1) Your joints are not watertight especially at beam and column junctions.
2) You have cast the slab in parts, and the joint has not been prepared properly before casting.
3) Your slab shuttering (formwork) was not done properly, and the slab has developed cracks due to non-rigidity or insufficient support.
4) You did not add water proofing compound to the concrete mixture (especially for a roof slab).
5) The compaction of the concrete was not done properly — hence there are voids and gaps in the concrete.
6) The concrete had too much water (high slump), or the mix proportions were not correct, leading to honeycombing in the concrete.
7) You used poor quality/deteriorated cement and/or poor quality sand or aggregates that have caused voids in the concrete.
8) The curing of the concrete was not done properly—leading to cracks.
9) Hard water (or water with high salt content) was used in the preparation of the concrete.
10) The slab reinforcement was not covered properly during concreting, or you have exposed slab reinforcement at the ends, or exposed column reinforcements that provide a parthway for water to travel through the concrete.
Overall, poor construction techniques, sloppy workmanship and use of bad materials can lead to problems with cast concrete structures which are very hard and expensive to rectify.
2) You have cast the slab in parts, and the joint has not been prepared properly before casting.
3) Your slab shuttering (formwork) was not done properly, and the slab has developed cracks due to non-rigidity or insufficient support.
4) You did not add water proofing compound to the concrete mixture (especially for a roof slab).
5) The compaction of the concrete was not done properly — hence there are voids and gaps in the concrete.
6) The concrete had too much water (high slump), or the mix proportions were not correct, leading to honeycombing in the concrete.
7) You used poor quality/deteriorated cement and/or poor quality sand or aggregates that have caused voids in the concrete.
8) The curing of the concrete was not done properly—leading to cracks.
9) Hard water (or water with high salt content) was used in the preparation of the concrete.
10) The slab reinforcement was not covered properly during concreting, or you have exposed slab reinforcement at the ends, or exposed column reinforcements that provide a parthway for water to travel through the concrete.
Overall, poor construction techniques, sloppy workmanship and use of bad materials can lead to problems with cast concrete structures which are very hard and expensive to rectify.
