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

With a brief reminder of the evolution from the original cement bentonite slurry to the more complex self-hardening slurries (SHS) using bentonite and other clays as suspension agents and binder combinations of Portland cement and its variations, slag cement, fly-ash F and C, with various chemical additives, the author examines the options that will remain in the future when modernization of steel production worldwide will cause the disappearance of slag cement as the miracle ingredient for SHS. The general adoption of the carbon calculator and carbon content pricing will also change the economic equation of everything we make. Since Portland cement availability and use will survive much longer despite its heavy carbon footprint, the author is investigating, as a preliminary step, a number of natural products or minerals that exist in abundance and have a silica rich content that may contribute to SHS formulations while requiring a significantly lower Portland cement content, thus reducing the mix’s carbon footprint. The thinking behind the study is the Ca/Si ratio imbalance of Portland cement C-S-H hydrate (main early strength contributor) at between 1.6 and 2.0 where the ideal is 1. This theory has been well studied with concretes where the W/C ratio varies between .35 and .5 but not with SHSs where it varies between 5 and 10, more than twentyfold. In as much as SHS applications may also concern grouting, soil mixing, voids backfilling, the author ‘s present focus lies primarily with cutoff wall construction where permeability is more important than strength. With essential focus on strength and hydraulic conductivity, tests results on clearly arbitrary formulations are given over a relatively long aging period up to 145 days, up to 365 days A narrowing of options became apparent offering as a conclusion a direction for further research.