Concrete

Question 1

Cement is made with:

Answer 1

Portland cement
Limestone
Clay
other elements including gypsum

Question 2

How many types of Cement is there and what is the most popular?

Answer 2

5 types

type 1 is the most popular

Question 3

In cement making, what is the definition of fine aggregate:

Answer 3

Such as sand which passes through a 1/4” sieve

Question 4

In cement making, what is the definition of coarse aggregate:

Answer 4

Such as pea stone and gravel.

generally the maximum size will be 1 1/2” or less.

Question 5

Coarse aggregate must be free

Answer 5

of soft stones or cherts which will cause “pop outs” in freezing weather

Question 6

Each 1 gallon of water added to 1 yard of concrete will

reduce the PSI strength by X PSI.

Answer 6

150 psi

Question 7

Ready mixed concrete should be totally

discharged from the truck within X hours of being mixed or prior to Y revolutions of the mixer, whichever comes first

Answer 7

1 1/2 hours

300 revolutions

Question 8

The purpose of Air Entrainment

Answer 8

Reduces internal expansion of hardened concrete and closes off channels during curing time.

Question 9

What are accelerators:

Answer 9

Help to remove water from the plastic concrete in freezing weather.

Question 10

Calcium chloride should not be used with reinforcing steel due to the probability of

Answer 10

creating corrosion

Question 11

What are Superplasticizers:

Answer 11

Reduce the water required in a mix design and

improves flow and workability.

Question 12

Superplasticizers provide a

high slump of 10” for concrete that would normally have a X

Answer 12

4”

Question 13

Freezing weather conditions require fresh concrete

Answer 13

to be protected, usually by a blanket

Question 14

For footings, how do you determine the footing size?

Answer 14

The soil bearing capacity

Question 15

Types of footings:
1
2

Answer 15

Bearing wall strip footing

Mat, raft, or floating foundation

Question 16

What type of footing do you use over poor soil load bearing capacity

Answer 16

A mat, raft, or floating foundation

Question 17

If the soil isn’t strong enough for a footing, what do you use?

Answer 17

Pilings (stilts) are driven down into the ground

Question 18

Metal reinforcement in footings requires a minimum of X of concrete coverage.

Answer 18

3 inches

Question 19

Concrete placed in foundation forms should not be dropped more than X feet. ( Use form releasing agents)

Answer 19

5 feet

Question 20

Concrete should be X after placement

Answer 20

vibrated after placement to avoid cold seams.

Seams created by previous pours

Question 21

In mild weather conditions, foundation forms generally can be removed X after placement of concrete, in severe weather conditions wait Y.

Answer 21

12 hours

5 to 6 days

Question 22

Rebar is measured in X

Answer 22

1/8 of inch

Question 23

Splices in rebar should not be less than X” overlaps

Answer 23

12 inches

Question 24

Wire fabric requires X” of concrete coverage.

Answer 24

2 inches

Question 25

New concrete shrinks as it sets. For example X lineal feet of concrete will shrink Y of an inch.

Answer 25

100 lineal feet

3/4 of an inch

Question 26

Control joints in walls are generally X feet apart

Answer 26

20

Question 27

What do expansion joints do

Answer 27

permit total freedom of movement

Question 28

Saw cut control joints should be made within X hours of placement. Completing a slab with a trowel finish should be done when the wet sheen disappears.

Answer 28

4-12 hours

Question 29

What do you do prior to concrete placement

Answer 29

Moisten sub grade with water prior to concrete placement.

Question 30

Adding water to the concrete mixer truck requires X revolutions to complete mixing.

Answer 30

30

Question 31

A test for determining the density of wet concrete is a

Answer 31

“slump test”

Question 32

darby:

Answer 32

A “darby” is a short handled bull float for finishing high and low spots.

Question 33

The temperature of concrete should be maintained at X degrees for Y days in cold weather conditions.

Answer 33

50 degrees

5 days

Question 34

Enclosed spaces heated with fossil fuels must be

Answer 34

vented to reduce carbon monoxide which also causes concrete surface “dusting”

Question 35

Curing is accomplished by

Answer 35

Curing is accomplished by spraying with a pre-mixed surface curing agent, or using a fog sprayer or other means to keep the top surface damp for a specific period of time.

Question 36

Concrete testing is accomplished by using X test cylinders of concrete. If concrete is to have a 4000 PSI at 28 days one of the cylinders can be tested at Y days. At Y days the cylinder should resist Z to W% of 4000 PSI.

Answer 36

Concrete testing is accomplished by using 3 test cylinders of concrete. If concrete is to have a 4000 PSI at 28 days one of the cylinders can be tested at 7 days. At 7 days the cylinder should resist 65 to 70% of 4000 PSI.

Question 37

Air entraiment mix ratio:

Answer 37

Generally 5 to 7 percent in mixes with 3/4” to 1 inch

aggregate when used in severe weather conditions