Very small projects can be completed in one day while larger projects may take multiple days. Small to mid-size projects often have a phase/day for demolition and form setting and a separate phase/day for pouring and finishing. Most commonly used concrete mixes take a minimum of a day to cure for foot traffic, a few days to cure sufficiently for car traffic, and 5-7 days for truck traffic. The PSI rating of concrete mixes is based on strength at 28 days. The curing process over time plots as a curve with most of the curing takes place after placement and gradually slowing. Concrete continues to strengthen incrementally even well past the 28-day rating.