and heat preservation functions, making it easy for the tester to observe the test situation inside the test box 1.

[0104] It is particularly noted that a plurality of anchor rods 422 with enlarged ends are provided on the inner side of the anchoring side wall 42. The enlarged ends of the anchor rods 422 help to strengthen the bond between the anchoring side wall 42 and the pavement bonding material sample 41, thereby preventing the anchoring side wall 42 from falling off and slipping during the shrinkage deformation of the pavement bonding material sample 41, thereby affecting the test accuracy.

[0105] It is particularly noted that the fixed base plate 2 is a metal plate. In order to reduce the friction between the plate specimen 4 and the fixed base plate 2 when shrinking and to affect the natural shrinkage deformation process of the pavement bonding material sample 41, it is advisable to first coat paraffin on the fixed base plate 2 and then place the plate specimen 4.

[0106] The device provided in this embodiment can adjust the ambient temperature and humidity in real time according to actual needs to simulate the level of anti-shrinkage cracking toughness of pavement cementing materials under real conditions.

[0107] Example 2

[0108] This embodiment provides a method for testing the shrinkage cracking toughness of pavement cementing materials, comprising the following steps:

[0109] S1. Test specimen preparation

[0110] The pavement bonding materials are molded and cured to obtain test specimens.

[0111] Specifically, the specific process of test specimen production is:

[0112] 1) Forming of plate specimen 4

[0113] A square plate specimen is prepared indoors. Specifically, a pavement cementing material is formed using a square plate to obtain a plate specimen 4.

[0114] 2) Maintenance

[0115] The plate specimen 4 was cured according to the standard curing method T0845 in JTG 3441-2024, and the curing period was 7 days. In the last day of the curing period, the plate specimen 4 was saturated with water for 24 hours. Finally, the surface of the saturated plate specimen 4 was wiped dry for standby use. The cured plate specimen 4 is the test specimen.

[0116] S2. Test specimen installation

[0117] An anti-friction coating is applied on the fixed bottom plate 2 of the test device, and a test specimen is placed on the anti-friction coating and installed and fixed.

[0118] Specifically, paraffin is coated on the fixed bottom plate 2 of the test box 1, and the cured plate specimen 4 (i.e., the test specimen) is placed on the fixed bottom plate 2. The convex base plate 421 is connected to the fixed column 21 using the first connecting screw 322, the second connecting screw 323, and the third connecting screw 331 to achieve installation and fixation of the plate specimen 4.

[0119] S3. Shrinkage cracking toughness test

[0120] Adjust the temperature and humidity of the test device, monitor the real-time data of the test specimen during the shrinkage deformation process through the shrinkage monitoring component 3, and collect the real-time data signal once every interval ΔT until the set time is reached; obtain the shrinkage load data F corresponding to the test specimen at the i-th collection i and shrinkage deformation data l i .

[0121] In step S3, each time data is collected, the shrinkage load data and shrinkage deformation data in the transverse direction of the test specimen, and the shrinkage load data and shrinkage deformation data in the longitudinal direction are obtained respectively.

[0122] Specifically, the temperature and humidity of the test box 1 are set by the central computer 5, the automatic working procedures of the deformation test unit 32, the environmental controller 13, the temperature sensor 14, and the humidity sensor 15 are turned on, the reading of the strain gauge sensor 321 is reset to zero, the equipment is started, and the shrinkage crack toughness test operation and real-time information collection are performed. The load data F of the strain gauge sensor 321 is recorded by the central computer 5 every time interval ΔT. i and shape variable data l i , until 168 hours of real-time monitoring is completed.

[0123] S4. Calculation of shrinkage cracking toughness

[0124] The shrinkage load data F collected above i and shrinkage deformation data l i , substitute into the following calculation formula to calculate the shrinkage cracking toughness SCT:

[0125]

[0126] Where:

[0127] SCT is shrinkage cracking toughness, J / cm 2 ;

[0128] N is the total number of times the shrinkage load data reaches the peak value during the shrinkage deformation process, times;

[0129] F i is the shrinkage load value of the test specimen at the i-th collection, N;

[0130] l i is the shrinkage deformation value of the test specimen during the i-th collection, mm;

[0131] l i-1 is the shrinkage deformation value of the test specimen during the i-1th collection, mm;

[0132] S is the cross-sectional area of ​​the test specimen, cm 2 .

[0133] In this embodiment, the shrinkage load value and the shrinkage deformation value of the test specimen are both obtained by testing the strain gauge sensor 321. The cross-sectional area of ​​the test specimen is the cross-sectional area of ​​the pavement cementing material sample 41.

