supply additional moisture and those that prevent moisture loss. Table 7-2 lists several of these methods and their advantages and disadvantages.
METHODS THAT SUPPLY ADDITIONAL MOISTURE. - Methods that supply additional moisture include sprinkling and wet covers. Both these methods add moisture to the concrete surface during the early hardening or curing period. They also provide some cooling through evaporation. This is especially important in hot weather.
Sprinkling continually with water is an excellent way to cure concrete. However, if you sprinkle at intervals, do not allow the concrete to dry out between applications. The disadvantages of this method are the expense involved and volume of water required.
Wet covers, such as straw, earth, burlap, cotton mats, and other moisture-retaining fabrics, are used extensively in curing concrete. Figure 7-52 shows a typical application of wet burlap. Lay the wet coverings as soon as the concrete hardens enough to prevent surface damage. Leave them in place and keep them moist during the entire curing period.
If practical, horizontal placements can be flooded by creating an earthen dam around the edges and submerging the entire concrete structure in water.
Table 7-2.-Curing Methods
|Sprinkling with Water or Covering with Burlap||Excellent results if kept constantly wet||Likelihood of drying between sprinklings; difficult on vertical walls|
|Straw||Insulator in winter||Can dry out, blow away, or burn|
|Moist Earth||Cheap but messy||Stains concrete; can dry out; removal problem|
|Pending on Flat Surfaces||Excellent results, maintains uniform temperature||Requires considerable labor; undesirable in freezing weather|
|Curing Compounds||Easy to apply and inexpensive||Sprayer needed; inadequate coverage allows drying out; film can be broken or tracked off before curing is completed; unless pigmented, can allow concrete to get too hot|
|Waterproof Paper||Excellent protection, prevents drying||Heavy cost can be excessive; must be kept in rolls; storage and handling problem|
|Plastic Film||Absolutely watertight, excellent protection. Light and easy to handle||Should be pigmented for heat protection; requires reasonable care and tears must be patched; must be weighed down to prevent blowing away|