All modern slipform pavers consolidate and shape concrete using an extrusion process that pulls or "slips" the forms continuously over and through the plastic concrete. Plastic concrete acts like a fluid, which means it cannot be compressed. When confined inside the paving machine, the energy applied to the concrete for consolidation or finishing is transmitted through the concrete in all directions back to the paver.
This is why uniformity is a critical issue in slipform paving. The squeezing of concrete must be constant to produce a continuous, uniform shape and finish. Uniformity in design (mix and geometrics), logistics (concrete supply and delivery), and energy levels (vibration, squeeze, and movement) are all vital for satisfactory machine performance and paving results.
Despite its modern complexities, the slipform paving process still consists of using a series of standard concrete tools to perform the functions of consolidation and finishing: an auger or paddle for uniform concrete distribution in front of the paver, a strikeoff, a tamper bar (also used for consolidation), and a finishing tool (the profile pan). Often additional equipment for secondary finishing of the concrete surface behind the paver is used to remove slight irregularities and provide a tight surface microtexture.