Improved testing device for testing cohesive strength of asphalt cement

Abstract

The utility model discloses an improved asphalt cement cohesive strength test device, which relates to the technical field of material detection, and comprises a pulling head and a base, a groove is arranged at the bottom of the pulling head, a pulling groove is arranged on the base, the shape and size of the pulling groove are the same as those of the groove, and when the pulling head is covered on the base, the pulling head is fixed on the base. An asphalt accommodating cavity is formed between the groove and the pulling groove; the pulling head is a stainless steel pulling head or a copper pulling head, and the base is a stainless steel base or a copper base. According to the utility model, based on a testing device in an original BBS (Binder bond strength) test, the pulling head and the base are improved, so that the accuracy and the pertinence of a test result of the cohesive performance of the asphalt cement after the action of a water environment are improved; compared with the original BBS test, the condition applicability of the test result of the cohesion performance of the asphalt cement under the action of the water environment is improved.

Description

Technical Field

[0001] This utility model relates to the field of materials testing technology, specifically to an improved asphalt binder cohesive strength testing device. Background Technology

[0002] Water damage to asphalt concrete is one of the main causes of early-stage distress in asphalt pavements, severely impacting driving comfort, safety, and durability. Water penetrating the interior of asphalt concrete weakens the adhesion properties of the asphalt-aggregate interface and the cohesive properties of the asphalt binder itself through physical and chemical processes. Under external loads, this accelerates adhesion and cohesive failure, ultimately leading to water damage phenomena such as pumping, spalling, loosening, and potholes. This process is the primary cause of water damage. Therefore, developing a testing device for the cohesive properties of asphalt binders under water conditions is of great significance for the prevention and control of water damage to asphalt pavements.

[0003] Existing test methods for the adhesion properties of asphalt to aggregates and the self-cohesive properties of asphalt binders under water conditions typically include the binder bond strength (BBS) test, as specified in ASTM D4541 (American Society for Testing and Materials) and AASHTO TP-91 (National Association for Highway Transportation). This test characterizes the decay characteristics of asphalt binder cohesive properties under water conditions by measuring the binder bond strength at different water exposure times. It is suitable for testing the adhesion properties of asphalt to aggregates and the self-cohesive properties of asphalt binders in both indoor and field pavement environments, and features low cost, convenient operation, and high repeatability of test results. The binder bond strength (BBS) test apparatus uses the equipment recommended by ASTM D4541—the pneumatic bond tensile tester (Posi Test AT-A). This tester mainly consists of a test unit, a pull-out sleeve, and a pull-out head. Power is supplied by an internal hydraulic pump, and the base is a smooth basalt slab made of the same material as the aggregates in the asphalt concrete.

[0004] However, the failure interface in BBS tests under aquatic conditions is usually not a single asphalt-aggregate interface, i.e., cohesive failure. It typically occurs under dry or short-term aquatic conditions because the acidic components in the asphalt react with the alkaline active sites on the aggregate surface, forming a strong chemical adsorption (i.e., generating structural asphalt), resulting in the adhesion strength of the asphalt-aggregate interface being greater than the cohesive strength of the asphalt binder itself. Under prolonged aquatic conditions, adhesion failure at the asphalt-aggregate interface, as well as coexistence of cohesive and adhesive failures, can occur. This is because the weakening effect of water on the adhesion performance of the asphalt-aggregate interface is greater than the cohesive performance of the asphalt binder itself. Therefore, the BBS test is suitable for characterizing the adhesion performance of asphalt-aggregate under aquatic conditions, as well as the combined adhesion and cohesive performance, but it is difficult to accurately characterize the cohesive performance of a single asphalt binder under aquatic conditions. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide an improved asphalt binder cohesion strength testing device.

[0006] The objective of this utility model is achieved through the following technical solution:

[0007] An improved asphalt binder cohesion strength testing device includes a pull-out head and a base. The pull-out head has a groove at its bottom, and the base has a pull-out groove with the same shape and size as the groove. When the pull-out head is attached to the base, an asphalt-containing cavity is formed between the groove and the pull-out groove. The pull-out head is a stainless steel pull-out head or a copper pull-out head, and the base is a stainless steel base or a copper base.

[0008] At least one notch is made in the groove wall surrounding the groove. Specifically, there is one notch at each of the four opposite positions on the groove wall surrounding the groove: top, bottom, left, and right.

[0009] The base is also equipped with a rubber ring that matches the size and shape of the bottom of the puller to restrict the asphalt from flowing outwards.

[0010] Preferably, a circular pull groove with a diameter of 18 mm and a depth of 0.1 mm is excavated on the surface of the base. The bottom of the pull head is a circular base plate with a diameter of 20 mm. A circular groove with a diameter of 18 mm and a depth of 0.1 mm is opened on the base plate. The groove wall around the groove is 1 mm wide. The thickness of the asphalt-containing cavity formed between the groove and the pull groove is 0.2 mm.

[0011] The beneficial effects of this utility model are:

[0012] (1) The present invention has a pull groove dug on a stainless steel base, so that water needs to diffuse in molecular form through a certain thickness of asphalt film before it can reach the asphalt-base interface, which increases the difficulty of water entering the asphalt-base interface and causes the failure interface after the water environment to appear at the asphalt-asphalt interface instead of the asphalt-base interface. Finally, the cohesive strength of the asphalt binder after the water environment is tested. Compared with the original BBS test, the device of the present invention improves the accuracy and pertinence of the test results of the cohesive performance of asphalt binder under the water environment.

