Chemo-mechanical study of cement paste degradation subjected to external weak sulfate attacks in geological nuclear waste disposals

Pouya, Julie; Neji, Mejdi; Windt, Laurent de; Péralès, Frédéric; Corvisier, Jérôme; Socié, Adrien

doi:10.46427/gold2022.9423

Cited by 1 publication

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“…In order to investigate the impact of the chemistry of the external solution on the degradation, the present results were compared with the results of a test performed in a volume of tank large enough to keep the solution chemistry constant and under pH regulation between 7 and 9 [46]. This configuration was almost equivalent to one in which the solution is continuously renewed [37].…”

Section: Impact Of the Boundary Conditions On The Degradationmentioning

confidence: 99%

Mineralogical Evolution and Expansion of Cement Pastes in a Sulfate-Confined Environment

et al. 2022

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The geologic disposal of radioactive waste could lead to confined conditions in which cementitious materials impose a moderate alkaline pH, in which the rocks supply sulfate ions at rather low concentrations. In this context, the purpose of this work was to study the degradation of cement pastes under such conditions using a non-renewed 30 mmol/L Na2SO4 solution without pH regulation. Samples were investigated through laboratory testing and numerical modeling. XRD, SEM–EDS, and micro-indentation acquisitions were performed to follow the evolution of chemical, mineralogical, and mechanical properties during the weak external sulfate attack. Reactive transport modeling was performed with the HYTEC code. Based on these results, the Young’s moduli of the degraded zones were estimated using analytical homogenization. Decalcification occurred despite the high pH value of the solution and significantly affected the mechanical properties. Macroscopic swelling and cracking were caused by the formation of expansive sulfate minerals after 60 days, despite the low sulfate content of the tank solution. The modeling supported the discussion on the evolution of the mineral fronts (ettringite, portlandite, and gypsum).

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Section: Impact Of the Boundary Conditions On The Degradationmentioning

confidence: 99%