What You'll Need The stronger the concrete grows as it cures more slowly. Concrete typically takes 28 days to fully cure. As the water in concrete evaporates, it cures. The key to shortening the curing period of concrete is to keep it wet. If it gets too dry, that will cause problems later. You can speed up the drying process by placing plastic sheeting over the concrete to prevent any moisture from escaping. This is called "blowing air" into the concrete. Or, if you want to be really scientific about it, you can add small amounts of accelerators or retarders to the mix to control the hardening reaction. These additives are usually colorless and transparent liquids that contain sulfur or nitrogen. They can either speed up or slow down the setting process depending on how they are formulated. There are two types of retarding agents: cold-weather materials such as salts and oils; and heat-treatment materials such as resins and latexes. Retarders are added to reduce the strength of concrete prematurely. This allows for easier mixing by reducing the need for coarse aggregate. Coarse aggregate is any rock larger than 1/4 inch that is used as a filler in concrete. It helps give the mixture structural integrity and provides some air space to allow for proper cement hydration.