Large Cast-In-situ Ground Floors ~ these are floors designed to
carry medium to heavy loadings such as those used in factories,
warehouses, shops, garages and similar buildings. Their design and
construction is similar to that used for small roads (see pages 132
to 134). Floors of this type are usually laid in alternate 4„500 wide
strips running the length of the building or in line with the
anticipated traffic flow where applicable. Transverse joints will be
required to control the tensile stresses due to the thermal
movement and contraction of the slab. The spacing of these joints
will be determined by the design and the amount of reinforcement
used. Such joints can either be formed by using a crack inducer or
by sawing a 20 to 25 mm deep groove into the upper surface of
the slab within 20 to 30 hours of casting.Surface Finishing ~ the surface of the concrete may be finished by
power floating or trowelling which is carried out whilst the
concrete is still plastic but with sufficient resistance to the weight
of machine and operator whose footprint should not leave a
depression of more than 3 mm. Power grinding of the surface is an
alternative method which is carried out within a few days of the
concrete hardening. The wet concrete having been surface finished
with a skip float after the initial levelling with a tamping bar has
been carried out. Power grinding removes 1 to 2 mm from the
surface and is intended to improve surface texture and not to
make good deficiencies in levels.Large Cast In-situ Ground Floors