In construction of any kind of RCC structure following are the most neglected think which i feel, i may not be true in all;
1. Cover to reinforcement bars - Reduces the durability of the structure if had less covers.
2. Lapping of the column reinforcement bars - Mostly i see a local builders who does small projects without deploying engineers, keep lapping column reinforcement bars all at same level without staggering it. I personally spoke with many small projects and guided them to do it staggered but always answer comes straight forward as their structural consultant want them to lap all bars at same level and almost every time i saw those laps in confinement zones i.e. - just above slab or in column beam junction.
3. Not bending the hooks of column stirrups at 135 degree - no one wish to make structure earthquake resistance because in earlier days they were building structures with hook at 90 degree and in their area there was never an earthquake, so they feel what they do is correct.
4. Adding the water in concrete when mason feels they cant finish it, no matter how big your company / project is, when it comes to a will power of mason and he want to get water added or improvement in workability of concrete, they can actually kill a pump operator or transit mixer operator if they do not comply to his wish. a strong supervision needed in order to do a control correction for improving workability, else results into reduction in strength of actual concrete.
5. Cleaning of reinforcement bars after concreting.
6. Making construction joint properly.
7. Curing of concrete to ensure concrete is remain wet at all time.