ITEM 256 Bonded Patching of Portland cement concrete Pavement
256.01
Description
256.02
Materials
256.03
Equipment
256.04 Removal
of Unsound Concrete
256.05
Preparation of Patch Area
256.06 Bonding
Grout Installation
256.07 Placing
Patching Material
256.08
Curing and Loading
256.09 Method
of Measurement
256.10 Basis of
Payment
256.01 Description. This work consists of
bonded patching of portland
cement concrete pavements at spall areas adjacent to cracks or joints or other
areas of the pavement as designated by the Engineer. This work involves
removing all loose and unsound concrete and asphalt material patches; removing
sound concrete as directed; preparing the surface; applying a bonding grout if
required; reconstructing the joint or crack; and mixing, placing, finishing,
and curing of the patching material called out in the pay item description.
256.02 Materials. Furnish materials conforming to:
Portland
cement....................................................... 701.05
Fine
aggregate.......................................................... 703.02
Coarse aggregate, No. 8
size.................................... 703.02
Curing
material........................................................ 705.07
Air-entraining
admixture.......................................... 705.10
Quick setting concrete
mortar.................................. 705.21
256.03 Equipment. Use a milling machine, concrete
saw, jackhammers, or other approved equipment to remove existing surface
material. Provide oil and moisture free compressed air for cleaning and
abrasive blasting the prepared area. Provide an on-site concrete mixer
capable of mixing a minimum of 2-cubic foot (0.06 m³) batches of patching
material. Provide chipping hammers not heavier than the nominal 35-pound
(16 kg) class.
256.04 Removal of Unsound Concrete. The
Engineer will locate and mark all areas to be repaired prior to concrete
sawing. Provide the Engineer with aerosol spray paint to outline the
areas for repair. Repair areas will be rectangular or square in shape
with dimensions as required to envelope the surface deterioration.
Saw
the perimeter of all areas designated for removal to a depth of 1 inch (25 mm)
to produce a vertical or slightly undercut face. Make additional saw cuts
as required to facilitate removal. Remove all unsound concrete, all
asphalt material, and all obviously loose and
disintegrated concrete within the patch area. Remove sound concrete where
required to achieve the minimum depth within the patch area. Remove
concrete by jack hammering or milling. The minimum depth of any partial
depth repair is 1 1/2 inch (38 mm) except at the perimeter saw cuts.
Operate chipping hammers at an angle of less than 45 degrees measured from the
surface of the pavement. During removal of unsound concrete, remove all
pavement reinforcing exposed in the patch areas using a cutting tool or a
torch.
256.05 Preparation of Patch Area. Before
applying bonding grout and/or the patching material, abrasive blast the exposed
concrete surfaces to which the patching material is to bond until free of loose
particles, oil, dust, traces of asphalt concrete and joint sealer, and other
contaminates. Remove all sandblasting residue with compressed air just
prior to placing the concrete bonding grout or the patching material. Do
not begin abrasive blasting operations until implementing reasonably available
engineering controls to limit fugitive dust that are acceptable to the
Engineer. Conform to State, regional, and local
government agency requirements regarding control of dust generated by the
blasting operation. For Types B and C patching materials that do not use water as the
activator, perform additional surface preparation according to the patching
material manufacturer’s recommendations.
Recreate
joints in or along the patch using a joint board that extends below the
prepared surface and has a width equal to the existing joint. One hour
after placing the patching material, remove the joint board in a manner that
does not damage the patch.
256.06 Bonding Grout Installation. For
bonding Type A patches, use grout that consists of
equal parts, by volume, of portland cement and sand,
mixed with sufficient water to form a stiff slurry. Using a stiff brush
or broom, apply a thin, uniform coating of grout to the prepared surface.
Scrub the grout onto the dry surfaces of the prepared area to be patched
immediately before placing the patching material. Do not allow excess
grout to collect in low spots. Do not allow the grout to dry before
placing the new concrete. Paint grout over all sawed joints between the
new and existing concrete immediately after completing the finishing.
For
bonding Types B and C patches, conform to the patching material manufacturer’s
recommendations.
256.07 Placement of Patch Material. Use Type
A, B, or C patch material as follows:
A. Type A. Provide patch material consisting of one part
high early strength portland cement, one and a half
parts fine aggregate, and one and a half parts No. 8 coarse aggregate by
volume. Add sufficient air-entraining admixture to maintain an air
content of 8 ±2 percent. Add enough water to obtain the minimum slump
practical for placing, and do not allow slump to exceed 4 inches (100
mm). Mix the materials on site. Do not use ready-mixed
concrete. Place the concrete mixture in the patch area while the bonding
grout is still wet. Slightly overfill, vibrate, and strike off the
concrete.
B.
Type B. Provide patch
material consisting of quick setting concrete mortar 705.21, Type 1 or 2. Mix and place the
mortar according to the manufacturer’s recommendations. Add coarse
aggregate, as needed, according to the manufacturer’s instructions. Place
the concrete mixture in the patch area. If the manufacturer’s requirements
specify using bonding grout, place the concrete mixture while the bonding grout
is still wet. Slightly overfill, vibrate, and strike off the concrete.
C.
Type C. Provide patch
material consisting of a blend of quick setting concrete mortar 705.21, Type 2 and selected aggregates with
an activator. Mix and place these materials according to the
manufacturer’s recommendations. Add coarse aggregate, as needed,
according to the manufacturer’s instructions. Place the concrete mixture
in the patch area. If the manufacturer’s requirements specify using
bonding grout, place the concrete mixture while the bonding grout is still
wet. Slightly overfill, vibrate, and strike off the concrete.
Screed patches
12 feet (3.7 m) and less in length parallel to the centerline. Screed
patches over 12 feet (3.7 m) in length perpendicular to the centerline.
While the
concrete is still in a plastic state, test the surface for trueness and for
being flush with the edges of the adjacent slabs using a 10-foot (3 m)
straightedge. Place the straightedge parallel to the pavement centerline
with the ends resting on the existing pavement and draw the straightedge across
the patch. Where the straightedge does not remain in contact with the
existing pavement while drawing it across the patch, correct all high or low
areas exceeding 1/8 inch in 10 feet (3 mm in 3 m). Recheck the concrete
surface after making corrections to assure that the patch area meets the
surface tolerance before the patching material hardens.
Texture
the new concrete surface similar to that of the surrounding pavement.
256.08 Curing and Opening to Traffic. Cure Type
A patches according to 451.10, except allow the patch to attain a
modulus of rupture of 400 pounds per square inch (2.8 MPa)
before opening to traffic. Cure Types B and
C patches according to the manufacturer’s
recommendations.
256.09 Method of Measurement. The
Department will measure the quantity of Bonded Patching of Portland Cement
Concrete Pavement, Type ___ by the number of square feet (square meters) of the
exposed surface of all patches, irrespective of the depth of the patch,
repaired in the complete and accepted work. If the actual measured area
of a patch is less than 2 square feet (0.2 m²), the Engineer will increase each
such measurement to 2 square feet (0.2 m²).
256.10 Basis of Payment. The
Department will pay for accepted quantities at the contract price as follows:
Item
Unit
Description
256
Square
Feet
Bonded Patching of Portland
(Square
Meter)
Cement Concrete Pavement, Type __