The investigation into the causes of the partial collapse of the 40-year-old Champlain Towers South condominium in Surfside, Fla., nearly a year ago will soon move into its next phase: invasive testing of samples taken from the debris pile.
Physical evidence from both the collapsed and imploded sections of Champlain Towers South is stored in a secure warehouse where it has been carefully cataloged and evaluated.
Ken Hover, NIST investigation project leader for material science, said during the meeting that investigators will first use non-destructive tests to refine their sampling locations and ensure samples are intact, and also to detect any questionable regions to avoid or study further.
Physical and Chemical Analyses
Once samples have been extracted, they
will undergo lab testing, Hover said. Investigators will
determine concrete samples’ deformability, compression and
tension characteristics, and the strength and ductility of
steel samples. The samples will also be examined under a
microscope for petrographic analysis so investigators can
observe the materials’ characteristics and see any effects
of exposure and loading, to better understand their state at
the time of collapse.
While all concrete is porous, the rates and depths of penetration can vary widely, and the nature of what's penetrating the material can have varying effects, Hover said. For example, carbon dioxide penetration acidifies concrete, reducing the corrosion protection it normally offers to embedded reinforced steel. Then, penetration of water, salt and oxygen could react with the steel to produce rust. The expanding rust could crack the concrete from the inside, and reduce the bond between the concrete and steel.
Because of space constraints in the warehouse where the physical evidence is being held, NIST is planning to move the to-be-tested materials to another location. Ahead of the move, they brought in an industrial hygienist to sample the air for asbestos fibers. Preparing the materials for the move and securing them in the new location will take several weeks.
“This is an important step in the investigation, one we are able to take only after months of careful investigation and preparation,” Glenn Bell, the co-lead investigator, said in a statement.