12-9.
When you perform the flexural-
strength tests for a mix design,
how many samples should be broken
at 7 days?
1.
Five
2.
TWO
3.
Three
4.
Four
12-10.
If the beam sample is too rough
for a proper seat to be formed
by the load surface, what action
should be taken?
1.
Grind the surface
2.
Use another beam
3.
Cap the surface
4.
Shift the beam to achieve
proper contact
12-11.
An average width and depth should
be obtained before performing the
flexural-strength test.
1.
True
2.
False
Figure 12A
IN ANSWERING QUESTIONS 12-12 THROUGH
12-14, REFER TO FIGURE 12A.
12-12.
What is the modulus of rupture for
the beam if P = 4,000 pounds,
b = 6 inches, and the fracture
occurs at point B?
1.
61.6 psi
2.
123.5 psi
3.
172.8 psi
4.
379.6 psi
12-13.
What is the modulus of rupture
for the beam if P = 6,000 pounds,
b = 4 inches, and the fracture
occurs at point C?
1.
250.0 psi
2.
277.8 psi
3.
388.9 psi
4.
583.3 psi
12-14.
If the beam ruptures at point A
under a load of 5,000 pounds, the
test results should be computed
by which, if any, of the following
formulas?
12-15.
The flexural strength of a test
beam is 625 pounds per square
inch. What is the approximate
compressive strength of the
concrete?
1.
3,700 psi
2.
3,800 psi
3.
3,900 psi
4.
4,000 psi
12-16.
The rebound method uses a hammer
to test what strength of the
concrete?
1.
Compressive
2.
Shear
3.
Flexural
4.
Load bearing
12-17.
The pullout-test method is
correlated with compressive
strength to determine what
information?
1.
In-place strength
2.
Flexural strength
3.
Load-bearing capacity
4.
Curing time
83
