ACI Field Testing Technician

Thermometers used to measure the temperature of freshly mixed concrete must be capable of measuring temperatures throughout a range of ___ to ___°F.

30 to 120 °F

Thermometers used to measure the temperature of freshly mixed concrete shall be capable of accurately measuring the temperature to +/- ______°F.

1°F

Reference thermometers used to verify the accuracy of thermometers used to test temperature of freshly mixed concrete shall be capable of accurately measuring temperature to +/- _____°F.

0.5°F

Verify the accuracy of thermometers in an oil or other suitable bath liquid at two temperatures at least _____°F apart.

30°F

Reject the thermometer if it differs in reading by _____°F from the reference temperature measuring device at either temperature.

1°F

Provide at least _____ inches of concrete cover in all directions around the sensor of the thermometer and submerge the thermometer a minimum of _____ inches into the freshly mixed concrete.

3 inches

Leave the thermometer in the freshly mixed concrete for a minimum of _____ minutes and a maximum of _____ minutes.

2 minutes minimum

5 minutes maximum

Report the temperature of freshly mixed concrete to the nearest _____°F.

1°F

Check the accuracy of the thermometer _____ or whenever there is a question of accuracy.

annually

To prevent ambient air temperature from affecting the reading, close the void left by inserting the thermometer by _____.

gently pressing the surface of the concrete around the thermometer

The elapsed time between obtaining the first and final portion of samples that will be used to fabricate a composite sample shall not exceed _____ minutes.

15 minutes

The individual samples shall be combined and remixed with a _____ the minimum amount of necessary to ensure uniformity.

shovel

Start testing for slump, temperature, and air content within _____ minutes after obtaining the final portion of the sample.

5 minutes

Start molding strength specimens within _____ minutes after fabricating the composite sample.

15 minutes

The minimum size of the sample when making strength specimens is _____ cubic foot.

1 cubic foot

Describe procedures for sampling concrete from a stationary mixer, revolving drum mixer, or continuous mixer.

passing a receptacle through the entire discharge stream or by completely diverting the discharge strength into a sample container

When sampling from pacing mixtures, wait until contents of the mixer have been discharged and sample from at least _____ portions of the pile.

middle

After fabrication a composite sample from a continuous mixer, wait a minimum of _____ minutes and a maximum of _____ minutes before beginning the test.

2 minutes

5 minutes

The process of removing aggregates that are larger than appropriate for the size of the molds or equipment used is called _____ _____.

wet sieving

When removing aggregates that are larger than appropriate for the size of the molds or equipment used.

Discard mortar adhering to the aggregate and put mortar adhering to the sieving equipment back into the batch

Slump test can be tested when a concrete mixture is designed to produce what range?

0.5 to 9 inches

Slump cone dimensions should be checked when _____.

at least annually

Metal molds shall have a minimum average thickness of _____ inches.

0.06 inches

A metal roll up tape may be used to measure the slump if it is marked in increments of _____ inches or smaller.

1/4 inch

Fill the slump cone in _____ layers of equal volume.

3 layers

Do you tap the slump cone when rodding?

No

After filling and striking off the slump cone, raise the slump come 12 inches in _____ seconds with a steady upward lift with no lateral or torsional motion.

5 +/- 2

Complete the slump test from start to finish within _____ minutes.

2.5 minutes

How to measure slump distance?

from the top of the mold to the displaced original center

How to strike off the slump cone?

with a screeding and rolling motion

When internal vibration is used to consolidate concrete for the density test, the frequency shall be at least _____ vibrations per minute.

9,000

The size of the measure used to test density is influenced by _____.

nominal maximum size of coarse aggregate

A glass or acrylic strike-off plate shall be at least _____ inch thick with a length and width at least _____ inches greater than the diameter of measure.

1/2 inch

2 inches

What are the measures of consolidating concrete for a 3 inch slump?

rodding or vibration

How many rods per layer?

25 times

If internal vibration is used, _____ layers are used and inserted _____ times.

2 layers

3 times

The pressure meter is used to determine air content of concrete made with _____.

relatively dense aggregates.

Vibration may be used to consolidate pressure meter concrete when the slump is _____ to _____inches. Always vibrate when the slump in less than _____ inches

1 to 3 inches

less than 1 inch

Only tap the sides 10 to 15 times when _____.

rodding

A _____ must be used when pressure meter measuring bowl to determine density.

strike-off plate

After strike-off, attached the cover assembly and add water through one petcock until _____ emerges from the opposite petcock.

water

Close both petcocks _____ pumping the air in the air chamber up to the intial pressure line and _____ releasing the pressure into the measuring bowl.

after pumping

before releasing

Pump the air pressure to the _____ line before releasing the air form the chamber into the measuring bowl.

3 line

Read the air content on the gauge to the nearest _____ % and subtract the aggregate correction factor before recording.

0.1%

Release the air by _____ before removing the cover.

opening both petcocks

The volumetric method may be used to determine the air content of concrete made with _____ type of aggregate.

any type

The point of adding alcohol to the meter first is to _____.

have little to no foam

If more foam than equivalent to _____ % air above the water level the test is invalid.

2%

Correction factors for the effect of alcohol is zero when the amount of alcohol added is less than or equal to _____.

2 pints

When the slump is less than 1 inch use _____ to consolidate the concrete for the volumetric method.

a rod

Fill the measuring bowl in _____ layers for the volumetric method.

2 layers

Strike off excess concrete with _____ for the volumetric method.

a steel or high-density strike-off bar

Insert the funnel and add _____ first for the volumetric method.

1 pint of water before adding alcohol

Repeat inverting, shaking, and upright process for a minimum of _____ seconds and until the concrete has broken free from the measuring bowl. Do not keep meter inverted for more than ____ seconds at a time

45 seconds minimum

5 seconds maximum

After completing the inverting, shaking, and upright process, tilt the meter approximately ______ degrees and vigorously roll the meter for approximately _____ minutes.

45 degrees

1 minute

The liquid level is considered stable when it does not change by more than _____ % with _____ minutes.

0.25%

2 minutes

For acceptance testing for specified strength, cylinders shall be _____ or _____.

4 x 8 inches

or

6 x 12 inches

Beam molds shall be _____ in cross section.

6 x 6 inches

If the slump of the concrete is greater than or equal to 1 inch rodding or vibration can be used. If the slump is less than 1 in vibration must be used for strength cylinders.

True

How many layers for a 4 x 8 inch cylinder?

2 layers

How many layers for a 6 x 12 inch cylinder?

3 layers

6 x 6 x 20 inch beam mold with a 4 inch slump, how many rods per layer?

(6*20)/2 = 60 rods

When rodding each layer of a beam, what is required after tapping the outside at least 10 times.

Spading along the sides and ends of beam mold

After cylinder specimens have been consolidated, strike off the surfacing using _____.

a tamping rod, float, or trowel

How long after fabricating strength specimens do they need to be placed in their initial curing location?

no more than 15 minutes

For concrete with a specified strength of 6,000 psi or less, maintain initial curing temperature between _____ °F and _____ °F

60°F and 80°F