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Vapour
barriers should be placed under all concrete ground level floors to
prevent the transfer of moisture and soil gases such as radon gas.
Sloping the landscape away from the building, placing a 100 mm granular
subbase between the soil and the slab, adding a subbase drainage
system, and using drain tiles and vapour barriers will reduce moisture problems.
After new concrete is poured and hardened it is roughened to make
a better bond with the next placement. Wood
forms should be oiled or treated with form release agent to prevent
damage to the concrete when they are removed. Reinforcing bars should
be clean and without loose rust and scale. Concrete
should be placed as close as possible to its final
destination. The placed concrete layer, usually 300 mm in depth, should
be consolidated, and made uniform and
horizontal, before the next layer is added. Concrete should not be poured into
piles and placed by moving it horizontally because it will segregate as the cement and water mixture moves ahead of
the aggregate. |
