A normal temperature creep test method for measuring damage accumulation rate of asphalt mortar

Abstract

The present application relates to a kind of asphalt mortar damage cumulative rate measurement constant temperature creep test method, comprising the following steps: (1) preparing asphalt and standard fine sand to be tested, after heating respectively, stirring is mixed, after aging a certain time after mixing, asphalt mortar is poured into mould and cast sample, i.e. the preparation of asphalt mortar sample is completed;(2) assemble creep loading device on direct tensile test loading frame;(3) install asphalt mortar sample to direct tensile test loading frame, apply constant load on pulley guide wire and carry out constant temperature creep test, collect measurement time and displacement;(4) calculate the damage cumulative rate of asphalt mortar according to the data in step (3). Compared with prior art, the present application provides a kind of test and analysis method for asphalt mortar damage cumulative rate determination, which makes up for the lack of existing test method and evaluation index for the evaluation angle of asphalt mortar crack resistance.

Description

Technical Field

[0001] This invention belongs to the field of architectural design and construction technology, and in particular relates to a room temperature creep test method for measuring the cumulative damage rate of asphalt mortar. Background Technology

[0002] Asphalt pavement is one of the most common pavement structures for highways and urban roads in my country, widely used due to its high driving comfort and short construction and maintenance periods. However, frequent pavement cracking seriously affects the service performance and lifespan of roads. Therefore, the crack resistance of asphalt mixtures is crucial, and this resistance mainly comes from the asphalt mortar component, which plays a binding role in the pavement structure. Accurately characterizing the crack resistance of asphalt mortar helps to predict the crack resistance of asphalt mixtures more scientifically and efficiently, which is beneficial for reducing cracking defects in asphalt pavements, ensuring the service quality and lifespan of asphalt pavements, and is of great significance for road construction, management, and maintenance.

[0003] Failure limit and damage accumulation rate are two important parameters reflecting the crack resistance of asphalt mortar. They interact and jointly affect the crack resistance of asphalt mortar. Existing evaluation methods for the crack resistance of asphalt mortar mostly rely on direct tensile tests, with evaluation indicators being fracture energy or strength. These methods only assess the crack resistance of asphalt mortar from the perspective of failure limit and lack experimental methods for measuring the damage accumulation rate of asphalt mortar.

[0004] Therefore, in order to conduct a more comprehensive test and evaluation of the crack resistance of asphalt mortar, there is an urgent need for a room-temperature creep test method to measure the cumulative damage rate of asphalt mortar, so as to provide technical support for the high-quality and high-level development of road construction. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing test methods in evaluating the room temperature crack resistance of asphalt mortar, and to provide a room temperature creep test method for measuring the damage accumulation rate of asphalt mortar.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A room-temperature creep test method for measuring the damage accumulation rate of asphalt mortar includes the following steps:

[0008] (1) Preparation of asphalt mortar samples: Prepare the asphalt to be tested and standard fine sand, heat them separately and stir them together. After aging the mixed asphalt mortar for a certain period of time, pour it into the mold to cast the sample, thus completing the preparation of the asphalt mortar sample.

[0009] (2) Assemble a creep loading device on a direct tensile test loading frame: The creep loading device includes a mounting block installed on the direct tensile test loading frame and a fixed pulley group provided on the mounting block. One end of the wire on the pulley group passes through the mounting block and is connected to the moving end of the direct tensile test loading frame, and the other end is used to apply a constant load.

[0010] (3) Collect test data: Install the asphalt mortar sample onto the direct tensile test loading frame, apply a constant load on the pulley guide to carry out the room temperature creep test, and collect the measurement time and displacement.

[0011] (4) Data processing: Calculate the damage accumulation rate of asphalt mortar based on the data in step (3).

[0012] Furthermore, in step (1), the heating temperature is generally not lower than 160°C, and the asphalt to be tested and the standard sand are mixed evenly at a mass ratio of 1:1.

[0013] Furthermore, in step (1), the aging time is 1.5-3 hours, preferably 2 hours.

[0014] Furthermore, the aging process was carried out at 163°C.

[0015] Furthermore, the standard sand used is No. 100 standard sand.

[0016] Furthermore, in step (1), the mixing process before molding the asphalt mortar sample requires that the asphalt mortar be gently stirred on a heating plate for 30 seconds, and then stirred at room temperature for 2 minutes.

[0017] Furthermore, in step (2), the creep loading device is placed at an ambient temperature of 10-20°C after assembly, preferably 15°C.

