I'll keep it short. FAA guidelines for Marshall acceptance tests refer ASTM D6926 as the method to use. Within, a face diameter for Marshall hammers must be around 100mm. This refers only to manual hammers. It states that mechanical hammers may be used if calibrated to the same density of the manual hammer.

Humboldt makes mechanical hammers, and as far as I know, they're the only ones who make them. The only size hammers the make are AASHTO spec, which is around 98mm. Not much of a difference, but this has caused a huge problem and debate on my current project.

My question is this: How are we supposed to use the right sized mechanical hammers if they don't exist without being fabricated at a machine shop? I understand that the correlation method is supposed to correct for the size difference by varying blow counts and plotting on a graph to match up with specific gravities, but the size of the hammer still makes asphalt squeeze past it when it's being hammered in the mold. Humboldt really needs to start making ASTM spec hammers, or at least not advertise that their equipment is within ASTM specs.

Thanks!