Abstract:
Geopolymers represent a class material that can be a more efficient, cost effective and environmentally friendly alternate to Portland cement. Geopolymers have been shown to offer several improvements in material properties over Portland cement including; resistance to chemical attack, less brittle and selfhealing properties. They are gaining acceptance in a diverse range of industries from oilfield to the precast market. There has been a comparable lag in developing geopolymers for use as an annular grout. Part of the reason might lie with the numerous demands placed on an annular grout material i.e. slurry design, pumpability, set times, material properties and the all important consideration of cost. This paper outlines how these challenges were met by formulating an aluminosilicate powder (typically fly ash) to a specific grade of sodium silicate. Slurry and material properties were further improved by the use of admixtures. An additional development was the use of gas generating additives to allow the option for an expanded, closed cell foam geopolymer. Mixtures were tested using Standard ASTM test methods used for cement-based grouts. The more promising formulations were then tested using a custom build tunnel boring machine simulator. The TBM simulator allowed for a large number of samples to test under real world conditions including confining pressure. The results presented show a geopolymer slurry can be formulated to a low viscosity slurry and is stable for up to three days. Gel times are controllable and upon setting yield a product that has adequate compressive strength with improved tensile and bond strength. Geopolymers were formulated to be at an equal or less cost than a Portland cement grout with a better environmental footprint.