G7- Learning Task 2-3 Flashcards
(16 cards)
What are the two required conditions for proper curing
Moisture and favourable temperature
What is considered a favourable air temperature for concrete curing
15-20 C and overcast
Explain hydration process
Chemical reaction of water and cement
List 4 methods of curing concrete
Water coating
Wet covering
Curing compound
Mechanical barrier
How are chemical hardeners used
Sprayed or sprinkled onto surface and floated in
Why are curing companies coloured
To show coverage
If two coats of curing compound are use, how is the second one applied
At a 90 degree angle to the first coat
What is the minimum curing time to allow the concrete to gain 70% of its 28 day strength
3 days
What causes plastic shrinkage cracking
Rapid water loss
What can cause a concrete slab on grand to sag and crack
Settling or heaving of subgrade
What causes spalling
Stripping techniques or stripped to soon
What causes efflorescence
Salts and chemicals in water or aggregate
What is the maximum aggregate size that should be used when repairing concrete
1/2 depth of patch
Why must you wet the area to be patched
To key the patch
What is the main minimum slump of repair concrete
50 mm
How long should a patched area be allowed to cure
3 days minimum
