Concrete Flashcards
Concrete is made of what?
Water, Portland cement, sand, and stone… Gravel or aggregate
Water cement ratio determines what?
AKA Weight Ratio determines quality and durability
Strong stone increases what?
Abrasion resistance
Large aggregate produces what?
More economical concrete
Which fiber tube forms require stiffeners?
Fiber tube forms over 15 feet
Maximum drop distance/pouring height?
5 feet
Who specifies when forms are to be removed?
The engineer
What test results are needed prior to remove shoring?
Compression cylinder test results
Epoxy coating on rebar prevents what?
Corrosion
Stirrup tolerance?
Plus or minus 1 inch
Saw joints should be installed when?
Between 4 and 12 hours after the concrete is poured
Wet ground under slab to prevent what?
Loss of water in concrete
Pump mix stone should be?
Rounded
What does the vibrator do?
Consolidates concrete. Makes stiff concrete more fluid.
Increase in temperature and effect on set up time?
20° increase in temperature reduces setup time by 50%
Temperature considered cold weather concrete?
Below 40°
Slab finishing sequence?
Edging last step after trowel finish. Troweling too soon will cause the slab surface to be rough
What does the bull float do?
Knocks down the highs and lows
Curing controls what? When does it start? And what does it help with?
Curing controls the drying of concrete. It starts immediately. It helps with strength and durability.
Cause of plastic shrinkage cracks?
Rapid evaporation
Temperature for curing cylinders at jobsite in box?
60° to 80°
Weight of concrete?
150lb/ft3
