hand-held breakers or high-pressure water may be
required to remove some of the microfractured
concrete.
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Use boom or vehicle mounted impact breakers or spring-action hammers or
drop balls to remove concrete in relatively thin sections or to break up
concrete which has been separated from the structure by other methods.
3.3.3.2
Hand-Held Breaker
Use hand-held breakers or chipping hammers for removal of concrete in small
or restricted areas, where the energy to be applied must be limited to
prevent damage to adjacent concrete, structures or facilities which are not
to be removed, and to complete removal where other methods have been used.
3.3.4
Milling
3.3.4.1
Hydromilling
Remove concrete from vertical or horizontal surfaces by means of high
pressure water applied though nozzles attached to a remotely-controlled
device or beam. Adjust water pressure and rate of movement as required to
remove concrete to the required depth and avoid excessive removal.
Supplement hydromilling with abrasive water-jet, high-pressure wand, or
other methods in areas not accessible to the hydromilling equipment.
Submit proposed hydromilling equipment and procedures to the Contracting
Officer for review and approval before beginning work. Remove slurry from
the prepared surface before it hardens.
3.3.4.2
Rotary Head Milling
Use rotary head milling for uniform depth removal on horizontal or vertical
surfaces. Use boom-mounted milling head for vertical surfaces. When
operating rotary head equipment from top of wall for removal from vertical
surfaces, provide communication between observer and operator to aid in
control of removal.
3.3.5
Presplitting
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NOTE: Presplitting only separates the concrete.
Other measures must be employed to remove
reinforcing steel and other embedded items. Hole
spacing and diameter are critical to proper
development of the presplit plane. A test break
should be performed to verify the proposed procedure.
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3.3.5.1
Expansive Agents
Use an expansive compound, manufactured for concrete and rock demolition.
Drill holes, including relief holes, of the size and at the spacing
recommended by the manufacturer. Mix and place the material in accordance
with the manufacturer's recommendations. Insert closed-end plastic tubes
into each hole prior to placing the expansive material to prevent dilution
of the material and to prevent slurry from entering existing cracks.
SECTION 03931
Page 53
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