A structural member can lose quality before concrete is discharged if its formwork and reinforcement are not ready. The forms define shape, carry fresh-concrete pressure and retain the cementitious paste; the spacers and chairs preserve the steel position assumed in design.
IS 456 requires sufficiently rigid formwork and joints that prevent loss of slurry. Check supports, ties, alignment, dimensions and tightness, especially at beam–column junctions, wall bases and penetrations. Remove sawdust, tie-wire pieces and rubbish. Apply release agent to the contact face without coating the reinforcement. IS 14687 gives further formwork guidance.
The specified nominal cover is not a convenient distance chosen by the placing crew. It is shown on the structural drawings after considering exposure, durability, fire performance and member requirements. Use suitable cover blocks, spacers and chairs, and check that walking boards, pump hoses and vibration cannot displace bars. Verify clear space for concrete to pass between bars and for the chosen vibrator to reach congested areas.
A gap that leaks slurry can create porous patches and honeycombing; a moved bar can reduce cover and change effective depth. These defects cannot be reliably corrected by a good test cube. Carry out a documented pre-pour inspection and correct the problems while the work is still visible.
The engineer’s clearance should include form stability, cleaning, joint sealing, reinforcement size and position, cover, embedded items, openings and vibrator access. This is a practical hold point: once the pour begins, many of these facts are hidden.
Key references: IS 456:2000, Clauses 11, 12 and 26.4; IS 14687 for formwork; project structural drawings and approved pour checklist.