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NIST Report: Video From Expert Team Investigating Surfside Condo Collapse Shows Evidence Of Extensive Corrosion

August 26, 2021 / 8:29 AM EDT / CBS Miami

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MIAMI (CBSMiami/AP) — It's been more than two months since the Surfside condo collapse killed 98 people and now new video released by a team of federal investigators shows more evidence of extensive corrosion and overcrowded concrete reinforcement in the building.

The National Institute of Standards and Technology also announced Wednesday it will conduct a five-pronged investigation into the Champlain Towers South collapse, which will be led by Judith Mitrani-Reiser, the associate chief of the Materials and Structural Systems Division in NIST's Engineering Laboratory who grew up in Miami.

"This team has an incredible amount of experience in forensic engineering, having studied many building failures," said Mitrani-Reiser. "We are going into this with an open mind and will examine all hypotheses that might explain what caused this collapse. Having a team with experience across a variety of disciplines, including structural and geotechnical engineering, materials, evidence collection, modeling and more, will ensure a thorough investigation."

The video, released by NIST, shows densely packed steel reinforcement in various sections of the building, along with extensive corrosion where one column met the building's foundation.

"The corrosion on the bottom of that column is astronomical," Dawn Lehman, a professor of structural engineering at the University of Washington, told CBS4 News partner The Miami Herald. She said that amount of corrosion should have been obvious and documented as part of the 40-year inspection that was ongoing when the building in Surfside, Florida, collapsed June 24.

"If there's that amount of corrosion, this should have been fixed," she said.

Screen capture from a video released by the National Institute of Standards and Technology. (Credit: NIST)

The images show beams, walls and columns that appear to be overcrowded with steel reinforcement, which suggests potential weaknesses, she explained.

"There is no reason there should be that kind of bar congestion," Lehman said.

The risk posed by "congested" vertical rebar in columns would have been even worse in spots where the rebar overlapped, which is known as "lap splice" regions, Abieyuwa Aghayere, a Drexel University engineering researcher who also reviewed the video, told the newspaper.

While it's already congested with rebar, at the splice regions, it would have been "even further congested," Aghayere told the Herald.

He said he was struck by how "powdery" and white the concrete in columns appeared in the newly released video. Stone-like aggregates used to strengthen concrete during construction typically remain visible but they were not in the images from the collapse site.

"The white color just stuns me," Aghayere told the newspaper. He added that instead of seeing aggregate material mixed into the concrete, "it's just homogenous," which is likely indication of saltwater damage.

He said it is impossible to tell from just the images whether the concrete used in original construction was weaker than the designs called for, or whether the apparent weakness was due to damage over time.

"It doesn't look like normal concrete to me. What's going on?" Aghayere said.

The NIST's technical investigation will be organized around specific projects that will seek to understand the full history of the building, including its design plans, construction, materials, modifications, site and environment, from its design to the moment of collapse.

NIST will provide regular updates on its progress during the investigation and is inviting members of the public to submit any information, including videos, photos or other documentation, that might help the investigation via the NIST Disaster Data Portal.