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February 28, 2018
Underground Construction Technology: Conference Presentation on Geopolymer Culvert Rehab

Posted by: Natalie Swift

Joe Royer, PhD, and Collis Parrish of Inland Pipe Rehab (IPR), presented on the successful application of a GeoSpray® geopolymer liner in the City of Vista, California, at the Underground Construction Technology (UCT) International Conference and Exhibition in January 2018 to an audience of asset owners, engineers and contractors involved in the trenchless industry. Tony White with the City of Vista was also a co-author on the presentation.

As part of an 80-acre business park construction, the city installed a 15-foot diameter corrugated aluminum multi-plate arch culvert (CMP) to cross under the main thoroughfare. The culvert provides maintenance vehicles and trucks access to the city’s sewer easement, serves as a crossing for wildlife and is also used by local joggers and bicyclists.

Corrosion of the culvert pipe structure progressed steadily and was tracked annually from the early 2000s on, and the city began seeking recommendations from engineering consultants to either remove or rehabilitate the structure with a limited work area footprint and minimal impacts to sensitive areas surrounding the project site, including coastal sage scrub and wetland habitats.

The primary design criterion was to support the earthen embankment and any live vehicular loading. The exposed culvert material had to support the embankment and vehicular loading and be non-flammable and resistant to heat. The rehabilitation needed to maintain the same profile because of its use as a roadway underpass for both sewer and fire trucks.

Seeking an alternative that would not only rehabilitate and stabilize the pipe, but also satisfy environmental requirements, the city chose a design/build solution that involved applying a high-strength fiber reinforced geopolymer liner directly to the host pipe in layers and requiring no specialized bonding application. Rehabilitation alternatives, specifically slip-lining and shotcrete, were also considered but not chosen. The structure served as a walking path and an access road, so the invert of the structure was filled with gravel and “paved” with GeoSpray mortar, then lined through a hand spray process. When the initial application was complete, a welded wire cage was added to provide support for seismic loads.

A crew of five and a project manager took under two months to complete the project. Upon completion, several measures were taken to verify the thickness of the installation, such as measuring set screws and comprehensive material testing in a lab. Twenty samples were tested and all were successful. The finished structure, which included expansion joints, has been inspected annually for two years, with heavy rains in the area, and there were no observed concerns.

A complete article is available in the September 2016 edition of Trenchless Technology magazine.

To subscribe to Trenchless Technology, click here.

To view the complete City of Vista case study, click here.

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Category: GeoSpray Geopolymer, Feature Articles

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