|FHWA > Engineering > Pavements > Concrete > HIF-07-019 > Appendix C|
Precast Concrete Panel Systems for Full-Depth Pavement Repairs: Field Trials
Sample Specification for Precast Full-Depth Concrete Pavement Repair
MICHIGAN DEPARTMENT OF TRANSPORTATION SPECIAL PROVISION FORPRECAST FULL DEPTH CONCRETE PAVEMENT REPAIR
a. Description. The work consists of fabricating and installing precast full-depth concrete pavement repairs at locations shown on the plans, or as directed by the Engineer. All work shall be according to the Standard Specifications for Construction and this special provision.
b. Materials. The concrete used in the fabrication of the precast panels shall be MDOT Grade P1 according to the Standard Specifications for Construction. The Engineer will provide the concrete mix proportions based on the contractor's materials selection.
The fabrication of the precast panels shall be done according to the special details included in this special provision.
Prior to stripping the forms, the precast panels shall have a minimum flexural strength of 500 psi. The precast panels shall have a 7 day continuous wet cure commencing immediately after final finishing with all exposed surfaces covered. The precast panels shall have a minimum cure of 14 days prior to placement.
The Contractor shall supply test data (slump, air voids, unit weight) for the fresh concrete, and flexural and compressive strengths for the hardened concrete after 7, 14, and 28 days (if applicable).
Concrete patching materials used to backfill the slots shall be selected from the Qualified Products List for Prepackaged Hydraulic Fast-Set Patching included in the Materials Source Guide. The patching material shall be extended with aggregate, up to the maximum amount specified in the Qualified Products List. If a curing compound is recommended by the manufacturer of the patching material, it shall be in accordance with subsection 903.05 of the Standard Specifications for Construction.
The leveling material shall be a flowable fill. The Engineer will provide the mix design.
The aggregate used in the patching materials shall be a dry, clean, crushed 26A gradation conforming to subsection 902.03 of the Standard Specifications for Construction, or equivalent as approved by the Engineer.
c. Construction. All the saw cutting on the existing concrete pavement shall be done in accordance with paragraph six of Section 603.03.B.1.b of the Standard Specifications for Construction. The Contractor is responsible for insuring that the precast patch and dowels will properly align with the removal area and the dowel bar slots.
The slots for the dowel bars shall be cut using a diamond-bladed saw machine. The machine shall be capable of cutting a minimum of three slots simultaneously that are centered over the edge of the repair. Three slots will be made in each wheel path. The bottom of the slots shall be have a minimum flat distance of 10 inches into the existing concrete pavement.
Any loose concrete shall be vacuumed or removed from the slots and all surfaces shall be dry, abrasive blast cleaned. Any exposed steel shall be blast cleaned to remove any rust or laitance. Immediately prior to placement of the patching material, the slots shall be final cleaned with moisture-free, oil-free compressed air having a minimum pressure of 90 psi.
The slot walls and bottom must be dry before placement of the patching material, unless otherwise recommended by the manufacturer.
The patching material shall be mixed with a portable or mobile mixer. The patching material shall be extended, by weight of the cement, with 26A aggregate up to a maximum extension rate as specified in the Qualified Products List, and placed according to the manufacturer's recommendations. The patching material shall then be consolidated using a hand-held vibrator if recommended by the manufacturer. The surface of each dowel-bar patch shall be finished flush with the surrounding concrete and cured according to manufacturer's recommendations, even if diamond-grinding of the concrete surface is to occur afterward.
The Engineer reserves the right to sample the patching material and conduct compressive strength testing to verify that the mixture is meeting the requirements stated below.
The area where the precast patch is to be placed shall be excavated to a minimum of 12 inches below the top of the existing concrete pavement and shall be free of all debris and standing water.
The existing granular base material shall be moistened just prior to the placement of the flowable fill to prevent absorption of mix water into the underlying granular base material.
Flowable fill shall be placed in the excavated pavement area and leveled to the appropriate depth below the top of the existing pavement to allow the precast panel to be placed level with the top of the existing concrete pavement.
The width of the transverse joints between the precast panel and the existing pavement shall be equal on both sides of the precast panel with a width of 3/4 inch ± 1/4 inch.
The smoothness of the roadway after placement of the precast pavement patches shall meet the straightedge requirements in paragraph three of subsection 603.03.B.8 of the Standard Specifications for Construction.
Joint sealing shall be done in according to requirements specified for resealing transverse and longitudinal pavement joints described in Section 603.03 of the Standard Specifications for Construction.
Patching of the lift holes shall be done using the same material used to back fill the dowel bars.
d. Opening to Traffic. Vehicular traffic shall not be permitted on the panel area until the prepackaged hydraulic fast set material used to fill the dowel bar retrofit slots has attained the proper curing time and compressive strength as specified by the product manufacturer.
e. Measurement and Payment.
Measurement forPrecast Pavement Patch,10 inch is based on each in-place precast patch.
Payment forPrecast Pavement Patch,10 inch includes all labor, equipment, and materials required to remove, and dispose of the existing concrete in the patch area, cut and clean the dowel bar slots, repair spalls, place the flowable fill, cast the precast patch, transport and install the precast patch, backfill the dowel bar slots and lift holes with a concrete patching material, sealing the joints, and cure the backfill material.