[0018] Furthermore, in step (2), the mounting block includes an upper block and a lower block, which are connected by a tenon and mortise joint, and the tenon and mortise joint is provided with a through hole for the wire to pass through.

[0019] Furthermore, the upper block is provided with a long slot for the installation and rotation of the fixed pulley assembly, and the pulleys of the fixed pulley assembly are all installed in the upper block by means of pins.

[0020] Furthermore, the bottom of the lower block is provided with a non-through hole that matches the size of the guide rod of the direct tensile test loading frame.

[0021] Furthermore, the non-through holes are symmetrically arranged on both sides of the mortise and tenon joint.

[0022] Furthermore, both the upper and lower blocks are stainless steel metal blocks.

[0023] Furthermore, in step (3), the frictional force generated between the fixed pulley system and the wire is small and can be ignored.

[0024] Further, in step (3), the asphalt mortar sample is kept at 10-20℃ for 1.5-3h before testing, preferably at 15℃ for 2h.

[0025] Furthermore, in step (3), a digital image correlation system (DIC) is used as a non-contact measuring tool, or other measuring systems such as an extensometer that can accurately measure the displacement of the sample are used to collect displacement data of the asphalt mortar sample as the test time changes.

[0026] Furthermore, the asphalt mortar sample exhibits a clear tensile mark, marking the end of the test.

[0027] Furthermore, in step (4), the specific calculation method for the damage accumulation rate of the asphalt mortar is as follows:

[0028] S1: Based on the time (t, s), displacement (x, mm) data and constant load (F, N) obtained in step (3), calculate the strain (ε) and cross-sectional area (A, mm) of the specimen during the loading process. 2 The stress (σ, MPa) and the stress (σ, MPa) can be determined by the following formula:

[0029] ε = 0.0006•x 2 +0.0537•x

[0030] A = 0.006·x 2 -0.926·x+24

[0031]

[0032] The creep compliance D(t) = ε / σ is calculated, and the creep compliance-time curve is plotted based on the calculation results.

[0033] S2: Using the formula D(t) = D0 + D1·t m The relationship between creep compliance and time is fitted, where D0, D1, and m are fitting coefficients. The rate of change of creep compliance is defined as the slope of the creep compliance-time curve at 1000 s, i.e., substituting t = 1000 into the equation.

[0034]

[0035] The damage accumulation rate is defined as the creep strain energy dissipated per loading cycle (DCSE / cycle):

[0036]

[0037] The smaller this value, the lower the damage accumulation rate of the asphalt mortar sample. The final result is the average of two parallel samples, and the variability is required to be no more than 15%.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) This invention assembles a creep loading device on a direct tensile test loading frame and uses a constant load loading mode to conduct a room temperature creep test on asphalt mortar samples, calculates the damage accumulation rate of asphalt mortar samples, makes up for the lack of evaluation perspective of crack resistance performance of asphalt mortar in existing test methods and evaluation indicators, and provides technical support for high-quality and high-level development of roads.

[0040] (2) The room temperature creep test method for measuring the cumulative rate of damage in asphalt mortar is simple to operate. The device structure is improved on the existing direct tensile test loading frame, and the design is novel and reasonable.

[0041] (3) The asphalt mortar sample of the present invention has a small volume and quick molding, which saves test materials and preparation time. It is also suitable for evaluating the damage accumulation rate of asphalt mortar of different sources and aging degrees.

[0042] (4) The creep loading device of the present invention has a simple structure, complete functions, good overall stability, strong practicality, and good promotion and application value. Attached Figure Description

[0043] Figure 1 This is a flowchart of the room temperature creep test method for measuring the cumulative damage rate of asphalt mortar according to the present invention.

[0044] Figure 2 This is a diagram of the device for the direct tensile test loading frame of the present invention.

[0045] Figure 3 This is a schematic diagram of the creep loading device of the present invention.

[0046] Figure 4 This is a schematic diagram of the creep loading device of the present invention after it has been installed on the direct tensile test loading frame.

[0047] Figure 5 This is a schematic diagram of the creep compliance-time curve of the present invention.

