1. Which one is not a chemically active pore filling material?
a) Silicate of soda
b) Aluminium
c) Chalk
d) Zinc
Explanation: Chemically active pore filling materials: silicate of soda, aluminium, zinc sulphates and calcium chloride.
2. Which one is not a chemically inactive pore filling material?
a) Aluminium
b) Chalk
c) Talc
d) Fullers earth
Explanation: Chemically inactive filling material: chalk, fullers earth and talc. And aluminium is active filling material.
3. Chemically active pore fillers __________ the setting of concrete.
a) Retards
b) Decrease
c) Accelerates
d) No change
Explanation: Chemically active pore fillers accelerate the setting of concrete and thus render the concrete more impervious at 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. Water repelling materials like soda, potash soaps, etc make the concrete pervious.
a) True
b) False
Explanation: Water repelling materials like soda, potash soaps, calcium soaps, waxes, fats, vegetable oils repel water and make the concrete impervious.
6. Entrapped air normally exists in the form of relatively __________ air voids.
a) Small
b) Absent
c) Large
d) Medium
Explanation: Entrapped air normally exists in the form of relatively large air voids, which are not dispersed uniformly throughout the mix, entrained air exists in the form of minute disconnected bubbles well distributed throughout the mix.
7. What are 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
Explanation: The organic substances or combinations of organic and inorganic substances, which allow a reduction in water content for the given workability, or give higher workability at the same water content.
8. Which one is an anionic surfactants?
a) Polyglycol esters
b) Hydroxylated carboxylic acids
c) Lignosulphonates
d) Carbohydrates
Explanation: Anionic surfactants such as lignosulphonates and their modifications and derivatives, salts of sulphonates hydrocarbons
9. What is the amount used of plasticizers in cement by weight?
a) 0
b) .1-.4%
c) 1%
d) 1-2%
Explanation: Plasticizers are used in the amount of 0.1 percentage to 0.4 percentage by weight of cement.
10. 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%
Explanation: A good plasticizer is one which does not cause air-entrainment in concrete is greater than 1-2%.