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Geopolymers: Promising Materials For Underground Applications
Fly ash serves as an attractive raw material for mass production of geopolymer concrete not only due to its chemical composition (a rich source of alumina and silica), but also because of its spherical shape and its particle size which is already in the cement fineness range (45 µm). Although fly ash has been used as a partial replacement of Portland cement to enhance durability, reduce costs and lower carbon footprint, geopolymer binder technology that utilizes 100 percent of fly ash as a binder offers an even lower carbon footprint and energy consumption, alongside the beneficial use of a larger volume of an industrial by-product that otherwise is likely to end up in a landfill.
Geopolymer and Trenchless Technology Center
The connection between geopolymer binders and the infrastructure construction industry was established in 2006, when a geopolymer laboratory was launched inside the Trenchless Technology Center (TTC) of Louisiana Tech University under the supervision of Dr. Erez Allouche. When geopolymer research began, it became apparent that the use of the technology could be relevant for underground rehabilitation if the material was used as a cementitious coating for deteriorated concrete sewer pipes. Geopolymer’s potential as a protective material in terms of corrosion resistance had already been proven by other researchers around the world, but it would be the first time that its use would address a particular real-life problem. The main challenge was to develop the material to a point where it could be applied using conventional mix, pump and spray equipment. Two years of work yielded a sprayable geopolymer formulation which is now a patented technology (Figure 1).
The importance of geopolymer research grew quickly. As soon as the first application was successfully developed, dozens of new product ideas – from corrosion resistant floors to rocket engine testing facilities – continued to emerge. The TTC research team took the approach of developing customized geopolymer products that would solve various problems, from corrosion and high temperature exposure to high strength and even a ‘programmable’ setting time to enable the material to be used in a number of applications, including coatings, grouts, structural concrete for pipes and manholes, and down-hole applications for the oil and gas industry. To date, the TTC has developed a dozen specialized formulations for a wide range of applications.