formed surfaces or surfaces congested with reinforcing steel.
Regardless of the method used, the resulting surfaces shall be free
from all laitance and inferior concrete so that clean, well-bonded
coarse aggregate is exposed uniformly throughout the lift surface. The
edges of the coarse aggregate shall not be undercut. The surface shall
be washed clean again as the last operation prior to placing the next
lift.
3.2.6.2
Air-Water Cutting
Air-water cutting of a construction joint shall be performed at the proper
time and only on horizontal construction joints. The air pressure used in
the jet shall be 690 kPa 100 psi plus or minus 70 kPa 10 psi, and the water
pressure shall be just sufficient to bring the water into effective
influence of the air pressure. When approved by the Contracting Officer, a
retarder complying with the requirements of COE CRD-C 94 may be applied to
the surface of the lift to prolong the period of time during which
air-water cutting is effective. Prior to receiving approval, the
Contractor shall furnish samples of the material to be used and shall
demonstrate the method to be used in applications. After cutting, the
surface shall be washed and rinsed as long as there is any trace of
cloudiness of the wash water. Where necessary to remove accumulated
laitance, coatings, stains, debris, and other foreign material,
high-pressure water jet or sandblasting will be required as the last
operation before placing the next lift.
3.2.6.3
High-Pressure Water Jet
A stream of water under a pressure of not less than 20.7 MPa 3,000 psi may
be used for cleaning. Its use shall be delayed until the concrete is
sufficiently hard so that only the surface skin or mortar is removed, and
there is no undercutting of coarse-aggregate particles. If the water jet
is incapable of a satisfactory cleaning, the surface shall be cleaned by
sandblasting.
3.2.6.4
Wet Sandblasting
This method may be used when the concrete has reached sufficient strength
to prevent undercutting of the coarse-aggregate particles. The surface of
the concrete shall then be washed thoroughly to remove all loose materials.
3.2.6.5
Waste Disposal
The method used in disposing of waste water employed in cutting, washing,
and rinsing of concrete surfaces shall be such that the waste water does
not stain, discolor, or affect exposed surfaces of the structures, or
damage the environment of the project area. The method of disposal shall
be subject to approval.
3.3
COARSE-AGGREGATE AND GROUT PLACEMENT
3.3.1
Coarse-Aggregate Washing and Screening
Coarse aggregate shall be washed, screened, and saturated immediately
before placement. Washing of the aggregate in the forms will not be
permitted. If more than one size of coarse aggregate is used, the
aggregate shall be weighed, batched, and mixed in the proper proportions
onto the wash screen. The wash screen may be a vibrating deck or revolving.
SECTION 03372
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