CE 3020 Construction Materials HOMEWORK Dr. Kurtis Question 1

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29 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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CE 3020 Construction Materials





HOMEWORK

Dr. Kurtis










Question 1

A concrete cylinder (6X12in.), tested in compression according to ASTM C469 with a
load rate of 30 psi/sec , fails under a 142,000 lb. load.

(a)

What is the compressive strength of
the concrete cylinder?


(b)

If the unit weight of the concrete is 140pcf, estimate the elastic modulus of the
concrete.


(c)

Would the compressive strength be
higher

or
lower

than the value calculated in part (a) if:



a 6 in. concrete cube was tested instead of a c
oncrete cylinder?



a 3X6 in. cylinder was tested instead of a 6X12 in. cylinder?



the load rate was 100 psi/sec?


(d)

Another 6X12 in. cylinder, produced from the same mixture as the cylinder tested in
compression, is tested according to the splitting tension

test (ASTMC496) and fails
under a 57,000 lb. load. What is the splitting tensile strength of the concrete?


(e)

Express the tensile strength as a % of the compressive strength. Is this within the
usual range for normal strength concrete?


Question 2

The dat
a in Table 1 was collected using a compressometer and a universal testing
machine during a compression test of a concrete cylinder performed according to ASTM
C 469. The specimen was a 6×12" concrete cylinder.



Table 1: Strain and load data

Microstrain
Load (lbs)
0
0
50
13996
200
42920
380
63448
590
83975
840
102636
1150
111966
1560
113521
1890
105746
2000
99526


Plot a st
ress
-
strain curve for this specimen. Stress (y
-
axis) should be in units of psi and
strain (x
-
axis) as microstrain (strain (in/in) × 10
-
6
). From your plot, determine:

-

the ultimate strength of the concrete

-

the strain % at failure


-

initial tangent modu
lus


-

chord modulus


-

secant modulus.



Question 3

Design a 1cu.yd. concrete mixture by the ACI absolute volume method. Produce results
which take into account field moisture conditions, according to the following
specifications and using materia
ls with the following characteristics:

(1)

Strength: 5000 psi, (no acceptance criteria)

(2)

Exposure to a moderate sulfate environment

(3)

No air entrainment

(4)

Slump = 2”

(5)

Cement = Type II; specific gravity = 3.15

(6)

Aggregate data:


COARSE AGGREGATE

MSA = 1.5”
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