This set of Tricky Concrete Technology Questions and Answers focuses on “Defects Occurring During Construction”.
1. What is the moisture content in slurry for wet process?
Explanation: The moisture content in slurry for wet process is 35-50%. 12% is the moisture content for dry process.
2. The use of crushed aggregates may results in 10 to 20% higher compressive strength. Is this statement true or false?
Explanation: The use of crushed aggregates may results in 10 to 20% higher compressive strength due to development of stronger aggregate-mortar bond.
3. In a dry environment, concrete strength will be loosed as much as ________ % in moist environment.
Explanation: Laboratory tests show that concrete strength will be loosed as much as 50% in dry environment as compared to moist environment.
4. After finishing concrete surface must be kept ________
b) First dry it and then wet it
c) First wet it and then dry it
Explanation: After finishing concrete surface must be kept wet, so that it’d be prevented from evaporation.
5. A _________ paste structure undergoes _________ creep.
a) Good, high
b) Poor, high
c) Good, average
d) Poor, low
Explanation: The amount of paste content and its quality is one of the most important factors influencing creep. A poorer paste structure undergoes higher creep.
6. The rate of creep rapidly _________ with time.
c) Doesn’t affect
d) Depends on the temperature
Explanation: The rate of creep rapidly decreases with time. The time taken by a concrete structure to attained creep is 5 years.
7. The rate of creep generally ____ with the ____ of the size of aggregates.
a) Increase, increase
b) Decrease, decease
c) Increase, decrease
d) 2.5, 12mm
Explanation: The rate of creep generally decreases with the increase of the size of aggregates. Time rate of deformation of a material subject to stress at a constant temperature. It is the slope of the creep vs. time diagram obtained in a creep test.
8. Reduction in the volume due to shrinkage causes _________
a) Low volume
b) Volumetric strain
c) Volumetric stress
d) W/c ratio
Explanation: Reduction in the volume due to shrinkage causes volumetric strain in freshly hardened concrete.
9. “Shrinkage in concrete is caused mainly by loss of water by evaporation or by hydration of cement”. Is this statement true or false?
Explanation: Shrinkage in concrete is caused mainly by loss of water by evaporation or by hydration of cement.
10. Dry intervals in surface wetting leads to ____________
c) High strength
d) Good workability
Explanation: Dry intervals or patches can lead to crazing or cracking on the slab surface. The effect of surface wettability on the dynamics of crack formation and their characteristics are examined during the drying of aqueous colloidal droplets containing nano particles.
Sanfoundry Global Education & Learning Series – Concrete Technology.
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