G4 - Slabs - LT# 1 Slabs-On-Grade Flashcards
on which kind of surface should a slab-on-grade be placed?
1) Suitable bearing
2) Compacted fill
What factors affect the durability of slabs-on-grade?
1) Protection from weather
2) Finishing
3) W:C Ratio
What factors affect the strength of slabs-on-grade?
1) Base mix 2) Concrete curing 3) Concrete mix
What should be done to walls or columns that pass through or beside slabs-on-grade?
Provide Isolation joint
Why is it important to compact the subgrade?
To give firm even bearing
Why are screeds and forms oiled before concrete placement?
Easy cleaning
How long should slab forms remain in place after concrete placement?
As long as possible
What is the minimum slope for drainage for an exterior slab?
1/8 per foot (1/96)
What does a give-and-take strip allow for?
1)Expansion & contraction
2) Differential movement
Describe pouring a monolithic slab.
Monolithic slab - Poured with the perimeter footing and any other slab thickenings at the same time.
What is one setback of pouring a monolithic slab?
The footing portion and the floor portion are under different building loads, which may cause stress cracks at these locations.
What is one advantage of a monolithic slab pour?
Economical and quick to form and place
Describe pouring an isolated slab on grade.
Isolated slab is poured AFTER the walls and footing have been placed.
Where does an isolated slab on grade have an isolation joint?
Usually between the slab and footings and an air and moisture barrier between the slab and wall
A slab on grade is only as strong as ______
The material it is placed upon
If existing soil (subgrade) is of suitable bearing, it only needs:
To be excavated down to a grade and levelled before placing the slab.
If a subgrade is not smooth after grading and leveling, what is laid down?
A sub-base, is usually a material that is more uniform in particle size.
If soil is not suitable for a slab on grade, then
It must be removed and replaced in compacted lifts with proper granular fill specified in the drawings
What tool is used to provide a firm and even bearing?
Plate roller or a ram-type roller
For forming a simple slab which is not too thick, what can be used as formwork?
Simple 2x4 to 2x12 depending on the thickness
For thicker edge slab-on-grades, what material is used to form a slab-on-grade?
Thicker edge forms, using plywood forms supported by studs and plates may be necessary. Strong backs and braces are used to plumb and straighten.