www.concreteinternational.com | Ci | MAY 2019 53
Fig. 4: Stone restoration specialist repairing broken corner on new
Pier 102 (photo courtesy of The Armbruster Company, Inc.)
wrapped in plastic sheeting and covered with an insulating
concrete blanket. We anticipated leaving it on for 2 weeks to
cure. Unfortunately, the blanket was stolen. Because the
weather was cool and damp, however, the concrete was left
exposed to cure.
After a failed attempt to patch the corner in January, we
waited until March and warmer weather to try again. One of
C.A. Lindman’s stone restoration specialists performed the
work (Fig. 4). First, he drilled a hole in the damaged area and
anchored a threaded stainless-steel rod using epoxy adhesive.
He then undercut the existing corner to ensure a good
mechanical bond around the repair perimeter. Next, the
worker saturated the damaged area with water and manually
mixed a small, low-slump batch of the same mixture used in
the pier, individually selecting the aggregate. He placed the
mixture with a trowel in the patch area, and shaped the surface
using a small piece of formwork, inserting the aggregate
individually. Then, he finished the patch with a trowel. When
the patch concrete was stiff enough, he gently removed the
sand and cement with a bristle brush to expose the aggregate.
The patch was left to air cure for 2 weeks.
In May, when the water service was turned on in the park,
the contractor returned and lightly washed the pier with a
1:10 solution of muriatic acid, using soft bristle brushes to
remove the fine film of cement residue on the surface of the
stones and sand. Lastly, the pier was rinsed with water. Figure 5
shows the completed corner repair on the replicated Pier 102.
Results of Study Phase
The lessons learned from the reconstruction of the pier
were incorporated in the project specifications. This process
proved that it was possible (but not easy) to achieve good
results with available materials.
Our company methodically documented the conditions of
the concrete, as well as the methods for cleaning, patching,
and sealing verified through our test program. Armbruster
Fig. 5: Completed repair of a corner on replicated Pier 102 (photo
courtesy of Robert Weinstein, architrave p.c., architects)
Fig. 6: The successfully
replicated Pier 102
(photo courtesy of The
Armbruster Company, Inc.)
methodically documented the entire process of searching for
the materials, screening available materials to get the propersized
aggregates and sand, and developing the mixtures. He
also provided a library of samples. C.A. Lindman replaced a
sample pier and patched a corner, proving it could be done
(Fig. 6). This documentation provided a solid foundation for
beginning the contract documents on Phases I and II of
restoration of the exposed aggregate concrete at the park.
The Phase I construction project was to be the sealing of
the horizontal and vertical cracks and replacing the wood slats
on the park benches. The exposed aggregate concrete
comprising the bench structure was scheduled to be repaired
under Phase II.
We characterized Phase I as a stitch in time—its primary
purpose was to slow the rate of deterioration. The contract
documents comprised 61 sheets of drawings and over 500 pages