Expert: Dan Griffin - 7/14/2008

Question
The top layer of a concrete floor in the building I am working in has began to disitagrate. This is not an old building and it appears that it is water damage to the concrete. The bigger problem I have is that there is an access floor on top of the slab with alot of electrical wiring, air ducts etc under it. removing all of this work to gain full access to the slap is not an option. Do you know of any products that could be used as a binding agent to renforce the top layer of the concrete? This needs to be done in order to insure structural stability of the access floor posts. Any assistance would be a big help.

Answer
Chris, there is no simple solution.  Water makes concrete get stronger, so I doubt that is the problem.  Spalled tops are usually caused by poor finishing (not waiting for the bleed water to come up), freeze within the first three days, or chemical abuse of the concrete.

From your description, I think there is good concrete there, just the top is spalling off.  YOu will need to remove the bad unbonded concrete.
Here is what I would consider:
Open enough computer flooring to access one support, remove that one support (shore as required).  Use a bushing hammer to remove the loose stuff, I would suggest a rotary hammer and one of these heads:
http://www.bamanufacturing.com/bushing_tools.html
It can be done by hand with one of these, but you will wear yourself out:
http://toolsmet.com/gxlt/
Remove all the loose stuff to get down to good solid concrete.

Make small batches of one of these:
Jet set
http://www.jetsetcement.com/products.php

mapei planitop 15 or panitop x
http://www.mapei.us/

These are very hard, fast setting, ultra bonding, VERY FAST SETTING repair mortars.  There may be others, but I have used these.  Replace the computer floor support and set.  Repeat as required.

They both make a pourable type which is somewhat self leveling.  YOu might be able to have a form like a ring cut from a 5 gallon bucket ready to use as a form and pour the repair for eah post.