This set of Concrete Technology Multiple Choice Questions & Answers (MCQs) focuses on “Admixtures”.
1. What do you mean by admixtures?
a) Ingredients which are added to in cement before or after concrete mix
b) Ingredients which are added to make aggregates healthier
c) Ingredients added in cement to make it shinier
d) Ingredients added in concrete to make good workability
Explanation: Admixtures are those ingredients in concrete other than Portland cement, water, and aggregates that are added to the mixture immediately before or after the concrete mix.
2. Which of the following statement is incorrect about the function of admixtures.
a) To accelerate the initial set of concrete, to speed up the rate of development of strength at early ages
b) To enhance the workability
c) To reduce the segregation in grout and concrete mixers
d) To retard the initial set, to keep concrete workable for a shorter time for placement
Explanation: To retard the initial set, to keep concrete workable for a longer time for placement is incorrect in the above statement.
3. Which of the following statement is incorrect about the function of admixtures.
a) To increase the strength of concrete by reducing the water content and by densification of concrete
b) To increase the durability of concrete to enhance its resistance to special conditions of exposure
c) To increase the capillary flow of water through concrete and to increase its impermeability to liquids
d) To control the alkali-aggregate expansion or alkali silica reaction
Explanation: To decrease the capillary flow of water through concrete and to increase its impermeability to liquids is incorrect in the above statement.
4. Which of the following option doesn’t come in chemical admixtures?
c) Super plasticizer
Explanation: Pozzolanic property comes under mineral admixtures not under chemical admixtures.
5. Classification of admixtures are classified into ________ types.
Explanation: Classification of admixtures are classified into 2 types i.e. chemical admixtures and mineral admixtures.
6. Which of the following option doesn’t come in mineral admixtures?
a) Set retarders
b) Blast Furnace Slag
d) Silica Fume
Explanation: Set retarders property comes under chemical admixtures not under mineral admixtures.
7. Admixtures which cause early setting, and hardening of concrete are called __________
c) Super plasticizer
Explanation: Accelerators helps the admixtures in causing early setting time and hardened the concrete.
8. Mid-range water reducers result in at least _________ %.
Explanation: Mid-range water reducers result in at least 8%. Mid-range water reducers provide more consistent setting times than standard water reducers.
9. What is the main function of set retarders?
a) Increase curing rate
b) Slows curing rate
c) Improves workability at low w/c ratio
d) Speeds up start of finishing operations
Explanation: Used to counteract hot weather conditions that cause increased rate of hardening. This makes placing and finishing difficult.
10. Super plasticizers reduce water requirement by ___________ %.
Explanation: Super plasticizers reduce water requirement by 12-30 %. Makes mix highly fluid and can be placed with little or no vibration or compaction.
Sanfoundry Global Education & Learning Series – Concrete Technology.
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