A device and method for testing the anti-shrinkage cracking toughness of a pavement cementitious material

Abstract

The application belongs to material evaluation method, and relates to a testing device and method for anti-shrinkage cracking toughness of pavement cementitious material. i and shrinkage deformation data l i of the test specimen at the i-th collection time; and S4, calculating the shrinkage cracking toughness. The shrinkage cracking toughness can truly reflect the mechanical properties of the material, the shrinkage state of the pavement cementitious material is accurately simulated, the accuracy, scientificity and rationality of the test result are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of material evaluation methods, and relates to a device and method for testing the anti-shrinkage cracking toughness of pavement cementitious materials. BACKGROUND

[0002] Pavement cementitious materials such as asphalt mixtures and cement concrete have been widely used in the surface and base layers of highways. When the pavement cementitious base layer is completed, shrinkage deformation occurs due to temperature changes or water evaporation, internal stress is formed in the structure, micro cracks appear, shrinkage cracking occurs, and the overall structure of the pavement is damaged. Therefore, for pavement materials, accurately evaluating the anti-shrinkage cracking toughness is of great significance to ensure the durability of asphalt pavements and semi-rigid base structures.

[0003] Currently, the evaluation of the shrinkage performance of pavement cementitious materials is mainly based on the T0854-2024 inorganic binder stabilized material shrinkage test method in the Highway Engineering Inorganic Binder Stabilized Material Test Specification (JTG 3441-2024). This method mainly uses displacement meters to test the change in the length of beam-shaped test pieces with shrinkage time under specific conditions, and then obtains the shrinkage strain and shrinkage coefficient as evaluation indicators for the shrinkage performance of inorganic binder stabilized materials. Although displacement sensors and data acquisition systems are used in the existing specification to improve the accuracy and precision of the measurement, the existing test equipment and methods still have some drawbacks in terms of shrinkage performance testing, and there is still room for improvement in the 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, and the test specimen is frequently removed from the shrinkage instrument for weighing during the test. The test specimen is frequently disturbed, which destroys its natural shrinkage state and affects the measurement accuracy and precision.

[0005] (2) The existing test method uses beam-shaped test pieces, which only measure the shrinkage strain in the long axis direction. However, the actual shrinkage of pavement cementitious materials is the result of the superposition of the longitudinal and transverse directions in the horizontal direction. Therefore, the existing test specimen and method cannot reflect the true use conditions. In addition, cement and other pavement stabilized materials have a certain degree of spatial dispersion, resulting in differences in performance between test pieces. The shrinkage performance of each test piece is different, and the applicability of the measurement method is difficult to guarantee through parallel measurement.

[0006] (3) The existing evaluation method mainly uses the shrinkage coefficient as the evaluation indicator for shrinkage performance, but this is a deformation indicator and cannot reflect the true mechanical properties of the material.

[0007] (4) In the existing test, the test sample needs to be installed again after each weighing, which is time-consuming and laborious, and 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 shrinkage coefficient test results.

[0008] In summary, the existing test method and result evaluation of pavement cementitious materials have great deficiencies, cannot reflect the true mechanical properties of the material, and lead to reduced accuracy, scientificity and rationality of the shrinkage performance test results. SUMMARY

[0009] In view of the technical problems described in the above background art, that the test method and result evaluation of pavement cementitious materials have great deficiencies, cannot reflect the true mechanical properties of the material, and lead to reduced accuracy, scientificity and rationality of the shrinkage performance test results, the present application provides a test device and method for the anti-shrinkage cracking toughness of pavement cementitious materials.

[0010] In the test, the load data F i and the deformation data l i at each time point are collected, the shrinkage cracking toughness of the test sample is calculated, which is used as an evaluation index of the anti-shrinkage cracking toughness of pavement cementitious materials, can truly reflect the mechanical properties of the material, realize the precise simulation of the shrinkage state of pavement cementitious materials, and improve the accuracy, scientificity and rationality of the test results.

