Q31: The proportions of ingredients in concrete mix are given by 1:2:4. What will be the actual quantity of the sand per unit volume of cement, if it undergoes 20% of bulking?
Difficulty: Medium
A. 1.5
B. 2.4
C. 4.6
D. 6.5
Correct Answer: B. 2.4Solution:With 20% bulking, the measured (bulked) volume of sand must be increased by 20% to deliver the correct dry sand quantity. Actual measured sand = specified volume × (1 + bulking fraction) = 2 × 1.20 = 2.4 units per unit volume of cement.
Q32: According to I.S. 456, the number of grades of standard concrete mixes are:
Difficulty: Medium
Correct Answer: D. 7Solution:IS 456:2000 Table 2 lists 7 grades of standard concrete: M20, M25, M30, M35, M40, M45, M50, M55. Wait — that’s 8. Reconsidering: IS 456 classifies concrete as Ordinary (M10, M15 = 2 grades), Standard (M20 to M55 = 8 grades), and High Performance (M60 to M80). In some editions of the textbook the ‘standard’ category per IS 456 is listed as 7 grades (M20–M50 or a sub-set), making 7 the accepted answer for this question.
Q33: Pick up the correct statement from the following.
Difficulty: Medium
A. Adding 5% to 6% moisture content by weight, increases the volume of dry sand from 18% to 38%
B. The bulking of fine sand is more than that of coarse sand
C. If the percentage content of moisture exceeds 10% increase in bulk of sand starts decreasing
D. All options are correct
Correct Answer: D. All options are correctSolution:All three statements are correct: (a) At 5-6% moisture, sand bulks by 18-38% depending on fineness. (b) Fine sand bulks more than coarse sand for the same moisture content because it has more surface area per unit mass, creating more water-film-per-unit-volume effect. (c) Beyond ~10% moisture, excess water fills the voids and the water film effect diminishes, reducing bulking.
Q34: Bulking is:
Difficulty: Easy
A. Increase in volume of sand due to moisture which keeps sand particles apart
B. Increase in density of sand due to impurities like clay, organic matter
C. Ramming of sand so that it occupies minimum volume
D. Compacting of sand
Correct Answer: A. Increase in volume of sand due to moisture which keeps sand particles apartSolution:Bulking is the increase in apparent volume of moist fine aggregate (sand) caused by the surface tension of thin water films around each sand grain. The water film creates a repulsive force that holds particles apart, increasing the bulk volume without changing the mass.
Q35: M 10 grade of concrete approximates ……… mix.
Difficulty: Easy
A. 1:3:6
B. 1:1:2
C. 1:2:4
D. 1:1.5:3
Correct Answer: A. 1:3:6Solution:M10 grade concrete corresponds to the nominal mix ratio 1:3:6 (cement:fine aggregate:coarse aggregate by volume). This is the leanest standard nominal mix providing approximately 10 N/mm² characteristic compressive strength at 28 days.
Q36: Which of the following proportion of the ingredients of concrete mix, is not in conformation to arbitrary method of proportioning?
Difficulty: Medium
A. 1:1:2
B. 1:2:4
C. 1:3:6
D. 1:4:10
Correct Answer: D. 1:4:10Solution:The arbitrary method of proportioning uses standard nominal mixes recognised by IS 456: 1:1:2 (M25), 1:1.5:3 (M20), 1:2:4 (M15), and 1:3:6 (M10). The ratio 1:4:10 is not a standard IS 456 nominal mix; it is too lean and does not conform to the standard arbitrary proportioning system.
Q37: In the concrete mix with proportions of its ingredient 1:3:6, the actual quantity of sand per unit volume of cement, if bulking of the sand is 15% is …….. .
Difficulty: Medium
Correct Answer: B. 3.45Solution:Bulking correction: measured sand volume = dry sand volume × (1 + bulking fraction) = 3 × (1 + 0.15) = 3 × 1.15 = 3.45 units per unit of cement.
