Question

Non suspended slab and suspended slab.What is the difference in details? Where is the location? What is the challenge to build it?

Explain the construction of both slab step by step in details.

Answer 1

Non suspended slabs are slabs which have a continuous layer of support underneath it. A classic example of non suspended slab is slab on grade wherein the structural slab is supposed off of the soil below. The flexural demand on the slab is generally minimal unless the soil is very flexible or there is very high load due to trucks in loading dock areas. The rebar is typically governed by temperature and shrinkage. Also, there would be construction and cold joints in the slab to control the pattern of cracking.

Suspended slab on the other hand is supported off of frame elements like building and column. In this case the flexural demand governs the design and detailing of rebar. There is no requirement for control or contraction joints in case of suspended slabs.

For slab on grade, excavation of soil needs to be done. After that a granular subgrade is prepared and installed on the soil to facilitate drainage of ground water. Above this layer, a layout of vapour barrier is installed to prevent ingress of moisture in the slab on grade. Finally concrete is poured which forms the slab on grade.

For suspended slab, the formwork needs to be installed first. After that, the rebar cage is laid out and finally concrete is poured to firm the slab. The formwork is stripped off typically 7-14 days after the concrete is poured.