Concrete and RCC structure checks in Kerala
Your columns and slabs carry everything above them for the life of the house. The days before each pour are when you can still see them.
The checks at this stage (5)
- Photograph before this is covered
What disappears at this stage: slab steel, spacing, cover and conduit routes, once the pour starts. It cannot be inspected again without breaking something, so the photos taken now are the only record that will ever exist. Skipping this stays on your handover record permanently.
- Cube samples taken and tested for this pour
The cube test is the only evidence of what strength you actually received. Without it, a weak pour is a matter of opinion, and the opinion that counts will be the contractor's.
- Shuttering not struck before the code minimum
Formwork (the mould the concrete is poured into) removed early is the most common cause of a slab that sags permanently. The concrete has not yet carried its own weight, and the deflection you get is the deflection you keep.
- Concrete grade and batching as specified, not "as usual"
The grade on the drawing is a structural decision. A site that batches by headpan and calls it M20 is producing something nobody has calculated, and the cube test will tell you months later — after the slab is up.
- The right sand in the concrete, and its silt checked
Sand is bought by the load and nobody weighs it. Dirty sand or the wrong grade quietly weakens every batch it goes into, and there is nothing to see afterwards.
What good work looks like
Laps, spacing and the 135-degree hook
Where bars overlap they need the full lap length, and the laps are staggered - never all at one line. Ties end in hooks bent back at 135 degrees so they stay closed under load; a 90-degree hook opens exactly when it is needed most.
- Overlaps staggered along the bar, full length each
- Stirrups packed closer near beam and column faces
- Every tie hook bent right back to 135 degrees
- All laps lined up at one section, or inside a joint
- Hooks bent to an easy 90 degrees
- Wide, lazy tie spacing near the column ends
IS 456:2000 Cl. 26.2, 26.3 · IS 13920:2016
Kerala is earthquake Zone III - detailing matters
Concrete frames here need earthquake detailing: closed 135-degree hooks and tightly spaced ties near the column and beam ends, where an earthquake works hardest. It costs a little steel and bending effort now; it cannot be added later.
- 135-degree hooks used throughout
- Tie spacing visibly tighter near the column faces
- Detailing matching the structural drawing, not habit
- Hooks and spacing relaxed where the drawing says tighten
- Detailing treated as optional because quakes feel rare
- No one checking the cage against the drawing before pour
IS 1893 Part 1:2016 · IS 13920:2016
Pipes through the slab - routed, not bunched
Electrical conduits run through slabs by plan: tied down, spread out, not bunched where they push the steel aside or thin the cover. Where they run is the engineer's call - not the electrician's convenience on pour morning.
- Conduits tied in place, spaced apart
- Steel not shoved aside to make room
- Routes agreed with the engineer before pour day
- A fat bundle of pipes crossing at one point
- Conduits lying loose to float up in wet concrete
- Cover visibly thinned where pipes pass
Engineer's instruction - no settled IS numeric limit
Pouring and vibrating without ruining the mix
Concrete is vibrated just enough to push air out - not so much that it separates. It is placed, not dropped from height. And no water is ever added at the site to make pumping easier: extra water is strength poured away.
- The vibrator used steadily through the whole pour
- Concrete placed close to position, not free-dropped
- Nobody adding water at the mixer or the pump
- Honeycomb voids where vibration missed congested steel
- Gravel separating from over-vibration or a high drop
- A water hose appearing to loosen the mix
IS 456:2000 Cl. 13
Curing - the cheapest strength you will ever buy
New concrete must be kept wet: about 7 days for ordinary cement and about 10 for the blended cements most Kerala sites use - longer in hot, dry spells. Feeling hard is not the same as being strong; stopping early costs strength you already paid for.
- Water ponded on slabs, wet cloth on columns and beams
- Wetting kept up for the full period, not the first days
- A dated note or photo trail of the curing days
- Curing stopped once the surface feels hard
- Ponding dried out and nobody refilled it
- Blended cement cured on the short ordinary-cement clock
IS 456:2000 Cl. 13.5
Taking the formwork down at the right time
Sides can come off within a day; the props under slabs and beams stay for one to three weeks depending on span and cement type - blended cements need roughly half again as long. The calendar alone is not the test; strength is.
- Stripping decided by cement type and span, not impatience
- Props kept standing under the floors below
- Longer prop time when blended cement was used
- Props pulled early to reuse them on the next slab
- Same stripping days used for every cement type
- Sagging or cracks appearing after an early strike
IS 456:2000 Cl. 11.3, Amendment 5 (2019)
Red flags and money traps
Adding water on site makes concrete easier to pour and permanently weaker - it breaks the water-cement ratio the grade was designed on. Workability problems are solved at the plant, not with a hose.
If you see it: Stop the pour and call the engineer. This one is worth the argument.
Formwork sides can come off in a day, but props under slabs and beams stay for one to three weeks by span and cement type. Pulling them early to reuse on the next pour trades your slab's flatness for the contractor's schedule.
Ask: Which cement, what span, and therefore which date the props actually come out.