You cannot operate a gasoline floor finisher without understanding the chemical cocktail mixed into the concrete truck. Concrete doesn't "dry"—it cures via a highly volatile exothermic reaction. And these days, the ready-mix plants are heavily modifying that reaction with chemical admixtures. If you don't know what's in the mud, you will either sink the machine or end up with a slab that turns to stone before you can put a blade on it.
For instance, when we pour a massive commercial driveway in the dead of winter, the plant will dose the mix with non-chloride accelerators. This rapidly speeds up hydration. If I am running a 1200 mm [approx. 46-inch] heavy-duty trowel, I have to be hyper-vigilant. The window between the "bleed water" evaporating and the slab becoming un-trowelable shrinks from an hour down to fifteen minutes. I have to fire up the high-torque gas engine much earlier than my instincts tell me, and I skip the float pan entirely, going straight to combination blades to aggressively open the surface.
Conversely, in the blistering heat of August, we use retarders. This slows the set time, but it can create a deceptive surface. The top 3 mm [approx. 1/8 inch] might look ready for the trowel, but the sub-surface is still pure liquid. If I drop a heavy gas-powered walk-behind onto that slab, the machine will suddenly punch through the crust and bury itself to the engine block. Running this machinery requires you to read the batch ticket from the concrete truck just as closely as you read the dipstick on your engine.