[0134] In step S4, the specific method for calculating the shrinkage cracking toughness is:

[0135] Substituting the shrinkage load data and shrinkage deformation data in the transverse direction into the shrinkage cracking toughness calculation formula, the shrinkage cracking toughness in the transverse direction is obtained;

[0136] The shrinkage load data and shrinkage deformation data in the longitudinal direction are used to obtain the shrinkage cracking toughness in the longitudinal direction;

[0137] Compare the shrinkage cracking toughness in the transverse direction with the shrinkage cracking toughness in the longitudinal direction, and take the minimum value as the calculation result of the shrinkage cracking toughness.

[0138] It is particularly noted that two sets of load data and deformation data of the strain gauge sensor 321 can be obtained for each test. Considering that the pavement cementing material sample 41 has directionality when shrinking, the test data set with the earliest fracture is taken as the most unfavorable situation to evaluate the shrinkage cracking resistance of the test sample. Therefore, the shrinkage cracking toughness in the transverse direction and the shrinkage cracking toughness in the longitudinal direction are compared, and the minimum value is taken as the calculation result of the shrinkage cracking toughness.

[0139] In particular, the shrinkage cracking toughness (SCT) indicates the ability of pavement cementing materials to resist deformation and fracture under shrinkage. The SCT value indicates the toughness of pavement cementing materials.

[0140] In this embodiment, a plurality of different pavement cementing material samples 41 are prepared and their shrinkage cracking toughness SCT is calculated. It is found that as the shrinkage cracking toughness SCT value increases, the toughness of the pavement cementing material increases, that is, the toughness of the pavement cementing material is positively correlated with the shrinkage cracking toughness SCT. Therefore, the shrinkage cracking toughness SCT can be used to evaluate the shrinkage cracking toughness of different pavement cementing materials in the future.

[0141] It is particularly noted that for the same material, the shrinkage cracking toughness SCT should be a certain value, which can facilitate the comparative analysis of the shrinkage cracking resistance of various materials.

[0142] It is particularly noted that the measurement of the shrinkage cracking toughness is automatically completed through the programming control software of the central computer 5, thereby reducing the operating errors of personnel.

[0143] The above characterization of the anti-cracking shrinkage toughness of pavement bonding materials by calculating the shrinkage cracking toughness can truly reflect the mechanical properties of the materials, achieve accurate simulation of the shrinkage state of pavement bonding materials, and improve the accuracy, scientificity and rationality of the test results; and then the size of the shrinkage cracking toughness is used to evaluate the toughness of pavement bonding materials.

[0144] In addition, in the test process of this embodiment, the shrinkage load data F collected for the i-th time is i and shrinkage deformation data l i , with the shrinkage deformation data l i is the horizontal axis, with the shrinkage load data F i As the vertical axis, the shrinkage load-shrinkage deformation curve is also plotted.

[0145] See also Figure 8 From the shrinkage load-deformation curve, it can be seen that the load and deformation values ​​first increase and then decrease with the increase of shrinkage test time. In the growth stage of the curve, as the shrinkage progresses, the load and deformation values ​​gradually increase, and the shrinkage stress inside the specimen also gradually increases; when the shrinkage stress reaches the allowable strength of the material, the plate specimen cracks and breaks, and the shrinkage stress inside the specimen is released, thus reducing the load and deformation values.

[0146] Obviously, the above embodiments are merely examples for clearly illustrating the technical solutions of the present invention, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above descriptions, and it is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the present invention.

Claims

1. A method for testing the shrinkage cracking toughness of pavement cementing materials, characterized in that: The following steps are involved: S1. Test specimen preparation Forming and curing the pavement cementing materials to obtain test specimens; S2. Test specimen installation Coating an anti-friction coating on a fixed bottom plate (2) of the test device, placing a test specimen on the anti-friction coating and installing and fixing it; S3. Shrinkage cracking toughness test The temperature and humidity of the test device are adjusted, and the real-time data of the test specimen during the shrinkage deformation process is monitored by the shrinkage monitoring component (3), and the real-time data signal is collected once every interval ΔT until the set time is reached; the shrinkage load data F corresponding to the test specimen at the i-th collection is obtained. i and shrinkage deformation data l i ; S4. Calculation of shrinkage cracking toughness The shrinkage load data F collected above i and shrinkage deformation data l i , substitute into the following calculation formula to calculate the shrinkage cracking toughness SCT: Where: SCT is shrinkage cracking toughness, J / cm 2 ; N is the total number of times the shrinkage load data reaches the peak value during the shrinkage deformation process, times; F i is the shrinkage load value of the test specimen at the i-th collection, N; l i is the shrinkage deformation value of the test specimen during the i-th collection, mm; l i-1 is the shrinkage deformation value of the test specimen during the i-1th collection, mm; S is the cross-sectional area of ​​the test specimen, cm 2 .

