One operator elevates entire system, without the use of a crane.

The Australian designed Self Climbing Electro-Hydraulic Slipform System may be defined as a method of continuously moulding, or forming concrete, with the use of a moving formwork. The rate of movement, or slipping, is controlled by the setting or curing rate of the concrete, which must be capable of supporting at least its own weight when exposed by the moving formwork. This is undoubtedly the most unique aspect of slipforming, the ability of concrete to stand safely and unsupported within 2 to 4 hours after being placed into the formwork in a plastic state.

Slipforming as a method of construction was first used in the early 1930's for the erection of storage silos and similar structures. The system involved the use of manually operated jacks and timber formwork.

An evolution of the method has been taking place gradually over the years by Fabquip Construction Systems.

Today, Fabquip Slipform Systems are well known and accepted for the rapid construction of reinforced concrete wall structures such as silo complexes, chimneys, reservoirs, medium to highrise housing, office buildings, hotels, hospitals, bridge piers, inground shafts, caissons, dam structures, power stations etc. Of recent times reinforced concrete offshore oil production platforms are being built with this efficient method.

Technical services

Full Slipform Systems consulting services are available through Fabquip central engineering office. Fabquip technicians are available to assist and train the contractor in the assembly and operation of the slipform system. Click here to contact us.

The system

The apparent simplicity of the Slipform concept tends to camouflage the actual complexities that need to be thoroughly understood in the practical application of the system.

Concrete is placed inside the forms in shallow and regular layers of around 150 - 200mm.  Each layer is vibrated with high frequency immersion type vibrators.

In commencing any Slipform project, the forms must first be filled by layering in the concrete as described above.

Within 2½ - 3 hours of initial placement of the concrete, the vertical slipping of the formwork can commence. The formwork, at all times, must be kept as full of concrete as possible to allow the concrete the maximum period of time in the forms to gain strength before being exposed beneath the sliding forms. As the forms are slid or jacked upward, concrete continues to be layered into the top of the forms.

The speed of jacking is determined by the setting characteristics of the concrete rather than by the speed of the jacking system. If jacking is too fast, plastic concrete will fall out as it is exposed from the bottom of the forms. Conversely if jacking is too slow, the concrete surface will become dry, generating considerable friction between the sliding faces of the formwork.

Jacks are used to lift the formwork.  They climb on jack rods, which are located centrally in the wall and cast into the concrete, the concrete providing lateral restraint against buckling of the jack rods.

Additional jack rods are added with the aid of screwed end couplings as the formwork rises.

Vertical reinforcement is located by reinforcement guides which are fixed to the Slipform. The horizontal reinforcement has to be threaded beneath yoke heads as the Slipform rises.

Penetrations are formed by fixing blocks of material such as polystyrene, precast weak concrete or timber frames to the reinforcement.

Slipforming is normally undertaken on repetitive work where speed or economy through the maximum reuse of the same formwork is possible.

Slipforming can be carried out continuously, 24 hours a day until the structure is completed; alternatively Slipforming can be done on a discontinuous basis during daylight hours only;
i.e. highrise core construction.

Continuous Slipforming is normal for the construction of silos or water retaining structures where monolithic walls are required.  On such projects, Slipforming can be carried out at an average speed of 300 to 400mm in height per hour.

Discontinuous slipforming

Discontinuous slipforming is preferred when building multi-story structures such as apartment building and commercial offices. For projects of this type, it is normal to Slipform one full floor height per day (i.e. 3 to 4 metres). The following day is used to install window, door and floor blockouts, fix all vertical reinforcement, install stairs and generally make ready for the next floor height pour which would be completed the following day. This arrangement gives a repetitive 2 day cycle per floor.

There are many factors which will influence the decision to Slipform continuously or discontinuously. For instance, where a slender or complicated structure is to be slipped, the rate of strength gain of the concrete and stability considerations, particularly where strong wind conditions are encountered, will dictate that a discontinuous or intermittent Slipform approach be adopted.

Structural design considerations will often dictate that discontinuous Slipforming be used. This will occur frequently when constructing service cores for high rise buildings. The core itself may not be stable if erected to its full height without some inter-action with the remainder of the structural frame of the building. Where this situation exists, it is normal to stage Slipforming at no more than 3 or 4 floors ahead of the construction of the remainder of the building.

Custom assembled to your specifications

It is possible to Slipform quite complex shapes.  Almost any rectangular, cellular, curved or convoluted shape can be slipped.

Generally, for economic reasons, the plan shape of a structure to be Slipformed should remain constant throughout its full height.

Whilst this is a desired requirement, it should not be taken as a limiting factor as it is quite possible to change wall thicknesses and to add to or remove walls from a Slipform during construction.

Since the formwork must slide past the face of the concrete wall it is essential that any horizontal projections from this face be eliminated or at least minimised. This requirement calls for special attention to floor slab and beam connections to Slipformed walls.

Where projections from the wall face have to be provided as an essential part of the structural design, such as corbels or haunches to provide seating for precast beams or panels, then these can be formed integrally with the Slipformed wall by the use of static formwork panels. These remain stationary in place as the Slipform rises. This type of detail tends to complicate a Slipform and as such should only be used where no alternatives are structurally or economically possible.