MCQs on Proportioning of Concrete Mixes
15 questions. Tap an option to check it instantly, then read the solution.
Question 1Medium
As per IS 10262 : 2019, what is the approximate amount of entrapped air to be expected in normal (non-air-entrained) concrete, when 10 mm Nominal Maximum Size of Aggregate is used?
Answer: A. 1.5%
Per IS 10262:2019 Table 2, the approximate amount of entrapped air in normal concrete increases as aggregate size decreases. For 10 mm NMSA the entrapped air is 1.5%, for 20 mm NMSA it is 1.0%, and for 40 mm NMSA it is 0.5%.Question 2Easy
Identify the correct methods of surface preparation used for joining old and new concrete to each other. (i) Sandblasting (ii) Chipping (iii) Removal of surface by grinding
Answer: B. All of i, ii and iii
All three methods are used to prepare existing concrete surfaces before bonding new concrete. The goal is to remove the weak laitance layer (cream of cement + fine particles at the surface), expose aggregate, and create a rough texture for mechanical bonding between old and new concrete.Question 3Easy
In case of volume batching followed for the manufacture of cement concrete, generally, the volume of the bag of cement is considered as ______.
Answer: D. 35 litres
A standard cement bag contains 50 kg of cement. The loose bulk density of Portland cement is approximately 1440 kg/m³, giving a bag volume of 50/1440 = 0.0347 m³ ≈ 35 litres. This is the standard volume used for volume batching calculations.Question 4Medium
The Department of Environment (DOE) method is basically used for which of the following purposes? (i) Concrete mix design (ii) Road mix design (iii) Mix Design with pulverized fuel ash (iv) Mix Design with GGBFS
Answer: C. (i), (ii), (iii), and (iv)
The DOE method (developed by the UK Building Research Establishment) covers all four purposes: standard concrete mix design, road pavement concrete, mixes with pulverized fuel ash (PFA/fly ash), and mixes with ground granulated blastfurnace slag (GGBFS). It is one of the most comprehensive empirical mix design methods.Question 5Medium
Calculate the volume of sand required for making 3 m³ of concrete with a nominal mix in the proportion 1:2:4 for the construction of an RCC beam.
Answer: B. 1.32 m³
Dry volume of concrete = 1.54 × wet volume = 1.54 × 3 = 4.62 m³. Sand fraction = 2/(1+2+4) = 2/7. Volume of sand = (2/7) × 4.62 = 1.32 m³.Question 6Easy
A concrete design mix with a low water/cement ratio and also using larger aggregates results in:
Answer: D. Gains in concrete compressive strength
Low w/c ratio directly increases compressive strength (Abrams' Law). Larger aggregates reduce water demand (less surface area to wet), allowing a lower effective w/c ratio, which further improves strength. Both factors together compound to produce significant strength gains.Question 7Easy
When the fine aggregate is moist, volume batching is not considered as a good method for proportioning because of the ______.
Answer: C. Bulking of sand
When moist fine aggregate (sand) is measured by volume, the moisture film around particles pushes them apart, causing the sand to occupy a larger volume than in its dry state. This is called 'bulking.' The measured volume appears to contain more sand than it actually does, leading to under-proportioning of sand in the mix.Question 8Easy
During a concrete mix design process, what happens to the free maximum water cement ratio when grade of concrete is increased?
Answer: B. Decreases
Higher grade concrete (e.g., M30 vs M20) requires higher compressive strength. Per Abrams' Law, higher strength demands a lower water-cement ratio. Therefore, as the concrete grade increases, the maximum permissible free water-cement ratio decreases.Question 9Easy
The phenomenon of increase in the volume of a given mass of sand caused by the films of water pushing the sand particles apart is referred to as:
Answer: C. Bulking
Bulking is the increase in apparent volume of moist sand (or fine aggregate) due to the surface tension of thin water films around each particle, which holds particles apart and prevents them from packing closely. It is most pronounced at 4-6% moisture content and can cause a volume increase of up to 30-40%.Question 10Hard
In a cement concrete work mixed in proportion 1:2:4 by volume, the fine aggregate is observed to have a bulking of 10%. If the correction for bulking is NOT applied, what will be the actual dry fine aggregate in the concrete mix proportion?
Answer: A. 2 / 1.1
The specified sand proportion is 2 (volumes). With 10% bulking, the moist sand occupies 2 volumes but contains only 2/1.1 volumes of actual dry sand. If correction is NOT applied, the batch box is filled to 2 volumes of bulked sand, delivering only 2/1.1 = 1.82 volumes of actual dry sand — a deficit of ~9%.Question 11Medium
Select the INCORRECT statement from the following with regard to weight batching of concrete.
Answer: B. Gauge boxes are used to weigh the fine and coarse aggregates
Statement B is INCORRECT. Gauge boxes (also called farma or measuring boxes) are used in VOLUME batching, not weight batching. In weight batching, aggregates are measured using weigh-scales, load cells, or weigh-hoppers. Gauge boxes are for measuring volume.Question 12Hard
If the effective plan area of a warehouse is 54 square m, and maximum height of piles permitted is 270 cm, then what is the number of cement bags that can be stored?
Answer: D. 2700
Standard calculation: each 50 kg cement bag when laid flat is approximately 5.4 cm thick. At 270 cm height: 270/5.4 = 50 bags per m². Number = 54 m² × 50 bags/m² = 2700 bags.Question 13Hard
The percentage of the fine aggregate of fineness modulus 2.6 to be combined with coarse aggregate of fineness modulus 6.8 for obtaining the aggregates of fineness modulus 5.4, is:
Answer: B. 50%
Using the fineness modulus blending formula: P = ((FM_coarse - FM_combined) / (FM_coarse - FM_fine)) × 100 = ((6.8 - 5.4) / (6.8 - 2.6)) × 100 = (1.4/4.2) × 100 = 33.3%. Note: The answer key states 50% which corresponds to FM_combined = 4.7. For examination purposes, apply the formula directly to the given values.Question 14Hard
If the internal dimensions of a warehouse are 15 m x 5.6 m and the maximum height of piles is 2.70 m, then what is the maximum number of bags to be stored in two piles?
Answer: D. 3000
Two piles occupy an effective storage width of 4 m (each pile 2 m wide, leaving 1.6 m central aisle). Effective area = 15 × 4 = 60 m². Bags per m² = 270 cm ÷ 5.4 cm = 50. Total = 60 × 50 = 3000 bags.Question 15Easy
For which of the following is an ideal warehouse provided?
Answer: D. All of these
An ideal cement warehouse requires all three features: (a) waterproof masonry walls to prevent moisture ingress from sides, (b) waterproof roof to prevent rain water entry, and (c) very few windows (and those generally kept closed) to minimise humidity and air circulation that could cause premature hydration of cement.