1. Dry intervals in surface wetting leads to ___________
a) Cracking
b) Fogging
c) High strength
d) Good workability
Explanation: Dry intervals or patches can lead to crazing or cracking on the slab surface.
2. Damp proofing ____________ resist water well enough.
a) Does
b) Does not
c) Doesn’t effect
d) Depends on the temperature
Explanation: Damp proofing does not resist water well enough to prevent oversaturation from ground water, or excessive and constant humidity.
3. Chemically active pore fillers ____________ the setting of concrete.
a) Retards
b) Decrease
c) Accelerates
d) No change
Explanation: Chemically active pore fillers accelerates the setting of concrete and thus render the concrete more impervious at an early age.
4. Chemically inactive pore fillers ____________ the workability.
a) Decrease
b) Increase
c) Don’t affect
d) Improve
Explanation: Chemically inactive pore fillers improve the workability and to facilitate the reduction of water for given workability and to make dense concrete which is basically impervious.
5. What do you mean by workability?
a) ASTM C 125 defines workability as the property determining the effort required to manipulate a freshly mixed quantity of concrete with a maximum loss of homogeneity
b) ASTM C 125 defines workability as the property determining the effort required to manipulate a freshly mixed quantity of concrete with minimum loss of heterogeneity
c) The strict definition of workability is the amount of useful external work, against the external friction between the individual particles in the concrete, necessary to produce full compaction
d) The workability is also defined as the ease with which a freshly mixed concrete can be properly compacted and also that it can be transported, placed, and finished
Explanation: The workability is defined as the ease with which a freshly mixed concrete can be properly compacted and also that it can be transported, placed, and finished.
6. Workability of concrete can be improved by the addition of __________
a) Iron
b) Sodium
c) Zinc
d) Sulphur
Explanation: Inorganic retardants include oxides of lead, zinc, phosphate and magnesium salts. Most retarders also act as water reducers.
7. Workability of concrete can be improved by __________
a) More sand
b) More cement
c) More fine aggregates
d) Fineness of coarse aggregate
Explanation: Workability of concrete can be improved by more cement and water with proper water cement ratio.
8. Workability of concrete can be improved by ___________
a) Increasing size of aggregates
b) Decreasing size of aggregates
c) Increasing fine aggregates
d) Increasing flaky aggregates
Explanation: Workability should be obtained by the use of a well-graded aggregate which has the largest maximum particle size possible.
9. Workability of concrete is directly proportional to __________
a) Grading of the aggregates
b) Time of transit
c) Aggregates cement ratio
d) Water cement ratio
Explanation: Grading of aggregate: Poor grading reduces consistency. That’s why it is directly proportional to grading of the aggregates.
10. Workability of concrete is inversely proportional to __________
a) Grading of the aggregates
b) Time of transit
c) Aggregates cement ratio
d) Water cement ratio
Explanation: Workability of concrete is inversely proportional to the Water cement ratio because if the amount of w/c ratio increases, workability decreases.