Concrete Flatwork Flashcards
(37 cards)
The term ___ ____ refers to the ground or the base that is directly under and supporting the concrete slab.
Sub-grade
Prep if sub grade includes proper levelling and compaction of the soil. T or F
T
Problem soils include clay and organic soils. T or F
T
What occurs when a slab is on soil which contains both hard and soft spots in close proximity?
Point loading. Causes a bridging effect. Cracks may develop.
The ____-____ is a thin layer of granular material that is placed on the prepared sub-grade.
Sub-base.
What are some acceptable materials for sub-base?
Crushed stone, gravel, mix of both
____ _____ should be placed under all abs where water or water diffusion through the slab may be a problem.
Vapour barriers
Vapour barriers also prevents moisture loss from the concrete to the sub-base during curing. T or F
T
Vapour barrier would not be used for things like sidewalks or roadways where the barrier is permanently exposed to the exterior. T or F
T
Reinforcement should be placed in the ____ portion of the slab and should be supported by small pieces of brick or block. Same with wire mesh.
Lower
A minimum design strength of ____ mPa at ____ days is desired for light duty-industrial or institutional and commercial floors.
28 mPa
28 days
Slumps of ____ to ____ are the normal range for slab floors.
50 (2”) to 100 (4”)
Including _____ ____ improves place ability, reduces surface bleeding and improves resistance to damage cause by freeze/thaw cycles
Entrained-air
______ joints may permit both vertical and horizontal movement between two adjacent but separate members.
Isolation
The material most commonly used for isolation joints is ____________.
Far-impregnated fibreboard.
What is the typical thickness for tar-impregnated fibreboard?
15 mm
____ _____ are used to control the location of cracking.
Control
A control joint should extend at least ____ and not more than _____ the depth of the slab.
1/4
1/3
_____ joints are placed where the concrete pour has been intentionally stopped.
Construction
When the concrete is cast directly upon the sub-grade or sub-base without the use of a moisture barrier, what must be done?
The surface should be dampened to reduce the loss of water from the concrete to the sub-base
Consolidation by surface vibration is done for slabs up to ____ thick.
200 mm (8”)
After consolidation, the final slab height is achieved through _____ or _____.
Screeding or strike-off
What is the goal of Screeding?
To remove the top of the placed concrete to the correct height.
What is the most important factor in the Screeding and consolidation process?
That it be completed before excess bleed water collects to the surface
