Back in the late 60's I used to see 40' boxcars with pallets of bricks. They were the kiln fired clay type.
Modeling BNSF and Milwaukee Road in SW Wisconsin
My impression is that plants that produce concrete blocks and bricks and similar things don't ship by rail, because their customers are far too close.
If ya wanna ignore that irritating idea, the car at the top of my list would be a bulkhead flat--easily loaded by fork lift. And the bulkheads help head off longitudinal load shift. Which, of course, is why they became popular.
Now, if your plant made some sort of sooper-special concrete product that hardly anyone else could make, then rail shipment starts becoming more likely.
Yeah, I'd go with bulkheads. And pallets, of course. And lots of banding. Lots.
Ed
My late 70's layout has a concrete plant. Inbound products include rock, sand, cement and fly ash. I would like to add an outbound product. The plant makes concrete blocks, bricks and other finished concrete products. Would those products be shipped by rail in late 70's? Flatcar? Boxcar?
Paul D
N scale Washita and Santa Fe RailroadSouthern Oklahoma circa late 70's