Contractors Guide To Quality Construction Flashcards
(25 cards)
The 4 things control tests are for measuring:
Slump
Air content
Compressive strength
Yield
Control test results should conform to _____ international standards.
ASTM
Slump test is used to measure the ________________ of the concrete.
Consistency
__________ gives an indication of the workability, also called flowability or plasticity, of the concrete.
Slump
_____-_____________ improves the concretes resistance to damage from freezing and thawing cycles.
Air-entrainment
Without the proper ____ __________, normal concrete that is exposed to cycles of freezing and thawing will scale and spall, resulting in a failure of the concrete.
Air content
_______________ ______________ measures estimated strength at a given time to make sure it meets a job’s specified strength.
Compressive strength
Compressive strength is measured testing concrete cylinders either 6” dia. x 12” height or 4” dia. X 8” height tested at 28 days. At 7 day strength should be at ___-____% of the 28 day strength.
65-70%
_____ _____ replaces part of the portland cement content & visually reduces the air content in air-entrained concrete.
Fly ash
The stronger and less porous the cement paste, the stronger and more durable the concrete. Any _________ not needed for workability simply dilutes the cement paste, weakening it.
Water
Concrete is typically batched by __________.
Weight
The ____” sieve is the dividing point between course and fine aggregates.
3/8
The largest allowable aggregate will be the most economical, although a maximum of ____” or less is recommended for high-strength concrete.
3/4
____________________ when properly used can increase early strength, ultimate strength, accelerate or retard setting time, increase workability, improve uniformity, reduce permeability and improve durability.
Admixtures
__________-______________ admixtures enhance the workability of the concrete, making it possible to reduce the water by 5% or more.
Water-reducing
______________________ or high-range water-reducing admixtures typically turns a 2”
slump into a 7-9” slump.
Superplasticizers
_________________ especially used with fly ash mixtures can cause extreme retardation (overnight or longer).
Retarders
The least costly and most efficient accelerator is ____________ _____________.
Calcium chloride
As a rule of thumb, adding ___ gal. of water per cubic yard of concrete will increase the slump by approx. ____ in. and will reduce compressive strength by _____ psi.
1 gal
1 in.
150 psi
True or false:
Most specifications allow water to be added more than once on the job.
False
The maximum delivery time is ____ min.
90
A shorter maximum delivery time usually ____ min is sometimes specified for hot weather.
60
For hot weather concreting, a max concrete delivery temp of ____*F is specified.
95
The consolidation of soil by vibrating, tamping, rolling or adding temporary weight.
Compaction
