A LOOK AT THE FUTURE OF SELF-HARDENING SLURRIES IN A DECARBONIZING WORLD-Paper

Paper

Pdf Summary

The paper investigates lower-carbon alternatives for self-hardening slurries (SHS) as ground blast-furnace slag cement becomes less available and carbon pricing may make Portland cement more costly. The authors explore whether silica-rich minerals can reduce Portland cement use by half while maintaining the strength and low hydraulic conductivity needed for cutoff walls. Their approach targets a calcium-to-silica ratio near one, and tests mixes containing 11% Portland cement, 5% bentonite, and various mineral additives against a 22% Portland-cement baseline.<br /><br />After roughly five to six months, several additives—including silica fume, pumice, diatomaceous earth, Red Lake Earth, and perlite ore—produced strength gains approaching twice the baseline. However, most did not meet the target hydraulic conductivity of less than 10⁻⁶ cm/s. Kaolin, attapulgite, bentonite, and perlite ore did meet that threshold; longer-term tests showed particularly low conductivity for bentonite and perlite ore after one year. The alternative mixes were also generally lighter and had rupture strains equal to or greater than the baseline.<br /><br />The study demonstrates the potential to reduce Portland cement content, but it does not establish the carbon savings quantitatively because reliable emissions data for mineral additives were unavailable. The authors recommend further testing and locally sourced alternatives, including recycled materials, to develop cost-effective, lower-carbon formulations. They also emphasize that SHS performance develops slowly: testing at 28 days may be inadequate, with meaningful maturity often taking six months or longer.

Keywords

self-hardening slurries

Portland cement reduction

lower-carbon alternatives

silica-rich minerals

hydraulic conductivity

ground blast-furnace slag

cutoff walls

bentonite

perlite ore

carbon pricing