Marina City’s concrete repair project: Acrophobics need not apply

6-Oct-09 – Suspended hundreds of feet above Dearborn Street, workers for Quality Restorations, Inc., will visit 16 balconies on each of 44 residential floors in two towers between now and December 2010. They are repairing problem areas in the exterior concrete that were identified during inspections in 2006 and 2007.

The work is noisy, dusty, and will cost the condo association at Marina City more than $1 million. But when completed, the City of Chicago should be satisfied there are no potential issues.

These images show what the work looks like, not from the ground but from where the chisel hits the concrete. Click on any image to view a larger version.

(Left) On the west side of the west tower of Marina City on Monday afternoon, brothers Cruz (left) and Hernando (right) Gonzales work from a “swing stage” scaffold suspended approximately 260 feet above Dearborn Street.

The first step in preparing old concrete for repair is to cut around the problem area. This provides a retaining boundary for the repair material, according to the U.S. Department of the Interior’s Guide to Concrete Repair. Here, a circular saw is used to remove concrete from a balcony on the 30th floor of the west tower.

Hernando Gonzales inspects the work.

In this image, a hairline crack is being enlarged so that it can be adequately repaired. They will also drill into weakened concrete, down to the rebar. The steel bars that reinforce concrete will then be sandblasted, sealed with epoxy, and covered with a specialized adhesive-added concrete.

Suspended just beyond the 29th floor of the west tower, Cruz and Hernando prepare to move on to the next balcony. In the upper left frame, you can see where nails have been hammered into the old concrete and areas cut around concrete that will be repaired. Cruz says they have been doing this kind of work for seven years and are not afraid of heights.

From across Dearborn Street, the suspended scaffold can be seen in the upper left frame, moved up to about the 43rd floor. Large semi-circular balconies give the residential towers at Marina City their distinctive appearance. Each balcony measures approximately 10 feet by 18 feet.

On Dearborn Street below, sidewalk canopies protect pedestrians from any falling debris.