ASTM C 31 Test Specimens

Question 1

The cross‐sectional dimensions for the standard sized flexural strength (beam) specimen are
A. 2x2 inches
B. 4x4 inches
C. 6x6 inches
D. 8x8 inches

Answer 1

6x6 inches

Question 2

For compressive strength specimens, when the nominal maximum size (NMS) of the coarse aggregate exceeds 2 inches
A. use a cylinder mold having a diameter of at least 9 inches.
B. wet sieve the sample of concrete over a 1‐1/2 inch sieve.
C. wet sieve the sample of concrete over a 2 inch sieve.
D. ASTM C 31 does not apply when the NMS of the coarse aggregate exceeds 2 inches.

Answer 2

wet sieve the sample of concrete over a 2 inch sieve.

Question 3

Technicians making and curing specimens for acceptance testing shall be certified as an ACI Concrete Field Testing Technician, Grade I, or equivalent.
(T or F)

Answer 3

True

Question 4

A 6x12 inch cylinder, which is consolidated by rodding, is filled in _____ layer(s) of approximately equal volume.
A. 4
B. 3
C. 2
D. 1

Answer 4

3

Question 5

When molding a 4x8 inch cylinder by rodding, use a tamping rod with a diameter of _____ inches.
A. 3/8
B. 1/2
C. 5/8
D. either 3/8, 1/2, or 5/8

Answer 5

3/8”

Question 6

When test specimens are to be molded, it is also necessary to determine the slump, air content, and
temperature of the fresh concrete.
(T or F)

Answer 6

True

Question 7

It is permissible to tap single‐use plastic cylinder molds 10‐15 times per layer with a mallet, so long as the mold is not damaged in the process.
(T or F)

Answer 7

True

Question 8

Standard cured specimens with a specified compressive strength of less than 6000 psi, shall be initially cured at a temperature range of
A. 58 to 78 F
B. 60 to 80 F
C. 68 to 78 F
D. 73.5 +/‐ 3.5 F

Answer 8

60 to 80 F

Question 9

Standard cured specimens shall initially be stored for a period of _____ at the specified temperature range and in an environment that prevents moisture loss.
A. exactly 24 hours
B. up to 24 hours
C. exactly 48 hours
D. up to 48 hours

Answer 9

Up to 48 Hours

Question 10

Specimens shall not be transported from the field and to the laboratory until at least _____ hours after final set.
A. 2
B. 4
C. 6
D. 8

Answer 10

8

Question 11

Cylinder specimens made for determining when a structure can be placed in service shall be removed from their molds
A. as soon as the concrete achieves final set.
B. at 7 days of age.
C. at the same time that the formwork is removed from the structure.
D. just prior to testing the specimens for strength.

Answer 11

At the same time that the formwork is removed from the structure

Question 12

The concrete used to mold test specimens shall be sampled before any on‐site adjustments in water or admixtures are made
(T or F)

Answer 12

False

Question 13

Specimens cured following standard curing requirements can be used
A. for acceptance testing for strength.
B. to evaluate the adequacy of curing and protection of concrete in the structure.
C. to determine whether a structure can be put in service or not.
D. to determine the density of fresh concrete.

Answer 13

for acceptance testing for strength.

Question 14

The diameter of a cylinder mold shall be at least ______ times the nominal maximum size (NMS) of the coarse aggregate.
A. 1
B. 1.5
C. 2
D. 3

Answer 14

3

Question 15

When consolidating a 4x8 inch cylinder by rodding, place the concrete into the mold in _____ layer(s).
A. 1
B. 2
C. 3
D. 4

Answer 15

2

Question 16

When consolidating a 6x12 inch cylinder by vibration, insert the vibrator _____ time(s) per layer of concrete
A. 1
B. 2
C. 3
D. 4

Answer 16

2

Question 17

When a cylinder is to be tested for acceptance, the size of the cylinder mold
A. must be 6x12 inches.
B. can be 3x6, 6x12, or 9x18 inches.
C. can be 4x8 or 6x12 inches.
D. is based on the slump of the mixture.

Answer 17

can be 4x8 or 6x12 inches

Question 18

After consolidating a layer of concrete in a beam mold by rodding
A. tap the outside of the mold no more than 10 times with the mallet.
B. tap the sides with the mallet, then spade along the sides and ends of the mold with a trowel.
C. tap the mold 10‐15 times with an open hand.
D. tape the sides of the mold 10‐15 times, and the ends 5‐10 times with the mallet.

Answer 18

tap the sides with the mallet, then spade along the sides and ends of the mold with a trowel.

Question 19

For a concrete with a slump of 3 inches, consolidate the concrete
A. only by rodding.
B. only by internal vibration.
C. only by external vibration.
D. either by rodding or vibration.

Answer 19

either by rodding or vibration.

Question 20

During final curing, store cylinders at a temperature of
A. 60 to 80 F
B. 68 to 78 F
C. 73.5 +/‐ 3.5 F
D. 73 +/‐ 3 F

Answer 20

73.5 +/‐ 3.5 F

Question 21

The length of a tamping rod shall be
A. no more than 4 inches greater than the depth of the mold and not more than 24 inches.
B. at least 4 inches greater than the depth of the mold but not more than 24 inches.
C. exactly 24 inches.
D. exactly 16 inches

Answer 21

at least 4 inches greater than the depth of the mold but not more than 24 inches.

Question 22

Record the identification of the sample, with respect to the location in the structure where the associated concrete was deposited, as well as the time the specimens were cast.
(T or F)

Answer 22

True