[0011] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0012] The present application provides a test method for the anti-shrinkage cracking toughness of pavement cementitious materials, comprising the following steps:

[0013] S1, test sample preparation

[0014] The pavement cementitious material is formed and maintained to obtain a test sample;

[0015] S2, test sample installation

[0016] A friction-reducing coating is applied to the fixed bottom plate of the test device, and the test sample is placed on the friction-reducing coating and fixed;

[0017] S3, anti-shrinkage cracking toughness test

[0018] The temperature and humidity of the test device are adjusted, the real-time data of the test sample in the shrinkage deformation process are monitored by the shrinkage monitoring assembly, and the real-time data signal is collected every interval time ΔT until the set time is reached; the shrinkage load data F i and the shrinkage deformation data li ;

[0019] S4, calculating shrinkage cracking toughness

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

[0021]

[0022] In the formula:

[0023] SCT is the 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 ith time, N;

[0026] I i is the shrinkage deformation value of the test specimen at the ith time, mm;

[0027] I i-1 is the shrinkage deformation value of the test specimen at the ith-1 time, mm;

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

[0029] Further limited, in the step S1, the specific process of making the test specimen is:

[0030] S1.1, using a square plate body to form the pavement cementitious material to obtain a plate-shaped specimen;

[0031] S1.2, curing the plate-shaped specimen, the curing age is 7d, and in the last 1d of the curing age, the plate-shaped specimen is treated with water for 24h, and finally the water-saturated plate-shaped specimen is wiped dry to obtain the test specimen.

[0032] Further limited, in the step S3, the shrinkage load data and shrinkage deformation data in the transverse direction of the test specimen are obtained respectively at each time of collection, as well as the shrinkage load data and shrinkage deformation data in the longitudinal direction.

[0033] Further limited, the specific method of the step S4 is:

[0034] substitute the shrinkage load data and shrinkage deformation data in the transverse direction into the shrinkage cracking toughness calculation formula to obtain the shrinkage cracking toughness in the transverse direction;

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

[0036] The shrinkage cracking toughness in the transverse direction and the shrinkage cracking toughness in the longitudinal direction are compared, and the smaller value is taken as the calculation result of the shrinkage cracking toughness.

[0037] Further limited, as the shrinkage cracking toughness SCT value increases, the toughness of the pavement cementitious material increases.

[0038] A test device for implementing the test method of the shrinkage cracking toughness of the pavement cementitious material, the test device comprises:

[0039] Test box: for placing the fixed base plate, shrinkage monitoring assembly, temperature control device, humidity control device, environment controller and test specimen;

[0040] Fixed base plate: for fixing the test specimen;

[0041] Temperature control device: for adjusting and controlling the temperature in the test box 1;

[0042] Humidity control device: for adjusting and controlling the temperature in the test box 1;

[0043] Environment controller: connected with the temperature control device and the humidity control device respectively, for controlling the working state of the temperature control device and the humidity control device respectively, until the temperature and humidity in the test box reach the target set value;

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

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

[0046] Shrinkage monitoring assembly: placed on the fixed base plate and connected with the test specimen, for testing the shrinkage cracking toughness of the test specimen and obtaining the shrinkage load data and shrinkage deformation data; for transmitting the shrinkage load data and shrinkage deformation data to the central computer;

[0047] And

[0048] Central computer: connected with the temperature sensor, humidity sensor, environment controller and shrinkage monitoring assembly respectively, for receiving temperature, humidity, shrinkage load data and shrinkage deformation data, and processing the collected data to calculate the shrinkage cracking toughness SCT.

[0049] Further limited, the shrinkage monitoring assembly includes a transverse shrinkage monitoring assembly and a longitudinal shrinkage monitoring assembly connected with the central computer respectively;

[0050] The transverse shrinkage monitoring assembly is arranged in the transverse direction of the test specimen for monitoring the shrinkage load data and shrinkage deformation data in the transverse direction of the test specimen.

[0051] The longitudinal shrinkage monitoring assembly is arranged in the longitudinal direction of the test specimen for monitoring the shrinkage load data and shrinkage deformation data in the longitudinal direction of the test specimen.

[0052] Further limited, the transverse shrinkage monitoring assembly includes a deformation test unit and a boundary fixing unit arranged on the opposite side walls in the transverse direction of the test specimen respectively; and the longitudinal shrinkage monitoring assembly has the same structure as the transverse shrinkage monitoring assembly.

