ITEM 258 LOAD TRANSFER RETROFIT
258.01 Description. This work consists of sawing slots across transverse cracks, cleaning the
slot, injecting caulking filler, placing a dowel or deformed bar in the slot, and filling the slot with a patching material.
258.02 Materials. Furnish a one part silicone sealant which does not require a primer for bond
to concrete and conforms to the following Table: Properties Requirements Flow, ASTM D5893 0.3 inches(7.6 mm) maximum Extrusion Rate, ASTM C1183 method A 75 to 350 grams/minute Tack free time @ 77 °F ±3 °F (25 °C ±2 °C) – ASTM C679 20 to 90 minutes Specific Gravity - ASTM D792, Method A 1.010 to 1.515 Durometer Hardness - Shore A, cured 7 days @ 77 °F ±3 °F (25 °C ±2 °C) and 45 to 55% R.H.; ASTM D2240 10 to 25 at 0 °F (-18 °C) Tensile Stress -@ 150% elongation, 7 day cure @ 77 °F ±3 °F (25 °C ±2 °C) and 45 to 55% R.H.; ASTM D412, Die C 45 psi (310 kPa) maximum Elongation - 7 day cure @ 77 °F ±3 °F (25 °C ±2 °C) and 45 to 55% R.H.; ASTM D412, Die C. 800% minimum Bond to Concrete Mortar Briquettes - Air cured 12 days @ 77 °F ±3 °F (25 °C ±2°C);[1] 50 psi (345 kPa) minimum Movement Capability and Adhesion [2] Extend 100% and compress 50%; No adhesive or cohesive failure after 10 cycles at 0 °F (-18 °C) Shelf Life 9 months from date of shipment from manufacturer [1] Bond to Concrete Mortar Briquettes molded in accordance with AASHTO T 132 sawed in half and bonded with a thin section of sealant and tested in accordance with AASHTO T 132. Briquettes will be dried to constant weight in oven at 212 °F ±9 °F (100 °C ±5 °C). [2] Movement Capability and Adhesion: Prepare 1-inch × 2-inch × 3-inch (25 mm × 50 mm × 75 mm) concrete blocks in accordance with ASTM C719. A sawed face will be used for bond surface. Seal 2 inches (50 mm) of block leaving 1/2 inch (13 mm) on each end of specimen unsealed. The depth of sealant will be 3/8 inch (10 mm) and the width 1/2 inch (13 mm). Subject sealant to movement in accordance with ASTM C719. The magnitude of the movement will be as specified, and the rate of extension or compression will be 1/8 inch (3.2 mm) per hour. Furnish materials conforming to: Aggregate .................................. 703.02.A.3 Curing material ................... 705.07, Type 2 Dowel bars ....................... 709.13 or 705.01 Deformed bars .................. 705.01 or 709.00 Bar chairs . 709.14 or non-metallic material Preformed filler ................................ 705.03 Patching material. Must meet the performance requirements of ASTM C928, Table 1, R3 concrete material with the following exceptions and additions: Final Set Time (ASTM C403) ................. ............................... 25 minutes minimum Length Change (ASTM C157) @ 4 days .................... ±0.13% maximum Freeze Thaw Durability Factor (ASTM C666) ...................... Procedure A @ 300 cycles ................. or Procedure B @ 350 cycles, Durability Factor: ............ 90% minimum Furnish patching material according to the Departments Qualified Products List (QPL) Mix prepackaged materials that contain all aggregates needed to produce the desired concrete as specified by the manufacturer. For bagged cementitious materials that need additional aggregates, grade the aggregate according to the patching material manufacturer’s recommendation except ensure that 100% passes the 1/2 -inch (12.5 mm) sieve and a minimum of 85 percent, by weight, passes the 3/8-inch (9.5 mm) sieve.
258.03 Equipment. Furnish equipment to create slots that has a power driven gang type
assembly, consisting of diamond blade saws, capable of sawing a minimum of six sawcuts at one time to the required dimensions, without damage to the surrounding pavement. Furnish jack hammers weighing less than 30 pounds (13.6 kg). Furnish abrasive blast equipment capable of removing the saw slurry or other foreign material from the exposed surfaces leaving a clean, newly exposed concrete surface free of spalls, laitance, and all contaminants detrimental to achieving an adequate bond. Ensure water blasting pressure with abrasives in the water is 10,000 psi (690 bar) or less.
