3.6.1.6
Concrete Toppings Placement
ACI 301. The following requirements apply to the placement of toppings of
concrete on concrete surfaces that are either freshly placed and still
plastic, or on hardened base slabs.
a.
Placing on a Fresh Concrete: Screed and bull float the base slab.
As soon as water sheen has disappeared, lightly rake surface of
the base slab with a stiff bristle broom to produce a bonding
surface for the topping. Immediately spread topping mixture
evenly over the roughened base before final set takes place. Give
topping the finish [indicated on the drawings] [specified].
b.
Bonding to a Hardened Concrete: When the topping is to be bonded
to a floated or troweled hardened base, roughen the base by
scarifying, grit-blasting, scabbling, planing, flame cleaning, or
acid-etching to lightly expose aggregate and provide a bonding
surface. Remove dirt, laitance, and loose aggregate by means of a
stiff wire broom. Keep the clean base wet for a period of 12
hours preceding the application of the topping. Remove excess
water and apply a 1:1:1/2 cement-sand-water grout, and brush into
the surface of the base slab. Do not allow the cement grout to
dry, and spread it only short distances a head of the topping
placement. Do not allow the temperature differential between the
completed base and the topping mixture to exceed -12 degrees C 10
degrees F at the time of placing. Place the topping and finish as
[indicated] [specified herein].
3.7
CURING AND PROTECTION
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NOTE: When the use of alkali-reactive aggregates is
permitted, add paragraph entitled "Additional Curing
When Using Alkali-Reactive Aggregates" as follows:
"Furnish ASTM C 39 test results to verify the
anticipated rate of strength development for the
proposed concrete design mixture. Submit an
increased curing period and minimum time to strip
formwork based upon the reduced rate of strength
development."
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a.
ACI 301 and ACI 308 unless otherwise specified. Prevent concrete
from drying by misting surface of concrete. Begin curing
immediately following final set. Avoid damage to concrete from
vibration created by blasting, pile driving, movement of equipment
in the vicinity, disturbance of formwork or protruding
reinforcement, by rain or running water, adverse weather
conditions, and any other activity resulting in ground vibrations.
Protect concrete from injurious action by sun, rain, flowing
water, frost, mechanical injury, tire marks, and oil stains. Do
not allow concrete to dry out from time of placement until the
expiration of the specified curing period. Do not use
membrane-forming compound on surfaces where appearance would be
objectionable, on any surface to be painted, where coverings are
to be bonded to the concrete , or on concrete to which other
concrete is to be bonded. If forms are removed prior to the
SECTION 03311
Page 38
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