Sika paste backfill admixtures: cost and strength insights for mine engineers
Reviewed by Tom Sullivan
First reported on Australian Centre for Geomechanics – News
30 Second Briefing
Optimising cemented paste backfill with admixture technology, Teresa Bellver-Baca and Ignacio Aguilar-Sánchez of Sika report that water-reducing and viscosity-modifying agents can cut yield stress while increasing solids content, improving pumpability over long underground pipelines. Field trials in an underground gold mine showed fresh paste yield stress falling even as solids content rose from typical 67–80%, and uniaxial compressive strength gains at 3, 7 and 28 days for mixes with 12% cement and 0–3% admixture by cement weight. The approach targets lower binder consumption in CPB, which can account for up to three quarters of backfill cost.
Technical Brief
- CPB rheology is controlled within typical targets: 50–300 Pa yield stress, 0.1–1.0 Pa·s plastic viscosity.
- Operational windows also specify 180–250 mm slump flow, 67–80% solids, <3% bleed water, 0.5–5 MPa UCS.
- Field work used industrial-scale tests in an operating underground gold mine, not only laboratory mixes.
- Uniaxial compressive strength was measured at 3, 7 and 28 days on mixes with 12% cement.
- Admixture dosages in the strength programme were stepped at 0%, 2% and 3% of cement mass.
- Rheological monitoring tracked yield stress changes against incremental solids content increases during live plant operation.
- Geological setting and ore-forming environment are linked to tailings mineralogy and chemistry, constraining admixture selection and dosage.
Our Take
With cementitious binder accounting for up to three-quarters of backfill expenses and CPB representing 10–20% of mine operating costs, Sika’s paste optimisation work is likely to be most attractive to high-cost underground gold operations such as Alamos Gold’s Island Gold Mine, where incremental OPEX reductions materially affect cut-off grades.
In our database of 1228 mining stories, only a subset of gold-tagged items focus on backfill and binder chemistry, so this Sika piece sits in a relatively specialised niche compared with more common coverage of Australian gold exploration and corporate moves such as the Barrick Mining restructuring or Lion One Metals’ financing issues.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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