ITEM 519 PATCHING CONCRETE STRUCTURES
519.01
Description
519.02
Materials
519.03 Removal
of Disintegrated Concrete
519.04
Preparation of Surface
519.05 Placing
of Reinforcing Steel
519.06 Placing,
Finishing, and Curing of Concrete
519.07 Method
of Measurement
519.08 Basis of
Payment
519.01 Description. This work consists of
removing all loose and disintegrated concrete; preparing the surface;
furnishing and placing reinforcing steel including welded steel wire fabric,
dowels, and expansion bolts; placing forms; and placing concrete patches,
including curing of same.
519.02 Materials. Furnish materials conforming to:
Concrete, Class QC 2
*........................................ 499, 511
Dowels......................................
709.01, 709.03,
or 709.05
Reinforcing
steel........................................................... 509
Welded steel wire
fabric.......................... 709.10 or 709.12
*
For aggregate for superstructure, conform to 703.02
and use No. 57 or 8 size.
519.03 Removal of Disintegrated Concrete. Remove
all loose and disintegrated concrete from the areas to be repaired in such a
manner and to such an extent as to expose a sound concrete surface.
Provide patches at least 4 inches (100 mm) deep, except on top horizontal
surfaces, provide patches at least 3 inches (75 mm)
deep. Remove sound concrete (beneath the disintegrated concrete) for a
depth of not less than 1/4 inch (6 mm) and not more than 1 inch (25 mm),
provided that the above minimum depth of patch is maintained. Make square
or, preferably, slightly undercut shoulders having a depth of not less than the
specified minimum depth of the patch at the edges of all patches.
Only
use pneumatic or hand tools that give results satisfactory to the Engineer in
the removal of the disintegrated concrete and in preparing and shaping the
areas to be patched.
If
working around reinforcing steel, avoid damaging or debonding
any reinforcing steel, that is un-corroded and
completely embedded in sound concrete. Ensure there is no shattering of
the concrete, beyond the area to be patched. If the area around the reinforcing
steel is either embedded in unsound concrete or the reinforcing steel is
exposed during removal, continue to remove the concrete around the reinforcing
steel to completely expose the reinforcing and provide at least a 1 inch (25
mm) clearance around the reinforcing. The 1 inch (25 mm) clearance may be
reduced to 1/2 inch (13 mm) if the patching concrete uses No. 8 coarse
aggregate.
Adequately
support reinforcement that is loose, and tie it back into place. Replace
reinforcement damaged during removing concrete.
519.04 Preparation of Surface. After
removing all disintegrated and loose concrete, properly shape the area to be
patched, and install dowels or expansion bolts as necessary to hold the wire
fabric to be used in the patch. Thoroughly clean the surface of the area
to be patched and all exposed reinforcing steel of all dirt, dust, or other
foreign materials with water, air under pressure, or any other method that
produces satisfactory results. Thoroughly drench the surface with clean
water. Before placing the concrete, allow the surface to dry to a damp
condition.
519.05 Placing of Reinforcing Steel. The
Department will not require reinforcement for patches on top horizontal
surfaces. Reinforce patches on other surfaces with welded steel wire
fabric either 2 x 2 inch (50 x 50 mm) using wire size number W 0.9, or 3 x 3
inch (75 x 75 mm) using wire size number W 1.4. Cover the entire area of
the patch with the fabric, and place and hold the fabric approximately 1 inch
(25 mm) from the completed exposed surface of the patch. Securely
fasten the fabric to the reinforcing steel in the original structure exposed in
removing the disintegrated concrete. If no reinforcing steel is exposed
or it is not practical to fasten the fabric to exposed steel, install dowels or
expansion bolts at a distance not to exceed 18-inch (0.5 m) centers in both
directions, and fasten the fabric to these dowels or bolts.
519.06 Placing, Finishing, and Curing of Concrete. Place and
finish Class QC 2 concrete according to Items 499
and 511.
Remove
the forms within 24 hours after placing the concrete, and finish all exposed
surfaces by rubbing to match the surrounding concrete. Apply membrane
curing according to 511.17, Method B,
immediately after rubbing the surfaces.
After
curing and before final acceptance, sound all patched areas. Remove and
replace all unsound or visibly cracked areas.
519.07 Method of Measurement. The
Department will measure Patching Concrete Structures by the number of square
feet (square meters) of the exposed surfaces of all completed patches,
irrespective of the depth or thickness of the patch. If a patch includes
corners or edges of members such as beams, curbs, and columns, the Department
will measure all of the exposed surfaces. If a patch extends completely
through a member of a slab, the Department will measure both exposed surfaces.
519.08 Basis of Payment. The
Department will pay for accepted quantities at the contract price as follows:
The
Department will not pay for replacing reinforcement damaged during concrete
removal.
The
Department will not pay for removing and replacing of patched areas that are
unsound or visibly cracked.
Item
Unit
Description
519
Square
Foot
Patching Concrete Structures
(Square Meter)