Slip forming construction process
Slip forming is an evolution of conventional formwork or tilt-up construction and is a process used to cast concrete elements of a structure. It is a continuous formwork technique that moves upwards as the freshly poured concrete is made to harden into an element such as a column or wall. This process is a significant time saver over conventional construction and is at the same time very cost effective.
Slip forming utilizes self climbing internal formwork to cast the element being constructed. This formwork is an independent structure that runs the entire height of the element and is made of steel, timber or composite panels. The formwork will usually include pull cords, rolling wheels and adjustable props to enable it to climb.
This construction technique is predominantly used for major civil engineering and architectural projects such as bridges, overpasses, and tall structures. Slip forming can be used in both precast and in-situ construction methods and is particularly efficient when forming large-scale elements such as retaining walls, bridge abutments, and bridge piers.
The requirement for a slip forming construction is a concrete mix that is amenable to casting. Therefore, prepared concrete must be readily available and be poured continually to ensure the wet mix does not transition to the dry state before completion.
The slip forming process begins with the foundation concrete being poured. Next, the formwork is placed onto the foundation and adjusted in order to the be level. The adjustable props and pull cords will we used to make sure the formwork is properly centered and securely fastened.
Once the formwork is in place, the prepared concrete is loaded into a hopper and released onto the formwork to a designated level. The pull cords and adjustable props are then re-adjusted to raise the formwork to a higher position and maintain it as the new layer is poured. As the formwork advances, it must continue to be level and securely fastened.
After each layer of concrete is poured and allowed to harden, more concrete is poured to the same height. This process is repeated until the desired height of the element is reached.
Once the element is complete, the formwork is then dismantled and re-used.
Slip forming is an effective construction technique that can greatly reduce construction time and cost. It is fast and economical and provides superior structural results over conventional formwork or tilt-up methods. Moreover, this method of casting allows complex and intricate elements to be produced quickly and efficiently.
