A Retrospective of 15 Years of Spray-Applied Geopolymer Mortar Linings

For buried infrastructure, conventional dig and replace has become a very expensive option for rehabilitating aging pipes. Over the past 50 years, the use of trenchless technologies has provided an affordable means of extending the life of storm and sanitary pipes. Over the last 15 years, the use of spray-applied pipe lining (SAPL), utilizing cementitious mortars, specifically geopolymers, has become a more preferred method of choice for rehabilitating large-diameter pipes and other buried structures. This paper reviews the history of over 500,000 linear ft of large-diameter pipes (>36″) and structures that have been structurally lined using this method around the globe. An overview of the advances in materials, spray distance, pumping distance, and equipment will be reviewed in detail, showing the evolution of the technology. The environmental impact of geopolymers in reducing greenhouse gas emissions by more than 75% compared to traditional cementitious materials, as well as the additional environmental advantages of the installation process compared with traditional and other trenchless processes, will be examined. The advances in standards, including ASTM, NASSCO, WRc, and others will be reviewed. In addition, the movement towards accepted design methodologies backed by detailed structural testing will be reviewed. Finally, several of the most interesting projects are highlighted, including a test project for the USEPA and others in the City of Houston, two phases of restoration of a trunk sewer in Ontario totaling over 10,000 linear ft of lining, as well as several smaller culvert projects conducted in Florida.