protected by erecting shades and windbreaks and by applying fog sprays of
water, the addition of monomolecular films, or wet covering. When such
water treatment is stopped, curing procedures shall be immediately
commenced. Plastic shrinkage cracks that occur shall be repaired in
accordance with paragraph: REPAIR, REMOVAL, REPLACEMENT OF NEWLY
CONSTRUCTED SLABS. Plastic shrinkage cracks shall never be troweled over
or filled with slurry.
3.3.4
Paving in Cold Weather
Cold weather paving shall conform to ACI 306R. Special protection
measures, as specified herein, shall be used if freezing temperatures are
anticipated before the expiration of the specified curing period.
Placement of concrete shall not begin unless the ambient temperature is at
least 2 degrees C 35 degrees F and rising. Thereafter, placement of
concrete shall be halted whenever the ambient temperature drops below 5
degrees C 40 degrees F. When the ambient temperature is less than 10
degrees C 50 degrees F, the temperature of the concrete when placed shall
be not less than 10 degrees C 50 degrees F nor more than 25 degrees C 75
degrees F. Heating of the mixing water or aggregates will be required to
regulate the concrete placing temperature. Materials entering the mixer
shall be free from ice, snow, or frozen lumps. Salt, chemicals or other
materials shall not be incorporated in the concrete to prevent freezing.
If allowed under paragraph: MIXTURE PROPORTIONS, an accelerating admixture
may be used when the ambient temperature is below 10 degrees C 50 degrees F.
Covering and other means shall be provided for maintaining the concrete at
a temperature of at least 10 degrees C 50 degrees F for not less than 72
hours after placing, and at a temperature above freezing for the remainder
of the curing period. Pavement slabs damaged by freezing shall be removed
full depth, by full slab width, to the nearest original joint, and replaced
at the Contractor's expense as specified in paragraph: REPAIR, REMOVAL,
REPLACEMENT OF NEWLY CONSTRUCTED SLABS.
3.4
CONCRETE PRODUCTION
**************************************************************************
NOTE: Designer must correlate these paragraphs with
paragraph EQUIPMENT. Delete item in brackets if
truck mixers are not permitted.
**************************************************************************
Batching, mixing, and transporting equipment shall have a capacity
sufficient to maintain a continuous, uniform forward movement of the paver
of not less than 0.8 m 2.5 feet per minute. Concrete shall be deposited in
front of the paver within 45 minutes from the time cement has been charged
into the mixing drum, except that if the ambient temperature is above 32
degrees C 90 degrees F, the time shall be reduced to 30 minutes. Every
load of concrete delivered to the paving site shall be accompanied by a
batch ticket from the operator of the batching plant. Tickets shall be on
approved forms and shall show at least the mass, or volume, of all
ingredients in each batch delivered, [the water meter and revolution meter
reading on truck mixers] and the time of day. Tickets shall be delivered
to the placing foreman who shall keep them on file and deliver them to the
Government weekly.
3.4.1
Batching and Mixing Concrete
Scale pivots and bearings shall be kept clean and free of rust. Any
equipment which fails to perform as specified shall immediately be removed
SECTION 02753
Page 55
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