Q.: We placed a concrete floor in an unheated 300,000-square-foot warehouse. Control joints were sawed on 20-foot centers each way. We filled the joints with epoxy but there has been quite a bit of joint movement and now the joint filler is pulling away from the concrete in spots. We've decided to remove the epoxy and fill the joints with something more pliable. Will the joint edges spall if we do this?
A.: Depending on the type of traffic over the floor you could have problems with joint spalling. Joint fillers should provide support at the edges, but a soft, elastomeric material won't give much support. Hard-wheeled traffic is likely to tear up concrete near the joint.
You don't say what kind of epoxy was used to fill the joints initially. It should be a semi-rigid material, sometimes called a flexibilized epoxy. There's a possibility that the gaps in the joint can be refilled without taking out the epoxy that's there now. This would help to accommodate the additional movement caused by shrinkage. Check with the epoxy manufacturers or a joint maintenance company to find out if this is feasible.