The asphalt water content test is an important method to evaluate the moisture content of petroleum asphalt, coal asphalt and emulsified asphalt. In this test, the asphalt sample is treated under heating conditions with specific equipment to determine the volume change of moisture to ensure the quality and construction safety of the asphalt. The method includes detailed steps and allowable error criteria, which provides a reliable basis for the application of asphalt.
Purpose and Scope of Application
The main purpose of the asphalt moisture content test is to determine the moisture content in different types of asphalt such as petroleum asphalt, coal asphalt and emulsified asphalt. The presence of moisture not only affects the physical and chemical properties of asphalt, but may also affect the safety and quality of the construction process. Therefore, this test is essential to ensure the performance of asphalt.
Instrument and material requirements
Moisture content meter
Glass flask - hard glass, round bottom short neck, diameter 100mm, volume 500mL.
Water Receiver - The shape meets the standard, the capacity is less than 0.3mL, there are 10 equal divisions, and each division is 0.2mL in the range of 1~10mL.
Condenser tube - inner tube diameter 10mm±1mm, length 350~400mm, end bevel cutting.
Iron frame - equipped with iron rings and iron clips.
Graduated cylinder - 100mL, minimum indexing 1mL.
Balance - inductance not more than 0.1g.
Heater – An electric or gas stove with a thermostat.
Solvent – Industrially pure xylene or a mixture of toluene and xylene.
Others – glass capillary (closed end), drying unglazed magnetic sheet, glass rod with rubber tip, etc.
Methods and Steps:
Preparation
Weighing glass flasks – the mass of the washed and dried flasks (m₁) is weighed to the nearest 0.1 g.
Sample preparation - the sample is fully shaken, or preheated to 50~80 °C, so that it is in a fluid state, and then injected into the flask about 100g (if the water is less than 25%) or 50g (if the water is more than 25%), and its total mass (m₂) is weighed, which is accurate to 0.1g.
Solvent addition – measure 200 mL of solvent with a graduated cylinder, inject it into a flask, shake well and add some glass capillaries or unglazed magnetic sheets.
Instrument assembly – Assemble the flask with the moisture receiver and condenser tube to ensure that the condenser tube coincides with the axis of the moisture receiver to avoid steam escape.
Test procedure
Heating - turn on the heater, heat the flask, control the reflux rate of the condensate, so that the bevel of the condenser tube keeps 2~5 drops of liquid per second.
Monitoring the Moisture Receiver – Before the water in the moisture receiver reaches its maximum volume, the heat is stopped, and when the solvent-free drip is removed, the receiver is quickly removed and the collected liquid is poured into a graduated cylinder.
End Heating – Stop heating when the volume of water in the receiver no longer increases and the upper solvent is completely transparent. If there are still water droplets on the inner wall of the condenser tube, rinse with solvent.
Cooling & Reading – Disassemble the instrument after allowing the glass flask to cool and record the volume (V) of water in the moisture acceptor.
Calculations & Reporting
The same specimen should be tested in parallel at least twice. When the difference between the two test results meets the allowable error requirements, the average value is taken as the test result.
Allowable error
For viscous petroleum asphalt, if the water in the receiver is less than 1mL, the allowable error of the repeatability test is 0.1mL, and if the water is in the range of 1.1~25mL, the allowable error is 0.1mL or 2% of the average value.
For emulsified asphalt, the permissible error of the repeatability test is 0.8%, and the reproducibility test is 2.0%.
summary
Asphalt moisture content testing plays a key role in asphalt production and construction. By accurately measuring the moisture in asphalt, construction problems caused by the influence of moisture can be effectively avoided, thereby improving the durability and safety of the project. The standardization and normalization of this method helps engineers to select the right asphalt material to ensure high quality and long-term use in road construction.
