Masonry Magazine June 1992 Page. 25
Upgrade Building Walls to Meet
Seismic Specs
Epoxy injection system helps Utah college building meet seismic specifications, prevent exterior brick fascia from falling off during an earthquake.
WHEN THE UNIVERSITY of Utah embarked on a renovation project of Talmadge Hall, a late 19th century building that houses the biology department on the Salt Lake City campus, the plan called for upgrading the building to prevent existing exterior brick fascia from falling off during an earthquake.
To meet seismic specifications, a new structural framework had to be integrated into the interior walls. This involved removing a section of each interior masonry wall, inserting a series of threaded rods into holes that extend to within 21/2" of the surface of of the exterior brick wall, and spraying the interior wall with a 4" thick layer of shotcrete.
The 34" diameter masonry wall anchors are spaced 48" on center vertically and horizontally in the mass of the wall with one vertical line of anchors, spaced 12" to 16" on center, at all corners, between windows and doors, around the periphery of the floor, and at the ends of the shotcrete coating. Approximately 5.000 anchors were used overall.
The Foil-Fast epoxy injection gel system, a joint development of the Rawlplug Company and Sika Corporation, was used to anchor the threaded rods in the wall. It was selected by the contractor, Lawrence Construction Company, Salt Lake City, because it was more economical than the other epoxy adhesive systems specified. In addition, in a series of on site tests conducted in both multiple brick layers and in single wythe brick, the system provided shear and tension load values. For example, peak loads were as high as 7000 pounds per anchor in both tests. The testing laboratory commented that... "in general, the failure was only in the mortar and/or brick.
There was no failure of the epoxy bond in any of the tests. Indeed, the epoxy was the next strongest part of the system after the steel bolt."
The Foil-Fast system consists of Sikadur injection gel, a two component structural epoxy that is dispensed from either a manual or pneumatically operated tool for accurate mixing. The gel is an amine based material that has a very high bond strength. In addition to providing a high strength anchorage, it produces no foul odor, and offers excellent resistance to moisture and chemicals. The adhesive meets the requirements of ASTM C-881.
Specially designed foil packs containing the epoxy adhesive components can be reloaded into the dispensing tool quickly and easily. One pack contains the base resin, and the other pack has either one of two hardeners. Each foil pack is labeled and
AFTER ONE-HUNDRED ¼" diameter holes are drilled into a wall section, left, the dispensing tool injects the epoxy gel into ½" screen tubes from the bottom up. Made from a 300 series stainless steel, the screen tubes are designed to confine the adhesive in the hole so that it will only partially penetrate the voids. As the threaded rod is inserted into the tube, right, the adhesive bonds to the solid areas of the masonry wall and forms a key lock in any hollow sections. Threaded rod installation was eased by using the slow set hardener in the epoxy mixture. This prevents the adhesive from hardening prematurely in the 100 hole pattern that was drilled at one time in each wall section.
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