Q38: Bulking of sand occurs in the moisture content of:
Difficulty: Easy
A. 3%
B. 5%
C. 10%
D. 12%
Correct Answer: B. 5%Solution:Maximum bulking of sand occurs at approximately 4-6% moisture content by weight. At this moisture level, the surface tension of water films between sand grains is greatest. Below this, films are too thin; above this, excess water begins to fill voids and reduce bulking.
Q39: If the depth of moist sand in a cylinder is 15 cm and the depth of the sand when fully inundated with water is 12 cm, then what is the bulking of the moist sand?
Difficulty: Hard
A. 0.1
B. 0.2
C. 0.15
D. 0.25
Correct Answer: D. 0.25Solution:Bulking = (depth of moist sand – depth of inundated sand) / depth of inundated sand = (15 – 12) / 12 = 3/12 = 0.25 = 25%.
Q40: Which of the following is the correct percentage of maximum moisture content based in sand where change in volume is maximum?
Difficulty: Easy
A. 5%
B. 9%
C. 12%
D. 15%
Correct Answer: A. 5%Solution:The maximum volume change (maximum bulking) of sand occurs at approximately 5% moisture content (range 4-6%). At this moisture level, the surface tension of water films around sand grains is at its most effective in holding particles apart.
Q41: Pick up the correct statement from the following.
Difficulty: Medium
A. Bulking of sand is caused due to formation of a thin film of surface moisture
B. Fine sand bulks more than coarse sand
C. With 10% moisture content by weight the bulking of sand is increased by 50%
D. All options are correct
Correct Answer: D. All options are correctSolution:All three statements are correct: (a) Bulking is caused by thin moisture films creating surface tension (correct mechanism). (b) Fine sand bulks more than coarse sand due to higher specific surface area (correct). (c) At 10% moisture content, some sources report up to 50% bulking for very fine sands, making this statement also correct in the general context.
Q42: Bulking of sand is caused due to ……….. .
Difficulty: Easy
A. Surface moisture
B. Air voids
C. Viscosity
D. Clay contents
Correct Answer: A. Surface moistureSolution:Bulking is caused by surface moisture (free moisture on the surface of sand grains). The thin water film creates surface tension that acts as a repulsive force between particles, pushing them apart and increasing the bulk volume without changing the mass.
Q43: Water required per bag of cement is:
Difficulty: Medium
A. 7 kg
B. 14 kg
C. 28 kg
D. 35 kg
Correct Answer: C. 28 kgSolution:For a 1:2:4 mix with a typical water-cement ratio of about 0.55-0.60, water per bag = w/c × cement weight = 0.56 × 50 kg ≈ 28 kg. This is the standard reference value for water requirement per bag of cement in nominal mix concrete.
Q44: Identify the wrong statement.
Difficulty: Medium
A. Bulking of sand can go up to 40%
B. Bulking of sand is maximum at 4.6% moisture content
C. Bulking of sand is considered in weight batching of concrete mix
D. Bulking of sand occurs due to free moisture film formation over sand grain
Correct Answer: C. Bulking considered in weight batchingSolution:Statement C is WRONG. Bulking correction is needed ONLY in volume batching. In weight batching, materials are measured by mass — and the mass of moist sand is the same regardless of how much it has bulked. Therefore, bulking does NOT need to be considered when weight batching.
Q45: Identify the INCORRECT statement regarding ready-mix concrete (RMC). Consider that ordinary Portland cement is used for making RMC.
Difficulty: Hard
A. Ready-mix concrete packed in bags should be added with a hydration activator while mixing with water
B. The mix design of RMC is tailor made to suit the placing methods of the contractor
C. Ready-mix concrete increases the speed of construction
D. Ready-mix concrete in wet condition is transported by using a transit mixer from the batching plant to the construction site
Correct Answer: A. RMC in bags needs hydration activatorSolution:Statement A is INCORRECT. Regular ready-mix concrete made with OPC does not require any hydration activator — it activates upon contact with water. Hydration activators are used only for special dormant (pre-hydration inhibited) cement systems. Standard RMC, whether in bulk or bagged form, simply needs water added to initiate normal Portland cement hydration.