[0013] (2) Based on the testing device in the BBS test, the stone slab base is replaced with a stainless steel base with better adhesion to asphalt, which improves the adhesion between asphalt and the base. This causes the failure interface after water environment treatment to appear at the asphalt-asphalt interface, and finally the cohesive strength of the asphalt binder after water environment treatment is tested. Compared with the asphalt-aggregate adhesion and the self-cohesive strength of the asphalt binder after water environment treatment characterized by the BBS test, this invention focuses on testing the self-cohesive strength of the asphalt binder after water environment treatment, thus improving the accuracy and relevance of the test results of the cohesive performance of the asphalt binder after water environment treatment.

[0014] (3) The stainless steel drawing head and base are replaced with copper material that is resistant to alkali and acid corrosion, so that the device of the present invention can be applied to seawater, saline-alkali land and acid corrosion environment, which improves the environmental applicability of the test results of the cohesive performance of asphalt binder under water environment compared with the original BBS test. Attached Figure Description

[0015] Figure 1 This is a front view of the pull-out head;

[0016] Figure 2 This is a schematic diagram of the bottom of the pull-out head;

[0017] Figure 3 This is a schematic diagram of the base;

[0018] In the diagram, 1-pull head, 2-groove wall, 3-notch, 4-groove, 5-base, 6-pull groove. Detailed Implementation

[0019] The technical solution of this utility model will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0020] See Figures 1-3 This utility model provides a technical solution:

[0021] An improved asphalt binder cohesion strength testing device includes a testing main unit, a pull-out head 1, and a base 5. A pull-out sleeve is connected to the testing main unit and can be fitted onto the pull-out head 1. The pull-out head 1 has a groove 4 at its bottom, and four notches 3 are formed on the groove wall 2 around the groove 4 at opposite positions (top, bottom, left, and right) to allow excess asphalt to flow out during testing. The base 5 has a pull-out groove 6, the same shape and size as the groove 4. The pull-out head 1 fits onto the base 5, forming an asphalt-accommodating cavity between the groove 4 and the pull-out groove 6. Both the pull-out head 1 and the base 5 are made of stainless steel. The base 5 is also equipped with a rubber ring adapted to the size and shape of the bottom of the pull-out head 1 to restrict the asphalt flow in all directions.

[0022] Specifically, the testing host uses a Posi Test AT-A testing instrument. A circular pull groove 6 with a diameter of 18 mm and a depth of 0.1 mm is carved into the surface of the stainless steel base 5. The bottom of the pull head 1 is a circular base plate with a diameter of 20 mm. A circular groove 4 with a diameter of 18 mm and a depth of 0.1 mm is opened on the base plate. The two sides of the groove wall 2 are 1 mm wide. The thickness of the asphalt-containing cavity formed between the groove 4 and the pull groove 6 is 0.2 mm.

[0023] In this embodiment, the test host is the pneumatic bond tensile tester (Posi Test AT-A) recommended by ASTM D4541, or the tester recommended by AASHTO TP-91 can be used as the test host.

[0024] As another embodiment, although stainless steel pull-out head 1 and base 5 are strong, easy to process, and inexpensive, stainless steel is not resistant to acid and alkali corrosion, making it difficult to accurately characterize the cohesive properties of asphalt binder after exposure to seawater, saline-alkali land, and acid rain environments. To make the test applicable to seawater, saline-alkali land, and acid rain environments, in this embodiment, base 5 and pull-out head 1 are made of copper.

[0025] How to use:

[0026] ① Place the stainless steel or copper base 5, the pull-out head 1, and the asphalt in an oven and heat them to 170℃, 90℃, and 150℃ respectively; ② Remove the stainless steel or copper base 5 and place a rubber ring at the pull-out groove 6 on its surface. Quickly drip the heated asphalt into the rubber ring. The rubber ring restricts the asphalt from flowing outwards; ③ Remove the pull-out head 1 from the oven and immediately press it onto the asphalt inside the rubber ring, and add a counterweight; ④ After the specimen has been cured in a 25℃ constant temperature chamber for 2 hours, test its pull-out strength; ⑤ Place the pull-out sleeve on the pull-out head 1 and set the pull-out rate of the testing host (Posi Test AT-A testing instrument) to 0.7MPa / s.

[0027] The above description is merely a preferred embodiment of this utility model. It should be understood that this utility model is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this utility model should be protected within the scope of the appended claims.

Claims

1. A modified asphalt binder cohesive strength testing device, characterized in that: It includes a pull head (1) and a base (5). The pull head (1) has a groove (4) at its bottom and a pull groove (6) on its base (5). The pull groove (6) has the same shape and size as the groove (4). When the pull head (1) is attached to the base (5), an asphalt-containing cavity is formed between the groove (4) and the pull groove (6). The pull head (1) is a stainless steel pull head (1) or a copper pull head (1), and the base (5) is a stainless steel base (5) or a copper base (5).

2. The testing apparatus according to claim 1, characterized in that: At least one notch (3) is provided on the groove wall (2) surrounding the groove (4).

3. The testing apparatus according to claim 2, characterized in that: A notch (3) is made at each of the opposite positions on the top, bottom, left and right sides of the groove wall (2) around the groove (4).

4. The testing apparatus according to claim 1, characterized in that: The base (5) is also equipped with a rubber ring that is adapted to the size and shape of the bottom of the pull head (1).

5. The testing apparatus according to claim 1, characterized in that: The base (5) has a circular pull groove (6) with a diameter of 18 mm and a depth of 0.1 mm. The bottom of the pull head (1) is a circular base plate with a diameter of 20 mm. A circular groove (4) with a diameter of 18 mm and a depth of 0.1 mm is opened on the base plate. The groove wall (2) around the groove (4) is 1 mm wide. The asphalt accommodating cavity formed between the groove (4) and the pull groove (6) has a thickness of 0.2 mm.

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