2. The test method for shrinkage cracking toughness of pavement cementing materials according to claim 1, characterized in that: In step S1, the specific process of making the test specimen is: S1.

1. Use a square plate body to shape the pavement cementing material to obtain a plate-type specimen (4); S1.

2. The plate specimen is cured for 7 days. In the last day of the curing period, the plate specimen (4) is saturated with water for 24 hours. Finally, the saturated plate specimen (4) is wiped dry to obtain a test specimen.

3. The test method for shrinkage cracking toughness of pavement cementing materials according to claim 1, characterized in that: In the step S3, each time the data is collected, the shrinkage load data and shrinkage deformation data in the transverse direction of the test specimen, and the shrinkage load data and shrinkage deformation data in the longitudinal direction are obtained respectively.

4. The test method for shrinkage cracking toughness of pavement cementing materials according to claim 3, characterized in that: The specific method of step S4 is: Substituting the shrinkage load data and shrinkage deformation data in the transverse direction into the shrinkage cracking toughness calculation formula, the shrinkage cracking toughness in the transverse direction is obtained; The shrinkage load data and shrinkage deformation data in the longitudinal direction are used to obtain the shrinkage cracking toughness in the longitudinal direction; Compare the shrinkage cracking toughness in the transverse direction with the shrinkage cracking toughness in the longitudinal direction, and take the minimum value as the calculation result of the shrinkage cracking toughness.

5. The test method for shrinkage cracking toughness of pavement cementing materials according to claim 4, characterized in that: As the shrinkage cracking toughness SCT value increases, the toughness of pavement bonding materials increases.

6. A testing device for implementing the testing method for the shrinkage cracking toughness of pavement cementing materials as claimed in claim 1, characterized in that: The testing device comprises: Test box (1): used for placing a fixed base plate (2), a shrinkage monitoring component (3), a temperature control device (11), a humidity control device (12), an environmental controller (13) and a test specimen; Fixed bottom plate (2): used to fix the test specimen; Temperature control device (11): used to adjust and control the temperature inside the test box (1); Humidity control device (12): used to adjust and control the humidity in the test box (1); An environmental controller (13) is connected to the temperature control device (11) and the humidity control device (12) respectively, and is used to control the working states of the temperature control device (11) and the humidity control device (12) respectively until the temperature and humidity in the test box (1) reach the target set values; Temperature sensor (14): placed in the test box (1) and connected to the temperature control device (11), and transmits the collected temperature data to the central computer (5); Humidity sensor (15): connected to the humidity control device (12) placed in the test box (1), and transmits the collected humidity data to the central computer (5); Shrinkage monitoring component (3): placed on the fixed base plate (2) and connected to the test specimen, used to perform shrinkage crack toughness test on the test specimen and obtain shrinkage load data and shrinkage deformation data; used to transmit the shrinkage load data and shrinkage deformation data to the central computer (5); and The central computer (5) is respectively connected to the temperature sensor (14), the humidity sensor (15), the environmental controller (13) and the shrinkage monitoring component (3), and is used to receive temperature, humidity, shrinkage load data and shrinkage deformation data, and process the collected data to calculate the shrinkage cracking toughness SCT.

7. The testing device according to claim 6, characterized in that: The contraction monitoring component (3) comprises a transverse contraction monitoring component and a longitudinal contraction monitoring component respectively connected to the central computer (5); The transverse shrinkage monitoring assembly is placed in the transverse direction of the test specimen, and is used to monitor the shrinkage load data and shrinkage deformation data in the transverse direction of the test specimen; The longitudinal shrinkage monitoring assembly is placed in the longitudinal direction of the test specimen and is used to monitor the shrinkage load data and shrinkage deformation data in the longitudinal direction of the test specimen.

8. The testing device according to claim 7, characterized in that: The transverse shrinkage monitoring component comprises a deformation test unit (32) and a boundary fixing unit (33), and the deformation test unit (32) and the boundary fixing unit (33) are respectively arranged on opposite side walls in the transverse direction of the test specimen; the longitudinal shrinkage monitoring component has the same structure as the transverse shrinkage monitoring component.

9. The testing device according to claim 8, characterized in that: The test specimen is obtained by curing a plate specimen (4), wherein the plate specimen (4) is composed of a pavement bonding material sample (41) and an anchoring side wall (42), and an anchoring side wall (42) is respectively arranged on the four side walls of the pavement bonding material sample (41); the deformation test unit (32) comprises a first connecting screw (322), a strain gauge sensor (321) and a second connecting screw (323) which are connected in sequence, wherein the first connecting screw (322) is connected to the anchoring side wall (42), and the second connecting screw (323) is hinged to a fixed column (21) arranged on a fixed base plate (2); and the strain gauge sensor (321) is electrically connected to a central computer (5).

Images