258.04 Construction. The Engineer will locate and mark cracks to be retrofitted. Provide the
Engineer with aerosol spray paint to mark the cracks to be retrofit. Construct 2 1/2-inch (65 mm) wide slots into the pavement to the required depth to place the center of the bar at mid -depth in the concrete slab. Ensure the slots are parallel to the centerline of the pavement. Saw the sides of the slots using the required sawing equipment. Make multiple saw cuts parallel to the centerline if necessary to properly remove material from the slot and to provide a level surface for the feet of the bar chairs. Chip out the concrete using jack hammers to create the slot. Do not operate jack hammers in a manner that causes damage to the surrounding concrete. Construct three slots, on one foot (0.3 m) centers, in each wheel path, as shown in the standard drawings. Do not allow traffic across the crack once the concrete has been removed from the slots until all six retrofit bars are in place, cured and completed. Do not allow the tires of construction vehicles to travel on slots where concrete has been removed. Clean the sides of the slots by approved blast methods to produce a rough surface. Ensure any blasting operation does not damage the surrounding pavement. 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. Caulk cracks at the bottom and sides of the slot with an approved silicone sealant in order to prevent any grout from entering the crack. Apply the sealant with a pressure applicator that forces it into the crack. Place a 1/2 inch (13 mm) thick preformed filler board on dowel bars to maintain the crack, as shown in the standard drawings. Ensure the filler board fits tight around the dowel and to the bottom and sides of the slot. Maintain the filler board in a vertical position and tight to all sides during placement of the patching material. Ensure the filler board extends from the bottom of the slot to the surface of the pavement. If for any reason the filler board shifts during placement of the patching material, r edo the dowel bar retrofit at no expense to the Department. Ensure the bar chair firmly holds the bar centered in the slot. Obtain the Engineer’s approval before using any bar chairs. The Engineer will reject any chair design that may allow movement of the bar during the placement of grout. Provide smooth dowel bars 1 1/2 inches (38 mm) in diameter and 18 inches (460 mm) long. Center the filler board on dowel bars. Coat dowel bars with a thin uniform coat of new light form oil as a bond- breaking material just prior to installation in the slot. Place an expansion cap on each end of dowel bars prior to installation. Ensure the expansion caps are tight fitting and made of non-metallic material which will allow 1/4 inch (6 mm) movement at each end of the dowel. Provide #11 (#36M) deformed bars 18 inches (460 mm) long. Use two chairs to firmly hold the bar in the slot during placement of the patching material. Furnish chairs that are a nominal 2 1/2 inches (65 mm) wide and center the bar across the crack. Ensure dowel bars vary no more than 1/4 inch (6 mm) from parallel to the pavement surface and the centerline of the pavement. Just prior to placement of the patching material, make one or more passes of an air blast to provide a dust-free, clean slot to insure an adequate bond of the patching material. Mix, place, and cure the patching material in accordance with the manufacturer’s recommendations. Consolidate the patching material using a vibrator approved by the Engineer . Place the patching material in the slot and finish to produce a smooth, even surface. Repair any damage to the pavement due to the Contractor ’s operation at no expense to the Department. Cure the patching material for a minimum of four hours before placing any vehicle loads on the repair, or as directed by the Engineer.
258.05 Method of Measurement. The Department will measure the quantity of Retrofit Dowel
Bars and Retrofit Deformed Bars by the actual number in the complete and accepted work.
258.06 Basis of Payment. Payment is full compensation for furnishing all materials including
paint; sawing and cleaning the slots; installing dowel chairs, dowels, deformed bars, bond breaker material, dowel bar end caps, sealant/caulking material, filler material, and patching material. The Department will not pay for additional work or materials required due to shifting of the filler board. The Department will not pay for any additional work to repair damage to the pavement caused by the Contractor. The Department will pay for accepted quantities at the contract unit price as follows: Item Unit Description 258 Each Retrofit Dowel Bar 258 Each Retrofit Deformed Bar 300 BASES
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