ACI Study Guide

Collecting a representative sample of concrete to bne tested is as important as executing the methods to obtain ________.

accurate results

This practice covers sampling from four types of equipment, which are ________, _______, _______, and _______.

stationary mixers, paving mixers, revolving truck mixers, continuous mixers

The elapsed time between obtaining the first and final portions of a composite sample shall not exceed __________.

15 minutes

Portions of a composite sample shall be thoroughly remixed before beginning tests on the sample? True or false?

true

Start tests for slump, temperature, and air content within _______ after fabricating the composite sample.

5 minutes

Start molding specimens for strength test within ________ after fabricating the composite sample.

15 minutes

The concrete sample must be protected from contamination and ____________.

evaporation (moisture loss)

The minimum size sample for making strength test specimens is ________.

1 ft³

When sampling from a stationary mixer, the batch must be sampled at ________ or more regularly spaced intervals during discharge of the middle portion of the batch.

two

When sampling from a paving mixer, obtain samples from at least _______ different portions of the pile and combine them into composite sample for test purposes.

five

When sampling from a revolving truck mixer, sample the concrete by collecting ________ or more portions taken at regularly spaced intervals during discharge of the middle protion of the batch.

two

Concrete samples from a truck mixer must obtained before any water or admixtures are added to the mixer at the job site.

false

When the concrete contains aggregate larger than the permitted for a particular test method, the sample of concrete must be _____________ before making the test.

wet screened

The stem of the thermometer is submerged a minimum of _______ into freshly mixed concrete.

3 inches

The thermometer shall be capable of accurately measuring the temperature of freshly mixed concrete to ______ throughout a range of ______.

+- 1 °F, 30 to 120 °F

The thermometer shall be verified within _____.

at least one year of its current use.

The temperature of concrete may be measured in a wheelbarrow. True or false?

true

The temperature of concrete may be measured in a wall form. True or false?

true

A composite sample of concrete is required even if the only purpose for obtaining the sample is to determine temperature. True or false?

false

What must be done to the concrete prior to sampling the concrete?

The sample container must be dampened with water prior to obtaining the sample.

What must be done to the concrete surrounding the thermometer after the device is submerged in the fresh concrete?

Fill the surrounding voids (if applicable) to ensure the stem of the thermometer is in full contact with the concrete.

How long must be the thermometer remain in the freshly mixed concrete?

2-5 minutes

After the temperature of the concrete is read, what is then required?

Record the temperature to the nearest 1°F.

The temperateure of the concrete is measured to the nearest ________.

1 degree

There is a specified maximum temperature of freshly mixed concrete. True or false?

false

The sample of concrete used for temperature determination must be rodded 25 times. True or false?

false

When the concrete contains aggregate larger than allowed for the slump test, the large aggregate must be ______.

wet screened over 1-1/2 in. [37.5 mm] sieve

The mold for making the slump test is in the shape of ______.

the frustum of a cone

The height of the slump mold is _____.

12 inches

The interior surface of the slump mold is allowed to have minor irregularities. True or false?

False

For use in the slump test, the tamping end or both ends of the tamping rod must be _______.

hemispherical

The slump mold should be in a dry condition before beginning the test. True or false?

False

The surface on which the slump mold will be placed must be ______.

flat, level, damp, nonabsorbent, and rigid

The slump mold is filled in ______ layers.

3

Each layer should fill approximately _______ the volume of the mold.

1/3

Rod each layer __ times uniformly over the cross section with the round end of the rod.

25

How deep should the tamping rod penetrate into each layer?

Throughout the current layer and 1 inch into the previous layer

What must be done if the concrete drops below the top of the slump mold while the top layer is being molded?

Additional concrete should be added to maintain excess concrete above the mold.

Prior to lifting the mold, concrete must be removed from ______.

the area surrounding the base of the mold

After the final rodding, the sides of the slump mold should be tapped lightly with the tamping rod. True or false?

False

When raising the slump mold, it should not be rotated or twisted. True or false?

True

How much time is allowed for lifting the slump mold?

5 +- 2 seconds

The measurement for slump is made from the top of the mold to what point of the concrete specimen?

The displaced original center of the top surface of the specimen.

The slump of concrete is measured and reported to the nearest ______.

¼ inch

How much time is allowed to conduct the slump test from beginning to completion?

2.5 minutes