When it comes to concrete slabs, there is one fact that must be faced by homeowners, contractors, and concrete subs alike: Concrete will crack. Period. The challenge for the concrete sub is to work with the material and make it behave in a way that is acceptable to both the customer and the contractor. The key to success is to control where the concrete is going to crack, and prepare the customer for the inevitable. Brittle Behavior Concrete does its best work under compression. It's great for driving cars on, rolling shopping carts on, even for raising elephants on. But it doesn't have great tensile strength. Picture a glass table cover at a restaurant: It works fine