Density of bitumen: the most simple measuring method

100 million tons of bitumen/asphalt are produced worldwide every year.  The industry faces new challenges in terms of researching and developing new, stronger materials. With demands rising, efficiency is a key factor in bitumen testing laboratories. However, measuring the density of bitumen in this industry is often done with pycnometers, a traditional, but time-consuming and tedious method. Time to break up with these obstacles – time-saving digital density meters might just prove to be a better lab partner for you.

Companies in the bitumen/asphalt industry face some challenges: Quality requirements for products like road pavements are increasing and the demand for new, even stronger materials requires intense research and development. Quality control during the production of bitumen/asphalt as well as researching new products have one thing in common: The resulting products are always thoroughly put to the test. If you are measuring the density of bitumen/asphalt in your lab every day, chances are good that you are using a pycnometer. This instrument requires a lot of your skill and time; in addition, it’s usually hard to clean up the mess bitumen/asphalt leaves behind.

So the question we are answering today is: How can you overcome those obstacles and simplify your everyday routine when it comes to measuring the density of bitumen?

The challenge

Laboratories that analyze bitumen are confronted with samples that can be hard to handle: Complicated handling and tedious cleaning procedures are a challenge in the busy lab routine. Especially when measuring with pycnometers, these tasks can take up a lot of time and also strain your nerves.

Handling of bitumen/asphalt can be messy

The standard test methods (ASTM D70 and EN 15326) ask for a pycnometer to be partially filled with the heated sample without splashing. In the process, the sample must not touch the inner sides of the pycnometer above the filling level – even though its neck is only about 2 cm (approx. 0.8‘’) wide. Then you have to fill the pycnometer with water and use the determined weights to calculate the density of your bitumen sample. This procedure is not only time-consuming and cumbersome, but also requires a lot of practice and skill. In addition, the achieved precision is moderate.

Pycnometers are hard to clean

“Messy” might also be the right word for having to clean containers that are crusted with bitumen/asphalt residues. After the measurement, the pycnometer needs to be heated in an oven to soften the bitumen which is then poured out. The leftovers in the container then have to be soaked in toluene or mesitylene and cleaned manually. All in all, a time-consuming and often uninspiring job.

Manual calculations

Density of bitumen/asphalt is measured at one specific temperature. If it is required to convert it to API numbers or relative density, these calculations have to be done manually.

The solution

Digital density meters that have been especially designed for bitumen/asphalt applications allow laboratory employees to save a lot of time and effort that is better put to use for other tasks than e.g. cleaning glassware.

Syringe filling, low sample volumes

Easy filling with a syringe spares the effort of pouring liquid bitumen from one container into the other. A nice side effect: The sample volume that is needed drops from 20 mL to 10 mL per measurement. This means: Changing to a digital density meter saves up to 50 % of sample volume.

Effective cleaning procedures

No heating, soaking, and scrubbing any more: The cleaning of the oscillating U-tube is also done via syringe. The required amount of solvents like toluene drops from up to 100 mL to 30 mL per measurement. That way, trading your pycnometer for a digital density meter means you have to spend up to 70 % less money on cleaning agents when it comes to measuring the density of bitumen.

Automated calculations

Conversion tables are usually already integrated into digital instruments for simple and fast calculations. None of your time will be wasted on making manual calculations any more.

Density of bitumen: key factors at a glance:

PycnometerDMA 4200 M
Duration of measurement (without sample preparation)2 hours12 minutes
Amount of cleaning agents60 mL to 100 mL per measurement30 mL per measurement
Handling, cleaningDifficultEasy

Correlating results

The industry standard EN 15326 (equivalent to ASTM D70) requires a pycnometer to measure the density of bitumen/asphalt. However, tests at the I.M.U. (Institut für Mineralölprodukte und Umweltanalytik”), an independent testing laboratory and consulting office specialized in petrochemical and environmental analysis, have shown that density measurements with the oscillating U-tube, in particular with the DMA 4200 M, achieve the same repeatability and even more precise results than pycnometers (read the corresponding article here).

In addition, other well-known standards – ASTM D4052 and ASTM D5002 – adopted digital measurements based on the principle of the oscillating U-tube as a suitable method. The DMA 4200 M complies with those standards needed in the petroleum industry and in the future a standard for measuring the density of bitumen/asphalt will follow. For more information on specs and standards, have a look on the product page:

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