Modeling of concrete carbonation in deep geological disposal of intermediate level waste

Abstract

Abstract.Simulations of atmospheric carbonation of Intermediate-Level Long-lived radioactive Waste (ILLW) concrete packages were conducted to evaluate their possible chemical degradations. Two-phase liquid water-air flow is combined with gas component diffusion processes leading to a progressive drying of the concrete. Complete drying of the 11 cm thick waste disposal package wall occurs over a period ranging from 2 years for the low-performance concrete to 10 years for the highperformance concrete. The drying process slows down when transport characteristics of concretes are enhanced. Carbonation depths in the order of 2 to 3 cm in 100 years are predicted for this cementitious component. However, these values are slightly overestimated compared to experimental data. Also the kinetic model of mineral reactivity requires improvements with respect to the protective effect of secondary carbonates and to thermodynamic data.

Valorization of waste concrete through CO2 mineral carbonation: Optimizing parameters and improving reactivity using concrete separation

“…Cementitious materials are interesting for MC due to the presence of reactive phases, especially portlandite (Ca(OH) 2 ) and calcium silicate hydrate (C-S-H) (Thouvenot et al, 2013). Table 1 summarizes the main carbonation processes and cementitious material uses that have been reviewed, along with the results.…”

CO2 sequestration using waste concrete and anorthosite tailings by direct mineral carbonation in gas–solid–liquid and gas–solid routes

“…The atmospheric carbonation of concrete involves these hydrate phases and the CO 2 that is dissolved in the aqueous phase (Thouvenot et al, 2013). Portlandite is the most soluble hydrated phase (1.6 g/L), giving a pH of 12.6 in the concrete (Alonso et al, 2010).…”

RTM for Waste Repositories

“…Further tests with the shrinking core model may succeed in reproducing these observations. In combination with this phenomenon, the decrease of reactivity when liquid saturation is below 0.3-0.4 has been observed (Thiery 2005;Thiery et al 2013) and implemented by Thouvenot et al (2013) but to calibrate such a function in codes requires more data.…”

“…A similar modeling approach was used by (Park 2008), although without the shrinking core model. RTM studies of concrete carbonation at the disposal cell scale are scarce, especially those covering typical ventilation times (~100 years) and coupling carbonation with concrete drying (Trotignon et al 2011;Thouvenot et al 2013). In these two studies, the geometries of the waste package and the tunnel structure were simplified and handled as a 1D problem.…”

“…Another noteworthy feature of this type of simulation is that the computing time can be quite long. For instance, due to the lack of an implicit scheme for the coupling of transport in the gas phase and RT in the aqueous phase in TOUGHREACT, the CPU time can be one to several months for 100 years of physical time (Trotignon et al 2011;Thouvenot et al 2013). Note that a recent development proposes an interesting "look-up table approach" for the two-phase reactive transport, which could partly help solve the simulation CPU time (Huang et al 2018).…”