Topic Thread

  • 1.  Parking Garage Floor Spalling

    Posted 08-12-2020 12:22 PM
    The concrete of the lowest level (at grade) of our parking garage is experiencing spalling. Are there any suggestions on what might cause this condition and the best way to prevent further spalling and repair these spalling locations.

    John O'Holleran P.E., M.ASCE
    Chicago IL

  • 2.  RE: Parking Garage Floor Spalling

    Posted 08-13-2020 08:46 AM

    I'll try to be brief, but one could write a book on this subject. The following is based on my experience in upstate NY, which has similar climate to Chicago, where I assume the garage in question is located.

    There are many potential reasons why the spalling has occurred. Freeze-thaw is a definite possibility. The ground level normally carries the heaviest chloride load and is the wettest, with cars bringing road salt and water in from the entrance roadway. This combined with the winter climate in Chicago result in challenging conditions for any exposed concrete. Other possibilities include inadequate concrete curing, low air entrainment, poorly finished concrete (water added or brought up to surface due to overworking) and alkali-silica reaction (ASR) due to poor reactive coarse aggregate in the concrete, although this should be evident throughout the structure.

    You can core the distressed concrete areas (and also the good concrete areas for comparison) and have them tested for chlorides, freeze-thaw resistance, ASR susceptibility, and petrographic analysis performed for air entrainment. Prevention of further damage is normally addressed by repairing the spalled areas, cleaning and sealing the entire surface of the ground floor with a penetrating type sealer. Chloride extraction is sometimes employed, depending on the level of intrusion, but this is typically not warranted.

    With regard to repair, the entire ground floor surface of the garage should be sounded (chain drag works great for this) and recorded to identify hidden spalls. There are other non-destructive methods (ground penetrating radar?) that may be able to be employed to record spalled or weak areas, but I've found a chain drag to be the most direct and reliable method, albeit time consuming. Repairs can be made by sawcutting the perimeter of spalls/hollow sounding areas and replacing with a concrete patching material following manufacturer's instructions for preparation, application and curing. Normally a fast curing material is used to prevent prolonged loss of garage use, and the repairs are made in stages to limit loss of parking.  I would direct you to Illinois DOT for recommendations on materials and methods for concrete repair, including the sealer, which can be applied when the curing period is over.

    David Kennicutt P.E., M.ASCE
    Senior Project Manager
    Binghamton NY

  • 3.  RE: Parking Garage Floor Spalling

    Posted 08-13-2020 02:30 PM
    Send some pictures and closeup of the damage. Then I'll right the book

    Robert Hinton, P.E- Life Member ASCE