[0048] Explanation of reference numerals in the attached figures:

[0049] 1-Lower block, 2-Upper block, 3-Fixed pulley block, 4-Pin, 5-Non-through hole, 6-Slot, 7-Groove, 8-Through hole. Detailed Implementation

[0050] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0051] like Figure 1 As shown, a room-temperature creep test method for measuring the cumulative damage rate of asphalt mortar includes the following steps:

[0052] (1) Preparation of asphalt mortar samples: Prepare the asphalt to be tested and No. 100 standard fine sand, heat them separately and mix them. After aging the mixed asphalt mortar for a certain period of time, pour it into the mold to pour the sample. After a few seconds, scrape off the excess mortar with a scraper to complete the preparation of the asphalt mortar sample.

[0053] (2) Assemble the creep loading device on the direct tensile test loading frame: The creep loading device includes a mounting block installed on the direct tensile test loading frame and a fixed pulley group on the mounting block. One end of the wire on the pulley group passes through the mounting block and is connected to the moving end of the direct tensile test loading frame, and the other end is used to apply a constant load. The assembled creep loading device is placed in an environmental chamber at 15°C.

[0054] (3) Data collection: The insulated asphalt mortar sample is installed on the loading frame, and a certain weight is suspended on the pulley guide to carry out a constant load room temperature creep test. The constant load (F, N) is the weight of the weight (F1 = mg, N) minus the weight of the moving end of the loading frame (F2 = Mg, N). The friction between the moving end and the guide rod is ignored (or subtracted after test measurement); and the measurement time and displacement are collected.

[0055] (4) Data processing: Based on the data obtained in step three, calculate the damage accumulation rate of asphalt mortar under normal temperature conditions.

[0056] In practice, the asphalt to be tested is first heated to 160℃ to ensure sufficient fluidity (the heating temperature can be increased appropriately for modified or aged asphalt). 20g of No. 100 standard sand is placed in a small box and heated to 160℃. Then, 20g of hot asphalt is added to the box and mixed thoroughly. Next, a heat aging treatment is performed at 163℃ for 2 hours. The mixed asphalt mortar is then mixed thoroughly again and poured into an assembled mold for molding. After a few seconds, excess mortar is scraped off with a scraper. Before molding the sample, the asphalt mortar is gently stirred on a heating plate for 30 seconds, then stirred at room temperature for 2 minutes. After demolding, the asphalt mortar sample is placed in a 15℃ environmental chamber for 2 hours and then vertically fixed on a loading frame. A room temperature creep test is then performed on the asphalt mortar sample under a constant load in a 15℃ environment.

[0057] like Figure 2As shown, the direct tensile test loading frame in this embodiment is a conventional testing instrument for asphalt tensile testing. In this embodiment, the assembled creep loading device is mounted on the direct tensile test loading frame. Figure 3 As shown, the creep loading device in this embodiment consists of a lower block 1, an upper block 2, a fixed pulley assembly 3, pins 4, and wires. The lower block 1 and upper block 2 form a mounting block, with the upper block 2 perpendicular to the lower block 1. The bottom surface of the upper block 2 has a groove 6 matching the size of the lower block 1. The upper block 2 and lower block 1 are connected by a tenon and mortise joint, with a through hole 8 for the wires to pass through at the tenon and mortise joint. The upper block 2 has a long groove for the installation and rotation of the fixed pulley assembly 3. The pulleys of the fixed pulley assembly 3 are all installed in the upper block 2 via pins 4. The top surface of the upper block 2 has two rows of grooves 7 for placing the pins 4 of the fixed pulley assembly 3. The bottom of the lower block 1 has non-through holes 5 matching the size of the guide rod of the direct tensile test loading frame. The non-through holes 5 are symmetrically arranged on both sides of the tenon and mortise joint. One end of the wire is connected to the upper moving end of the loading frame through the through hole 8 between the assembled lower block 1 and upper block 2, and the other end passes over the pulley block 3 and hangs down naturally to suspend the weight. See the final installation diagram. Figure 4 In this embodiment, the friction between the pulley block 3 and the wire is small and can be ignored.

[0058] In this embodiment, the room-temperature creep test method for measuring the cumulative damage rate of asphalt mortar uses a digital image correlation (DIC) system as a non-contact measurement tool to collect displacement data of the asphalt mortar sample as the test time changes. The test ends when the sample shows obvious tensile stress.

[0059] In this embodiment, the method for calculating the damage accumulation rate of asphalt mortar under normal temperature conditions is as follows:

[0060] 1) Based on the time (t, s), displacement (x, mm) data and constant load (F, N) obtained in step 3, calculate the strain (ε) and the cross-sectional area (A, mm²) of the specimen during the loading process. 2 The stress (σ, MPa) and the stress (σ, MPa) can be determined by the following formula:

[0061] ε = 0.0006·x 2 +0.0537·x

[0062] A = 0.006·x 2 -0.926·x+24

[0063]

[0064] Creep compliance D(t) = ε / σ, plotted based on the calculation results as follows: Figure 5 The creep compliance-time curve is shown.

