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Analysis of Samples Removed from a Damaged Pipeline

Published

Author(s)

Paul E. Stutzman

Abstract

A set of specimens adhered to a pipe, provided by National Safety Transportation Board (NTSB), were examined for microstructure evaluation. The section of a 40.6 cm diameter gasoline pipeline from which the specimens were obtained showed signs of mechanical gouging and had experienced a rupture in service. The gouges were partly filled with a partially indurated material of undetermined origin. The Building Materials Division of the National Institute of Standards and Technology was contacted by NTSB to assist in characterizing the material and to determine if it was a portland cement-based material. If it was determined to be portland cement based, to compare the specimens to determine if it was related to concrete used in any construction subsequent to the installation of the gasoline pipeline. The following conclusions were made based upon the examinations:The microstructure of two concrete samples extracted from nearby construction contains a portland cement paste comprised of phases are typically found in hardened concrete pastes. In addition, an entrained air-void system is present and is unique to this subset of specimens. The air void system is a network of bubbles ranging in size from about 1 mm to about 10 m that serves to protect the concrete from freeze-thaw cycling damage.The specimens removed from the pipe are not portland cement-based materials. They do not exhibit compositional or microstructural features typical of a portland cement paste, mortar, or concrete. The specimens appear to be comprised of soil containing sandy mono- and poly-mineralic grains, clay, and mica cemented by calcium carbonate that appears to be in the form of the mineral calcite. The calcite is irregularly distributed with some regions extensively filled and some containing only isolated masses. Iron-bearing were common in the extensively cemented areas and appear to be either corrosion product from the pipe or iron sulfide, possibly pyrite.The backfill material contains a well-graded sand and dense, uniform clay matrix. These features make this specimen unique from the others examined in this study. Two of the specimens (I and J) removed from the gouges contain some fragments that appear similar to the backfill.
Citation
NIST Interagency/Internal Report (NISTIR) - 6737
Report Number
6737

Keywords

concrete, microstructure, mortar, petrography, portland cement

Citation

Stutzman, P. (2001), Analysis of Samples Removed from a Damaged Pipeline, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860349 (Accessed May 19, 2024)

Issues

If you have any questions about this publication or are having problems accessing it, please contact reflib@nist.gov.

Created April 15, 2001, Updated February 19, 2017