At the Kansas Winter Q in Great Bend KS, where the cook teams set up is also the staging area for the professional drag strip. The drag strip operators were concerned with some grease spills that would get on racing slicks and cause problems. The method they use (and Kent Romine & I used) is like this. First they saturate the concrete with laquer thinner, then use a stiff bristle broom (or brush for a small area) to scrub the laquer thinner in. Then they use a weed burner to burn off the laquer thinner. Then they use a water hose to soak the concrete and spread Tide laundry detergent which is then scrubbed with a clean stiff bristle broom. Then it is rinsed off with water.
This is a lot of effort but it really does pull the grease out of the concrete. The drag strip crew said they have tried lots of other methods, but this is the only one that worked. Also, they suggest the guy spreading the laquer thinner not be the guy using the torch.