A Novel pH-neutral Silicate Gel for Bottom Seals-PPT Presentation

PPT Presentation

Pdf Summary

The presentation introduces <strong>Neutrogel</strong>, a novel pH-neutral silicate gel for constructing deep, unreinforced excavation bottom seals in groundwater without uplift anchors. It may also be used to strengthen sandy ground.

Conventional silicate grout was restricted by German authorities from around 1995 because it could produce a highly alkaline mixture (pH about 12.5), high electrical conductivity, and potentially release aluminium ions. German approval requirements for grout eluate include a pH no higher than 10.5, limited electrical conductivity, no visible or sensory contamination, restricted metals and organic carbon, and tests for toxicity, growth inhibition, and mutagenicity.

Rather than trying to reduce the pH of conventional grout after mixing, Keller developed a formulation designed to reach approximately neutral pH. The approach replaces sodium aluminate hydrate hardener with a substance containing no metal ions and uses a natural acid as the hardener, with the reaction intended to occur preferentially in acidic conditions.

The presentation describes development trials and a case study involving a sealed excavation slab in Karlsruhe, Germany. The site comprised river terrace deposits with a reported permeability of 4.04 × 10⁻⁴ m/s and a groundwater difference of 4.5 m. Grouting pipes were installed and used to inject the material; the measured residual water inflow was 1.5 litres per second per 1,000 metres. The presentation also shows excavated grouted soil as evidence of the completed work.

Keywords

Neutrogel

pH-neutral silicate gel

excavation bottom seal

groundwater uplift

unreinforced excavation

sandy ground stabilization

silicate grout

German grout regulations

Karlsruhe case study

groundwater grouting