Development of a geopolymer-based cementitious coating for the rehabilitation of buried concrete infrastructure

The current research project was devoted to the incorporation of geopolymers as a new material for Trenchless projects, taking advantage of their properties in a field in which they had not been used before, providing a substantial help to municipalities to meet their rehabilitation needs. Trenchless Technologies are a family of methods, materials and equipment capable of being used for the installation of new or replacement or rehabilitation of existing underground infrastructure with minimal disruption to surface traffic, business, and other activities. The dissertation research work described herein is divided into six primary objectives: (1) the evaluation of geopolymer as a suitable candidate material for the rehabilitation of aging buried concrete infrastructure; (2) the study of the main parameters behind the process of geopolymerization; (3) the development of a geopolymer-based rehabilitation method with enhanced workability by means of a surface-active agent; (4) the evaluation of copper-substituted geopolymer with possible biocide properties; (5) testing and field validation of the resulting material; and (6) the study of its commercialization potential. Materials of a new generation are needed to suit the growing rehabilitation needs of buried concrete infrastructure. Many municipalities currently undergo difficult material selection processes; based on the best match between low cost and high quality. An optimal solution is not easy to achieve since ordinary Portland cement (OPC) provides low cost and good workability, but, in many cases, does not provide extended durability; on the other hand epoxies and other organic polymers often resist biogenic corrosion well, yet are many times not within the budget of municipalities. Geopolymers are cementitious materials of a new generation. Their outstanding properties are the object of growing research all over the world, especially in France, Australia and the USA. However, regardless of their excellent mechanical strength and corrosion resistance properties, geopolymers are often seen by the construction industry as materials with poor workability and unsuitable for big scale projects. This perception and other drawbacks are addressed in the present work. The dissertation begins with the identification and study of the main variables controlling the geopolymerization process and their influence on the final material properties. A selection of materials is then conducted and the design of an appropriate formulation is achieved. The next step was to solve the problem of turning geopolymers into a friendly material for contractors. As spray coatings are a very common and convenient method for the application of cementitious materials, this process was especially emphasized throughout the dissertation. Several additives and mixing methods were experimented with during this research project to help on this objective. Having produced a sprayable geopolymer admixture, work was then conducted to evaluate the final properties of the resulting material and a comparison with products currently used by the industry. The encapsulation of copper with the intention of a future evaluation as a biogenic agent embedded in geopolymer was also considered. Important conclusions are made in this regard. An evaluation of the commercialization potential of this material is further discussed