Concrete, mortar, and grout must be cured to achieve their potential strength, durability, and watertightness. If they are not properly cured, concrete, mortar, and grout can lose up to 50 percent of their strength. There are several types of curing materials and techniques available, including ponding, wet burlap, membrane compounds, paper and plastic sheets. Use and opaque material to cure concrete that will be exposed to direct sunlight. A few don'ts to remember: don't use wet earth, sand, straw, or hay for curing; don't pond structural slabs unless the shoring and formwork are designed for it; and don't use plastic sheets for curing colored slabs because they result in uneven coloring. A few reminders regarding technique: (1) don't neglect slab edges, column bases, and other hard to get at places when curing. (2) Firmly secure curing paper, film, and burlap against wind forces. (3) Overlap curing paper and film by a wide margin, and securely tape the edges in place. (4) Check for pipe leakage and nozzle clogging when spraying and fogging. (5)Make every effort to keep sprayer lines and nozzle free from clogging. And (6) follow manufacturer' directions carefully, especially when using a membrane curing compound, and take particular note of the amount of curing agent to be applied.