MCQs on Ingredients of Concrete
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Q61: The machine used for testing abrasion resistance of coarse aggregate is
Difficulty: Easy
Solution:
The Los Angeles (LA) abrasion test is the standard method for measuring the abrasion resistance and toughness of coarse aggregate. It uses a rotating steel drum with steel balls and the aggregate sample.
Q62: Good cement contains
Difficulty: Medium
Solution:
C3S (Tricalcium Silicate) is the compound primarily responsible for early strength development in cement. A good cement with high C3S content develops strength rapidly and achieves higher early strength.
Q63: Good sand for construction should never be taken from
Difficulty: Easy
Solution:
Sea bed sand contains salt (mainly sodium chloride) and shell particles. Salt accelerates corrosion of steel reinforcement and disrupts the concrete’s setting, making it unsuitable for construction without very thorough washing.
Q64: The aggregate impact value is used for determining the property of aggregate known as
Difficulty: Easy
Solution:
The Aggregate Impact Value (AIV) test measures the resistance of aggregates to sudden impact (shock loads), which is a measure of toughness, not hardness or abrasion resistance.
Q65: The fineness modulus of fine aggregate is
Difficulty: Medium
Solution:
The fineness modulus (FM) is a numerical index that indicates the average size of particles in an aggregate. A higher FM indicates coarser aggregate; a lower FM indicates finer aggregate. It is an indicator, not strictly a proportional relationship.
Q66: One bag of cement contains
Difficulty: Easy
Solution:
In India, one standard bag of Ordinary Portland Cement (OPC) contains 50 kg of cement. This is the standard packaging unit defined by IS 269 for all 43-grade and 53-grade OPC.
Q67: Fine aggregates are those which are retained on
Difficulty: Medium
Solution:
Fine aggregates PASS through a 4.75 mm IS sieve; they are not defined by being ‘retained on’ any single small sieve. The option ‘None of these’ is correct because fine aggregate includes all particles passing 4.75 mm, down to 75 microns.
Q68: The coarsest sand is available in zone
Difficulty: Easy
Solution:
IS 383 classifies fine aggregate into four grading zones (Zone I to Zone IV), with Zone I being the coarsest and Zone IV being the finest. The coarsest sand is therefore available in Zone I.
Q69: Fineness modulus of fine aggregate varies from
Difficulty: Medium
Solution:
The fineness modulus (FM) of fine aggregate (sand) ranges between 2.0 and 3.5 as per IS 383 grading zones. Zone IV (finest) has FM around 2.0, and Zone I (coarsest) reaches up to FM 3.5.
Q70: In which type of sand, salt is found?
Difficulty: Easy
Solution:
Sea sand is collected from seashore and sea beds. Due to its marine origin, it naturally contains salt (sodium chloride and other chlorides) from the seawater, making it unsuitable for reinforced concrete without thorough washing.
Q71: The most common alternative material used in place of cement in cement concrete is
Difficulty: Easy
Solution:
Fly ash is the most widely used supplementary cementitious material (SCM) globally. It is a by-product of coal combustion in thermal power plants and is used in partial replacement of cement in concrete to improve workability, reduce heat of hydration, and enhance long-term durability.
Q72: The number of ingredients in concrete are
Difficulty: Easy
Solution:
Concrete has four primary ingredients: cement, fine aggregate (sand), coarse aggregate (stone/gravel), and water. Sometimes admixtures are added, but the basic mix contains exactly four components.
Q73: Quantity of water used per cubic meter of concrete
Difficulty: Hard
Solution:
The water content in concrete is approximately 5% of the weight of aggregate (to wet aggregate surfaces) plus 30% of the weight of cement (to hydrate the cement). This empirical relationship gives a useful estimate for initial water quantity estimation.
Q74: The maximum size of aggregate to be used in a gravity dam should not exceed
Difficulty: Medium
Solution:
For gravity dam concrete, IS 456 and dam design guidelines permit aggregate up to 40 mm as the standard maximum size. The large volume of mass concrete in dams allows for larger aggregate, which reduces cement content and heat of hydration.
Q75: Lightweight aggregates are usually made from
Difficulty: Easy
Solution:
Most natural lightweight aggregates (such as pumice, scoria, and cinder) originate from volcanic activity, which produces vesicular (pore-filled) rock structures. Their low density results from the large number of internal voids formed by gas trapped during volcanic eruption.