Getting Consistent Results in the Plant Lab—Gyratory Specimens

Gyratory Papers – Who knew they were so important?                              

We recently saw an interesting article in Asphalt Pro Magazine concerning gyratory compactors and obtaining consistent results. This is important for both asphalt mix design and in the field with the validation of those targeted volumetric properties. I do realize that our gyratory machines are not getting worked over like in the past since changes to the SC-M-400 specification were made to adopt gradation as an acceptance criterion in lieu of volumetrics.

The good ole days of us doing the old Marshall design are long gone for most of us and occasionally you may have a special project that may require this old method. Those printed paper disks had the logos so you always made sure they were logo side up so that was a constant reminder to flip the molded specimens over prior to compacting them again. I also recall when the papers meant more to the mix design folks, and we often set optimum binder content by looking at the papers by looking at the amount of free or excess binder that stuck or saturated into the papers.

All reminiscing aside, this article determined that the thickness of the paper can influence your BSG values. I do think most of you purchase these paper disks from your laboratory equipment supplier or perhaps even have gone the extra mile to put company logos printed on them. These papers are not only used to assist the technician with cleanup practices, but also reduce the wear and tear of your gyratory compactors that are not cheap.