Stability Evaluation Of N-Sodium Silicate Chemical Grouts by Means of Rheology and Syneresis Testing-Paper

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The study evaluates two N-sodium silicate chemical grout mixes using rheological testing and syneresis measurements in Ottawa sand. An advanced rheometer tracked grout behavior from mixing through gelation, while sand specimens of different sizes were monitored for mass and volume changes over 250 days.<br /><br />Rheological results showed that both grouts initially behaved like viscous fluids, then became increasingly elastic as they gelled. The onset of gelation was identified by a drop in the phase angle, occurring at 19 minutes for mix AA and 27 minutes for mix T1. This change appeared before any measurable increase in viscosity or shear resistance, suggesting that phase-angle monitoring can detect gel initiation earlier and more precisely than conventional viscosity or cup-tilt methods. Mix AA ultimately developed a higher storage modulus and a more elastic response than mix T1.<br /><br />During syneresis testing, specimens lost mass but showed no detectable volume change. Mass loss was more closely related to exposed surface area than to initial specimen mass; normalizing by surface area produced a consistent relationship across specimen sizes. Grouted sand lost approximately 8–16% of its initial mass over 250 days. Testing conditions also strongly affected the results: repeatedly unwrapping specimens reduced surrounding humidity and roughly doubled the measured syneresis rate compared with specimens measured only once.<br /><br />The findings indicate that laboratory syneresis tests should reproduce expected field moisture conditions. For field risk assessment, monitoring groundwater fluctuations and the moisture environment around grouted soil is important, since water loss may affect long-term grout performance.

Keywords

N-sodium silicate

chemical grout

rheological testing

syneresis

Ottawa sand

phase angle

gelation onset

storage modulus

mass loss

groundwater fluctuations