week 4 Flashcards
(20 cards)
What is a footing slab?
A footing slab is a concrete floor with a separately poured strip footing. It doesn’t function as a raft footing
What are the advantages of a footing slab system?
It minimizes floor construction time, requires minimal formwork, and typically only two concrete pours are needed.
When is the footing slab system suitable?
It is well suited for buildings on sloping, un-reactive, and “S” shaped sites.
Does the edge beam in a footing slab need to be tied to the slab?
The edge beam may need tying to the slab depending on site classification and termite protection requirements.
What is a typical construction detail of a footing slab?
The slab and strip footing are poured separately, with edge beams acting as support elements.
What is a stiffened raft slab?
A stiffened raft is a reinforced concrete slab with stiffening beams supporting the structure.
How many concrete pours are required for a stiffened raft?
Typically, only one concrete pour is required, making it economical.
Are internal beams always required in stiffened rafts?
Internal beams are generally not needed on stable sites but are necessary on more reactive sites for support.
How does the reinforcement in stiffened rafts vary?
Beam sizes and reinforcement amounts vary depending on site conditions.
What is the main structural feature that differentiates stiffened raft from other slabs?
The inclusion of stiffening beams within the slab to support loads and reduce bending stresses.
What distinguishes slab on ground from stiffened raft slabs?
Slab on ground acts as a raft footing without stiffening beams and has an integral edge beam.
Where is slab on ground most commonly used?
In domestic construction on stable and moderately reactive soils.
What is an important step in slab on ground construction?
Placing a moisture-proof membrane and sealing all joints before pouring concrete.
How is reinforcement placed in slab on ground?
Reinforcement is placed with overlaps and supported by reinforcement chairs before pouring.
Why is curing important in slab on ground construction?
Proper curing ensures the slab gains strength and durability while preventing cracks.
What is a waffle raft slab?
A waffle raft is a stiffened raft with a grid of spaced ribs and suspended slab panels between ribs.
What materials are used for creating the voids in a waffle raft?
Cardboard or polystyrene void formers are used to create the rib grid.
On what type of site is a waffle raft most suitable?
It is best suited for levelled sites but can also be designed for support on piers or piles.
What is the structural benefit of waffle raft construction?
It reduces the amount of concrete needed while maintaining strength via the ribbed structure.
How does the waffle raft support loads?
Loads are distributed through the ribbed concrete beams, reducing slab thickness and weight.
