6. Discuss the different types of volume change in concrete at early and long-term ages.
6. Discuss the different types of volume change in concrete at early and long-term ages.
8. A center-point loading flexural test was performed on a concrete beam having a size of
100×100×500 mm. The beam is sitting on two supports located at 25 mm from each edge of
beam. If the failure load was 17.5 kN, find the flexural strength.
9. Considering the two tests of flexure, 3-points and 4-points, which one is more suitable for
bending test and why?
10. The compression strength test was performed on several samples of concrete molded in four
types of molds cubes of 0.100 m×0.100 m ×0.100 m and of 0.150 m×0.150 m × 0.150 m, and
cylinders having a cross section of d=100 mm by H=200 mm and d=150 mm by H=300 mm,
respectively. If the weight of the samples and the loads at failure are as given in the Table. Both
cubes and cylinder samples are cast from the same concrete batch under the same conditions
and subjected to the same curing method.
11. Calculate the density (in kg/m3
) and the compressive strength of the concrete (in MPa or
N/mm2
) for all samples from each type. Why the strength is different between the cubes and
the cylinders? explain
Cubic Sample of 100 mm Weight (kg) Load (kN)
1 2.52 655.8
2 2.59 670.9
3 2.47 675.9
Cubic Sample of 150 mm
1 8.43 1485
2 8.61 1492
3 8.53 1498
Cylindrical sample of 100×200
1 3.94 457.5
2 3.75 430.0
3 3.83 413.8
Cylindrical sample of 150×300
1 12.86 1056
2 13.0 1005
3 13.12 1020
12. A normal-weight concrete has an average compressive strength of 20 MPa.
What is the estimated flexure strength?
What is the estimated tensile strength?
13. Comparing ordinary normal Portland Cement Concrete (PCC) with mild steel, answer the following
questions:
a. Which one is stronger?
b. Which one has a higher modulus of elasticity or stiffness?
c. Which one is more brittle?
d. What is the range of compressive strength for a typical normal PCC?
e. What is the range of compressive strength for a high-strength concrete?
f. What would be a reasonable range for PCC modulus elasticity?
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