Rev 8-14-97 CEMENT CONCRETE PAVEMENT
CRACKING AND SEATING The Standard Specifications are revised as follows: SECTION 311, BEGIN LINE 1, INSERT AS FOLLOWS: SECTION 311 -- CEMENT CONCRETE PAVEMENT CRACKING AND SEATING 311.01 Description. This work shall consist of cracking and seating existing cement concrete pavement prior to placement of a HMA overlay. 311.02 Equipment. The device used for cracking shall be an impact hammer capable of delivering such energy as may be necessary to satisfactorily crack the pavement as described below. The hammer shall be designed to prevent penetration into or spalling of the existing surface. A pneumatic-tire roller with a body suitable for ballasting with water, with a minimum gross weight of 36 Mg (40 tons), shall be used to seat the cracked pavement. The roller shall have four rubber-tired wheels equally spaced across the full width and mounted in line on a rigid steel frame such that all wheels carry equal loads, regardless of surface irregularities. Tires shall be inflated to the pressure necessary to obtain the surface contact pressure to satisfactorily seat the pavement slab. Ballast loading shall be regulated so as to allow the roller to be emptied for crossing bridge structures or other weight-restrictive features. Gauges shall be such that the gross roller weight may be determined in the field. The roller shall be towed with a rubber-tired prime mover. 311.03 Cracking and Seating. Subsurface drains shall be installed along the edges of pavement prior to the cracking of the cement concrete pavement. The existing concrete pavement shall be cracked so as to produce full depth, generally transverse, hairline cracks at a nominal longitudinal spacing of 450 to 600 mm (18 to 24 in.). Occasional spacing may be up to 750 mm (30 in.). Not more than 20 percent of the area, as determined by check sections, may be spaced at greater than 600 mm (24 in.) spacing. A continuous longitudinal crack shall not be formed. The device used for cracking shall not strike directly on existing cracks, joints, or D cracked areas. Such device shall be operated so that the existing crack or joint becomes a part of the desired cracking pattern. The height of the impact hammer shall be 600 mm (24 in.). If this height causes destruction or visible damage to the pavement, the 600 mm (24 in.) dimension may be lowered in 50 mm (2 in.) increments until a cracking pattern determined to be satisfactory is obtained. The height shall not be less than 450 mm (18 in.). The Contractor shall furnish and apply water to dampen the cracked section to enhance the visual determination of the cracking pattern. Flour may be used in lieu of water if it adequately shows the cracking pattern. It may be difficult or impossible to obtain transverse cracks during daylight hours when the ambient and pavement temperatures are high and the pavement is in a high compression mode. When these conditions exist, it may be required that the cracking operation be accomplished at times other than daytime hours. The pavement temperature will be monitored to determine the most feasible time period. Relief joints of 75 mm to 100 mm (3 to 4 in.) width shall be cut at a minimum of approximately every 450 m (1,500 ft) and a maximum of approximately every 600 m (2,000 ft) throughout the length of the pavement that is to be cracked and seated. The relief joints shall be located in pavement areas which are determined to be in structurally sound condition. They shall be cut no closer than 3 m (10 ft) from the nearest contraction joint and at least 24 h prior to the start of the crack and seat operation. The device used to cut the relief joints shall not leave a smooth face on the sides of the joint. The saw cut shall be through the concrete pavement, but shall not cut into the subbase material for a depth of more than 50 mm (2 in.). The cracking operation shall start 600 mm (24 in.) from the first saw cut relief joint and proceed toward the next cut relief joint. If longitudinal cracking occurs at the same point along the 600 m (2,000 ft) section, the breaker shall be moved to the next previously sawed relief joint. The direction of operation shall be reversed to eliminate as many longitudinal cracks as possible. Following cracking, the concrete pavement shall be rolled with the specified pneumatic roller. Three passes shall be made. The Contractor shall furnish and apply water or flour onto a section of pavement a minimum of once each day to verify that the specified crack pattern is being maintained. Additional check sections will be required if problems are encountered. Adjustments shall be made to the energy or striking pattern when the Engineer deems necessary, based on the sections checked or the field conditions. Once the cracking procedure is completed, the relief joints shall be filled with class A concrete in accordance with 702. However, the coarse aggregate shall be size No. 11 stone and the cement content shall be a minimum of 446 kg/m3 (752 lb/cu yd). The concrete shall be consolidated during placement to eliminate voids. All relief joints shall have dowel bars inserted across them to provide load transfer in accordance with 311.04. Cracked and seated pavement shall not be exposed for more than 15 calendar days before HMA operations are initiated. The placement of HMA surface materials shall be completed on the pavement lanes prior opening to traffic.
311.04 Dowel Bar Placement. Dowel bars shall be used to provide load transfer at each existing random crack location. Dowel bars shall be smooth and epoxy coated, 32 mm (1.25 in.) in diameter by 460 mm (18 in.) long. Chairs used to support dowels shall be of a plastic type for clearance of 13 to 25 mm (1/2 to 1 in.) above the bottom of the saw slot. The separator shall be field constructed with a 3 mm (1/8 in.) minimum foam core construction board. The separator shall be at least as thick as the width of the crack at the time of repair. End caps shall be plastic and shall slide over the end of the dowel bar leaving 13 mm (1/2 in.) for contraction. Type III cement in accordance with 901.01(b) shall be used. Slots of 55 to 65 mm (2 1/4 to 2 1/2 in.) width shall be made in the pavement as required to accommodate chairs. The length shall be sufficient to permit the dowel bar with cap and chairs to rest on the bottom of the saw slot. The depth shall be D/2 + 16 mm (D/2 + 0.625 in.) plus the effective height of the chair. The saw slot shall be cleaned by means of sand blasting. Remaining sand shall be removed by means of compressed air. The bar shall be placed with chair, end cap, and separator attached in the slot. End caps shall be placed on alternate ends of the dowel bars. The separator shall extend from the bottom of the slot to the top of the existing pavement. The separator shall be placed in line with one edge of the sawed relief joint. The same edge shall be used for all dowel bars. The dowel shall be tamped into place. The slot shall be filled with type III cement mortar and consolidated with an internal vibrator. Aggregate may be added to the mix only in the material used over the top of the dowels. The filled slot shall be troweled to match the existing pavement. Curing shall be in accordance with the manufacturer's specifications. The filled slot shall be covered during curing with a plastic sheet when the ambient temperature is above 29E C (85E F). The area shall be opened to traffic after curing is complete.
311.05 Method of Measurement. Cement concrete pavement cracking and seating will be measured by the square meter (square yard). Saw cutting of relief joints will be measured by the meter (linear foot) of joint cut. 311.06 Basis of Payment. Cement concrete pavement cracking and seating will be paid for at the contract unit price per square meter (square yard) complete in place. The cutting of the sawed relief joints will be paid for at the contract unit price for full depth saw cut. Payment will be made under: Pay Item Metric Pay Unit Symbol (English Pay Unit Symbol)
Cement Concrete Pavement Cracking and Seating................. m2 (SYS) The costs of maintaining the cracked and seated pavement in suitable condition for traffic, if required; placement of dowel bars and concrete filling mixture; all labor; equipment; materials; and necessary incidentals shall be included in the costs of the pay items.
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