Physical and Mechanical Properties of Cementitious Specimens Exposed to an Electrochemically Derived Accelerated Leaching of Calcium

Abstract

Simulating natural leaching process for cementitious materials is essential to perform long-term safety assessments of repositories for nuclear waste. However, the current test methods in literature are time consuming, limited to crushed material and often produce small size samples which are not suitable for further testing. This paper presents the results from the study of the physical (gas permeability as well as chloride diffusion coefficient) and mechanical properties (tensile and compressive strength and elastic modulus) of solid cementitious specimens which have been depleted in calcium by the use of a newly developed method for accelerated calcium leaching of solid specimens of flexible size. The results show that up to 4 times increase in capillary water absorption, 10 times higher gas permeability and at least 3 times higher chloride diffusion rate, is expected due to complete leaching of the Portlandite. This coincides with a 70 % decrease in mechanical strength and more than 40 % decrease in elastic modulus.

Effects of calcium leaching on the physical and mechanical properties of aerial lime-cement mortars

“…This indicates that the loss in compressive and flexural strength is in the same range. Similar results have been reported by other authors (Forster et al, 2014;Babaahmadi et al, 2015).…”

“…Carde et al (1996) noted that the global loss of strength of cement paste because of complete dissolution of Ca(OH) 2 can reach up to 70 per cent. Similar results have also been reported by several researchers (Choi and Yang, 2013;Babaahmadi et al, 2015). In contrast, carbonated hydraulic lime mortars lost between 73 and 91 per cent of their compressive strength during 169 days of immersion in NH 4 NO 3 (Banfill et al, 2016) and the uncarbonated hydraulic lime mortars lost between 96 and 99.5 per cent over the same duration of immersion in the aggressive solution (Forster et al, 2014).…”

Understanding the sulfate attack of Portland cement–based materials exposed to applied electric fields: Mineralogical alteration and migration behavior of ionic species

“…In addition to the situations mentioned above, we believe that the simplified approach for the thermodynamic modeling study proposed in this paper can be more broadly applied in investigating the behavior of cement-based materials under applied electric fields. Future studies may involve the use of this approach in accelerated electrochemical leaching tests [37,38], other types of chemical attacks, and in concrete technologies involving electrochemical methods (e.g., chloride extraction, realkalinization, and electrochemical deposit [32][33][34]).…”

“…In these techniques, certain types of ions are designed to migrate, but the migrations of other ions have to be considered because they may induce side effects [36]. Electric migration is also a useful tool for laboratory acceleration tests, e.g., the chloride ion penetration tests (ASTM C1202), calcium leaching acceleration tests [37,38], etc. Recent studies proposed that electric migration tests can be potentially used in the acceleration of sulfate attacks [39][40][41].…”

Cement and Concrete for Nuclear Waste Management

“…This combination of features makes it very difficult to identify which of the non-linear processes will ultimately control concrete degradation and crack development under a given set of service life conditions by expert judgement alone. For example, decalcification caused by the dissolution of the cement hydrate minerals and expansive reactions due to precipitation of secondary minerals and corrosion of steel components can all contribute to crack development in concrete (Okutsu et al 2005;Ferraris et al 1997;Hirano et al 2016;Babaahmadi et al 2015;JAEA 2018). Once established, groundwater flowing into the crack could either cause further decalcification thereby widening the crack and reducing the strength of the concrete (Höglund 2014) or else cause the precipitation of secondary minerals resulting in clogging and/or densification, which could lead to an increase in the strength of the concrete (Babaahmadi et al 2015;Metcalfe et al 2017).…”