MCQs on Joints in Concrete Works
Questions 1–12 — Tap an option to check your answer.
Q1: Which type of joint is a temporary joint left between subsequent concreting operations?
Difficulty: Easy
Correct Answer: B. Construction jointSolution:A construction joint is the interface formed when fresh concrete is placed against already-hardened concrete. It arises whenever concreting is deliberately or unavoidably halted. It is not designed to allow movement (unlike expansion joints); rather it is a work-sequence joint where structural continuity must be restored through proper surface preparation.
Q2: Interval for expansion and contraction joints in India for smooth interface laid in winter?
Difficulty: Hard
Correct Answer: B. 50 to 60 metresSolution:IRC specifications: for concrete pavements laid in winter (Oct–Mar) over a smooth interface, joint spacing is 50 m for 15 cm and 20 cm slabs, and 60 m for 25 cm slabs — giving the range 50–60 m. Winter slabs experience greater thermal expansion in summer, requiring closer joint spacing than summer-laid slabs.
Q3: In expansion joints, loads are transferred through:
Difficulty: Medium
Correct Answer: B. Dowel barsSolution:Dowel bars (smooth, round mild steel bars, typically φ25–32 mm at 300 mm c/c) provide vertical load transfer across expansion joints while allowing horizontal movement. One end is bonded in the concrete; the other is free (greased/sleeved) to slide. Tie bars are used at longitudinal joints to prevent lane separation, not for vertical load transfer.
Q4: Horizontal construction joints in concrete walls are generally provided at:
Difficulty: Easy
Correct Answer: D. All of the aboveSolution:All three are standard locations for horizontal construction joints in walls. Floor (plinth) level marks the transition from substructure to superstructure; window sill level is a natural pour-stop before window frames are set; soffit level is the junction of the wall with the roof slab or beam — a major formwork change point. IS 456 requires surface roughening and wetting at all these joints.
Q5: A construction joint is provided where:
Difficulty: Easy
Correct Answer: D. All of the aboveSolution:All three criteria apply: construction joints are placed where bending moment is small (reduces flexural stress at the joint), where shear force is small (reduces shear demand on joint friction/interlock), and where one member is supported by another (natural structural junction). In huge structures, joints are also not placed more than 18 m apart.
Q6: The surface where two successive placements of concrete meet is known as:
Difficulty: Easy
Correct Answer: C. Construction jointSolution:A construction joint is, by definition, the hardened surface of previously placed concrete against which new concrete is cast. It is a work-sequence boundary — not a gap (expansion joint) nor a controlled crack plane (contraction joint). Reinforcement is continuous through the joint; the surface must be roughened and cleaned to restore structural continuity.
Q7: Expansion joints are provided if the length of concrete structures exceeds:
Difficulty: Medium
Correct Answer: D. 45 mSolution:IS 456:2000 specifies that expansion joints should be provided when the plan dimension of a building exceeds 45 metres. Beyond this length, thermal movement (ΔL = α·L·ΔT) becomes too large for the structure to absorb without cracking or damage. Joints are typically provided every 30–45 m in large buildings.
Q8: Pick up the correct statement about construction joint placement:
Difficulty: Medium
Correct Answer: D. All of the aboveSolution:All three are correct per IS 456: (A) columns get joints 10–15 cm below beam soffit; (B) at bottom of haunch where haunches exist; (C) beams and slabs get joints in the middle third of span (where BM and SF are both at moderate values). All three follow the principle of locating joints away from high-stress zones.
Q9: Construction joints are provided:
Difficulty: Easy
Correct Answer: D. All of the aboveSolution:All three conditions apply: construction joints are located where BM and SF are minimum, at member support junctions, and at maximum 18 m spacing in massive structures. These are complementary, not alternative, requirements — a well-designed construction joint satisfies all applicable conditions.
Q10: Pick up the correct statement about joints in concrete:
Difficulty: Easy
Correct Answer: D. All of the aboveSolution:All three statements are correct: construction joints must be planned (not accidental cold joints) at positions of minimum BM/SF; expansion joints specifically accommodate thermal expansion (their primary function); and construction joints also help control shrinkage cracking by dividing the pour into manageable segments, limiting the length over which shrinkage strain accumulates.
Q11: According to IS 456-1978, expansion joints:
Difficulty: Medium
Correct Answer: D. All of the aboveSolution:IS 456 (Clause 27) specifies all three: expansion joints at re-entrant corners where building plan changes abruptly (L, T, H, E shapes); filled with compressible material to ensure minimum resistance to thermal movement; and supported on twin/separate columns so each building portion can move independently without transmitting horizontal forces to the other side.
Q12: The construction joints in cement concrete:
Difficulty: Medium
Correct Answer: B. Should not be provided at cornersSolution:Only B is correct: construction joints must NOT be provided at corners (stress concentration zones). Options A and C are the opposite of correct practice — joints must be at minimum SF and BM locations. Option D is wrong: the correct spacing for huge structures is not more than 18 m (not 3 m) per IS 456:2000.