7/24/2019 Measures to Avoid Cracking in Fresh Concrete
1/2
Generally, the contractor shall allow for all necessary measures
to monitor and avoid cracking in
fresh hydrating concrete, regardless the size or volume of the
pour. Such measures shall be to the
satisfaction of the Engineer and shall be such that maximum
surface crack width on hardenedconcrete measure immediately after
the pour does not exceed 0.00 times the nominal cover of
the main reinforcement.
!he contractor shall allow for and provide approved
instrumentation for the measurement of
internal temperature changes in large pours. !he maximum
concrete temperature at the point ofdelivery shall not in general
exceed the lower of either "# degree $, or % degree $ above the
prevailing shade temperature in accordance with the
recommendations of &$'. !he limiting
internal temperature differential measured across the extreme
faces of concrete mass shall notexceed () degrees $ at any
time.
$uring of hardened concrete shall be executed in accordance with
the curing specification.
Generally, the element surface shall not be cooled to dissipate
heat from the concrete. $uring
methods, such as the wetting of heated concrete elements exposed
to prolonged and directradiation, which induce temperature
gradients within the concrete mass are strictly prohibited.
*or large pours, the contractor shall allow for and take extra
precautions to reduce concrete
temperature gradient and to prevent the loss of surface
moisture. Such measures include but are
not limited to+
eeping all mix constituents shaded where possible to reduce
their temperatures in the
stockpile
$ooling of mixing water and-or replacing part or whole of the
added water with ice.
educing the cement content by the use of admixtures /but not
below that reuired for
the durability1
2sing a cement with a lower heat of hydration
'n3ecting liuid nitrogen after mixing of concrete
estring the time between mixing and placing of the concrete to
not more than ( hours
4roviding approved surface insulation continuously over all
exposed surfaces to prevent
draughts and to maintain uniform temperature through the
concrete mass
'nitiating curing immediately after final tamping and continue
until the approved surface
insulation system is fully in place
4roviding shade to the concrete surface to prevent heat gain
from direct radiation.
