API Audio Accessories 7-22-10 Specifications download pdf (Page 20)

07/22/10 03001-5

A. Notify Engineer a minimum of 24 hours prior to commencement of concreting operations.

B. Equipment for chuting, pumping and pneumatically conveying concrete must be sized and

designed as to insure a practically continuous flow of concrete at the delivery end without

separation of the materials.

C. Prevent separation or loss of materials when conveying concrete from mixer to place of final

deposit.

D. No concrete that has partially hardened or been contaminated by foreign material may be

deposited on the Work nor retempered.

E. Deposit as nearly as practicable to its final position to avoid segregation due to rehandling or

flowing.

F. During placement, thoroughly work concrete around reinforcement and embedded fixtures and

into the corners of the forms.

G. At all times, concrete is to be plastic and flow readily into the space between the bars.

When concreting is once started, carry on as a continuous operation until the placing of the panel

or section is completed. The top surface to be generally level.

H. Consolidate placed concrete by mechanical vibrating equipment supplemented by hand-spading,

rodding or tamping. Use vibrators designed to operate with vibratory element submerged in

concrete.

3.06 UNDER-WATER PLACING (Done only on approval of Engineer)

A. When conditions require placing through water, a tremie or drop-bottom bucket should be used

and the Work must be well supervised. Every precaution must be taken to prevent the cement

from washing out of the concrete. The tremie is to be water-tight and large enough to allow a free

flow of concrete. It must be kept filled with concrete at all times while depositing. Discharge

concrete and spread by moving the tremie as to maintain as nearly as practicable a uniform flow

and avoid dropping the concrete through water. If the charge is lost while depositing, the tremie

must be withdrawn and refilled. Maintain concrete slump between 6 and 7 inches. Tremie

concrete must be pumped into place instead of gravity placed.

3.07 COLD WEATHER PLACEMENT

A. Provide adequate equipment for heating the concrete materials and protecting the concrete during

freezing or near-freezing weather. No frozen materials or materials containing ice can be used.

B. All concrete materials and all reinforcement, forms, fillers and ground with which the concrete is

to come in contact must be free from frost. Whenever the temperature of the surrounding air is

below 40 degrees F, all concrete placed in the forms must have a temperature of between 70

degrees F and 80 degrees F, and adequate means to provide for maintaining a temperature of not

less than 70 degrees F for 3 days or 50 degrees F for 5 days. The housing covering or other

protection used in connection with curing must remain in place and intact at least 24 hours after

the artificial heating is discontinued. No dependence can be placed on salt or other chemicals for

the prevention of freezing.

3.08 HOT WEATHER PLACEMENT

A. Cool ingredients before mixing to maintain concrete temperature at time of placement below 90

degrees F. Mixing water may be chilled, or chopped ice may be used to control the concrete

temperature, provided the water equivalent of the ice is calculated to the total amount of mixing

water.

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API Audio Accessories 7-22-10 Specifications Page 20

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