ITEM 258 DOWEL BAR RETROFIT

258.01 Description

258.02 Materials

258.03 Equipment

258.04 Construction

258.05 Method of Measurement

258.06 Basis of Payment

 

258.01 Description. This work consists of sawing slots across transverse cracks, cleaning the slot, injecting caulking filler, placing a dowel in the slot, filling the slot with a patching material, and establishing a joint by saw cut.

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, C1183 method A

75-350 grams/minute

Tack free time @ 77 F 3F (25C 2C) ASTM C679

20-90 minutes

Specific Gravity - ASTM D 792, Method A

1.010-1.515

Durometer Hardness - Shore A, cured 7 days @ 77F 3 F (25C 2C) and 45-55% R.H.; ASTM D 2240

10-25 at 0F (-18C)

 

Tensile Stress -@ 150% elongation, 7 day cure @ 77F 3F (25C 2C) and 45-55% R.H.; ASTM D 412, Die C

45 psi (310 kPa) maximum

 

 

Elongation - 7 day cure @ 77 F 3F (25C 2C) and 45-55% R.H.; ASTM D 412, Die C.

800% minimum

 

Bond to ConcreteMortar:Briquets - Air cured 12 days @ 77 F 3F (25C 2C);**

50 psi (345 kPa) minimum

 

Movement Capability and Adhesion ***

Extend 100% and compress 50%; No adhesive or cohesive failure after 10 cycles at 0F (-18C)

Shelf Life

9 months from date of shipment from manufacturer

 

**Bond to ConcreteMortar:Briquets 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. Briquets will be dried to constant weight in oven at 212 F 9F (100C 5C).

***Movement Capability and Adhesion: Prepare1-inch x 2-inch x 3-inch(25 mm x 50 mm x 75 mm ) concrete blocks in accordance with ASTM C 719. 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 C 719. 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

Curingmaterial......................................... 705.07, Type 2.

Dowel bars.............................................. 709.13 or 705.01

Dowel 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 manufacturers 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 three slots 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, latence, and all contaminants detrimental to achieving an adequate bond. Ensure water blasting with abrasives in the water is 10,000 psi (690 bar) or less.

258.04 Construction. The Engineerwill locate and mark cracks to be retrofitted. Provide the Engineer with aerosol spray paint to mark the cracks to be retrofit.

Cut two and one-half inch (65 mm) wide slots into the pavement to a depth which places the center of the dowel at mid-depth in the concrete slab. Make the slots parallel to the centerline of the pavement. 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 dowel bar chairs. Cut three slots, on one foot centers (0.3 m), 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 dowel 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 edge of the slots by approved blast methods to produce a rough surface. Insure 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 to maintain the crack, as shown in the plan details. Ensure the filler board fits tight around the dowel and to the bottom and edges of the slot. Maintain the filler board in a vertical position and tight to all edges during placement of the patching material. Ensure the filler board extends from the bottom of the slot to no more than 1-1/2 inches (38 mm) from the surface of the pavement. If for any reason the filler board shifts during placement of the patching material, redo the dowel bar retrofit at no expense to the Department.

Ensure the dowel bar chair firmly holds the bar centered in the slot. Obtain the Engineers approval before using any dowel bar chairs. The Engineer will reject any chair design that may allow movement of the bar during the placement of grout.

Use dowel bars 1-1/2 inches (38 mm) in diameter and 18 inches (460 mm) long. Center the filler board on the dowel. Coat the dowel bars with a thin layer of oil or other bond-breaking material just prior to installation in the slot. Place an expansion cap on each end of the dowels 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.

Use two chairs to firmly hold the dowel bar in the slot during placement of the patching material. Furnish chairs that are a nominal 2-1/2 inch (65 mm) wide and center the dowel bar across the crack. Ensure the bar varies 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 manufacturers 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. Cut a 1-1/2 inch (38 mm) deep by 1/4 inch (6 mm) wide saw cut, using a hand pushed single blade saw, to re-establish the crack. Make the saw cut within four hours of placing the patching material.

Repair any damage to the pavement due to the Contractors 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 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, bond breaker material, dowel bar end caps, sealant/caulking material, filler material, and patching material; and re-establishing the crack.

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