Use of a migration technique to study alteration of compacted sand–bentonite mixture in contact with concrete

Calcite Precipitation at Cement–Bentonite Interface. Part 2: Acceleration of Transport by an Electrical Gradient

“…Experimental investigations on the cement-clay interfaces often use composite specimens consisting of cement/mortar/concrete and compacted clay (Sugiyama and Tsuji 2008;Dauzeres et al 2010;Shafizadeh et al 2015;Fernández et al 2016;Yamaguchi et al 2016;Balmer et al 2017) same as the first paper. More recently, long-term in-situ experiments in underground research laboratories (URL) on the cement-clay interfaces have also been conducted (Read et al 2001;Gaboreau et al 2012;Mäder et al 2017).…”

“…Several techniques have been employed to accelerate the slow transport and mineral transformations in liquid-saturated compact or solid samples, including experiments at elevated temperatures (Nakayama et al 2004;Balmer et al 2017), application of electrical gra-dients (Saito et al 1992;Maes et al 1999;Sugiyama and Tsuji 2008), and chemical acceleration in concentrated ammonium nitrate solutions (Carde et al 1997;Choi and Yang 2013). Electrochemical migration techniques, which exploit electrical gradients, are traditionally used to accelerate ion transport (Ottosen et al 2008).…”

“…Rachmadetin et al (2019) applied electromigration method to discuss precipitation processes of calcium carbonate in compacted bentonite saturated with NaHCO 3 solution. Sugiyama et al (2005) and Sugiyama and Tsuji (2008) used the electromigration method for evaluating degradation at the interface between concrete and bentonite caused by calcium leaching from concrete to bentonite in the composite specimens.…”

“…In this study, we repeat the experiments from our first study (Nakarai et al 2021) on the evolution of cement-bentonite composite specimens by accelerating the ionic migration across the interface by applying an electric potential. The applied electrochemical migration technique was already used successfully to accelerate migration of ions across cement-clay interfaces (Sugiyama et al 2005;Sugiyama and Tsuji 2008). As before, we investigated the possibility of controlling dissolution/precipitation at cement-bentonite interfaces by premixing different amount of sodium (hydrogen) carbonate into a bentonite-sand mixture.…”

Nondestructive Integrated CT-XRD Method for Research on Hydrated Cement System

“…At present, for a subsurface low-level waste disposal facility in Japan, geological repository with a given engineered barrier system is planned for construction of 50-100 m underground with horizontal tunnels about 10 m in diameter (Niwase, Hironaga, & Tsuji, 2006). The barrier system consists of a multilayer system with compacted bentonite and cement-based materials (Sugiyama & Tsuji, 2008). The compacted bentonite is used as a buffer material for its low water permeability, self-sealing characteristics due to its swelling capacity, and the adsorption of radionuclides.…”