Retention of strontium in high- & low-pH cementitious matrices – OPC vs. model systems

Matan E. Shiner, Ofra Klein-BenDavid, Emilie L'Hôpital, Alexandre Dauzères, Mejdi Neji, Nadya Teutsch, Alva Peled, Gabriela Bar-Nes

Research output: Contribution to journalArticlepeer-review

Abstract

Strontium can be found in low/intermediate level radioactive waste streams, often solidified by Ordinary Portland Cement (OPC) matrices. Amorphous silica is added to improve wasteform performance, leading to low-pH systems. Our aim is to identify the phases controlling strontium immobilization in OPC matrices. The novelty of this work resides in combination between two approaches: 1) Comparing OPC systems to model systems based on alite, yielding matrices containing only major phases, emphasizing the relative role of minor phases; 2) Comparing high- & low-pH pastes. Pastes were characterized using calorimetry, XRD, DTG, SEM/EDS and porosimetry. Leaching experiments were conducted to study Sr retention and diffusivity. Strontium diffusivities in low-pH pastes are lower with respect to high-pH equivalents, despite their higher porosities, due to preferred Sr sorption to low Ca/Si C-S-H. OPC pastes show better Sr retention relative to model systems, suggesting that minor phases (like ettringite and AFm) improve Sr retention.

Original languageEnglish
Article number106659
JournalCement and Concrete Research
Volume152
DOIs
StatePublished - 1 Feb 2022

Keywords

  • CS
  • Leaching
  • Low-pH cement
  • Portland cement
  • Radioactive waste
  • Strontium immobilization

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