In early 2016, a US chain of gas stations was opening a new location in St. Peters, Missouri. The proposed store was in a prime location, but the buildable footprint was incredibly tight.
To compound the design challenges, the construction site was located at the bottom of a slope, with an existing building and parking lot right above on the other side of the property line. The project couldn't move forward without replacing the slope with a retaining wall that could support the existing parking lot and make room for the new store.
With the existing parking lot abutting right up to the backside of the gas station's new retaining wall, a barrier was required to keep drivers from accidentally driving over the top of the wall.
"It was important that the top of that system be strong enough to resist impact loading," said wall designer Clint Hines, PE of JC Hines & Associates.
Knowing that construction space was tight, the designers of this project needed a gravity retaining wall that would allow them to maximize usable space. For a solution, they turned to Redi-Rock, which is known for building great-looking, tall gravity walls. Redi-Rock also has an incredibly efficient reinforced retaining wall solution that integrates seamlessly with gravity walls to create a cohesive, efficient wall system.
But installing a secure barrier system like the one required for this project on top of a normal Redi-Rock wall hasn't historically been easy. "It can be very challenging to figure out how to attach barriers to the top of the retaining wall without compromising the wall's structural integrity," Hines said.
Seeing the need for an effective, easy-to-install barrier and fencing solution that integrated with Redi-Rock retaining walls, Redi-Rock launched the new hollow core freestanding unit, dubbed the "Magic blockTM." The Magic block's freestanding hollow core design allows efficient, aesthetic barriers to be built on top of Redi-Rock retaining walls. It also makes it simple to integrate fencing into a wall without compromising the integrity of the wall.
"It's a specialized product that solves a real problem," said Jeff McKay, representative for local Redi-Rock manufacturer Schreiter Concrete. "There's no other barrier or median wall an installer could do comparably."
Hines said using Magic blocks made wall design easier for this project. The Magic blocks paired with a reinforced concrete core and cap allow for many different types of rail and fence attachments using just anchor wedges. The vast assembly options using this system are much easier to install and no longer require core drilling into the wall.
"Where it shines is that our standard traffic barrier would've been set back from the wall and used more real estate," an engineer for the chain said. "But the hollow core block on top made it all work with the same system and gave us a slimmer footprint."
With Magic blocks eliminating the need to core drill, installers placed and tied two courses of hollow core blocks to the top of the Redi-Rock Positive Connection (PC) System wall. The hollow core blocks had both horizontal and vertical rebar inserts, adding more reinforcement for the barriers.
Adjusting to a new block was challenging at first, but installers quickly caught on. "Now that they've done it, they've got a feel for what it takes," McKay said.
After installation finished, the retaining walls stood at 9 feet (2.75 meters) tall with multiple Redi-Rock blocks and accessories. The above ground, freestanding hollow core portion of the wall next to the neighbor's parking lot has been filled with reinforcing steel and concrete, providing a strong barrier to keep cars on top of the wall where they belong. The only thing left for the project now is landscaping.
"It turned out really well," the gas station chain's engineer said. "The Ledgestone texture adds a high-end look."