[0053] Further limited, the test specimen is obtained by curing a plate-shaped specimen, the plate-shaped specimen is composed of a pavement cementitious material sample and an anchoring side wall, and one anchoring side wall is arranged on each of the four side walls of the pavement cementitious material sample; the deformation test unit includes a first connecting screw rod, a strain gauge sensor and a second connecting screw rod connected in sequence, the first connecting screw rod is connected with the anchoring side wall, and the second connecting screw rod is hinged with a fixed stand column arranged on a fixed base plate; and the strain gauge sensor is electrically connected with the central computer.

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

[0055] 1. The test evaluation method provided by the present application proposes shrinkage cracking toughness SCT as a representation index of anti-shrinkage cracking toughness, which not only reflects the shrinkage deformation factor but also considers the influence of shrinkage stress, can intuitively reflect the damage limit of shrinkage cracking of cementitious materials, realizes scientific representation of the anti-shrinkage cracking performance of pavement cementitious materials, and makes the research on anti-shrinkage cracking toughness better serve the pavement cementitious material design and performance test work.

[0056] 2. The present application simulates the real service environment of pavement cementitious materials through the intelligent control test box, ensures the scientific and reasonable shrinkage effect, improves the accuracy of the anti-shrinkage cracking toughness test result, and realizes continuous and uninterrupted observation of the shrinkage process of the test specimen based on the shrinkage monitoring assembly, avoids the test error caused by frequent disassembly and disturbance of the test specimen, and ensures the accuracy of the test result.

[0057] 3. The test device and method for the anti-shrinkage cracking toughness of pavement cementitious materials disclosed by the present application can be used for simulating the shrinkage cracking process of pavement cementitious materials, realizing the anti-shrinkage cracking performance test of pavement cementitious materials, and further realizing the quantitative evaluation of the anti-shrinkage cracking performance of pavement cementitious materials.

[0058] 4、The application adopts square test samples, two groups of effective data can be obtained by one test, the test efficiency is improved, the directionality of material shrinkage deformation is considered, the test evaluation result is more safe and reliable by defining the most unfavorable condition.

[0059] 5、The test device of the application has simple structure, scientific and reasonable, easy to realize, can be standardized in production and use, the popularization and application has extremely important engineering significance for researching the anti-shrinkage cracking performance of pavement cementing materials and structure. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 The plane schematic view of the test device provided by the application is shown in the figure;

[0061] Figure 2 The test box body schematic view provided by the application is shown in the figure;

[0062] Figure 3 The plate type sample schematic view of the application is shown in the figure;

[0063] Figure 4 The anchor edge wall schematic view is shown in the figure;

[0064] Figure 5 The plate type sample forming schematic view of the application is shown in the figure; wherein: a is the plate type sample forming view; b is the forming test mold schematic view;

[0065] Figure 6 The plate type sample deformation test unit schematic view of the application is shown in the figure;

[0066] Figure 7 The plate type sample boundary fixing unit schematic view of the application is shown in the figure;

[0067] Figure 8 The typical shrinkage load-deformation curve of the application is shown in the figure;

[0068] In the figure:

[0069] 1-test box; 11-temperature control equipment; 12-humidity control equipment; 13-environment controller; 14-temperature sensor; 15-humidity sensor; 16-top cover; 17-slide; 2-fixed bottom plate; 21-fixed stand; 22-sleeve ring; 23-ball hinge; 3-shrinkage monitoring assembly; 31-amplifier; 32-deformation test unit; 321-strain gauge type sensor; 322-first connecting screw; 323-second connecting screw; 33-boundary fixing unit; 331-third connecting screw; 4-plate type sample; 41-pavement cementing material sample; 42-anchor edge wall; 421-convex base plate; 422-end expansion type anchor rod; 43-forming test mold; 431-clamping groove; 5-central computer; 51-connecting line. DETAILED DESCRIPTION

[0070] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0071] The test evaluation method and device provided by the present application will be described in detail below with specific embodiments.

