Silica sol for rock grouting: Laboratory testing of strength, fracture behaviour and hydraulic conductivity
Journal article, 2009

A recently introduced non-cementitious grout silica sol is a refined product of colloidal silica, where the particle sizes have been reduced to between 5 and 100 nm. Laboratory tests were performed to determine the behaviour of silica sol as a permeation grout in hard rock. The tests have involved methods Such as fall-cone, unconfined compression, triaxial, and oedometer tests. Samples were tested at different time intervals and in different storage environments. Results showed that the initial strength of silica sol, a few kPa, increases over time. Silica sol has a ductile behaviour during the first few days and then becomes elastic-plastic. Its hydraulic conductivity ranges from 10(-10) to 10(-11) m/s. When immersed in water, silica sol hardens and a thin layer of weaker strength is formed at the surface. However, this layer only extends a couple of millimetres into the sample; beyond that the silica sol is not affected, rendering breakdown by erosion a negligible risk. The conclusions are: (1) the strength obtained in silica sol after hardening is sufficient to withstand most grouting conditions; (2) when sufficiently confined, silica sol is able to withstand loading and unloading cycles: (3) a pH environment of around 11 does not appreciably change the strength of the silica sol; (4) silica sol is a material with low risk of failure under blasting vibrations: and (5) due to its low hydraulic conductivity, silica sol can be compared to low permeable clays.

Triaxial tests

Silica sol

Mechanical behaviour



Hydraulic conductivity


Christian Butron

Chalmers, Civil and Environmental Engineering, GeoEngineering

Magnus Axelsson

Chalmers, Civil and Environmental Engineering, GeoEngineering

Gunnar Gustafson

Chalmers, Civil and Environmental Engineering, GeoEngineering

Tunnelling and Underground Space Technology

0886-7798 (ISSN)

Vol. 24 6 603-607

Subject Categories

Geophysical Engineering



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