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Increased
water
demand, slump loss, setting rate, plastic cracking,
rapid surface water loss, entrained
air problems, and early curing start, are problems encountered when
placing concrete in hot
weather.
Adding water to the
concrete mix is not very effective because it decreases strength,
durability and
watertightness, gives the surface a non uniform appearance,
and increases
drying shrinkage. Hot weather concrete problems can be resolved by
cooling the concrete materials before mixing; protecting the
concrete mixers,
belts, hoppers and pump lines from sunlight with shade, white
paint, or wet burlap covers;
moistening the subgrade the evening before concreting without leaving
puddles; restricting concrete placement to
early morning, evening or night; making sure adequate personel are
available to
transport and place the concrete quickly; erecting sunshades over the
concrete during finishing operations; covering the concrete surface
with
white polyethylene between finishing operations; hosing water on to the
concrete surface and letting it run down inside the loosened forms;
spraying fog
without leaving puddles between placing and finishing;
tining concrete immediately after troweling; spraying evaporation
retarders on the concrete right after screeding; spraying fog into
the ambient air to raise the relative humidity while waiting for a
curing material to be applied to the concrete; reducing the time
between placing and curing. |
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