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Curing Concrete |
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After concrete is placed, a satisfactory moisture content and temperature (between 50°F and 75°F) must be maintained, a process called curing. Adequate curing is vital to quality concrete. Curing has a strong influence on the properties of hardened concrete such as durability, strength, watertightness, abrasion resistance, volume stability, and resistance to freezing and thawing and deicer salts. Exposed slab surfaces are especially sensitive to curing. Surface strength development can be reduced significantly when curing is defective. Curing the concrete aids the chemical reaction called hydration. Most freshly mixed concrete contains considerably more water than is required for complete hydration of the cement; however, any appreciable loss of water by evaporation or otherwise will delay or prevent hydration. If temperatures are favorable, hydration is relatively rapid the first few days after concrete is placed; retaining water during this period is important. Good curing means evaporation should be prevented or reduced. Cure the concrete immediately after finishing by: • Plastic sheets or waterproof paper are very effective in hot weather. Ponding water is the most effective, however, generally impractical. • Fog spraying is also very effective, but also impractical in most cases. Evaporation retardant is an effective alternative. • A wet burlap cure requires frequent watering and is very effective for commercial and paving work. |
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