Proposed Improvements to Laboratory Testing Programs For The Design Of Self-Hardening Slurry Cutoff Walls-Paper

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Self-hardening slurry (SHS) trench cutoff walls are formed by excavating with a cementitious slurry that hardens in place. Their performance depends on varied binders, clays, additives, water chemistry, soil solids, and field conditions. Common specifications focus on hydraulic conductivity and unconfined compressive strength (UCS), but standard laboratory tests do not adequately capture the processes that shape the finished wall.<br /><br />The paper recommends expanding laboratory programs to better represent field production. Tests should account for slurry workability over the excavation period, temperature changes, additive dosages, bentonite hydration, filtration, and the settlement or segregation of soil particles. In particular, conventional API filtrate-loss testing uses pressures far higher than those typical of trenches and may give misleading results. The authors propose testing at realistic pressures for longer periods and developing larger-scale apparatus to examine changes in composition and properties across a wall’s thickness.<br /><br />UCS is best treated mainly as a consistency check, not as a simple measure of required wall strength. Because slag-rich mixes cure slowly, 28-day results may not represent their eventual strength or hydraulic conductivity; testing at 90 or 180 days, and sometimes longer, may be more informative. The effects of confinement, deformation, brittleness, and post-failure permeability also merit research for projects where these properties matter.<br /><br />The paper further encourages investigating alternative formulations, including mixes without Portland cement and those using other clays, which may reduce filtration, additive demand, and cost. Since field walls can be heterogeneous, design and specifications should recognize variability rather than assume uniform properties.<br /><br />The authors conclude that comprehensive, independently supported research can improve the link between laboratory results and field performance, leading to better-informed specifications, more reliable designs, and potentially lower construction costs and risks.

Keywords

self-hardening slurry

trench cutoff walls

hydraulic conductivity

unconfined compressive strength

slurry workability

bentonite hydration

filtration loss

soil particle segregation

slag-rich mixes

field performance variability