Journal
CEMENT AND CONCRETE RESEARCH
Volume 152, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.cemconres.2021.106659
Keywords
Strontium immobilization; Low-pH cement; C3S; Portland cement; Leaching; Radioactive waste
Funding
- Israel Atomic Energy Commission (IAEC)
- IRSN
- High-tech, Bio-tech and Chemo-tech scholar-ship of Kreitman School of Advanced Research of Ben-Gurion University of the Negev
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The study aims to identify the phases controlling strontium immobilization in Ordinary Portland Cement (OPC) matrices. Experimental results show that OPC pastes exhibit better strontium retention compared to model systems, suggesting that minor phases (such as ettringite and AFm) can improve strontium retention.
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.
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