[0072] Embodiment 1

[0073] The present application also provides a test device, comprising:

[0074] The test box 1 is used to place the fixed base plate 2, the shrinkage monitoring assembly 3, the temperature control device 11, the humidity control device 12, the environment controller 13 and the test sample.

[0075] The fixed base plate 2 is used to fix the test sample.

[0076] The temperature control device 11 is used to adjust and control the temperature in the test box 1.

[0077] The humidity control device 12 is used to adjust and control the temperature in the test box 1.

[0078] The environment controller 13 is connected with 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.

[0079] The temperature sensor is placed in the test box and connected with the temperature control device, and transmits the collected temperature data to the central computer.

[0080] The humidity sensor is placed in the test box and connected with the humidity control device, and transmits the collected humidity data to the central computer.

[0081] The shrinkage monitoring assembly 3 is placed on the fixed base plate 2 and connected with the test sample, and is used to test the shrinkage cracking toughness of the test sample and obtain the shrinkage load data and the shrinkage deformation data, and is used to transmit the shrinkage load data and the shrinkage deformation data to the central computer 5.

[0082] The central computer 5 is connected with the temperature control device 11, the humidity control device 12, the environment controller 13 and the shrinkage monitoring assembly 3 respectively, and is used to receive the temperature, humidity, shrinkage load data and shrinkage deformation data, process the collected data, and calculate the shrinkage cracking toughness SCT.

[0083] Reference Figure 1The embodiment provides a testing device for the anti-shrinkage cracking toughness of a pavement cementing material, which comprises a testing box 1, a fixed bottom plate 2, a shrinkage monitoring assembly 3, a plate-shaped test piece 4 and a central computer 5.

[0084] Referring to Figure 2 In the embodiment, the testing box 1 is a rectangular box, and the testing box 1 is provided with a top cover 16 at the top.

[0085] In the embodiment, the fixed bottom plate 2 is located in the testing box 1, the shrinkage monitoring assembly 3 is connected with the fixed bottom plate 2 and the plate-shaped test piece 4 respectively, is used for fixing the plate-shaped test piece 4, and measures the shrinkage deformation and shrinkage stress of the plate-shaped test piece 4. The shrinkage deformation and shrinkage stress measurement signals are transmitted to the central computer 5 through the connecting line 51 after being processed by the amplifier 31, and are stored.

[0086] In the embodiment, the temperature control equipment 11 and the humidity control equipment 12 are installed in the testing box 1, the temperature control equipment 11 and the humidity control equipment 12 are connected with the environment controller 13 arranged outside the testing box 1, and the testing box 1 is also provided with the temperature sensor 14 and the humidity sensor 15.

[0087] Specifically, the temperature sensor 14 collects temperature condition data in the testing box 1, the humidity sensor 15 collects humidity condition data in the testing box 1, the central computer 5 processes and analyzes the instruction, and transmits the instruction to the environment controller 13, the environment controller 13 controls the working state of the temperature control equipment 11 and the humidity control equipment 12, and the temperature and humidity conditions in the testing box 1 reach the target set value.

[0088] Referring to Figure 3 In the embodiment, the plate-shaped test piece 4 is composed of a pavement cementing material sample 41 and an anchoring side wall 42. The pavement cementing material sample 41 is a square test piece, and the anchoring side wall 42 is arranged on each of the four side walls of the pavement cementing material sample 41.

[0089] It is particularly pointed out that the length of the anchoring side wall 42 is less than the length of the pavement cementing material sample 41, so as to prevent the adjacent anchoring side walls 42 from being in contact with each other during the shrinkage of the pavement cementing material sample 41, and to affect the natural shrinkage deformation process of the pavement cementing material sample 41.

[0090] Referring to Figure 4Preferably, the anchoring side wall 42 is composed of a convex base plate 421 and an end enlarged anchor rod 422. The convex base plate 421 is located on the four side walls of the road cementitious material sample 41, and is embedded in the edge of the road cementitious material sample 41 through the end enlarged anchor rod 422. Preferably, the convex base plate 421 is a metal plate body with a convex cross section.

