DelDOT Large Diameter Metal Plate Arch Rehabilitation with Unreinforced Geopolymer Mortar

Delaware DOT (DelDOT) completed their first large scale geopolymer mortar pipe rehabilitation project in February 2022. The geopolymer liner design assumed that the existing pipes were fully deteriorated and utilized the distributed beam over partial ring design method (distributed beam for short) requiring an unreinforced geopolymer mortar liner ranging from 2.4 to 3.2 in. thick on arch structures up to ~17′ wide. This created a structurally independent, corrosion-resistant, new pipe inside the old pipe structure. This paper discusses the trenchless options considered, why DelDOT selected geopolymer mortar, what is a geopolymer, liner design methodology, H&H hydraulic analysis, and construction including internal/external bypass, cold weather construction QAQC, and lessons learned. It provides perspectives from the owner, design consultant, contractor, and material manufacturer.