Chemical anchors tackle
tough construction dilemmas

Adhesives formulated to meet the demanding needs of jobsites, no matter the material or the weather.

All-weather, all-purpose acrylic advances stone work on Idaho ski country site Contractors working in winter weather on a ski resort style home in Idaho found a chemical adhesive system that could work in all temperatures. It proved to be truly a product for all seasons.

Brett Sullivan of Sullivan Contracting says the Powers AC100 system allows his crews to work much faster on the 14,000 sq.-ft. custom-designed home in Idaho’s Sun Valley. It features over 700 tons of large sandstone blocks.

“Even in near-zero temperatures, we were achieving setting times much closer to what we generally see working in normal temperatures. It makes our work much faster,” says Sullivan.

Sullivan first used the adhesive to install stone pieces over exterior overhangs and archways. To fasten overhangs on a three-car garage entrance, Sullivan injected the adhesive into holes drilled in each sandstone block, then placed the block over bolts protruding from hollow block walls. He hung the stones over the dramatic archways in a similar fashion. In three fireplaces, Sullivan used the adhesive to attach the 800 to 2,000 lb. hearth and mantlepiece stones to the wall with rod.

The adhesive also worked well to fasten stone stairway steps and attach windowsill pieces. He also used it to build a distinctive oval stone window by fastening stones to diamond mesh with the adhesive.

“The adhesive allowed me to fasten stone in corners of window pieces where there was only a 3/4" thickness of material. It also allowed me to bond stones together vertically to make columns,” Sullivan says.

While AC100 was chosen for this job because of the cold, high mountain desert conditions, the adhesive dispenses and cures quickly in warm temperatures as well. It’s an ideal choice when a fast set is needed.

Powers' AC100 Plus, a new epoxy acrylate formula, is stronger, safer, faster curing and odor-free. It is also the first non-flammable epoxy acrylate sold in the United States, so it can be used in confined spaces including tunnel and lift-well applications.

Quake-proofing the 
San Francisco-Oakland Bay Bridge
Suspension bridges define the look of the San Francisco Bay. Unfortunately, fault lines also define the area and to reduce chances an earthquake could take down the suspension bridges, the California Department of Transportation (CALTRANS) is investing $2.6 billion to reinforce the bridges to withstand earthquakes as severe as 8.3 magnitude.

“The purpose of the retrofit is to bring the bridge’s service level up to a higher anticipated earthquake demand,” says Mark Reno, CALTRANS senior project engineer. Reinforcing the 120'-deep caisson foundation is a key part to the seismic retrofit project.

The logistics of getting material from shore to bridge base piers was a challenge. “We were looking at ease of placement and constructability,” says Reno.

To gain access inside the caissons, crews had to jack-hammer through several walls of concrete up to 2' thick. Tools, equipment and materials had to fit through openings often no more than 3'x 3'. The towers were strengthened with 8' hold-downs that attach to the steel towers with 3"-diameter rods. These were installed through the existing caisson caps. The mass of concrete in the caisson caps was increased and collector plates were added about 12' below the caps. They are evenly spaced around the inside of the caisson.

Crews used Simpson Epoxy Tie (SET) to anchor eight 1"-diameter rods to each collector; high-strength steel rods run from the caisson cap to the collector plates. This design will transfer the bending moment over a much larger area of the footing in an earthquake.

Roger Brown, West Coast Bridge job superintendent, says his company selected the adhesive because it was cost-effective, his crews liked working with it and it passed on-site tension testing.

With space and time at a premium, crews liked how the adhesive worked. “It’s the way the system is put together," Brown says. “The tools are designed to handle the viscosity of the epoxy and different mixing nozzles are available to match the dispensing rate to the hole size.

“When you pressurize an epoxy with a pneumatic dispensing tool, other products sometimes leak out of the back side of the tubes and cause a big mess.

“We have used hundreds of those tubes and they cause dust all over the place. We don’t like that. The installers don’t want to get the stuff all over. We didn’t have any big hassles and no waste,” Brown says.

