This set of Concrete Technology Multiple Choice Questions & Answers (MCQs) focuses on “Mass Concrete and Chemical Action – Sulphate Attack”.
1. The breaking up of cohesion in a mass of concrete is called ________
a) Workability
b) Segregation
c) Bleeding
d) Creep
View Answer
Explanation: Segregation in concrete is commonly thought as separation of some size groups of aggregates from cement mortar in isolated locations with corresponding deficiencies of these materials in other locations.
2. The separation of water or water-cement mixture from the freshly mixed concrete is known as bleeding.
a) True
b) False
View Answer
Explanation: The separation of water or water-cement mixture from the freshly mixed concrete is known as bleeding.
3. The continuous strain, which the concrete undergoes due to application of external loads, is called __________
a) Workability
b) Segregation
c) Bleeding
d) Creep
View Answer
Explanation: The continuous strain, which the concrete undergoes due to application of external loads, is called creep.
4. Harshness in concrete is due to the excess of _____________
a) Water
b) Finer particles
c) Middle sized particle
d) Coarser particle
View Answer
Explanation: It is the rough finishing property of concrete and causes improper proportioning, less compaction, low water content, excess of medium sized aggregates, deficiency of sand etc.
5. In order to avoid segregation, the concrete should not be thrown from a height.
a) True
b) False
View Answer
Explanation: In order to avoid segregation, the concrete should not be thrown from a height of 100 cm.
6. Reinforced cement concrete is equally strong in taking __________
a) Tensile and compressive stresses
b) Compressive and shear stresses
c) Tensile, compressive and shear stresses
d) Tensile and shear stresses
View Answer
Explanation: According to IS 456:2000, Reinforced cement concrete is equally strong in taking Tensile, compressive and shear stresses.
7. Plain cement concrete is strong in taking ___________
a) Tensile stress
b) Compressive stress
c) Shear stress
d) Tensile, compressive and shear stresses
View Answer
Explanation: Plain cement concrete is strong in taking compressive stress and week in tensile stress.
8. How many types of sulphates attack occur in concrete?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: There are two types of sulphates attack in concrete and mortar i.e., internal attack and external attack.
9. What is internal sulphates attack?
a) Sulphate are more usually are a result of high-sulphate soils
b) Sulphate are more usually are a result of ground water
c) Industrial waste water
d) Hydraulic cements
View Answer
Explanation: Internal sulphates attack are rarer but originates from such concrete-making materials.
10. What is internal sulphates attack?
a) Presence of natural gypsum in the aggregates
b) Soil may contain excess of gypsum
c) Sulphate are more usually are a result of ground water
d) Industrial waste water
View Answer
Explanation: Internal sulphates attack are rarer but originates from such concrete-making materials like Presence of natural gypsum in the aggregates.
11. What is external sulphates attack?
a) Industrial waste water
b) Presence of natural gypsum in the aggregates
c) Hydraulic cements
d) Portland cement might be over-sulphated
View Answer
Explanation: External sources of sulphate are very common and are usually are a result of high-sulphate soils and ground waters or can be result into industrial pollution.
12. Fly ash affects the sulphate attack.
a) True
b) False
View Answer
Explanation: The addition of a pozzolanic admixture e.g. fly ash. It reduces the C3A content of cement which cause sulphates attack.
13. Low w/c ratio helps to control sulphate attack.
a) True
b) False
View Answer
Explanation: Low water cement ratio directly cause low permeability which is the best protection towards sulphate attack.
Sanfoundry Global Education & Learning Series – Concrete Technology.
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