Slipforming

Slipforming is a civil engineering construction method in which a continuously moving formwork is used to cast a concrete structure, such as a tower, silo, dam wall or road pavement, in one continuous pour rather than in separate sections. The form is raised or advanced gradually, typically by hydraulic jacks climbing a set of vertical rods, at a rate matched to the concrete's curing so that the material has enough strength to support itself as it emerges from the bottom of the form. Slipforming produces a seamless structure without the construction joints that section-by-section pours leave, and it has been used to build tall concrete towers, grain elevators and the elevator and stair cores of high-rise buildings.