Poured concrete foundations are an alternative to block or treated wood foundations. The process involves building a form to hold the concrete in place, installing reinforcing rods and then pouring the concrete. Once cured the concrete provides a secure and stable foundation for the home that will be built above. The proper curing time and process is vital for the construction of the home.
Poured concrete establishes about half of its final strength after about one week of curing. Curing is defined as a chemical process the concrete goes through in the days immediately after it is poured. While full strength does not occur for 28 to 60 days, depending on conditions, the building process can begin when the foundations are about 50 percent cured.
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Proper curing occurs when the concrete is warmer than 50 degrees Fahrenheit. Do not pour concrete in temperatures below 20 degrees. The poured foundation should be kept as uniform as possible in temperature during the curing process. All of these steps help speed the curing process and also result in an overall stronger foundation wall once the curing is complete. Temperatures of 70 degrees compared to 50 degrees, for example, reduce the 50 percent strength curing time from 6 to 4 days.
Apply sealants to the concrete as soon as the forms are removed and the surfaces appear dry. This helps maintain moisture within the concrete necessary for the curing chemical reaction. Other options include wrapping the foundation in plastic sheeting or waterproof paper. All these materials help the curing process produce a stronger foundation.
Backfill is the process of filling dirt in the portion of the excavation outside the foundation. This is done after the forms are removed and any sealant material is applied. Many builders wait until the floor joists are built above the foundation before doing the backfill. The joists serve as braces at the top of the foundation, making the walls sturdier and less prone to damage if the equipment used in the backfill process were to strike the foundation.