This set of Concrete Technology Multiple Choice Questions & Answers (MCQs) focuses on “New Generation Plasticizers”.
1. What is plasticizers?
a) Which adds water for workability
b) Which reduces water for workability
c) Which decreases workability at the same water content
d) Which oxidizes water for workability
View Answer
Explanation: The organic substances or combinations of organic and inorganic substances, which allow a reduction in water content for the given workability, or give a higher workability at the same water content.
2. Which one is an anionic surfactants?
a) Polyglycol esters
b) Hydroxylated carboxylic acids
c) Lignosulphonates
d) Carbohydrates
View Answer
Explanation: Anionic surfactants such as lignosulphonates and their modifications and derivatives, salts of sulphonates hydrocarbons.
3. What is the amount used of plasticizers in cement by weight?
a) 0
b) .1-.4%
c) 1%
d) 1-2%
View Answer
Explanation: Plasticizers are used in the amount of 0.1% to 0.4% by weight of cement. Plasticizers or water reducers, and superplasticizers or high range water reducers, are chemical admixtures that can be added to concrete mixtures to improve workability.
4. What is the limitation of plasticizers?
a) A good plasticizer is one which does not cause air-entrainment in concrete > .1-.2%.
b) A good plasticizer is one which does not cause air-entrainment in concrete > 5%.
c) A good plasticizer is one which does not cause air-entrainment in concrete > 10-20%.
d) A good plasticizer is one which does not cause air-entrainment in concrete > 1-2%.
View Answer
Explanation: A good plasticizer is one which does not cause air-entrainment in concrete > 1-2%. Plasticizers or water reducers are chemical admixtures that can be added to concrete mixtures to improve workability.
5. At constant workability, what is the reduction in mixing water?
a) 1-2%
b) 50%
c) .1-.4%
d) 5-15%
View Answer
Explanation: At constant workability, the reduction in mixing water is expected to be of the order of 5% to 15%.
6. Where do we use plasticizers?
a) Where low degree of workability is required
b) Where medium degree of workability is required
c) Where high degree of workability is required
d) Where very low degree of workability is required
View Answer
Explanation: Where low degree of workability is required like Deep beams, column and beam junctions.
7. What is super plasticizers?
a) Which adds water for workability
b) Which reduces high range of water for workability
c) Which decreases workability at the same water content
d) Which oxidizes water for workability
View Answer
Explanation: The organic substances or combinations of organic and inorganic substances, which allow a high reduction in water content for the given workability at the same water content.
8. What is the allowed reduction of water with super plasticizers without reducing workability?
a) 10%
b) 20%
c) 30%
d) 40%
View Answer
Explanation: Super plasticizers permits reduction of water content about 30% without reducing the workability.
9. Is it possible to use w/c ratio as low as 5?
a) Yes
b) No
View Answer
Explanation: It is possible to use w/c ratio as low as 0.25 or even lower and yet to make flowing concrete to obtain strength of order 120Mpa or more.
10. What is the limitation of Carboxylic acids in High range water reducers?
a) 0
b) .1%
c) .2%
d) .3%
View Answer
Explanation: It is the standard value of limitation of Carboxylic acids in High range water reducers i.e. .1%.
Sanfoundry Global Education & Learning Series – Concrete Technology.
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