A micro- and macro-scale study of colloidal silica treated Sydney River sand for ground improvement

<p dir="ltr">Colloidal Silica (CS) is an emerging low-carbon binder used for the ground improvement of a wide range of soil types. In this study, the CS gelling mechanism is studied at a microscopic scale using Photo-induced Force Microscopy (PiFM). Macro-scale experimental studies were also conducted to determine the gelling time of CS grout alone and Sand+CS grout. This study investigates the effect of different sand types on the CS gelling time and gelling mechanism. The Unconfined Compressive Strength (UCS), compressibility, and permeability of two different Sydney River sands (fine and coarse) were investigated to analyse the mechanical behaviour of CS-stabilized sand.</p><p dir="ltr">The results revealed that CS stabilization increased the strength and reduced the permeability of both sands, whereas the gelling time, gelling mechanism, failure pattern, post-peak behaviour, and compressibility of CS-stabilized sand depended mainly on the particle size, shape, and elemental composition of the sand.</p><p dir="ltr">This work advances the understanding of CS-stabilized sand and its application in sustainable ground improvement. It gives valuable insights into how different sand characteristics affect the gelling time and mechanism, compressibility, and failure pattern, thereby directly influencing the effectiveness of grouting and the mechanical strength of CS-stabilized sand.</p>