X-raying concrete slabs for buried services

Hello Baby Guinness,

In "the good old days" we found things so much easier.

All services buried in concrete were compulsorily inside a metal pipe, so it was easy to use a metal detector.

Of course in those days, extensive "As Built" drawings were always made, along with black & white (later colour) photos before concrete pours, to ensure there were no subsequent problems.

However, those halcyon days are over, and the use of plastic conduits, and the inclusion of other services direct into concrete, (cheap but bad practice), means the tried and trusted metal detector a.k.a. mine detector type, will not work accurately.

Your floor slab is probably some 200 - 250mm thick, and thus I would be going the CAT metal detector system, which will have minimal effect on personnel working nearby, providing you follow the precautions normally taken.

Apart from "Services" ensure you do not cut into important structural steel, or there may be a damages claim coming to haunt you in later years.

If necessary, and you do have to cut rebar/structural steel extensively, best to make steel frames and weld the cut steel to those frames, inserted into the floor as a "steel bridge or rectangular ring" around the "hole" for your bus ducting.

Carefully box up the hole, and pour (tamp down) high strength concrete grout, wait 7 days or more, before removing any formwork.

You won't forget the fireproofing of the "hole" around your Busduct, of course.

It is true that a picture is worth a thousand words - I used to take plenty of photos before, during, and on completion of the works.

Those pictures, often more than a thousand or two, more on the larger Projects, were wonderful evidence later, in any conflicts regarding extra work/increased costs.

In a large Project, recovery could be worth several $million, because the evidence could be provided, of each change to the Contract, every time any alteration, deletion, addition was made.

At times you can be paid for a deduction, because you could prove by photos you had done the Works, then because of design change, or Client or Architect's whim, you could also be paid for removing that installed thing, then paid again for the replacement.

All fair of course, because "The labourer is worthy of his hire".

In these days of cheap digital cameras, there is really no excuse not to photograph almost every section of any works, complete with the digitally imprinted date of the picture.

If you do this, you may find it advantageous to offer the client a selection of your photos on a CD or DVD, to include as part of their "as built" records.

Those pictures are worth money to you or your Company.

Be careful what you share, ensure you mark each picture with the © Copyright © Information ©, and remember to charge the Client for them, along with the Condition those photos always are your Intellectual Property, and you are only selling them a Licence to use them, but they must never share or publish same (Take a leaf out of Software makers book)

Kind Regards.....