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PERFORMANCE EVALUATION OF AN INNOVATIVE FIBER REINFORCED GEOPOLYMER SPRAY-APPLIED MORTAR FOR LARGE DIAMETER WASTEWATER MAIN REHABILITATION IN HOUSTON, TX
Matthews, J., W. Condit, S. Vaidya, AND R. Stowe. PERFORMANCE EVALUATION OF AN INNOVATIVE FIBER REINFORCED GEOPOLYMER SPRAY-APPLIED MORTAR FOR LARGE DIAMETER WASTEWATER MAIN REHABILITATION IN HOUSTON, TX. US EPA Office of Research and Development, Washington, DC, EPA/600/R-14/443, 2014.
Many utilities are seeking emerging and innovative rehabilitation technologies to extend the service life of their infrastructure systems. However, information on new technologies is not always readily available and not easy to obtain. To help to provide this information, the U.S. Environmental Protection Agency (EPA) developed an innovative technology demonstration program to evaluate technologies that have the potential to reduce costs and increase the effectiveness of the operation, maintenance, and renewal of aging water distribution and wastewater collection systems. The intent of the program is to make the technologies’ capabilities better known to the water and wastewater industries.
This report describes the performance evaluation of a fiber reinforced geopolymer spray-applied mortar, which has potential as a structural alternative to traditional open cut techniques used in large-diameter sewer pipes. Geopolymer is a sustainable green material that incorporates recycled industrial byproducts and has been shown to have improved chemical and physical properties compared with ordinary portland cement (OPC). GeoSprayTM, produced by Milliken Infrastructure Solution, LLC (Milliken), was used to rehabilitate a 60-in. reinforced concrete pipe (RCP) sewer main in Houston, Texas. The 25-ft depth of the pipe and other site-specific conditions precluded open cut excavation and the need for a shortened bypass time contributed to the selection of the GeoSprayTM technology. The project was completed in a two-week timeframe including four spraying passes on 160 ft of 60-in. RCP. The host pipe was severely deteriorated with corroded and exposed steel reinforcements and several locations of heavy water infiltration, which led to the product being manually spray applied by hand rather than using a sled. The material was successfully installed in a severely deteriorated pipe environment. The post-lining inspection via closed-circuit television (CCTV) showed the rehabilitated pipe to be infiltration free, with no signs of exposed rebar or cracking, and no significant defects were noted in the GeoSprayTM lining the day after application. A lining thickness of approximately 3.3 in. was sprayed in the pipe, which is more than the design minimum value of 1.9 in. The third-party test results for compressive strength averaged 8,635 pounds per square inch (psi) at 28 days, which is above the manufacturer stated claim of 8,000 psi at 28 days. However, the samples collected by the research team tested under the manufacturer-stated claims (e.g., measured at 7,881 psi or 1.5% below specification for compressive strength). Based on the lower density of the mixture, it is hypothesized that the lower values in these samples were attributable to light rain experienced during sample collection. However, it is assumed that the rain had no impact on the material sprayed in the pipe as the mixer was covered during the installation. Overall, it is recommended that sampling and testing procedures be further examined to ensure that the quality control (QC) samples are indicative of the final material properties as installed in the field. Recommendations are made related to measuring the “as installed” lining thickness, bond strength testing, and the use of shaker tables to minimize voids. For structurally rehabilitating a 60-in. pipe via geopolymer spray-applied lining, the costs would range from $400 to $600 per linear foot (for projects of similar complexity and including bypass pumping). The project resulted in an estimated carbon footprint of 24.10 short tons (48,200 lb) of carbon dioxide (CO2) equivalents, which was gauged to be 60% less than an equivalent excavation project (if feasible). In addition, CO2 equivalent emissions from the manufacture of geopolymers have been shown in the literature to be as much as 65% to 90% less than emissions for OPC.