The chemical composition of asphalt is tested using a three-component method, which analyzes the content of asphaltene, gum and oleowax by extraction technology. This method mainly uses solvents such as n-heptane, benzene and ethanol to systematically separate and quantify road petroleum asphalt. The results provide important data for the evaluation of asphalt properties and help optimize the use of asphalt materials.
The three-component method of asphalt testing is designed to analyze the chemical composition of road petroleum asphalt. By dividing asphalt into three parts: asphaltene, gum and oil wax, this method can provide basic data for the physicochemical properties, performance evaluation and engineering application of asphalt. It is suitable for asphalt quality analysis and control in the fields of road engineering, materials science, etc.
Instrument and material requirements
Must-have instruments
Erlenmeyer flask – 200 mL with ground glass stopper for bitumen samples and solvents.
Condenser tubes – straight or curved to ensure efficient reflux of the evaporated solvent.
Beakers – 250 mL and 1000 mL for solvent mixing and reaction.
Funnel – approx. 9 cm in diameter for liquid transfer and filtration.
Fat extractor – 500mL, designed for continuous extraction.
Suction filter flask – 500mL, collect the filtered liquid.
Analytical balances – sensitive volumes up to 0.1mg ensure accurate weighing.
reagent
N-heptane – used to dissolve asphaltenes.
Benzene, absolute ethanol, methyl ethyl ketone (butanone): used for the extraction of gum and oil wax.
Silica gel - microspherical, particle size 0.35~0.125mm, pore size greater than 8nm, used for adsorption and separation.
Other materials
Industrial alcohol, dry ice, absorbent cotton, horn spoons, pipettes, surface dishes, glass rods, enamel plates, jars, etc.
Detection steps
Preparation
Sample preparation
Prepare asphalt specimens according to standard method T0602 to ensure specimen representativeness and uniformity.
Instrument cleaning
Erlenmeyer flasks, beakers, funnels and other utensils are cleaned sequentially with lotion and distilled water, and then placed in an oven at 110 °C to dry to remove moisture and impurities. Once cooled, store the appliance in a dryer for later use.
Determination of asphaltene content
Dissolve asphalt
Weigh about 1g of asphalt sample (m) and place it into a pretreated Erlenmeyer flask. Add 30 mL of n-heptane (40 mL for viscous bitumen) and install the condenser. The Erlenmeyer flask is heated on a sand bath and the solvent is kept refluxed for 0.5~1 hour to fully dissolve the asphalt.
Sedimentation and filtration
After the Erlenmeyer flask has cooled slightly, seal it and leave it in the dark overnight to allow asphaltene to settle. The next day, gently remove the Erlenmeyer flask without agitating the pellet and filter the upper n-heptane solution into a clean beaker. Wash the residue in the Erlenmeyer flask with a small amount of hot n-heptane until the filter paper and filtrate are colorless.
Residue treatment
Dissolve the residue on the filter paper with hot benzene, transfer it back to the original Erlenmeyer flask, and wash with hot benzene until colorless. The benzene solvent was recovered and baked in an oven (110 °C ± 5 °C) to constant weight (m₁) to an accuracy of 0.1 mg.
Determination of gum content
Silica gel activation
Place the microspherical silica gel in a large beaker, add distilled water and boil for 30 minutes, stirring to prevent spilling. After cooling, the upper layer of water is decanted and washed 1~2 times. Pour the silica gel into an enamel dish and raise to 150 °C after drying at 105 °C for 5 h. Cool and store in sealed bottles for later use.
Adsorption of gums
The activated silica gel was gradually added to the n-heptane solution with asphaltene removed, and stirred for 6~8 hours until the upper solution was light yellow. After that, the silica gel was loaded into a filter paper tube, the oil wax was extracted, and 200 mL of n-heptane was used for heating and reflux, and it was kept for at least 16 hours.
Extract gum
Add 200mL of benzene and ethanol (4:1 volume ratio) mixture to the flask, install the extraction cylinder and condenser, and heat the extraction time for no less than 20 hours. After the filtrate is recovered, it is subjected to subsequent treatment.
Determination of oil and wax content
Cooling and filtration
The glass funnel, suction filter bottle and mixture are cooled in a freezer at -20°C. Cooling and filtration were carried out with a cooled methyl ethyl ketone-benzene mixture to ensure the separation efficiency.
Collect the filtrate
At the end of filtration, the filtrate is transferred to a weighed Erlenmeyer flask for final drying and weighing.
Calculations and results reporting
At the end of the experiment, at least two parallel tests are performed on the same specimen. If the error between the two test results and the average value does not exceed 10%, the average value will be taken as the final result.
summary
The three-component method is an important detection method in asphalt analysis, which can provide a scientific basis for material selection and performance evaluation of road engineering through the accurate determination of asphalt chemical components. This method not only simplifies the experimental process, but also improves the accuracy of the analysis results, which provides reliable support for the application and research of asphalt.
