§ 6-124. Placing concrete.

(a)

Generally.

(1)

Only those methods and arrangements of equipment shall be used which will reduce to a minimum any segregation of coarse aggregate from the concrete.

(2)

Every consideration shall be given toward proper placement of all concrete and proper care of concrete after placement.

(3)

Sufficient capacity of placing equipment and manpower shall be provided so that the work may be kept free from "cold" joints.

(4)

Concrete shall be deposited into the forms or onto the grade as nearly as practicable to its final position and in such a manner that the concrete will completely fill the forms.

(5)

The use of vibration as a method of moving concrete after placing shall not be allowed.

(6)

Concrete placed on a slope shall begin at the lowest end of the slope and progress upward.

(7)

No concrete that has partially hardened or has been contaminated by foreign materials shall be deposited on the work.

(8)

Specified design slumps shall not be altered by workmen at the job site by the addition of water to the mix in order to compensate for a lack of proper placing equipment and personnel.

(9)

Concrete shall not be placed on mud or frozen ground.

(10)

Subgrades shall be wetted in advance of concrete placement.

(11)

Care shall be taken to see that reinforcing steel or mesh has proper cover in accordance with design.

(12)

Care shall be taken to see that all joint materials, dowels and embedded items remain true to line and grade.

(13)

No mud or other foreign material shall be tracked into the concrete during placement operations.

(b)

Depositing. Concrete shall be deposited without segregation as near to its final position as practicable.

(1)

Concrete shall not be placed on frozen, muddy, or sponge base.

(2)

All mud, freestanding water, debris and loose earth shall be removed prior to concreting.

(3)

Footings shall be side formed by sound and stable earth or by assembled forms.

(4)

Placing operations shall be conducted in such a manner as to eliminate sloughing of earth into the footing during concreting.

(c)

Vibrating.

(1)

Mechanical internal vibrators shall be used in all formed concrete work where possible.

(2)

Systematic spacings (twelve (12) to twenty (20) inches apart) of vibrator insertion shall be established to ensure that all concrete is thoroughly consolidated.

(3)

Vibrators shall be inserted and withdrawn vertically with five-to fifteen-second vibration periods.

(4)

Vibrators shall be inserted to a depth which will ensure penetration into previous lift.

(5)

Form vibration or hand spading is required at points inaccessible to thorough internal vibration.

(6)

At all times during vibrating operations standby vibrators shall be immediately available.

(d)

Strike-off.

(1)

Strike-off screeds shall be set to proper grade for all slab concreting. Grade tolerance for screeds shall not exceed one-eighth inch plus or minus in seven (7) feet.

(2)

Strike-off shall be accomplished by use of straight edge of adequate weight and length.

(3)

Vibrating strike-off screeds, or other approved methods of strike-off, shall be used when concrete is under three (3) inches and slab thickness is over four (4) inches.

(4)

Jitterbug shall not be used as a strike-off tool.

(e)

Under water.

(1)

Any water flow shall be stabilized or controlled prior to placing concrete.

(2)

Tremies shall be used in all cases unless otherwise approved by the inspector.

(3)

Tremies shall be equipped with watertight valves or caps at the bottom.

(4)

Once concreting is started the lower end of the tremie shall be kept submerged in fresh concrete at all times.

(Code 1974, § 5-13)