Preserving the Great Stone 
Church at San Juan Capistrano
The swallows continue their annual trek to the San Juan Capistrano Mission in Orange County, California. Their arrival and departure mark the passage of time. But with that passage of time, the mission, which is over 200 years old, continues to deteriorate. Even with preservation efforts, the site has been placed on the 2002 list of 100 most endangered historical sites by the World Monuments Watch program.

Preservation efforts focus on stabilizing the sagging structure which includes fortifying crumbling walls and reinforcing the weight-bearing stone that makes up the church’s four stone window frames.

Pointe Construction completed much of the project to strengthen and preserve the walls and facades of the church. To stabilize the church’s 4'- to 5'-thick walls and preserve the facade, Pointe Construction crews drilled holes through the walls and installed stainless steel pins that are anchored in place with ITW Ramset’s Epcon A-7 epoxy adhesive.

The pins tie a new pour of concrete that forms an inner bond beam at the tops of the walls to the outside face.

The most daunting part of the project was reinforcing the weight-bearing stone that makes up the church’s four 4' x 3' windows. Pointe Construction first planned to drill six 1/2"-diameter holes 3' to 4' deep at a 45-degree angle into the stone wall above each window frame. From there, they planned to insert 3/8" stainless-steel threaded rod into chemical adhesive that was pumped into the hole, effectively pinning the stones in place.

Bernie Botitch, site manager for Pointe Construction and Nels Roselund, consulting architectural engineer on the project, knew an overhead epoxy application was not going to be easy. Epoxy adhesives can sag or drip before they set, creating waste and mess. They experimented with Epcon A7, a fast-dispensing, fast-curing acrylic adhesive. It did not drip or sag in overhead installations, plus it set up in about five minutes without stiffening. It was also temperature-independent; it can be used at temperatures as low as 0 F without preheating.

Botitch’s crew used a rotary drill to make 28" to 42" deep holes at a 45-degree angle on each side of the window frame. Before filling with epoxy, workers used a nylon brush to remove any loose material in the hole. The crew also devised a vacuum and compressed air extension to remove any other loose material in the deep holes.

The crews completely filled the holes with the Epcon A7 adhesive with a pneumatic gun, then inserted a steel rod in each hole. Each window took about an hour to complete. The reinforcement worked, stabilizing the structure for years to come.

Epoxy anchors bridge on busy Florida highway
The Ortega Peninsula Bridge carries the traffic from the Ortega Peninsula to Jacksonville, Florida. Peninsula residents are affluent and influential, and any road disruption gets attention.

Steve Shade, vice president of adhesives and technical services at U.S. Anchor received an urgent call from Florida DOT engineers.

“The project was already many months behind schedule,” says Shade, “Then all of the specially manufactured 5' x 1 1/2" wedge anchors pulled out when a partial load was applied.”

More than 30 of these high-strength mechanical anchors were used in the project. “They failed because they were too closely spaced,” Shade says.

The consulting engineer on the project thought an epoxy-based adhesive may be the answer.

“We found a solution for him, using U.S. Anchor Ultrabond 2 Epoxy dispensed by a pneumatic tool and mixed in a specially designed high-flow 1"-diameter mixing nozzle," says Shade.

The mixer was fitted with a 4' extension to make sure the epoxy reached the bottom of the hole without trapping air.

“The Ultrabond 2 formula has an extended working time so the epoxy could be injected and the 6' x 1 1/2" diameter steel threaded rods installed before the epoxy could harden.

“The epoxy was the fastest and best solution to this problem because all that had to be done was to remove the failed rods and simply install new ones with our epoxy,” Shade says.

The anchors were put in place in one day, then pre-tensioned to over 170,000 lbs. “The bridge was in full operation within two weeks of setting the anchors with Ultrabond Epoxy,” he says.

Published in the September/October 2002 issue of Contractor Tools and Supplies magazine.

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