Concrete Foundation Walls - Structural Deterioration And Damage
Problem: Cracks and spalling from poor construction practices - 4.
Cause: Inadequate cold weather protection - below 41°F (5°C).
Where concrete freezes before it is cured, it will suffer permanent loss of strength and water tightness.
Solutions: Provide cold weather protection strategies.
- Ensure qualified site supervision.
- Keep the temperature of the concrete above 50°F (10°C) during placement and for three days afterwards. For walls, leave forms in place for two days to enhance the heat of hydration. Cover slabs with insulating materials or straw covered with tarpaulins or polyethylene.
- Use a concrete mix with low water content, adding plasticizers as necessary. Specify high early-strength concrete.
- Have the supplier provide heated concrete by using hot water and dry aggregates.
- If calcium chloride is used as an accelerator, li9mit the amount to less than 2% of the weight of the cement. Note that accelerators can increase the likelihood of shrinkage cracking. Calcium chloride must not be used in concrete that has mental inclusions. Non-chloride accelerators must not be used. Do not use calcium chloride in the excavation to melt ice.
- Builders who work in northern climates often cast floor joists into foundation walls, making it easier to cover them with tarpaulins and heat them.
If heaters are used inside the building, be sure to provide adequate ventilation. Heaters will produce significant quantities of carbon monoxide, which can result in carbonation )dusting) on the surfaces of the concrete. As carbon monoxide is heavier than air, air should be exhausted from neat the floor.