Use of Ultrafine Silica Reagents to Improve S/S Material Performance



Use of Ultrafine Silica Reagents to Improve S/S Material Performance

Presenter:  George  Onorato. P.E. (GEI Consultants, Inc.)
Author:  George Onorato, P.E. (GEI Consultants, Inc.)


This case study discusses the in-situ solidified/stabilized (S/S) mix design and treatability study results for the former Florida Ave MGP site, where ultrafine silica reagents improved the treated material’s geo-mechanical properties and thus enhanced strength and permeability performance, while reducing the  leachability of constituents of interest from the matrix.   The site included typical MGP related impacts such as arsenic, lead, VOC’s and PAHs.      This presentation discusses a different perspective in which the soil/waste’s geo-mechanical properties in combination with the treatment admixture reagents enhance the S/S performance and effectiveness through the use of soil-impacts-reagent gradation curves, particle shape characteristics, mineralogy, and how these properties interact with each and affect performance.  We present the results of a case study using ground granulated blast furnace slag (GGBFS), Portland cement (PC), bentonite and ultrafine silica fume (SF) to enhance performance of treated soils.     The results clearly demonstrate that the addition of ultrafine silica significantly reduced the permeability characteristics of the S/S material by reducing pore-space volume and reduced the mass flux leached by greater than 90 percent, as determined using EPA method 1315M (LEAF) analyses.

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