A Novel pH-neutral Silicate Gel for Bottom Seals-Video

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Video Summary

Keller developed a new sodium-silicate grout, branded Neutral Gel, to meet sustainability goals and stringent European and German environmental regulations. Conventional alkaline grouts raised concerns about high pH and aluminum. After testing numerous options, the team shifted to an acidic formulation, using a different hardener and fruit acids. Although its components are acidic, the resulting eluate is neutral and meets regulatory limits.<br /><br />The grout is designed mainly for temporary excavation sealing slabs, where low permeability and erosion resistance matter more than high strength. It may also provide short-term cohesion for sands in tunnel excavations. Laboratory tests and controlled trials informed the mix design and application method.<br /><br />A field trial in a 3,600-square-meter excavation in Karlsruhe successfully sealed fluvial sands and gravels. Despite summer temperatures approaching 40°C, the mixture was adapted, residual inflow remained low, and excavation revealed grout bulbs roughly two meters in diameter. The project demonstrated the material’s potential as an alternative to conventional grout.

Keywords

sodium-silicate grout

Neutral Gel

excavation sealing

environmental regulations

Karlsruhe field trial