Precast Panel Repair With Sika Products
The reinforcing steel in the “eyebrows” that surround the windows in this nine story office building had corroded. For this to happen two conditions must exist. The first is the presence of moisture on the surface of the embedded steel and the second is the change in the PH level of the surrounding concrete brought about by the chloride salts that the moisture carries. A galvanic condition, producing hydrated ferric oxide, rust, is the result. Rusting steel expands up to eight times creating a force that the concrete, an inflexible material, can’t resist. On this building chunks of concrete “spalled” off and fell to the ground.
The moisture that made its way to the reinforcing steel came through failed sealant joints; the ones between the precast concrete panels or and/or the window perimeter joints. These were restored before the concrete repairs were completed.
Concrete repairs to the precast “eyebrows” on this building involved the following steps. First the loose concrete was removed, then the rust was completely removed from the reinforcing steel. Sika Armatec® 110 EpoCem® rust inhibitor / bonding agent was then applied to the steel and the concrete surface. Next, one “lift” of Sika Corporation, SikaTop®-123 Plus mortar was applied. The maximum amount of that material that can be applied in each lift is 1 1/2”. The depth of most of the damaged areas was less than an inch-and-a-half so in those spots only one lift was needed. Others were deeper so those spots required additional repair if the building was to be restored to its original form.
The next step, where additional lifts were needed would have been to apply SikaRepair® SHA, repair mortar to a depth that would bring the repair out to the existing surface. Color matching the repaired portions of the building with the original, weathered surfaces was not attempted.
Wall ties and or pins can be included in repairs like this to provide structural reinforcement and stabilization of the repair bed-joint. Helifix is a source for these fasteners, the tools to install them and information on their use. Additional sources can be found on the Fasteners, Anchors and Wall Ties page.
