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Concrete Decor - Index

Concrete Decor - Concrete Decor Magazine, The Journal for Decorative Concrete - Index

EXTERIOR: FIRST PLACE:
Black Hills Hardscapes Inc., based in Hot Springs, S.D., for
restoration of an outdoor amphitheater in Hot Springs, S.D.
IN THE WORDS OF: Kelvin Lorenz, Black Hills Hardscapes Inc.
The project involved a facelift for an amphitheater originally
carved into the rocky canyon walls of Fall River in 1936 by the
band director at Hot Springs High School. As the picture (lower
left) indicates, 71 years of Mother Nature and neglect had taken
their toll.
As a lifelong resident of Hot Springs and alum of HSHS, when
the Hot Springs High School Alumni Association approached
me about restoring this historic site, I agreed with the need,
accepted the challenge, and offered to donate the decorative
portion of the work.
Since most of the cracked and crumbling surface had succumbed
to the elements over the years, we began the project by
removing roots, weeds and accumulated debris and then proceeded
to expose underlying sound concrete by jackhammering,
scarifying and bush-hammering every square inch of the old
structure. All cracks were then routed and ground out, fi lled with
epoxy, and sealed with fi berglass mesh.
Since parts of the structure had settled, its drainage was poor,
resulting in trapped and retained water. This problem was
resolved by sloping all horizontal surfaces with a polymer-modifi
ed cement to establish proper drainage. The entire surface
was then covered again with fi berglass mesh embedded in a
polymer-modifi ed cementitious base coat, with double coverage
on all corners.
The original sandstone sign positioned at the top of the bandstand
was historically inaccurate and in a state of disrepair, so
it was replaced with a cut limestone slab bearing the correct
history of the era. The exposed rock face of the canyon wall
that cradles the structure was sealed with a pneumatically applied
mix of polymer-modifi ed, fi ber-reinforced cement that was
integrally colored using pigments from Davis Colors to match the
surrounding rock and historic sandstone buildings in the area.
14 www.ConcreteDecor.net Dec. ’07/Jan. ’08
Before
This was then further blended and antiqued using three colors
of Semco stain, providing a seamless transition from the sealed
rock to the surrounding features and vegetation.
The vertical surfaces of the bandstand were then base-coated
with a trowel-applied mix utilizing white and gray portland cement,
metakaolin, polymer, silica sand, fused silica and Davis
pigments, followed by two pneumatically applied topcoats of the
same color. Semco stains were also used sparingly here to add
movement and depth.
Given the historic nature of the town, one of our biggest challenges
on this project was to restore the structure and its old
warmth and charm without making it look too modern, pristine
and new. This was accomplished in part with a product made by
ArcusStone that we used for the seating areas. We tinted the ArcusStone
with pigments from B&J Colorants and trowel-applied
the material to the surface after priming with the recommended
bonding agent. We wrapped the ArcusStone 4 inches over the
edges and inserted mortar joints about every 3 feet, simulating
large, thick pieces of cut limestone. We intentionally distressed
the fresh surface to help achieve the warm, well-used look
that we were after. Upon initial curing, the horizontal surfaces
were polished using a DS-301 polisher, imparting a shine that
resembles 71 years of surface patina where cut limestone meets
backside denim. To guard against the elements and graffi ti,
the entire surface was sealed with a silicone rubber sealer from
Professional Products of Kansas.
The restoration of the amphitheater benefi ted not only its looks,
but also its acoustics. We noticed that during the restoration
process, the acoustics also steadily improved to a point where,
upon completion, a “sweet spot” developed at a location dead
center in the structure, where, if one speaks even softly toward
the back wall, it reverberates back to the speaker as though in
stereo, fi lling both ears with one’s own words.
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