[0065] 2) Use the formula D(t)=D0+D1·t m The relationship between creep compliance and time is fitted, where D0, D1, and m are fitting coefficients. The rate of change of creep compliance is defined as the slope of the creep compliance-time curve at 1000 s, i.e., substituting t = 1000 into the equation.

[0066]

[0067] The damage accumulation rate is defined as the creep strain energy dissipated per loading cycle (DCSE / cycle):

[0068]

[0069] The smaller this value, the lower the damage accumulation rate of the asphalt mortar sample. The final result is the average of two parallel samples, and the variability is required to be no more than 15%.

[0070] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A room-temperature creep test method for measuring the cumulative damage rate of asphalt mortar, characterized in that, Includes the following steps: (1) Preparation of asphalt mortar samples: Prepare the asphalt to be tested and standard fine sand, heat them separately and stir them together. After aging the mixed asphalt mortar for a certain period of time, pour it into the mold to cast the sample, thus completing the preparation of the asphalt mortar sample. (2) Assemble the creep loading device on the direct tensile test loading frame: The creep loading device includes a mounting block installed on the direct tensile test loading frame and a fixed pulley group provided on the mounting block. One end of the wire on the pulley group passes through the mounting block and is connected to the moving end of the direct tensile test loading frame, and the other end is used to apply a constant load. (3) Data collection: The asphalt mortar sample was installed on the direct tensile test loading frame, and a constant load was applied on the pulley guide to carry out the room temperature creep test. The measurement time and displacement were collected. (4) Data processing: Calculate the damage accumulation rate of asphalt mortar based on the data in step (3). The specific calculation method is as follows: S1: Based on the time t, displacement x, and constant load F obtained in step (3), calculate the strain ε, cross-sectional area A at the center of the specimen, and stress of the specimen during the loading process. And the creep compliance was derived. ; ； ； ； ； Plot the creep compliance-time curve based on the calculation results; S2: Using the formula The relationship between creep compliance and time is fitted, where D0, D1, and m are fitting coefficients; Define the rate of change of creep compliance as the slope of the creep compliance-time curve at 1000 s, and substitute t=1000 into the equation: ; Define the damage accumulation rate as the creep strain energy dissipated per loading cycle: 。 2. The room-temperature creep test method for measuring the cumulative damage rate of asphalt mortar according to claim 1, characterized in that, In step (1), the heating temperature is not lower than 160°C, the asphalt to be tested and No. 100 standard sand are mixed evenly at a mass ratio of 1:1, and the aging time is 1.5-3h.

3. The room-temperature creep test method for measuring the cumulative damage rate of asphalt mortar according to claim 1, characterized in that, In step (2), the creep loading device is placed at an ambient temperature of 10-20℃ after assembly.

4. The room-temperature creep test method for measuring the cumulative damage rate of asphalt mortar according to claim 1, characterized in that, In step (2), the mounting block includes an upper block and a lower block, which are connected by mortise and tenon joints. The mortise and tenon joints are provided with through holes for wires to pass through.

5. The room-temperature creep test method for measuring the cumulative damage rate of asphalt mortar according to claim 4, characterized in that, The upper block has a long slot for the installation and rotation of the fixed pulley group, and the pulleys of the fixed pulley group are all installed in the upper block by pins.

6. The room-temperature creep test method for measuring the cumulative damage rate of asphalt mortar according to claim 4, characterized in that, The bottom of the lower block has a non-through hole that matches the size of the guide rod of the direct tensile test loading frame.

7. The room-temperature creep test method for measuring the cumulative damage rate of asphalt mortar according to claim 6, characterized in that, The non-through holes are symmetrically arranged on both sides of the mortise and tenon joint.

8. The room-temperature creep test method for measuring the cumulative damage rate of asphalt mortar according to claim 1, characterized in that, In step (3), the asphalt mortar sample is kept at 10-20℃ for 1.5-3h before testing.

9. The room-temperature creep test method for measuring the cumulative damage rate of asphalt mortar according to claim 1, characterized in that, In step (3), a digital image correlation system or an extensometer is used to collect displacement data of the asphalt mortar sample as the test time changes.

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