Concrete Properties and Proportions Quiz

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What is the criterion of quality concrete in structural member design?

Flexural strength

Compressive strength (correct)

Tensile strength

Shear strength

At what age are concrete specimens typically tested to determine compressive strength?

14 days

21 days

35 days

28 days (correct)

In what modes can the failure of concrete occur during compressive strength testing?

Columnar fracture only

Shear and splitting failure (correct)

Flexural failure

Tensile failure only

What is the specified minimum value for the compressive strength of concrete according to NSCP 2015 Section 401.2.2?

17 MPa Signup and view all the answers

What is the type of loading condition used when testing 28-day-old concrete cylinders for compressive strength?

Static load Signup and view all the answers

What is the relationship that influences the performance of a reinforced concrete member under load?

Stress-strain relationship of concrete and steel Signup and view all the answers

What is the compressive strength range of normal weight concrete at about 28 days?

10 MPa to 40 MPa Signup and view all the answers

What are the disadvantages of lightweight structural concretes?

Higher cost, more care in placing, greater porosity, and more drying shrinkage Signup and view all the answers

What is the main reason for using lightweight concrete?

To reduce dead load Signup and view all the answers

What type of concrete is typically used in radiation shields and counterweights?

Heavyweight concrete Signup and view all the answers

Which type of specimen shape leads to lower compressive strength values?

6in x 12in cylinders Signup and view all the answers

At what age does the development of strength start for normal weight concrete?

7 days Signup and view all the answers

What factor can increase the strength of concrete?

Increasing the cement content Signup and view all the answers

How do special admixtures affect concrete?

Improve quality and strength Signup and view all the answers

What effect does using a vibrator have on concrete?

Lessens the percentage of air voids Signup and view all the answers

How does the curing time influence the strength of concrete?

The longer the curing time, the greater the strength Signup and view all the answers

When is concrete typically tested for strength?

At 28 days Signup and view all the answers

What happens to the compressive strength of concrete under sustained loads?

Reduces by 30% Signup and view all the answers