Date: January 1, 2010

News - Curing Concrete

The two most important aspects of curing are maintaining adequate moisture content and maintaining proper temperatures within the concrete during its early stages to ensure that it achieves the desired strength.
How to keep the concrete moist:
Concrete in a dry environment can lose up to 50 percent of its potential strength, because without enough moisture the cementitious materials in concrete cannot react to form the strong bonds that hold the aggregates together. Keeping fresh concrete covered while it cures will help maintain proper moisture. Here are a few materials you can use to cover your concrete:
  • Burlap or cotton mats and rugs used with a soaker hose or sprinkler. Coverings should not absorb water from the concrete.
  • Straw that is sprinkled with water regularly.
  • Damp earth, sand, or sawdust for curing flatwork, especially floors.
  • Liquid membrane-forming curing compounds. Apply to the concrete surface one hour after finishing. Do not apply if there is still bleed water on the surface.
  • Plastic sheets: dark colored sheets when ambient temperatures are below 60°F and reflective sheets when temperatures more than 85°F.  
Equally important as keeping your concrete moist is regulating the temperature—concrete should be maintained at above 50ºF for the concrete to gain adequate strength. In high temperatures, concrete will gain early strength quickly but later strengths may be reduced.
Concrete placed in cold weather will take longer to gain strength, which will delay form removal. Keep the concrete insulated with materials like foamed vinyl blankets or polystyrene sheets while using the natural heat of hydration for warmth to keep it from freezing until it reaches a compressive strength of at least 500 psi. 

Other news articles from January 2010