Little more than a decade ago, slip-form paving was a novelty on the American construction scene. Spurred by a number of factors- including the need for lower manpower requirements, economy, and the tremendous impetus given to pavement construction by the Interstate Highway System- slip-form pavinghas developed into a widely accepted method of paving.
Depending on the type of slip-form paver used, it can do the finish grading; spread the concrete over the subgrade; vibrate, tamp, strikeoff and shape the concrete to the desired thickness and surface conformation. Concrete used in slip-form paving is the same as that used in conventional form paving. The concrete should have a uniform consistency, a slump of about 2 inches. It is deposited directly in front of the paving machine or into a hopper box. The slip-form paver then goes into action. It spreads the concrete by means of a paddle. This is followed by vibrators, tampers, and oscillating bars in various configurations. After the consolidation, a extrusion meter extending the complete pavement width creates the correct surface conformation for the slab. There is little hand finishing required. A pigmented membrane curing compound is applied immediately. One of the big advantages of slip-form paving is economy. The reduction in personnel required and the speed at which the pavement can be laid often add up to considerable savings. The smoothness of slip-form pavement is also excellent with surface irregularities being caused by slumping of the concrete and/or an interruption of the forward movement of the slip-form paver.