lines in a rectangular pattern in line with the formwork panels. After
concrete removal, the surface shall be thoroughly cleaned by high pressure
washing to remove all loose material. Surfaces shall be kept continually
saturated for the first 12 of the 24 hours immediately before placing
mortar and shall be damp but not wet at the time of commencing mortar
placement. The Contractor, at his option, may use either hand-placed
mortar or mortar placed with a mortar gun. If hand-placed mortar is used,
the edges of the cut shall be perpendicular to the surface of the concrete.
The prepared area shall be brush-coated with a thin coat of neat cement
grout. The repair shall then be made using a stiff mortar, preshrunk by
allowing the mixed mortar to stand for 30 to 45 minutes and then remixed,
thoroughly tamped into place in thin layers. If hand-placed mortar is
used, the Contractor shall test each repair area for drumminess by firm
tapping with a hammer and shall inspect for cracks, both in the presence of
the Contracting Officer's representative, immediately before completion of
the contract, and shall replace any showing drumminess or cracking. If
mortar placed with a mortar gun is used, the gun shall be a small
compressed air-operated gun to which the mortar is slowly hand fed and
which applies the mortar to the surface as a high-pressure stream, as
approved. Repairs made using shotcrete equipment will not be accepted.
The mortar used shall be the same mortar as specified for damp-pack mortar
repair. If gun-placed mortar is used, the edges of the cut shall be
beveled toward the center at a slope of 1:1. All surface applied mortar
repairs shall be continuously moist cured for at least 7 days. Moist
curing shall consist of several layers of saturated burlap applied to the
surface immediately after placement is complete and covered with
polyethylene sheeting, all held closely in place by a sheet of plywood or
similar material rigidly braced against it. Burlap shall be kept
continually wet.
3.11.2.2
Repair of Deep and Large Defects
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NOTE: Use this paragraph only for areas where the
designer considers this degree of repair acceptable;
otherwise require removal and replacement of
concrete containing these types of defects.
**************************************************************************
Deep and large defects will be those that are more than 150 mm 6 inches
deep and also have an average diameter at the surface more than 450 mm 18
inches or that are otherwise so identified by the Project Office. Such
defects shall be repaired as specified herein or directed, except that
defects which affect the strength of the structure shall not be repaired
and that portion of the structure shall be completely removed and replaced.
Deep and large defects shall be repaired by procedures approved in advance
including forming and placing special concrete using applied pressure
during hardening. Preparation of the repair area shall be as specified for
surface application of mortar. In addition, the top edge (surface) of the
repair area shall be sloped at approximately 20 degrees from the
horizontal, upward toward the side from which concrete will be placed. The
special concrete shall be a concrete mixture with low water content and low
slump, and shall be allowed to age 30 to 60 minutes before use. Concrete
containing a specified expanding admixture may be used in lieu of the above
mixture; the paste portion of such concrete mixture shall be designed to
have an expansion between 2.0 and 4.0 percent when tested in accordance
with ASTM C 940. A full width "chimney" shall be provided at the top of
the form on the placing side to ensure filling to the top of the opening.
A pressure cap shall be used on the concrete in the chimney with
SECTION 03300A
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