Thesis
An experimental investigation on the strength evolution of colloidal silica grout during curing and rehealing, and on its modification using clays and polymers
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2026
- Thesis identifier
- T18113
- Person Identifier (Local)
- 201971469
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Colloidal silica (CS) is a novel, environmentally friendly grout with water-like viscosity and nano-scale particle size, which forms rigid gels with low hydraulic conductivity in precisely controllable durations. CS grout has great promise as an injectable barrier and soil stabiliser in a range of fields, but its large-scale application has so far been limited. This thesis presents an experimental investigation into the process by which CS grout increases in strength during curing, and the factors which affect it, and it is also the first work to study the re-healing ability of CS grout, and its combination with clays and polymers. Shear vane and compression tests found the strength of CS grout and grouted soil to increase with curing time via power laws, with this attributed to continuous deposition and condensation of silicates at joining points between particles in the network. Samples of each were also found to re-heal after breaking before increasing in strength again, although at a slowed rate. After breaking, gel fragments are proposed to quickly reconnect due to the continued presence of the original gelation conditions, before gaining strength again through a similar mechanism to that in curing. Higher silica mass fraction, NaCl concentration, and smaller particle size each increased the strength of the grout, and adding NaCl could be used to offset loss in strength from small reductions in silica content. Higher ionic strength in water surrounding samples gave a linear increase in their strength, and those cured in fresh water were relatively weaker due to diffusion of ions out of the grout. Surrounding water at pH 9 also gave higher strength than pH 7; it is suggested that electrolyte and alkaline conditions reinforce the gel by promoting redistribution of silica to weak points in the network by increasing its solubility. Additional CS in surrounding water also strengthened samples, as the added silica could be presumably be redistributed onto the existing gel network. Secondary injection of alkaline salt solution, or additional CS, could therefore be used to increase grout strength after application, or to promote re-healing. Adding kaolin and bentonite clays each increased CS’s viscosity and accelerated its gelation, but bentonite had a stronger effect due to its swelling behaviour. Kaolin increased the strength of CS grout, although it had less effect than varying silica content; it could therefore be used to partially replace mass of silica to lower costs, with a small reduction in strength. Polyethylene glycol (PEG), polyacrylamide (PAM), and polyvinyl alcohol (PVA) were combined with CS to produce novel gels. CS/PEG variants were identified which deformed plastically and dried without cracking, with potential for use as impermeable barriers, as well as other variants which had improved water retention. PAM gels using the crosslinker polyethylenimine had high flexibility but were difficult to combine with CS due to agglomeration of silica. CS/PVA variants were produced which were soft and plastically-deformable, providing crack resistance, or that were condensed, likely with lower hydraulic conductivity and greater strength. Ultra-strong and flexible PVA and CS/PVA gels were also created via drying and freeze-thaw methods.
- Advisor / supervisor
- Draper, Emily R.
- Lunn, Rebecca J.
- Pedrotti, Matteo
- Resource Type
- DOI
- Funder
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PDF of thesis T18113 | 2026-09-22 | Public | Download |