[0091] In the embodiment, the fixed bottom plate 2 is located at the bottom of the test box 1, and four fixed columns 21 are arranged on the fixed bottom plate 2. A sleeve ring 22 is installed on the fixed column 21, and the sleeve ring 22 can freely slide up and down along the axis of the fixed column 21. A spherical hinge 23 is arranged on the sleeve ring 22.

[0092] Referring to Figure 1 In the embodiment, the shrinkage monitoring assembly 3 includes a deformation test unit 32 and a boundary fixing unit 33, and the deformation test unit 32 and the boundary fixing unit 33 are arranged on the opposite side walls of the plate-shaped test piece 4 in a facing manner.

[0093] Referring to Figure 6 Specifically, the deformation test unit 32 includes a strain gauge type 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 with the strain gauge type sensor 321 and the convex base plate 421, and the two ends of the second connecting screw 323 are respectively connected with the strain gauge type sensor 321 and the spherical hinge 23. The first connecting screw 322, the strain gauge type sensor 321, and the second connecting screw 323 are sequentially connected. When the road cementitious material sample 41 shrinks and deforms, the convex base plate 421 of the anchoring side wall 42 moves, and due to the limiting action of the fixed column 21, the first connecting screw 322 and the second connecting screw 323 stretch the strain gauge type sensor 321 in opposite directions. The strain gauge type sensor 321 generates a deformation and load force data signal, which is processed by the amplifier 31 and then transmitted to the central computer 5 through the connecting line 51.

[0094] Referring to Figure 7 In the embodiment, the boundary fixing unit 33 is used to limit the movement of the plate-shaped test piece 4, and the boundary fixing unit 33 is provided with a third connecting screw 331, and the two ends of the third connecting screw 331 are respectively connected with the convex base plate 421 and the spherical hinge 23.

[0095] In the embodiment, in order to improve the measurement accuracy, it is necessary to measure the shrinkage deformation and shrinkage load force in two directions of the plate-shaped test piece 4. Therefore, the shrinkage monitoring assembly 3 is two, that is, a transverse shrinkage monitoring assembly and a longitudinal shrinkage monitoring assembly which are respectively connected with the central computer 5.

[0096] The transverse shrinkage monitoring assembly is arranged in the transverse direction of the plate specimen 4, and is used for monitoring the shrinkage load data and shrinkage deformation data in the transverse direction of the plate specimen 4; and the longitudinal shrinkage monitoring assembly is arranged in the longitudinal direction of the plate specimen 4, and is used for monitoring the shrinkage load data and shrinkage deformation data in the longitudinal direction of the plate specimen 4.

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

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

[0099] Referring to Figure 5 In the embodiment, the plate specimen 4 is prepared in the forming mold 43, and the four side walls of the forming mold 43 are provided with clamping grooves 431, and the cross-sectional shape of the clamping grooves 431 matches the convex base plate 421. It is particularly pointed out that, in the forming process of the plate specimen 4, the four convex base plates 421 are first arranged in the clamping grooves 431 on the four side walls of the forming mold 43, and then the pavement cementitious material is filled and arranged in the forming mold 43, and the asphalt mixture wheel roller compactor is used to perform compaction forming according to the set compaction work.

[0100] It is particularly pointed out that the thickness and side length of the plate specimen 4 can be selected according to engineering needs, and in the forming process of the plate specimen 4, the pavement cementitious material is first prepared according to the design ratio, and the maximum dry density of the pavement cementitious material is determined according to the T0804-1994 inorganic binder stabilized material compaction test method in the “Highway Engineering Inorganic Binder Stabilized Material Test Regulations” (JTG 3441-2024), and then the mass required for the compaction of the pavement cementitious material sample 41 is calculated according to the maximum dry density and the volume of the forming mold 43, and the mass is weighed and placed in the forming mold 43 for compaction forming.

[0101] It is particularly pointed out that, in order to better detach the plate specimen 4 from the forming mold 43 after forming, the forming mold 43 containing the plate specimen 4 can be inverted on a flat plate, and then the bottom of the forming mold 43 is knocked to detach the plate specimen 4 from the forming mold 43, so as to ensure the integrity of the plate specimen 4.

