Mechanical properties of dense Ca-smectite clay

Börgesson, Lennart; Broc, Daniel; Plas, F.

doi:10.1016/0013-7952(90)90025-v

Cited by 5 publications

(3 citation statements)

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“…The high swelling capacity of the bentonite barrier and the availability of water will cause the clay to swell to fill these spaces, removing their ability to transmit fluids and effectively sealing the waste away from the environment. Studies have looked at the material behaviour at ambient and elevated temperatures, examining the swelling capacity [9][10][11]34] and swelling (or suction) pressure, both at steady-state and over time [33,[35][36][37][38][39][40][41][42][43][44][45][46][47][48]. The most recent studies [47,48] have investigated the development and evolution of swelling pressure within the barrier, looking at a case where the void space is nearly equivalent in size to that of the clay material.…”

Section: Introductionmentioning

confidence: 99%

Gel Formation at the Front of Expanding Calcium Bentonites

et al. 2021

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The removal of potentially harmful radioactive waste from the anthroposphere will require disposal in geological repositories, the designs of which often favour the inclusion of a clay backfill or engineered barrier around the waste. Bentonite is often proposed as this engineered barrier and understanding its long-term performance and behaviour is vital in establishing the safety case for its usage. There are many different compositions of bentonite that exist and much research has focussed on the properties and behaviour of both sodium (Na) and calcium (Ca) bentonites. This study focusses on the results of a swelling test on Bulgarian Ca bentonite that showed an unusual gel formation at the expanding front, unobserved in previous tests of this type using the sodium bentonite MX80. The Bulgarian Ca bentonite was able to swell to completely fill an internal void space over the duration of the test, with a thin gel layer present on one end of the sample. The properties of the gel, along with the rest of the bulk sample, have been investigated using ESEM, EXDA and XRD analyses and the formation mechanism has been attributed to the migration of nanoparticulate smectite through a more silica-rich matrix of the bentonite substrate. The migration of smectite clay out of the bulk of the sample has important implications for bentonite erosion where this engineered barrier interacts with flowing groundwater in repository host rocks.

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Section: Introductionmentioning

confidence: 99%

Gel Formation at the Front of Expanding Calcium Bentonites

et al. 2021

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“…5.1 and 5.4), (2) the specific surface and the plastic limit change with materials, therefore implicitly account for the material type, (3) changes in pore water chemistry should result in different values of the plastic limit, as they do for the liquid limit (Borgesson et al, 1988); the suggested water content ratios may still be able to account for the effects of changes in the pore geometry.…”

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confidence: 99%

“…a: Water content (w) is computed using the relation Se = Gw, where S = degree of saturation (100% in this calculation), e = void ratio, G = specific gravity of the clay. 1968; Mitchell, 1976, p. 45;Yon and Warkentin, the other 10% of the materials have a negligible effect on the permeability, the refined Kozeny-Carman equation has been used to check measured permeabilities (C/S granular bentonite) reported in Chapter 3, as well as those of MX-80 bentonite reported by Borgesson et al (1988). The plastic limit and specific gravity are 50% and 2.92 for the C/S granular, 70% and 2.9 for the MX-80.…”

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confidence: 99%