MCQs on Concrete Operations
17 questions. Tap an option to check it instantly, then read the solution.
Question 1Easy
How does the age of concrete affect its compressive strength, considering the age limit as 28 days with continued curing?
Answer: A. Compressive strength increases as the age of concrete increases
Concrete primarily gains strength through the hydration of cement. This ongoing process reduces the effective water-cement ratio over time, leading to continuous (though slowing) strength gain. The maximum strength is largely achieved by 28 days, but gradual gain continues over the concrete's lifetime.Question 2Easy
Which method of transportation of concrete is useful for transporting concrete to a relatively greater distance from the batching plant?
Answer: C. Transit mixer
A transit mixer is a truck-mounted revolving drum that mixes or agitates concrete during transport over long distances, making it the primary equipment used in Ready Mix Concrete (RMC) operations. The drum rotates at 2-6 rpm during transit to prevent setting.Question 3Hard
As per IS 2770 (Part 1), the load at failure in a pull out test was found to be 180 kN. Calculate the bond strength if the bar diameter is 20 mm and its embedded length into concrete is 300 mm.
Answer: A. 30/π N/mm²
Bond Strength = Load / (π × bar diameter × embedded length) = (180 × 10³) / (π × 20 × 300) = 180,000 / 6000π = 30/π N/mm².Question 4Medium
As per IS 13311 (Part 1), the natural frequency of transducers for a path length of more than 1500 mm is:
Answer: C. Greater than or equal to 20 kHz
IS 13311 (Part 1) specifies that for a path length exceeding 1500 mm, the transducer natural frequency should be ≥ 20 kHz. Longer paths require lower frequencies because high-frequency waves attenuate more rapidly over distance.Question 5Medium
Which of the following parts of a rebound test apparatus moves with the mass attached to the spring after bouncing back?
Answer: A. Rider
In the rebound hammer test, after the plunger is pushed against the concrete surface, the spring-loaded mass strikes the plunger and rebounds. The Rider is the component that travels with the rebounding mass along the graduated scale, recording the rebound number.Question 6Medium
Which of the following problems are observed during the pouring of freshly prepared concrete in hot weather? (i) Rapid rate of hydration (ii) Quick setting (iii) Greater plastic shrinkage (iv) More finishing times
Answer: D. Only (i), (ii) and (iii)
Hot weather causes rapid hydration, quick setting, and greater plastic shrinkage — all true. However, finishing time is REDUCED (not increased) in hot weather because concrete stiffens faster, leaving less time for the finisher to work the surface. Statement (iv) is therefore incorrect.Question 7Easy
A proper compaction of freshly prepared concrete results in: (i) Achieving maximum strength (ii) Expelling entrapped air (iii) Change in fineness modulus of aggregate
Answer: B. Both (i) and (ii)
Proper compaction expels entrapped air (ii) and allows the concrete to achieve its maximum possible strength (i). However, compaction has absolutely no effect on the fineness modulus of the aggregate (iii), which is a property determined by gradation analysis — a physical property of the aggregate itself, not changed by compacting the mix.Question 8Easy
As per IS 7861 (Part 1), concreting done at atmospheric temperatures above ________ is termed as hot weather concreting.
Answer: A. 40°C
IS 7861 (Part 1): 1975 defines hot weather concreting as any concreting operation carried out at atmospheric temperatures above 40°C (excluding steam curing). Special precautions are mandatory to prevent quality deterioration.Question 9Easy
As per IS 7861 (Part 2), concreting done at atmospheric temperature ________ or below is termed as cold weather concreting.
Answer: B. 5°C
IS 7861 (Part 2) defines cold weather concreting as any concreting operation where the atmospheric temperature is 5°C or below. At this temperature, hydration slows drastically, and there is risk of freezing of mix water before concrete gains strength.Question 10Easy
The application of curing on the prepared concrete results in:
Answer: D. Increase in compressive strength
Curing provides moisture and temperature conditions necessary for continued hydration of cement. As hydration progresses, the capillary pores fill with C-S-H gel, increasing density and strength. Without curing, hydration stops prematurely and the concrete never reaches its design strength.Question 11Medium
For compacting plain concrete road surface of thickness less than 20 cm, we use:
Answer: B. Screed vibrator
Screed vibrators (surface vibrators) operate on the top surface of the concrete and are ideal for shallow sections like roads, slabs, and canal linings less than 20 cm thick. Internal (immersion) vibrators are needed for deeper sections (60 cm or more), where screed vibrators cannot penetrate effectively.Question 12Easy
Which of the following is the result of proper batching of concrete? A. Economy B. Durability C. Workability D. Strength
Answer: D. A, B, C and D (all)
Proper batching ensures accurate measurement of all ingredients — cement, aggregates, water, and admixtures — in the specified proportions. This directly delivers economy (no wasted cement), durability (correct w/c ratio), workability (correct water content), and strength (correct cement content).Question 13Easy
________ are used to press mortar and spread it uniformly.
Answer: C. Floats
Floats are flat boards (typically wooden or steel, 60–150 cm long and 20 cm wide) used after screeding to press the mortar and spread it uniformly across the concrete surface. Floating removes surface irregularities left by the screed and closes the surface for troweling.Question 14Easy
In small works, concrete is transported using:
Answer: C. Pans
For small works and very short distances, concrete is manually transported in pans (cane or metal baskets) carried on workers' heads. While labour-intensive, this method is simple, requires no equipment, and is economical for small volumes.Question 15Medium
How many types of machine mixers of concrete are available?
Answer: A. 2
This question was invalidated by the examining commission. However, the fundamental classification used in most Indian civil engineering textbooks is 2 main types: (1) Batch Mixers and (2) Continuous Mixers. Batch mixers (tilting drum, non-tilting drum, reversing drum, pan mixer, transit mixer) produce concrete in discrete batches; continuous mixers produce a steady stream.Question 16Easy
For concreting tunnel linings, transportation of concrete is done by which of the following?
Answer: D. Pumps
Tunnel linings are poured in confined, often long, curved spaces where conventional transport methods cannot reach. Pumps are the only practical method — they can push concrete through flexible pipes to any point along the tunnel alignment, including overhead sections of the lining.Question 17Easy
Compacting of concrete is done to:
Answer: B. Remove air bubbles
During mixing and placing, air gets entrapped between aggregate particles and in the cement paste, creating voids. Compaction (vibration, tamping, or rodding) causes these air bubbles to rise to the surface and escape, making the concrete dense, impermeable, and strong.