Inspection of deteriorating asbestos cement force mains with georadar technique

Our plain-English summary of Inspection of deteriorating asbestos cement force mains with georadar technique, by S. Smolders, L. Verhoest, G. De Gueldre, et al (Water Science and Technology, 2009).

The study

• Authors: S. Smolders, L. Verhoest, G. De Gueldre, B. Van De Steene
• Journal: Water Science and Technology
• Published: 2009;60(4):995-1001
• Read it: PubMed · Publisher

Abstract

Several breaks on asbestos cement force mains indicated a problem with these kind of force mains. An inspection technique that could give a good idea about the state of asbestos cement pipes was searched for. A georadar technique already existed to inspect drinking water mains and gravity sewers. The technique measures the wall thickness of cement containing materials and it can differentiate between 'healthy' and deteriorated material. The technique was applied on four wastewater force mains in Flanders. The results indicated a rapid deterioration of the asbestos cement. A deterioration mechanism called 'calcium leaching' was known from asbestos cement drinking water mains. Further it was known that H(2)S is produced in force mains and that it can attack concrete containing materials by mains of biogenic sulphuric acid attack. This research checked if both deterioration mechanisms cause the measured rapid deterioration of the asbestos cement force mains. Finally deterioration speeds and minimum required wall thickness were calculated. With the results the residual lifetimes of the force mains were calculated and these could be applied in an asset management program.

In plain English

This engineering study did not examine human health or asbestos disease. It used a non-destructive georadar technique to measure the remaining sound wall thickness of four asbestos cement wastewater pressure pipes (force mains) in Flanders, Belgium, aged 16 to 30 years. Most were scanned from outside on dug-up sections; Berlare's 60-metre outlet section was inspected from inside with a camera combined with radar. Wastewater samples were also tested for aggressiveness toward cement. Where only calcium leaching was believed to act, the fastest wall loss was 0.29 mm per year. At one Brugge location, where hydrogen sulphide was believed responsible, it was 0.73 mm per year, and 40% of the original wall had gone in 23 years. Using a German design standard, the authors estimated remaining lifetimes of 0 years for two force mains, 11 years for one and 6 years for the Brugge main. The authors concluded that georadar was a useful tool and that asbestos cement force mains deteriorated faster than asbestos cement drinking water pipes. Lacking repeat measurements, they assumed deterioration speed stayed constant.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Engineering field inspection study of pipe condition, using non-destructive georadar measurement of wall thickness plus wastewater chemistry (Langelier Saturation Index). No human health outcomes were studied.
• Who was studied: Four asbestos cement wastewater force mains (pressure pipes) in Flanders, Belgium: force main A in Herselt (16 years old, inspected at three locations), B in Wuustwezel (28 years, two locations), C in Berlare (30 years, the 60-metre outlet section inspected from inside by camera with radar) and D in Brugge (23 years, one location).
• Exposure: The pipes' exposure to wastewater. Two deterioration mechanisms of the asbestos cement were examined: calcium leaching, and biogenic sulphuric acid attack from hydrogen sulphide (H2S). No asbestos fiber type is named in the article.
• Main results:
  • Without the influence of H2S gas, the maximum deterioration speed of the pipe wall was 0.29 mm per year.
  • With the influence of H2S, the maximum deterioration speed was 0.73 mm per year. This was measured at the one inspected location on force main D in Brugge.
  • At the inspected location on force main D, a 23-year-old pipe, 40% of the original wall thickness had disappeared.
  • For force main A, the minimum required wall thickness under the ATV A127E standard was calculated at 11.7 mm. The original wall thickness was 13.1 mm, and the minimum measured strong wall thickness was around 8 mm, so its residual lifetime was zero years.
  • Residual lifetimes of force mains B, C and D were calculated at 11 years, 0 years and 6 years respectively. These figures used the maximum deterioration speeds and the minimum measured wall thicknesses.
  • Wastewater entering force main A had a clearly negative Langelier Saturation Index, indicating potential corrosiveness. Force main D's wastewater had a positive index, indicating scaling potential.
• The authors' conclusion: The authors concluded that georadar was a useful tool for estimating the condition of asbestos cement force mains. They also concluded that these force mains deteriorated faster than asbestos cement pipes for drinking water, and that the results could be used to prioritize inspection and renovation.
• Limitations the authors state:
  • There were no repeated measurements over time on the same force main, so it is unknown how the deterioration speed changes over time. The authors assumed it was constant.
  • The Langelier Saturation Index is only an indication. It was based on samples taken at one moment, which say nothing about past conditions or other circumstances such as rainy days.
  • Force main D was inspected at only one location, and that inspection was hindered by a high groundwater table.
  • The cause of the faster deterioration at a higher point of force main C is unknown.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement.

Related studies

• Development of an animal model, techniques, and an exposure system to study the effects of asbestos cement dust inhalation — A.P. Wehner, G.E. Dagle, et al. (1978)
• Evaluation of the Webler-Brown model for estimating tetrachloroethylene exposure from vinyl-lined asbestos-cement pipes — L.A. Spence, A. Aschengrau, et al. (2008)
• Radiographic asbestosis is not a prerequisite for asbestos-associated lung cancer in Ontario asbestos-cement workers — M.M. Finkelstein (1997)
• Colorectal cancer in asbestos cement workers in Denmark — E. Raffn, E. Villadsen, et al. (1996)
• Absence of radiographic asbestosis and the risk of lung cancer among asbestos-cement workers: Extended follow-up of a cohort — M.M. Finkelstein (2010)
• Biological effects: asbestos-cement manufacturing — H. Weill (1994)

Browse return to medical research.