Knowledge Centre

Frequently asked questions?

Here you’ll find answers to the most common questions we are asked about our products. If you don’t find the answer you need here, call our office on 1300 763 288

How do armoured joints work?

Armoured joints which also act as leave-in-place formwork (such as our AlphaJoint and BetaJoint) are used to create a boundary in which to contain a day’s concrete pour. As the concrete sets and contracts, the two sides of the joint (held together with frangible rivet connectors) are gradually pulled apart horizontally. Dowels fixed through the centre stop the slabs moving vertically and allow for load transfer between the two sections of the floor. Once the floor has contracted, the gap between the two sides can simply be filled with a suitable joint sealant.

Why should I use Armoured Joint?

  • Armoured joints have several benefits:
  • they act as permanent formwork and as day joints, helping to speed up the process of the concrete pour, and ensuring a reliable result;
  • they control the movement of the concrete as it contracts, preventing random cracks from occurring in the slab;
  • they protect contraction and expansion joint arrises from damage once the building is in use, preventing costly repairs to both the floor and materials handling vehicles;
  • they facilitate load transfer between the two sides of the slab, so the slab remains consistent and even during use

How do I know which armoured joint to use?

This will depend on several things, such as the type of building, how it will be used, and the type of vehicles that will pass over the joint. Often there will be more than one suitable option, and it may also be that more than one kind of armoured joint or formwork is needed for your project. We can help you find the best combination.

What height of armoured joint do I need?

This depends on the depth of the concrete slab being poured. Normally you would choose a rail size 30mm less than the depth of your slab – so if your nominal slab depth was 190mm you would use a 160mm high joint.

What are the joint heights less than the slab depths?

Firstly, it's to allow for variances in the sub-base. The sub-base usually has a tolerance of +/- 1cm; so if the sub-base is created slightly out of tolerance, there is still space for the joint to move freely. The joint will not work if it is dug into the sub-base.Secondly, it gives a tolerance for levelling the surface.