A layer of fat is usually
found on top of a freshly placed concrete slab after vibration. This layer is
required for floating and trowelling, as it ensures that there is no exposed
When installing a slab with armoured joints, it is important to ensure
that the joint armour is clear of fat at all times. Failure to do so will
result in part of the slab protruding upwards when it has hardened which, if
caught by an MHE wheel, can cause damage. This makes that area of the slab more
vulnerable to further impacts from MHE wheels.