Slipforms and jumpforms are units of mechanical climbing formwork that get used to create concrete walls for large or tall structures.

They climb to systematically form the walls at each level of the structure. They can also be known as a ‘climb-form’ system, or less commonly, as a ‘slide’.

Read on to find out the difference between the two.

What are slipforms and jumpforms used for?

Jumpforms and slipforms are commonly used to create:

• Shear walls
• Core walls
• Lift shafts
• Silos
• Chimneys
• Stair shafts
• Bridge pylons

The untrained eye probably wouldn’t tell the difference between the two. However, although they are very similar, the methods in which they are used differ.

How are they similar?

Both slipforms and jumpforms are self-climbing molds made up of shuttering and props. Concrete gets poured into the molds to form walls. The molds raise using electric or hydraulic rams until the desired height of the structure is reached.

Neither need support from anything other than the structure they’re building. Once the bottom section of concrete is poured, the formwork is self-sufficient.

Both use decks or platforms for people to work from or for materials to be stored on. These decks are part of the structure, so climb with the formwork as it climbs. Each deck on each slipform/jumpform has their own specific weight capacities, so workers need to keep an eye on how much weight goes on them.

Concrete gets poured into the formwork at the top. The most common method to pour, particularly at height, is using a placing boom. But cranes also pour the concrete, using concrete skips.

Although slipforms and jumpforms are very similar, there are some key things that differentiate them.

Jumpforms

As the name implies, jumpforms use a system where the formwork gets jumped from one level of a concrete structure to the next. Each ‘jump’ is supported by the cured concrete that has been poured below.

For example, if a lift shaft is being built, the first level of the wall gets poured. Once the concrete cures, it gets used to support the form as it rises to the next level, and so on until the desired lift shaft height.

Here is a simplified example of one way a jumpform gets made.

1. Rebar walls get made up in the shape of the structure to reinforce it.
2. Formwork and propping gets made up both sides of the rebar.
3. Concrete gets poured inside, then left to cure, leaving some rebar starter bars sticking out the top of the concrete.
4. The temporary formwork gets removed.
5. Brackets get fixed to the sides of the concrete walls.
6. Work decking gets built on the brackets to hold workers, materials, and supports for the next phase.
7. The rebar that is sticking out gets extended to form the next part of the wall above.
8. Shuttering and propping gets formed around that rebar.
9. Concrete gets poured inside, then left to cure. This forms the next level.
10. The temporary shuttering gets removed.
11. The next lot of brackets get installed on the concrete walls.
12. Upper platforms get mounted onto the brackets.
13. The lower work decking gets removed and platforms get lowered to replace them.
14. The two platforms join each other using hydraulic jacks.
15. The next phase of rebar gets installed on top of the walls.
16. Framework gets built above the hydraulic jacks.
17. Shutters get mounted on runners around the rebar.
18. Concrete gets poured inside, then left to cure.
19. The shutters slide away from the walls on the runners.
20. The whole frame structure gets jacked up to the next level.
21. A latching arrangement gets fitted inside of the core.
22. The upper platform bracket fixes to the wall, using the latching arrangement.
23. The cylinders on the hydraulic jacks close to raise the bottom platform bracket. This then also fixes to the walls, using the latching arrangement.
24. Additional decks and ladders get installed underneath, for access, repairs, and cleaning.
25. The jacking procedure gets repeated until each level is formed and the finished height is achieved.

Check out this short video of a jumpform being jumped.

The most common types of jumpform:

• Self-climbing jumpforms
• Guided jumpforms
• Traditional jumpforms

Self-climbing jumpforms

These are what have been explained above. These jumpforms climb on their own using jacks, with no need for cranes to lift them.

Guided jumpforms

Guided jumpforms are similar to self-climbing, in that they attach to the concrete structure that they’ve poured. Except, with these, cranes raise them to the next level, rather than them jacking themselves up.

Traditional jumpforms

Traditional jumpforms are solely lifted to each level using cranes.

Slipforms

Unlike jumpforms, slipforms pour concrete as the formwork rises.

Once the bottom section of concrete is poured and cured, the supporting part of the slipform and rams get tied into the concrete, often using steel or scaffolding. The slipform then slowly climbs at the same time as the concrete getting poured into the mold. This creates less need for waiting for the concrete to cure before the next pour. Some slipforms are poured 24/7.

This method is usually used for structures where the finished concrete won’t be covered up, because it creates minimal joints, and the concrete can be buffed smooth while it isn’t fully cured yet. Unlike jumpforms, slipform shuttering doesn’t get removed between pours.

Slipforms are usually made up of 3 levels. The bulk of materials get stored and distributed on the top level. As stated previously, weight restrictions apply. The concrete also gets poured into the formwork form there. The middle level is where most of the work is done, like fixing rebar, checking dimensions and levels, and maintenance. The lowest level is where the concrete finishing gets done. It gets smoothened before it has fully cured.

Slipforms are usually more expensive than jumpforms. And they often require more workers on them for longer hours because of the continuous pouring.

Types of slipform/jumpform formwork

Whether it’s slipform or jumpform, there are certain types that get used, as listed here:

• Conical formwork system
• Egg-shaped system
• Cantilever system
• Vertical system
• Horizontal system
• Tapered system

Conical system

Conical slip forming can create structures that have varying wall thicknesses and walls that taper.

Egg-shaped system

This is used in jumpforms. It can be adapted to any geometric shape, including curvatures, by adjusting both the axis and circumferential slope. Each side of the walls can be adjusted independently.

Cantilever jumpform system

This is typical, but not exclusive to, what was previously covered in the jumpform section above. The cantilever system is a self-climbing system that doesn’t require any lifting by cranes. The whole unit gets raised with rams.

Vertical system

This is typical of what was described in the slipform section above. The formwork gets raised by jacks as the concrete gets poured in, which can facilitate continuous pouring, depending on how quickly the concrete cures below as it is raised.

Horizontal system

This is a slipform system. Horizontal slipforms are similar to vertical slipforms, except they’re used for things like pavement and traffic separation walls, rather than tall structures like lift shafts.

But it uses the same method of moving the formwork along at the same as concrete pouring, vibrating, and finishing.

Tapered system

The tapered method is a form of conical formwork. It’s a slipform system that can be used to make tall structures that vary in diameter and shape, as well as wall thickness. This can be used to build things like piers, cooling towers, and conical chimneys.

The formwork gets made up of sections that can overlap to slide over one another for variation.

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