NCDOT Online Concrete Test Flashcards
While performing the Volumetric Method air test, two pints of alcohol were used to dispel the foam. Which of the following statements is true?
When pouring Drill Pier Concrete, what is the minimum sampling frequency for test specimens?
Each load
When used to determine unit weight, the concrete in the mold must be struck off with what?
The reading on the gauge of a pressure meter is 6.2%. The aggregate used has a correction factor of 0.3%. The final air reported is what?
Which percent range most nearly represents the amount of paste volume in a concrete mix?
20-40%
The air content for incidental and structural concrete ranges from ___ to ___ percent.
Components of concrete that are heated due to cold conditions are heated to a maximum temperature of ___ degrees F by NCDOT specifications.
150
When water is added to concrete in the mixer at the job site, the minimum number of revolutions placed on the mixer is what?
25
After consolidation of the unit weight sample, a small amount of concrete can be added to correct for any deficiencies. T/F
True
Calculate the air content using the following weights: Theoretical Unit Weight 150.05 pcf, Actual Unit Weight 140.75 pcf
The minimum size sample for one set of concrete test specimens is what?
1 cubic foot
The minimum set(s) of cylinders to be made on an NCDOT project for class AA concrete on an 87 yd3 pour is what?
By NCDOT specifications, fly ash may be substituted for Portland Cement up to ___ percent by weight of the required cement.
20%
The slump test has to be completed within ___ minutes from the time concrete is introduced into the cone.
2.5
________ is used to dissolve the entrained air bubbles when performing the Chace Air Indicator test.
70% isopropyl alcohol
A curing day is defined as any consecutive ___ period, during which the air temperature adjacent to the mass does not fall below ___ degrees F.
24 hour, 40
The purpose of air entrainment is to retard the concrete, thereby increasing allowable placement time. T/F
Falso
The allowable pH requirements for mixing water used to batch concrete in NCDOT projects ranges from ___ to ___.
4.5 - 8.5
The chemical reaction between water and cement is called what?
Hydration
The type of cement which has the highest fineness and the highest amount of tricalcium silicate, both factors contributing to accelerated strength gain is?
Type III
One gallon of water weighs…
8.33 pounds
Time, temperature, and moisture are three factors that affect the ______ of the concrete mix.
Curing
The bonding agent used in a concrete mix is?
Cement
The number one reason for using air in NCDOT concrete is?
Durability
Admixtures must be dispersed into the mixer with what?
Water
Any opportunity, service, accommodation, used of facility, or other benefit made available for less than the fair market or normal value given in exchange for being influence in the discharge of one’s duties or responsibilities defines _______.
An approved set retarding admixture is required when placing concrete on in the superstructure of a bridge.
True
Only a few power plants produce an ideal fly ash that has a combination of high fineness and low carbon content.
True
Increasing the amount of cement in a concrete mix while maintaining the same amount of water will most likely result in what?
If a slump exceeds the maximum specified limit, a separate sample is immediately obtained from the same truck load and an additional test is performed.
True
If the average of two slump test results exceeds the specified maximum slump, the load of concrete is _______.
Rejected
When placement of concrete is by pumping, take the concrete acceptance sample from the discharge end of the pump. T/F
True
After placing the concrete, cure it for a period of ___ full curing days.
7
Apply moisture from a nozzle under pressure directly upon the concrete when using the water curing method.
False
The 2012 NCDOT Standard Specifications require a minimum of 3,000 pounds per square inch compressive strength in 7 days for latex concrete. T/F
True
Do not load trucks used to agitate concrete with more than ___% of the gross volume of the drum.
For central mixers, where mixer performance texts are made, the minimum mixing time shall not be less than ___ seconds.
50
According to the 2012 Standard Specifications, the minimum amount of concrete which can be mixed or agitated in a transit mixer is?
The component most easiest and practical to cool is what?
Water
Mix designs for structural concrete shall be submitted to the Engineer ___ days before proposed use.
35
When using central dispatching, each plant location must have a __________ indirect control of the batching operation.
Certified Batcher
Any person who knowingly falsifies an inspection report or test report required by the Department of Transportation in connection with the construction of highways shall be guilty of a Class H Felony. T/F
True
Transport compressive strength specimens to the laboratory within ___ after they are made.
72 hours
The _______ provides information about the moisture calculations made by the batcher on the mix design during batching and is sent out with the first and the last load.
The mixture of cement paste and fine aggregate is called?
Alkali Silica Reactivity is what?
A chemical reaction that deteriorates hardened concrete
All members are to ensure that an atmosphere of ethical behavior is promoted and maintained at all times. T/F
True
For the slump test, the cones should be filled in ___ layers.
3
Should the air under the insulation fall below ___ degrees F during the protection period, immediately cover the concrete with canvas and framework and apply heat uniformly at a rate such that the air surrounding the concrete is less than 50 degrees F for the remainder of the protection period.
50
Acceptance of a concrete mix design for use on an NCDOT project is a _____ process.
Twofold