ASTM C31/C31M - Standard Practice for Making and Curing Concrete Test Specimens in the Field

Question 1

Practice C31/C31M gives standardized requirements for ______, ______, __________, and __________ for the test specimens.

Answer 1

Making
Curing
Protecting
Transporting

Question 2

What diameter tamping rod is used if the diameter of the test cylinders or width of beam is:

less than 6 inches = ______
6” or greater = ______

Answer 2

3/8” (less than 6”)

5/8” (6” or greater)

Question 3

Minimum frequency of an internal vibrator used in this procedure is:

Answer 3

9,000 vibrations/minute

Question 4

The sampling receptacle shall be:

one of three things

Answer 4

Heavy gauge metal Pan
Wheelbarrow
Flat, clean non-absorbent board

Question 5

Cylindrical specimens diameter shall be at least ___ times the nominal maximum size of the coarse aggregate?

Answer 5

3 times

Question 6

Maximum aggregate size for a 4”x8” cylinder mold is __?

Maximum aggregate size for a 6”x12” cylinder mold is __?

Answer 6

1.25 inches for 4” x 8” cylinder mold

2 inches for a 6” x 12” cylinder mold

Question 7

The sample of concrete used in molding test specimens must be obtained in accordance with what ASTM practice?

Answer 7

C172

Question 8

When strength specimens are to be made, what three other tests must be made?

Answer 8

Air content
Slump
Temperature

Question 9

The supporting surface on which specimens are stored shall be level within ___ per foot?

Answer 9

1/4” per foot

Question 10

Number of vibrator insertions for a 4” diameter cylinder mold is?

Answer 10

1

Question 11

Number of vibrator insertions for a 6” diameter cylinder mold is?

Answer 11

2

Question 12

Number of vibrator insertions for a 9” diameter cylinder mold is?

Answer 12

4

Question 13

When Vibrating, how many layers of concrete are required for a beam mold between 4” and 8” wide?

Answer 13

1

Question 14

When vibrating beams under 6” wide, insert the vibrator at internals not exceeding ____ inches along the _______ of the long dimension of the specimen.
For specimens wider than 6”, use alternating insertions along _____ lines?

Answer 14

6 inches
Centerline
2 lines

Question 15

When rodding a beam, how do you determine how many roddings are required per layer?

Answer 15

1 insertion for every 2 square inches of the top surface area of the beam
[ (L x W) /2 ]

Question 16

When vibrating beams, after each layer has been vibrated, tap the side of the mold sharply at least ____ times with the mallet to close holes left by vibrating and to release entrapped air voids.

Answer 16

10 times

Question 17

When vibrating, how many equal layers of concrete are required for cylinder mold (4”, 6” or 9” diameters)

Answer 17

2 layers

Question 18

When rodding, how many equal layers of concrete are required for the following cylinder molds:
4” diameter?
6” diameter?
9” diameter?
How many roddings for each layer of each mold?

Answer 18

4” diameter mold - 2 layers, 25 roddings per layer
6” diameter mold - 3 layers, 25 roddings per layer
9” diameter mold - 4 layers, 50 roddings per layer

Question 19

When rodding a beam mold, how many equal layers of concrete of:
beams between 4” and 8” wide?
beams over 8” wide?

Answer 19

2 layers for beams between 4” and 8” wide

3 layers or more for beams greater than 8” (not to exceed 6”)

Question 20

For concrete with a slump less than 1”, consolidation much be done by what method?

Answer 20

Vibrator

Question 21

For concrete with a slump between 1” and 3”, consolidation must be done by what method?

Answer 21

Vibrator or rodding

Question 22

For concrete with a slump of over 3”, consolidation must be done by what method?

Answer 22

Rodding

Question 23

Concrete mixtures with specified strengths of 6000 psi or greater, maintain the initial curing temperature between ___* to ___*F

Answer 23

68* to 78*F

Question 24

For concrete mixtures with a specified strength less than 6000 psi, maintain the initial curing temperature between ___* to ___*F

Answer 24

60* to 80*F

Question 25

Generally, no more than ___ seconds of vibration should be required for each insertion to adequately consolidate concrete w/ slump greater than 3". Longer if less than 3"

Answer 25

5 seconds

Question 26

Initial curing - Store standard-cured specimens for a period up to ___ hours after molding to maintain the specified temperature and moisture conditions.

Answer 26

48 hours

Question 27

Shield specimens from direct exposure to ____ and, if used, radiant heating devices.

Answer 27

Sunlight

Question 28

Record the minimum and maximum _________ achieved for each set of specimens during the initial curing period.

Answer 28

Temperatures

Question 29

Store the specimens in an environment that controls the loss of ________?

Answer 29

Moisture

Question 30

If the specimens are made and STANDARD CURED, the resulting strength test data when the specimens are tested are able to be used for the following purposes. (check all that apply) a - Determination of whether a structure is capable of being put in service b - Quality Control c - Form or shoring removal time requirements. d - Acceptance testing for specified strength e - Checking adequacy of mixture proportions for strength.

Answer 30

d - Acceptance for strength e - Adequacy of mixture proportions for strength. b - Quality Control

Question 31

If specimens are made and FIELD CURED, the resulting strength test data when the specimens are tested are able to be used for the following purposes. (check all that apply) a - Determination of whether a structure is capable of being put in service b - Quality Control c - Form or shoring removal time requirements. d - Adequacy of curing and protection of concrete in the structure e - Acceptance testing for specified strength f - Comparison with test results for standard cured specimens or with test results from various in-place test methods

Answer 31

a - Is structure capable of being put in service f - Comparison to standard cured test results d - Adequacy of curing and protection of concrete in the structure c - Form or shoring removal time requirements.

Question 32

Cylinders that are _____ cured, are stored in or near the structure and protected same as the structure.

Answer 32

field

Question 33

The diameter of a round vibrator shall be no more than __/__ the diameter of the cylinder mold or __/__ the width of the beam mold.

Answer 33

1/4 & 1/4

Question 34

The combined length of the vibrator shaft + vibrating element shall exceed the depth of the section being vibrated by at least __ mm [___ in.]

Answer 34

75 mm [ 3 inches ]

Question 35

Transportation time shall not exceed ____ hours

Answer 35

4 hours

Question 36

Ensure that specimens have been moved to the initial curing location no later than ___ minutes after molding operations have been completed.

Answer 36

15 minutes

Question 37

Final Curing of Cylinders - Upon completion of initial curing and within ___ minutes after removing the molds, cure specimens with free water maintained on their surfaces at all times at a regular temperature of 73.5 +/- 3.5*F

Answer 37

30 minutes

Question 38

TRUE or FALSE: Final curing of beams to be done in the same manner as cylinders, except that they shall be stored in water saturated with calcium hydroxide at 73.5 +/- 3.5*F

Answer 38

True

Question 39

When field curing, store cylinders in or on the ________ as near to the point of deposit of the concrete represented as possible.

Answer 39

Structure

Question 40

When field curing, protect all surfaces of the cylinders from the ________ in as near the same way as the _______ work.

Answer 40

Elements | Formed

Question 41

When field curing, provide the cylinders with the same ___________ and ________ environment as the structural work.

Answer 41

Temperature | Moisture

Question 42

TRUE or FALSE: Specimens made for the purpose for determining when a structure is capable of being put in service shall be removed from the molds at least 1 hour prior to removal of the form work.

Answer 42

False - specimens shall be removed from the molds AT THE TIME of removal of form work.