PORTLAND CEMENT CONCRETE - Materials for Civil and Construction Engineers - page 302

7.26 The flexure strength test was performed on a concrete beam having
a cross section of 0.15 m by 0.15 m and a span of 0.45 m. If the load
at failure was 35.7 kN, calculate the flexure strength of the concrete.
7.27 A normal-weight concrete has an average compressive strength of 20
MPa. What is the estimated flexure strength?
7.28 Discuss two nondestructive tests to be performed on hardened con-
crete. Show the basic principles behind the tests and how they are
performed.
7.29 Discuss the concept of concrete maturity meters.
7.30 Discuss four alternatives that increase the use and application of
conventional concrete.
7.31 What is self-consolidating concrete? How are its properties
achieved? How are these properties measured?
7.32 What is flowable fill? Discuss its ingredients and its advantages.
7.33 Discuss the concept of high-performance concrete. Discuss some of
its properties that make it preferred over conventional concrete.
7.34 Comparing PCC with mild steel, answer the following questions:
a. Which one is stronger?
b. Which one has a higher modulus or stiffness?
c. Which one is more brittle?
d. What is the range of compressive strength for a typical PCC?
e. What is the compressive strength for a high-strength concrete?
f. What would be a reasonable range for PCC modulus?
7.35 In a ready-mix plant, cylindrical samples are prepared and tested
periodically to detect any mix problem and to ensure that the com-
pressive strength is higher than the lower specification limit. The
minimum target value was set at 4000 psi. The following compres-
sive strength data were collected.

Compressive Compressive

Sample No. Strength (psi) Sample No. Strength (psi)

1 4914 14 5772

2 4732 15 4270

3 5670 16 5096

4 4310 17 4670

5 6110 18 5174

6 4316 19 5434

7 5240 20 3692

8 4950 21 4510

9 5230 22 3680

10 4190 23 4100

11 5770 24 3680

12 4524 25 3910

13 4056