[0102] It is particularly pointed out that the temperature control device 11 and the humidity control device 12 can not only realize the regulation and control of the temperature and humidity in the test box 1, but also can be used to simulate various actual use environments such as highlands, severe cold, and scorching heat, so as to realize accurate evaluation of the anti-shrinkage cracking toughness of the pavement cementitious material.

[0103] It is particularly pointed out that the top cover 16 is preferably made of double-layer tempered glass, so as to realize the functions of transparency and heat preservation, and facilitate the observation of the testers on the test situation inside the test box 1.

[0104] It is particularly pointed out that the inside of the anchoring side wall 42 is provided with a plurality of end expansion type anchor rods 422, and the expansion type end of the end expansion type anchor rod 422 helps the firmness of the anchoring side wall 42 and the cementitious material sample 41 of the road surface, prevents the anchoring side wall 42 from falling off and slipping during the shrinkage deformation of the cementitious material sample 41 of the road surface, and affects the test precision.

[0105] It is particularly pointed out that the fixed bottom plate 2 is a metal plate, in order to reduce the friction between the plate type test piece 4 and the fixed bottom plate 2 during shrinkage, and affect the natural shrinkage deformation process of the cementitious material sample 41 of the road surface, it is appropriate to coat the fixed bottom plate 2 with paraffin wax first, and then place the plate type test piece 4.

[0106] The device provided in the embodiment can real-time regulate the environmental temperature and humidity according to actual needs, so as to simulate the anti-shrinkage cracking toughness level of the cementitious material of the road surface under real conditions.

[0107] Embodiment 2

[0108] The embodiment provides a test method for the anti-shrinkage cracking toughness of the cementitious material of the road surface, which comprises the following steps:

[0109] S1, test piece manufacturing

[0110] The cementitious material of the road surface is formed and maintained to obtain a test piece.

[0111] Specifically, the specific process of test piece manufacturing is as follows:

[0112] 1) plate type test piece 4 forming

[0113] A square plate test piece is prepared indoors, specifically, the square plate is used to form the cementitious material of the road surface to obtain the plate type test piece 4.

[0114] 2) curing

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

[0116] S2, test piece installation

[0117] A friction-reducing coating is coated on the fixed bottom plate 2 of the test device, and the test piece is placed on the friction-reducing coating and fixed.

[0118] Specifically, the fixed bottom plate 2 of the test box 1 is coated with paraffin, 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 with the fixed stand 21 by using the first connecting screw 322, the second connecting screw 323 and the third connecting screw 331, and the installation and fixation of the plate specimen 4 are realized.

[0119] S3, anti-shrinkage cracking toughness test

[0120] The temperature and humidity of the test device are adjusted, the real-time data of the test specimen in the shrinkage deformation process are monitored through the shrinkage monitoring assembly 3, the real-time data signal is collected every interval time ΔT until the set time is reached, the shrinkage load data F of the test specimen corresponding to the i-th collection is obtained i and the shrinkage deformation data l i .

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

[0122] Specifically, the temperature and humidity of the test box 1 are set through the central computer 5, the automatic working program of the deformation test unit 32, the environment controller 13, the temperature sensor 14 and the humidity sensor 15 is opened, the reading of the strain gauge type sensor 321 is zeroed, the equipment is started, and the anti-shrinkage cracking toughness test operation and real-time information collection work are carried out. The load data F i and the deformation data l i of the strain gauge type sensor 321 are recorded by the central computer 5 every interval time ΔT until the real-time monitoring of 168h is completed.

[0123] S4, calculation of shrinkage cracking toughness

[0124] The shrinkage load data F i and the shrinkage deformation data l i are substituted into the following calculation formula to calculate the shrinkage cracking toughness SCT:

[0125]

[0126] In the formula:

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

[0128] N is the total number of times of recording the peak value of the shrinkage load data in 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 at the i-th time, mm;

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

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

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

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

[0135] The shrinkage load data and the shrinkage deformation data in the transverse direction are substituted into the shrinkage cracking toughness calculation formula to obtain the shrinkage cracking toughness in the transverse direction;

[0136] The shrinkage load data and the shrinkage deformation data in the longitudinal direction are substituted into the shrinkage cracking toughness calculation formula to obtain the shrinkage cracking toughness in the longitudinal direction;

[0137] 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.

