Asphalt viscousity test is an important method for evaluating the performance of modified asphalt, especially for SBR modified asphalt. The test is performed at a defined temperature and quantifies the viscotoughness and toughness of the asphalt by measuring the load and deformation generated during the tensile process and calculating the area enclosed by the load-deformation curve. This test method helps to determine the modification effect of modified asphalt and ensure its reliability and durability in practical applications.
Purpose and Scope of Application
The asphalt viscotoughness test is mainly used to determine the viscotoughness of modified asphalt to evaluate its modification effect after adding modifiers, especially for SBR (styrene-butadiene rubber) modified asphalt. The test was carried out at 25°C with a tensile speed of 500 mm/min, which is an important criterion for evaluating the properties of asphalt.
Test equipment and materials
equipment
Tensile testing machine - can achieve constant velocity tensile of 500mm/min, the maximum loading capacity is 1kN, equipped with a Recorder, which can record the tensile deformation and load curves at the same time.
Thermostatic Water Tank – controlled at 25°C±0.1°C and equipped with a perforated rack for specimens.
Stretch hemispherical round head – radius 11.1mm, surface roughness up to Ra3.2um, with connecting screw for mounting.
Specimen holder – metal, 55 mm inner diameter, 35 mm deep.
material
Modified asphalt samples
Trichloroethylene (for cleaning)
Thermometer (range 0~50°C, graduation value 0.1°C)
Balances (sensitivity: 1 g and 1 mg)
Methods and Steps:
Preparation
Specimen preparation – Prepare bitumen specimens according to the method of Procedure T0602. For modified asphalt, it is necessary to add modifiers and stir fully as required.
Preheat the specimen container – preheat the specimen container in an oven at 60~80°C for 1 hour.
Cleaning equipment – wipe the round head of the stretching hemisphere with trichloroethylene and install it in the positioning bracket for later use.
Injection of the specimen – The hot asphalt specimen is gradually injected into the preheated specimen container with a mass of 50g±18g, taking care to avoid air bubbles being mixed.
Fixing the specimen - quickly immerse the tensile hemispherical round head into the asphalt, fix it with a positioning nut, make the hemispherical round head flush with the asphalt surface, stand for 1~1.5 hours, and adjust the positioning nut if necessary to maintain the position.
Thermostatic insulation – The installed viscotoughness Tester and specimens are kept warm in a Thermostatic Water Bath for at least 1.5 hours.
Test procedure
Take out the viscosity Tester from the Thermostatic Water Bath, quickly pour out the water on the asphalt surface, and install the upper connecting rod of the Tester and the specimen into the fixture of the Tensile Testing Machine, keeping the position of the hemispherical round head and the asphalt unchanged.
Adjust the Recorder, set the Y-axis as the load and the X-axis as the time, and immediately start stretching at a speed of 500mm/min until it ends at 300mm.
The load and tensile time are recorded during the test to ensure that the Tester is removed for no more than 1 minute before the end of the test.
Data calculations
In the load-deformation curve diagram, the straight line of the BC segment is extended to point E, which is represented by a dashed line.
The area enclosed by the measurement curves ABCE and CDFE is denoted as A1 and A2, respectively. It can be calculated using an integrator, the number of squares on the record paper, or the mass ratio method.
The mass per unit area is weighed on a record paper with a known area, and the area enclosed by the curve is calculated using the relevant formula.
At least 3 parallel tests are carried out on the same specimen, and the average value is taken as the test result, accurate to 1 decimal place. The result is valid when the difference between the maximum or minimum value and the mean value does not exceed 3 standard deviations.
Application and significance of results
The results of asphalt viscosity and toughness test are mainly used to evaluate the performance of SBR modified asphalt, rubber and resin asphalt, especially the effect of applying high-viscosity modified asphalt in drainage pavement construction. This test has been included in the "Technical Code for Highway Asphalt Pavement Construction" (JTG F40-2004) and is an indispensable part of road engineering construction.
conclusion
Asphalt viscotoughness test is an important means to evaluate the performance of modified asphalt, which can provide reliable data support for road construction. Through systematic test procedures and standardized operation procedures, this method effectively ensures the quality of asphalt materials, thereby improving the safety and durability of the project.
summary
The asphalt viscotoughness test provides a reliable basis for evaluating the modification effect by measuring the tensile properties of modified asphalt at a constant temperature. The test focuses on the relationship between load and deformation, and quantifies the viscotoughness and toughness of asphalt by analyzing the area of the load-deformation curve. The application of this method in road engineering not only ensures the performance reliability of the material, but also provides scientific support for the development and application of modified asphalt, which is one of the important indicators for evaluating the quality of asphalt.
