3.5.2
[Slipformed Facing Elements]
A slipformed conventional concrete face shall be constructed on the
upstream face of the dam [and [_____]]. Concrete for the slipformed facing
elements shall conform to requirements of this section. The configuration
for the facing elements shall be as shown. The concrete mixture for the
facing elements shall be proportioned by the Contractor to be formed by a
slipform curbing machine and to have sufficient early strength to allow
compaction for RCC against its surface within 4 hours.
3.5.2.1
Prequalification of Equipment
Prior to placing any slipformed facing elements for incorporation into the
dam, a demonstration of the slipform equipment and concrete mixture as a
part of the test section shall be performed by the Contractor. The
Contractor shall form one side of the test section using his proposed
slipforming equipment, in accordance with paragraph RCC TEST SECTION. If
necessary, the Contractor shall adjust the concrete mixture and make any
adjustments or modifications to the slipforming equipment and concrete
supply procedures and equipment as may be required to produce a
satisfactory slipformed facing element. A starting block shall be
constructed to enable the first facing element to be formed without
modification to the slipform.
3.5.2.2
Slipform Operations
The equipment shall be operated in such a manner as to prevent damage to
the RCC surface and facing element. The slipformer shall carry a surge
hopper of sufficient capacity to enable the slipformer to continue to
extrude facing element between concrete deliveries. If the slipformer is
stopped, concrete shall be thoroughly consolidated, a joint shall be made,
and unacceptable concrete shall be removed from the mold. The slipformer
shall have an automated guidance system which shall guide the slipformer
within the specified tolerances. A smooth, mortar-tight joint between
successive elements shall be achieved. Molds and vibrators shall be
available in sufficient quantities to replace worn or damaged ones.
Vibrators shall be capable of being adjusted and relocated to achieve
complete consolidation.
3.5.2.3
Slipforming - Preparation for Placing
Placement shall not begin until after all preparations are complete and the
authorized representative of the Contracting Officer has approved in
writing completion of all preparations for that placement. No facing
element concrete shall be placed until the surfaces to receive facing
element concrete are free of deleterious substances including but not
limited to: uncompacted, loose, deteriorated, or improperly cured RCC or
facing element concrete, laitance, dirt, ice, curing compounds, and visible
free surface water.
3.5.2.4
Slipforming - Placing
All joint surfaces more than 24 hours old, or in any other way damaged or
not meeting the specification requirements, shall be wet sandblasted,
washed with air-water jets, and surface dried prior to placement of
adjoining facing elements. The molds for the slipform shall be kept
continually full, and concrete vibrated, to prevent voids. The slipformed
facing element shall be uniform, dense, and free of surface blemishes and
tears.
SECTION 03701
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