Below is an excerpt of a BFI investigation performed on a Railroad Terminal Facility to help the client determine the cause of damage.
Excerpt:
A brief investigation was made of the subject demolition site. The scope of the investigation expanded to consider the pre-existing conditions of the original concrete. Observations suggested that demolition on the west end had been exceedingly aggressive and variable, with unreasonably high forces applied by the breaker point being responsible for excessive depths and extents of removals. Delaminations found by hammer soundings were present below the surfaces exposed by demolition making the work unsuitable to receive repair or strengthening materials. Additional investigation and removals are required prior to commencement of strengthening. However, the immediate surface of the concrete generally had a profile and texture to which repair materials could readily adhere.
Further, observations strongly suggest the likelihood that some of the cracking and pre-existing distress in the demolished concrete had been affected by ASR. Accordingly, ASR was considered as a potential cause of the relative ease of concrete by hydro-demolition, and thus could be considered as an unknown, pre-existing condition. Examination of the concrete surface which supported the rabbit track on the east side of the demolition area was judged to be a region which generally went unaffected by whatever demolition activities it experienced. Therefore, the rabbit track surface was sounded for drummy areas and very few such areas were suspected along it to be delaminated, and none were positively confirmed.
In summary, it is the opinion of the undersigned that the mechanical demolition efforts employed were too aggressive for the work contemplated. Furthermore, the mechanical demolition efforts weakened the substrate such that the hydro-demolition work penetrated more deeply, affected a volume of concrete greater than perceived when applied, and removed a greater volume of concrete than otherwise it would have.
Notwithstanding the effects of ASR, over half of the removal surfaces present appear to be dense, durable, sound, and suitable to contemplated improvements. As much as approximately one third of the prepared surfaces are in some way weakened, partially, or fully delaminated and additional removals are required so that continuity can be established between the existing concrete foundations with planned improvements. The extent of delamination is much more severe on the west end than the middle or east sides of the project.
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