1.At constant workability, what is the reduction in mixing water?
a) 1-2%
b) 50%
c) .1-.4%
d) 5-15%
Explanation: At constant workability, the reduction in mixing water is expected to be of the order of 5% to 15%.
2. 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
Explanation: Where low degree of workability is required like Deep beams, column and beam junctions.
3. 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
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.
4. What is the allowed reduction of water with super plasticizers without reducing workability?
a) 10%
b) 20%
c) 30%
d) 40%
Explanation: Super plasticizers permits reduction of water content about 30% without reducing the workability.
5. Is it possible to use w/c ratio as low as 5?
a) Yes
b) No
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.
6.What is the limitation of Carboxylic acids in High range water reducers?
a) 0
b) .1%
c) .2%
d) .3%
Explanation: It is the standard value of limitation of Carboxylic acids in High range water reducers i.e. 0.1 percentage.
7. What is accelerator?
a) Which speed up the initial set of concrete
b) Which delays the initial set of concrete
c) Which speed up the final set of concrete
d) Which delays the final set of concrete
Explanation: An admixture used to speed up the initial set of concrete is called accelerator.
8. What is retender?
a) Which speed up the initial set of concrete
b) Which delays the initial set of concrete
c) Which speed up the final set of concrete
d) Which delays the final set of concrete
Explanation: An admixture used to delay the initial set of concrete is called retender.
9. NaOH is the example of retenders.
a) True
b) False
Explanation: NaOH speed up the initial rate of hydration of cement and also speed up the initial set of concrete.
10. Zinc is the example of retenders.
a) True
b) False
Explanation: Zinc delays the initial rate of hydration of cement and also delays the initial set of concrete.