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A key Massachusetts highway engineer refused approval of a fast-setting epoxy adhesive blamed in the fatal collapse of a Big Dig ceiling panel in 2006, according to documents released Friday, July 27.
Clement Fung, deputy director of materials research for the Massachusetts Highway Department, raised two key questions about performance of fast-set epoxy systems, and said he would not approve use of the fast-set material. That information comes from a memo dated August 19, 1999, filed by Vincent E. Sagan, representing an engineering firm called Simpson, Gumpertz & Heger, Inc. The engineering firm had been hired to seek approval of the NRC Epoxy Anchor System provided by Powers Fasteners of Brewster, NY.
Fung declined approval of the fast-setting epoxy because “the time is too short to make adjustments during construction,” according to the memo. The maximum gel time is 20 minutes for the fast-setting epoxy and 45 minutes for the standard materials. Cure times are three hours for the fast set and seven hours for the standard set.
The major issue with the material, however wasn’t set-up time — it was its ability to withstand sustained loads over time. Powers Fasteners was heavily criticized by the National Transportation and Safety Board for failing to adequately inform contractors of the poor “creep” performance of the fast-setting material over time.
It was not clear why the fast-setting epoxy was used despite lack of approval from Fung, who did not return calls by Design News.
Another memo released by Powers Fasteners showed that Glenn R. Bell, chief executive officer of Simpson, Gumpertz & Heger, discussed the creep issues with Fung. “For the Quick Set anchors, he (Fung) wants to see the high-temperature creep test results,” reported Bell. “He indicated his approval of the Quick Set anchors will hinge on how close or far the anchors came to meeting the high-temperature creep tests.”
The Quick Set materials did not meet the creep test results. At least 1,000 units of the fast-setting material was shipped to the tunnel contractor in July, 1999, ostensibly for use on tiles and wall panels. Powers Fasteners also supplied 120 units of its standard-setting material at the same time to anchor 2,500 threaded stainless steel bolts, about eight inches in length. Units contain hardener and resin with a nozzle. Total cost: $1,287.60.
Powers Fasteners released the memos in an effort to show that it had made state agencies aware of the creep characteristics of its epoxies. It was not clear to what extent, if at all, Powers Fasteners had conducted discussions with the project contractors on creep. Schwartzman said she was not aware of similar document reporting conversations with contractors.
Slowly, small amounts of light are being shed on the role epoxies played in the collapse of the Interstate 90 tunnel on July 10, 2006 when 20 ceiling anchors failed, releasing 10 precast concrete panels and hardware weighing about 52,000 pounds.
Powers Fasteners maintains its innocence, claiming that contractors must have mistakenly switched the standard- and fast-setting epoxies. There seems to be little doubt that the wrong epoxy was used. Installation of the ceiling panels began July 29, 1999. Powers Fasteners shipped the standard epoxy on August 3, 1999, Powers’ spokesperson Karen Schwartzman told Design News.
Powers Fasteners introduced the two types of epoxies in the early 1990s. One has a red label and the other blue. Both products are marketed as Power Fast. To what extent workers were aware of the differences, or even that there were differences, is not clear. Was any effort even made to inform the contractor of the differences? Even that is up for debate. The materials were provided by a local distributor Newman, Renner Colony LLC. Adding to the confusion: The Big Dig epoxy had a special gold label branded NRC for its local distributor.
Is epoxy of any type acceptable for sustained overhead load conditions? The NTSB isn’t taking any chances. It has banned use of epoxy in those applications until more testing is completed.