MTA New York City Transit (NYCT) currently has 473 stations on its rapid transit system, approximately 280 of which are underground. The great majority of these stations were built between the 1900s and 1930. The age of the system requires an extensive exploration and investigation of these underground stations.
KS Engineers, P.C. (KSE) provided Building Materials Forensic Specialist Consulting services to NYCT to determine the overall condition and efficacy of the station envelope at those stations that were constructed with a terracotta tile ceiling substrate. This investigation required taking visual inspections and destructive testing including the extraction of core samples at both deteriorated and sound portions of the structures at station areas of the accessible to the public.
The scope of work included provision of technical support, document review (including archive drawings and inspection reports), Visual Conditions Surveys (at 36 stations), close-up visual inspection of evident deficiencies, probe inspections, in-situ testing, material studies, laboratory analysis, and reports and recommendations.
The following material tests were conducted on samples extracted at station platform ceiling locations:
- Representative masonry samples were extracted from the ceiling for cold and boiling water absorption in accordance with ASTM C67 Standard Test Methods for sampling and testing brick and structural clay tile, in order to determine the materials’ cold water absorption and saturation coefficient.
- Representative terracotta samples were tested for freeze thaw durability as per ASTM C67 Standard Test methods for sampling and testing brick and structural clay tile, in order to determine the materials potential to spall or deteriorate from freeze-thaw distress.
- A water-soluble chloride analysis was performed according to ASTM C1218, Method for Water-Soluble Chloride in Mortar and Concrete at representative samples.
- A petrographic examination of the interface at representative masonry prism extractions was performed in a quantity as deemed necessary.
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