Abstract:
Grouting can be a very effective ground improvement process by filling pores, fissures, and/or voids in natural or synthetic materials with a fluid that alters their response. Chemical grouting refers to the use of fluid grouts, with or without colloidal suspensions but without any suspended solid particles, with the aim of treating finer gradation soils. The groutability of a chemical grout into a specific soil matrix is dependent on the grout viscosity and the soil gradation. Silicate-based chemical grouts are widely used by contractors due to their low cost and flexibility in adjusting gelation time. The paper presents results from evaluating the stability of various sodium silicate grout mixes based on their rheological and syneresis properties. Prior to gelling, sodium silicate grouts are visco-elastic colloids and therefore, the shear strain lags behind the shear stress by a phase angle. As the grout starts getting, it starts behaving more like an elastic material (at very small strains) and the phase angle decreases to zero. An advanced Anton Paar Physica MCR 301 rheometer is used to obtain pre- & post-gelation gel properties, and pinpointing the start of gelation based on the change in measure phase angle (which occurs much earlier than gelling times measured from the tilting cup method). After a select set of grouts are deemed rheologically stable, syneresis testing was performed on the grout and the grouted soil specimens to determine their long-term shrinkage properties. Keywords: Chemical Grouting, Sodium Silicate, Syneresis, Gelling Time, Rheology, Advanced Testing