As I am, by training, of the Electrical Engineering persuasion, with a necessary amount of Mechanical knowledge obtained over the years, I comment upon matters pertaining to Civil Engineering mostly by osmosis. One of the basic elements of good concrete is the simple fact that, once the concrete commences being poured into the shuttered area which has been filled with the required re-bar, the workers immediately shove ‘vibrating pokers’ into the concrete mass, to ensure that both all the volume of the shuttered area is filled homogeneously with the concrete, but also to ensure that all air bubbles are expelled from the mix before it commences hardening. To allay any fears regarding my use of the term ‘vibrating poker’, I feel I should explain that the average diameter of a ‘poker’ is around 75mm., with the weight somewhere around fifteen kgs. The vibrator crew usually walk in the concrete, dragging the vibrators with them, the noise is usually horrendous, and the work is both strenuous and really, really necessary, because without good homogeneity, the concrete will fail if stress is later placed upon it.
Another source of worry, to Civil Engineers that is, is to either restrict or eliminate any pauses during the filling of deep or large pours of concrete, mainly because, once the concrete has commenced hardening during a delay, no further mix should be poured until the initial surface has been roughened or ‘scarified’, so as to provide a seamless and problem-free continuity of concrete for the rest of the work. It is a definition of good concrete work that all delays beyond a certain time limit are treated with scarifying equipment, because without such treatment, a joint will fail under pressure!
I would now present two photographs and one video, as a commentary, by an independent observer sited some thousands of miles away from site, of the quality problems of the Panama Canal Expansion.
Photo shows a concrete section removed from the Cocoli Locks compex.
Full views of the size and reach of the leaking water in the lock cill.
Oh dear; It does not look Good!
For those not up-to-speed with the Canal Lock system, the huge, super-thick concrete cill is what the rolling lock gate rests against when the lock actually fills with water; hence the concern about the actual strength of the cill concrete: because if the cill wall fails, the lock gate moves, all the water drains out, and the ship would be sitting on the concrete deck of the lock, with nowhere to go. As I remarked; Oh dear!
(Acknowledgements to my mates Kumar, Mark and Benji for the thorough introduction to large concrete works.)