Little more than a decade ago, slip-form paving was a novelty on the American construction scene. Spurred by a number of factors-ncluding the need for lower manpower requirements, economy, and the tremendous impetus given to pavement construction by the Interstate Highway System- slip-form paving has 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, strike off 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, an 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 the 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.