Case Study #3
Restoration of a Deteriorated Parking Structure

Problem:

Shortly after construction, drying shrinkage cracks appeared within the single-level suspended deck of a reinforced concrete parking structure. The extensive number of cracks reflected through the thin traffic bearing membrane coating system and the owners were concerned about the potential for accelerated deterioration as well as the fact that salt-laden water was leaking and dripping onto cars parked below.
Over an almost three-year period several attempts were made to seal the cracks, but they still continued to leak - and more cracks continued to occur. At this time the services of PJ Materials Consultants were retained to investigate why the cracks could not be sealed, to determine why more cracks continued to reflect through the membrane, and to correct the deficiency.

Solution:

An investigation revealed that the deck was constructed using fusion-bonded epoxy coated rebar and lack of adequate restraint to avoid shrinkage and thermal movement was causing the unusual cracking. Further investigation revealed that an unusually large amount of movement was occurring during temperature changes and this was causing the cracks to widen beyond the capability of the membrane and the crack sealant - the low internal restraint provided by the epoxy coated rebar increased the widening of the cracks.

The answer was to apply a thick membrane system over the old coating - after testing to ensure that the cold-applied reinforced sheet membrane could adequately bond to the prepare substrate. (This saved over $25,000, compared to removing the old system and applying a new thin system.) For this method of rehabilitation to be effective, it was important that the saturated concrete could adequately dry and this was confirmed by the trapped moisture dripping through the cracks once the right conditions were achieved. The concrete subsequently dried and, after more than 7-years to date, the cracks have remained sealed.