Slipform Construction Technique refers to casting concrete in dynamic or moving formwork in contrast to the most commonly used formwork that needs dismantling & re-installing at frequent intervals. This system of construction ensures that the entire formwork system keeps moving upwards steadily even as the concreting progresses. This method is quite suitable for large diameter silos, chimneys or similar structures. For small-scale work of similar nature, however, jumpform system may have an edge over slipform technique both from time as well as economic point of views. Practically, silos, chimneys etc. with base diameters of more than 60 – 70m are ripe for adoption of this method of casting. Apart from ensuring continuous, monolithic pour of concrete, it also renders jointless, smooth outer appearance.
Slipform technique of concreting necessitates round the clock pouring including during weekends. Nevertheless, for a tall structure which tapers substantially as it’s height increases, breaks in concreting may be needed in order to facilitate reduction of forms which becomes necessary as the diameter decreases considerably at greater heights. Such breaks are carefully pre-planned and are subjected at suitable elevations depending on the quantum of taper and the height of the structure.
Slipform technique demands careful preplanning, especially concerning production, placing & curing of concrete; control of setting time of concrete; control on lifting, changing of stack parameters like diameter, wall thickness, inclination of stack etc.; selection of materials for slipform; operation & maintenance of the slipform equipment and so on.
In here, some more details on this technique of construction will be briefly discussed in the following posts. (continued in part-II)