Figure 11-50.—Rolling a longitudinal joint.HOT JOINTS.— A hot joint is a joint between twolanes of bituminous mix placed at approximately thesame time by pavers working in echelon. This type oflaydown produces the best longitudinal joint, becauseboth lanes are at, or near, the same temperature whenrolled. The material compacts into a single mass underthe roller, resulting with little or no difference in densitybetween the two lanes. When you are paving in echelon,the breakdown roller following the lead paver leaves a3- to 6-inch unrolled edge that the second paver follows.The second paver and roller should stay as close aspossible to the first paver to ensure a uniform density isobtained across the joint. The roller following thesecond paver compacts the hot joint on its first pass(fig. 11-51).COLD JOINTS.— A cold joint is a joint betweentwo lanes, one of which has cooled overnight or longerbefore the adjoining lane is placed. Because of thedifference in temperature between the two lanes, thereis a difference in density between the two sides of thejoint. The longitudinal joint should be rolled directlybehind the paver.Breakdown RollingBreakdown rolling may be accomplished with staticor vibratory steel-wheel rollers. Breakdown rollingshould start on the low side of the hot bituminous mat,which is usually the outside of the lane being paved, andprogress toward the high side. The reason for this is thathot bituminous mixtures tend to migrate towards the lowside of the mat under the action of the roller. If rollingis started on the high side, this migration is much morepronounced than if the rolling progresses from the lowside. When adjoining lanes are placed, the same rollingprocedure should be followed, but only after com-paction of the longitudinal joint.A rolling pattern that provides the most uniformcoverage of the lane being paved should be used. Rollersvary in width, and a single recommended pattern thatapplies to all rollers is impractical. For this reason, thebest rolling pattern for each roller being used should beworked out and followed to obtain the most uniformcompaction across the lane.The rolling pattern not only includes the number ofpasses but also the location of the first pass, the sequenceof succeeding passes, and the overlapping betweenpasses. Rolling speed should not exceed 3 mph. Inaddition, sharp turns and quick starts or stops are to beavoided.For thin lifts (a lift of less than 2 inches compactedthickness), a recommended rolling pattern for staticFigure 11-51.—Rolling a hot longitudinal joint.11-27
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