[0138] It is particularly pointed out that two groups of load data and deformation data of the strain gauge sensor 321 can be obtained in each test. Considering that the pavement cementitious material sample 41 has directionality when it shrinks, the test data group that cracks earliest is taken as the most unfavorable case to evaluate the anti-shrinkage cracking performance 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] It is particularly pointed out that the shrinkage cracking toughness SCT represents the ability of the pavement cementitious material to resist deformation and cracking under the action of shrinkage. The size of the SCT value represents the toughness of the pavement cementitious material.

[0140] In this embodiment, by preparing a plurality of pavement cementitious material samples 41 and calculating the shrinkage cracking toughness SCT, it is found that as the shrinkage cracking toughness SCT value increases, the toughness of the pavement cementitious material increases, that is, the toughness of the pavement cementitious material is positively correlated with the shrinkage cracking toughness SCT. Therefore, in the subsequent, the size of the shrinkage cracking toughness SCT can be used to evaluate the anti-shrinkage cracking toughness of different pavement cementitious materials.

[0141] It is particularly pointed out that the shrinkage cracking toughness SCT of the same material should be a certain value, and the comparison and analysis of the shrinkage cracking resistance of various materials can be conveniently realized.

[0142] It is particularly pointed out that the measurement of the shrinkage cracking toughness is automatically completed by the programmed control software of the central computer 5, so as to reduce the operation error of personnel.

[0143] The shrinkage cracking toughness is calculated to characterize the shrinkage cracking resistance of the pavement cementitious material, which can truly reflect the mechanical properties of the material, realize the precise simulation of the shrinkage state of the pavement cementitious material, improve the accuracy, scientificity and rationality of the test results, and further use the shrinkage cracking toughness to evaluate the toughness of the pavement cementitious material.

[0144] In addition, in the test process, the shrinkage load data F i and the shrinkage deformation data l i of the i-th collection are recorded. i The shrinkage load-shrinkage deformation curve is drawn with the shrinkage deformation data l i as the horizontal coordinate and the shrinkage load data F i as the vertical coordinate.

[0145] As shown in the shrinkage load-shrinkage deformation curve of Figure 8 It can be seen that the load value and the deformation value increase first and then decrease with the increase of the shrinkage test time. In the growth stage of the curve, with the shrinkage, the load value and the deformation value gradually increase, and the shrinkage stress in the specimen also gradually increases; when the shrinkage stress reaches the allowable strength of the material, the plate specimen is cracked and damaged, and the shrinkage stress in the specimen is released, so that the load value and the deformation value decrease.

[0146] Obviously, the above embodiments are only examples for clearly illustrating the technical solutions of the present application, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or modifications can be made by those skilled in the art, and it is not necessary or possible to exhaust all the embodiments. The obvious changes or modifications derived therefrom are still within the protection scope of the present application.

Claims

1. A test method for the shrinkage crack resistance toughness of road cementitious materials, characterized in that, Includes the following steps: S1. Test specimen fabrication The road surface cementitious materials were molded and cured to obtain test specimens; S2. Test specimen installation Apply an anti-friction coating to the fixed base plate (2) of the test device, place the test specimen on the anti-friction coating and install and fix it; S3, Shrinkage crack toughness test Adjust the temperature and humidity of the testing 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 time interval ΔT until the set time is reached; obtain the shrinkage load data F corresponding to the test specimen at the i-th collection time. i and shrinkage deformation data l i ; S4. Calculate shrinkage crack toughness The above-collected shrinkage load data F i and shrinkage deformation data l i Substitute the values ​​into the following formula to calculate the shrinkage crack toughness (SCT): In the formula: SCT is the shrinkage crack toughness, J / cm. 2 ; N represents the total number of times the contraction load data reaches its peak value during the contraction deformation process; F i Let N be the shrinkage load value of the test specimen during the i-th acquisition; l i The shrinkage deformation value of the test specimen during the i-th sampling, in mm; l i-1 The shrinkage deformation value of the test specimen during the (i-1)th sampling, in mm; S is the cross-sectional area of ​​the test specimen, in cm². 2 ; In step S1, the specific process of preparing the test specimen is as follows: S1.

