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Maintaining and Repairing Aging Infrastructure with Geopolymers

August 26, 2021
Completed underpass
Completed underpass.

The aging infrastructure in the U.S. is experiencing increased maintenance and repair costs. Specific types of structures requiring significant maintenance attention include bridges for vehicles, trains, pedestrians, pipe racks, etc. 

Bridges require additional maintenance as they are experiencing heavier loads, increased frequency of traffic, exceeding their functional longevity, experiencing challenging environmental conditions and changing weather conditions, as well as seismic activity and wind loads. These major factors are rapidly accelerating the aging cycle of these structures.

New technologies are being used to minimize significant maintenance cost, increase the strength of the structure, and/or increase its functional longevity. One newer technology available is a geopolymer in combination with a geosynthetic grid/textile. These type of repair products can be installed without having to modify the structure or requiring major construction activities or time. It also minimizes distribution of traffic during the repair.

Below are some typical aging structures that can be repaired while increasing the strength of the structure and increasing the functional longevity of the structure using a geopolymer/geosynthetic system.

Bridge deterioration
(From left): Load deterioration, stress deterioration, and weather deterioration.

Montana Rail Link (MRL) is a Class II regional railroad company that operates more than 900 route miles of track in Montana and Idaho. Goods shipped by Montana Rail Link include coal, industrial products, grain, intermodal, and vehicles. The state of Montana has major swings in climate conditions and soils and environmental influences that can be aggressive to steel and concrete structures, which is a concern for MRL. The company’s inspection group continuously reviews their infrastructure and identifies required structures and rail repairs. 

The inspection group identified a bridge in Laurel, Montana that needed repairs as the concrete showed signs of distress due to climate and environment conditions. The below images highlight the condition of the concrete structures before the repair.

Existing bridge
(From left): Existing girder conditions, existing bridge underpass, existing column condition

MRL called Shotcrete Montana, based in Billings, to resurface the foundation walls with a geopolymer/geogrid system. This halted the distressed concrete from continuing to deteriorate further. Shotcrete Montana purchased their geopolymer and geogrid from Full Moon Enterprises. Full Moon Enterprises is a supplier of a unique geopolymer called GeoSpray from GeoTree Solutions. 

GeoSpray is usually classified as a cement mortar by engineers but has the chemistry of a polymer that acts like an engineered stone and exhibits a range of unique behaviors such as: bonding strength, permeability, flexural strength that exceeds all cement mortars systems available. GeoSpray can be applied by trowel or sprayed. 

The repair consisted of preparing the surface with a thorough cleaning, applying a thin layer of GeoSpray, applying the geogrid, spraying the GeoSpray over the geogrid, and then hand trowelling to make a smooth surface for aesthetics.

The total amount of surface that was repaired was a little over 5,000 sq ft with the work completed in just five days without daytime closure to vehicle traffic. The bridge’s walkway was opened at the end of each workday.

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Editor's Note: Scranton Gillette Communications and the SGC Infrastructure Group are not liable for the accuracy, efficacy and validity of the claims made in this piece. The views expressed in this content do not reflect the position of the Roads & Bridges' Editorial Team.

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