Concrete Slabs U3 480/s

Concrete slabs for Update 3. This is a Tier2 BP, using mixer3 and gas kilns, but it should downgrade the mixers, if you don't have that tier yet. Fills a T3 belt with some excess, since the math isn't even. 450 items is roughly 9.3 mixers, and there's 10 in this BP. However, this does provide a good method for collecting cement which can be traded.