3.3.6.4
Additional Compaction
If more than four passes are required to achieve the required density, the
additional passes shall be made at no additional cost to the Government.
3.3.6.5
Consolidation of Bedding and Other Conventional Concrete
In no case shall vibrators be used to transport concrete. The vibrator
shall be inserted vertically at uniform spacing over the entire area of
conventional concrete placement area. The distance between insertions
shall be approximately one and one-half times the radius of action of the
vibrator. The vibrator shall penetrate rapidly to the bottom of the layer
and at least 150 mm 6 inches into any preceding plastic layer if such
exists. The vibrator shall be held stationary until the entrapped air is
forced to the surface (up to 6 seconds) and the concrete is consolidated
and then withdrawn slowly. An adequate number of vibrators shall be on
hand to meet placing requirements, and spare vibrators shall be available
to maintain production in the event of breakdown.
3.3.7
Lift Joints
The entire RCC mass shall be placed with sufficient continuity
so that it
hardens and acts as one monolithic block without discontinuous
joints or
potential planes of separation. All lift joints shall be kept
clean,
uncontaminated, free from ponded water, and continuously moist
until
placement of the succeeding RCC or other concrete.
3.3.7.1
Regular Lift-Joint Treatment
Lift joints that have not hardened or dried and are less than 72 hours old
shall be given the regular lift-joint treatment. Regular lift-joint
treatment and maintenance shall include:
a. Maintaining 100 percent of each compacted lift-joint surface
continuously moist,
b. If necessary, removing all loose contaminants or deteriorated RCC
by low-pressure washing and/or vacuuming, and
c. Application of a 6 to 13 mm 1/4 to 1/2 inch thick bedding mortar
over the entire placement surface area immediately before placement of
the next lift.
For regular lift-joint treatment, no washing or vacuuming will be necessary
provided damage or contamination of the lift surface is prevented.
3.3.7.2
Cold Joints
A cold joint is any vertical or horizontal RCC surface:
a.
That does not receive the next RCC lift within 72 hours,
b.
In which the RCC has been allowed to dry, or
c. That has been contaminated to the extent that contaminants cannot
be removed using low-pressure water.
Cold joints shall be prepared for the next lift by the methods and
procedures in paragraph SURFACE PREPARATION prior to resumption of RCC
SECTION 03701
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