Poor Workmanship in Housing Construction 

(3)

You thought that you are designing the column base as "fixed", then you found the actual situation at site was far from your ideal assumption. What would happen to the structural performance when completed even after you had repaired? 
What caused this defect?  

If you look at the photograph closely, you will see the aggregates segregating at the base and the aggregate sizes are irregular. These aggregates are un-sieved river gravels, with some exceeding 50mm. 
The steel bars are not vertical and evenly distributed, in fact forcefully bent here and there. The starter bars from below the ground beams are not aligned with column bars above the ground floor.

So you can see many basic problems from this construction:

(a) Setting up. The survey or measurement was not done properly, therefore the vertical bars were not installed at the exact locations. (In fact, after putting up the brick wall, the rooms were found to be not rectangular or squarish),

(b) Formwork. If the formwork was not tight, leaking of cement grout could cause honeycombs,

(c) Concrete mix. Concrete was one of the most uncertain material when ready-mix was not available. Site mix was so variable that until you tested it, you wouldn't know the result. 
(Concrete is made up of cement, fine aggregates, coarse aggregates and water. The designer often specifies Grade 20, 25 or 30 for the structures, while lean concrete uses Grade 15. Grade 20 means that the concrete will achieve at least 20N/sq.mm compressive strength in 28 days. In the past, the concrete was specified with 1:2:4, 1:1.5:3 or 1:1:2 mix to achieve Grade 20, 25 or 30 respectively. 1:2:4 means one part of cement, 2 parts of fine aggregates and 4 parts of coarse aggregates. 
Is the cement fresh or properly stored? Cement deteriorates fast if it is not properly stored. 
Then the aggregates are another big uncertainties. Are they from quarries, blasted and manufactured from igneous or metamorphosed or limestone rocks? Generally, these quarry-made aggregates are more uniform and well controlled, but thiswhich also depends on quality of machineries and management control. 
But if the aggregates are river gravels, are there proper sieving procedures to obtain required sizes and cleaning to remove all the dirts, sticky silt and clay? The same applies to the fine aggregates, quarry made or river sands? Fine aggregates have generally four different zones, which zone of the fine aggregates at your site belongs to?
In buildings, the coarse aggregates specified should not exceed 20mm generally, it appeared that this construction did not comply based on the larger aggregates dug out at the problem area. When large gravels are used, they would stopped by the stirrups used as perimeter bars, then concrete would not be able to flow down to the bottom.
Finally, how much water should be added to the mix ? Water-cement ratio of 0.45 is an idealistic proportion, it will give best strength, but it is too dry for concreting work in small column. Therefore, you may need to go to 0.6 for ease of compaction and construction. Often, admixture is added to improve the workability (high slump) without sacrificing the strength. But admixture is expensive. Thus it is easier by just putting in more cement and water to achieve the same slump.
To achieve the required strength and slump, trial mix must be done much earlier before any concrete mix and materials can be approved to use at the site. It appears this site had no such trial mix,

(d) Concreting. Concrete is time dependent, the longer you wait the more difficult to work. Concrete must be poured, the best within half an hour after the mix and probably within one hour by adding chemical admixture . The moment it is hardened, it will difficult to put into place even with internal vibrators. Engine-run internal vibrators must be used to ensure that the concrete is properly compacted with no gap and holes. Otherwise, honeycombs will appear. But avoid over-compaction because it will lead to segregation of coarse aggregates at the bottom. Sometimes, you will see the workers pouring water into the concrete when they find the concrete is dry and this in fact reduce the concrete strength drastically with a higher water-cement ratio. Concrete cubes made from concrete before adding water does not reflect the actual concrete quality.

(e)  Supervision. The supervision team really has to improve the skill. Unfortunately, this supervision team who was not competent enough to do the work, was sent by the client. The Designer has to keep on reminding and writing instructions to such team,

(f)  Design has to be conservative when facing poor Contractor, incompetent supervision team and indifferent Client. Also avoid using too small columns, often requested by Architect, even though they might slander you by branding you lousy engineer if you didi not comply. The final liability is still with the Engineer.  Now the new Eurocode requires at least 200mm width for structures to reduce this kind of concreting problem.

Below is another photograph also showing slender column, probably large aggregates, conjested steel reinforcements, insufficient compaction, causing holes and honeycombs.