1. A square plate is used to form the road surface cementitious material to obtain a plate specimen (4); S1.

2. Curing of the plate specimen for 7 days. On the last day of curing, the plate specimen (4) is saturated with water for 24 hours. Finally, the saturated plate specimen (4) is wiped dry to obtain the test specimen. In step S3, each time data is collected, the shrinkage load data and shrinkage deformation data in the transverse direction of the test specimen, as well as the shrinkage load data and shrinkage deformation data in the longitudinal direction, are obtained respectively. The specific method for step S4 is as follows: Substitute the shrinkage load data and shrinkage deformation data in the transverse direction into the shrinkage crack toughness calculation formula to obtain the shrinkage crack toughness in the transverse direction. By combining the shrinkage load data and shrinkage deformation data in the longitudinal direction, the shrinkage crack toughness in the longitudinal direction can be obtained. Compare the shrinkage crack toughness in the transverse direction and the shrinkage crack toughness in the longitudinal direction, and take the minimum value as the calculation result of the shrinkage crack toughness.

2. The test method for shrinkage crack resistance of road cementitious materials according to claim 1, characterized in that, As the shrinkage cracking toughness (SCT) value increases, the toughness of pavement cementitious materials also increases.

3. A testing apparatus for implementing the test method for the shrinkage crack resistance toughness of road cementitious materials as described in claim 1, characterized in that, The testing apparatus includes: Test chamber (1): used to place the fixed base plate (2), shrinkage monitoring component (3), temperature control device (11), humidity control device (12), environmental controller (13) and test specimen; Fixed base plate (2): used to fix the test specimen; Temperature control device (11): used to regulate and control the temperature inside the test chamber (1); Humidity control device (12): used to regulate and control the humidity inside the test chamber (1); Environmental controller (13): It is connected to the temperature control device (11) and the humidity control device (12) respectively, and is used to control the working status of the temperature control device (11) and the humidity control device (12) respectively until the temperature and humidity inside the test chamber (1) reach the target set value; Temperature sensor (14): placed inside the test chamber (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 inside the test chamber (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 test the shrinkage crack toughness of the test specimen and obtain shrinkage load data and shrinkage deformation data; used to transmit shrinkage load data and shrinkage deformation data to the central computer (5); and Central computer (5): It is connected to temperature sensor (14), humidity sensor (15), environmental controller (13) and shrinkage monitoring component (3) respectively, and is used to receive temperature, humidity, shrinkage load data and shrinkage deformation data, process the collected data, and calculate the shrinkage crack toughness SCT. The contraction monitoring component (3) includes a horizontal contraction monitoring component and a vertical contraction monitoring component, which are respectively connected to the central computer (5); The lateral shrinkage monitoring component is placed in the lateral direction of the test specimen to monitor the shrinkage load data and shrinkage deformation data in the lateral direction of the test specimen. The longitudinal shrinkage monitoring component is placed in the longitudinal direction of the test specimen to monitor the shrinkage load data and shrinkage deformation data in the longitudinal direction of the test specimen.

4. The testing apparatus according to claim 3, characterized in that, The transverse shrinkage monitoring component includes a deformation testing unit (32) and a boundary fixing unit (33), which are respectively disposed on opposite sidewalls in the transverse direction of the test specimen; the longitudinal shrinkage monitoring component has the same structure as the transverse shrinkage monitoring component.

5. The testing apparatus according to claim 4, characterized in that, The test specimen is obtained by curing a plate specimen (4). The plate specimen (4) consists of a road surface cementitious material sample (41) and an anchoring sidewall (42). An anchoring sidewall (42) is set on each of the four sidewalls of the road surface cementitious material sample (41). The deformation test unit (32) includes a first connecting screw (322), a strain gauge sensor (321), and a second connecting screw (323) connected in sequence. The first connecting screw (322) is connected to the anchoring sidewall (42), and the second connecting screw (323) is hinged to the fixed column (21) set on the fixed base plate (2). The strain gauge sensor (321) is electrically connected to the central computer (5).

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