Plastic cracking on the surface of a concrete slab may not affect its serviceability but you could end up with a very dissatisfied owner. Know when the potential for cracking is highest could save time and your reputation. Now there's a free tool, developed at Southern Illinois University, for you computer or smart phone that will tell you on an hour-by-hour basis the anticipated evaporation rate for your zip code and what the risk is for cracks. And best of all, it's free. To go to the risk calculator, click here.