[EarthResearcher333]

They used real-time computers to weigh the "mix" on the moving conveyor belt and automatically injected sands and materials to keep the mix within specs "on-the-fly". They never mentioned what type of 1960's computer, but many interesting types come to mind. These were out in the field. They had to be in special large enclosures.

[mad_as_he$$]

Most likely some version of PDP.

One of my uncle’s ran an excavation business during that timeframe. I drove pusher and a towed pan for him in the very late 60’s. We built several earthen dams for farmers. I was always struck by how the dirt moved when dumped or pushed. Clods would move like they had a mind of their own, different types of soil would behave with completely different settling characteristics. Aeration played a big factor. The more you moved it the more air it had and getting it compacted often became a very difficult.