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Effects of Leachate on the Permeability of Sand–Bentonite Mixtures
Published in T. H. Christensen, R. Cossu, R. Stegmann, Landfilling of Waste: Barriers, 2020
Andrea Cancelli, Raffaello Cossu, Francesca Malpei, Alessandra Offredi
Bentonite is a natural clay, whose peculiar characteristics (high swelling, tixotropy, gelling ability and cohesion) offer several different uses, both in engineering applications (sealing, slurry trenching, etc.) and in industrial activities (foundry, etc.). It consists mainly of the clay mineral montmorillonite, followed by beidellite. Both these minerals belong to the smectites group.
Execution of grouting works
Published in Christian Kutzner, Grouting of Rock and Soil, 2020
The flow diagram of a colloidal mixer is shown in Figure 7.25. With very rapid rotation of the disc in the range of more than 1200 rpm very strong shear forces and turbulences act on the solid particles which results in complete particle separation and individual moistening. Cement of common properties and suspensions down to W/C-ratios of 0.3 are reliably mixed. For different solids such as cement and sand differently shaped discs are in use. Addition of sand to a suspension of cement requires a second mixer and a secondary mixing process. Colloidal mixers are also used to process bentonite.
A suggested methodology for assessing the technical equivalency of GCLs to CCLs
Published in R. M. Koerner, E. Gartung, H. Zanzinger, Geosynthetic Clay Liners, 2020
The essence of a GCL, of course, is the layer of bentonite which is held between or on carrier layers of geotextiles or a geomembrane. Bentonite is a unique clay mineral with very high swelling potential and water absorption capacity. When wetted, bentonite is the least permeable of all naturally occurring, soil-like minerals. Of the two major types of bentonite, sodium bentonite predominates in North American GCLs, while calcium bentonite is usually used in European manufactured GCLs, see Madsen & Nüesch (1995) for details. Bentonite is a chemically stable mineral that has undergone complete weathering and will last, in effect, indefinitely.
An innovative approach to replace bentonite in hematite ore pelletizing with organic binder
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Jagannath Pal, A. Ammasi, Brati S. Bandyopadhyay, Srinivas Dwarapudi, Indrajit Paul
In iron ore pelletizing binder is a very important factor because it controls the green pellets as well as indurated pellet properties. Bentonite is suitably used as a binder for iron ore pellet making from the very beginning because of its excellent binding property in green as well as dry pellet throughout the temperature region of operation, thermal shock resistance, abundant availability, easy handling, low toxicity, inexpensiveness, etc. However, due to the high silica and alumina content in bentonite, the gangue (SiO2 and Al2O3) content of iron ore pellet proportionally increases with the addition of bentonite. This increasing gangue increases the slag volume in blast furnaces resulting in increasing energy consumption, decreasing productivity, etc., and leads to an increase in the unit cost of steel production.
Laboratory investigation of cemented silt improved with bentonite and phosphogypsum in DCM walls
Published in European Journal of Environmental and Civil Engineering, 2022
Jianwen Ding, Xing Wan, Hanrui Zhao, Chen Guo, Ning Jiao
Bentonite, a type of hydrated clay mineral consisting primarily of montmorillonite, has been widely used in civil engineering, e.g. soil-bentonite vertical cut-off walls, in addition to cement mortars (Bian et al., 2019; Por et al., 2015, 2017; Shi, Gao, et al., 2021). There are several types of bentonite, such as Ca-bentonite and Na-bentonite. The latter is characterised by high swelling index and favourable properties such as sealing materials. However, it is reported that in some developing countries such as China and India, high-quality Na-bentonite is scarce (Du et al., 2015). In contrast, Ca-bentonite, a low-swelling bentonite, occupies for about 90% of the total amount of bentonite (Fan et al., 2014). It may be noted that Ca-bentonite has a better improvement in strength compared with Na-bentonite at early curing age, according to a few reports (Latifi et al., 2016; Tingle & Santoni, 2003). In addition, compared with soil-bentonite vertical cut-off walls, the requirement of seepage proofing is lower for the retaining walls in excavation construction. Thus, it might be feasible and meaningful to apply low-quality Ca-bentonite in construction of DCM walls.
Surface modification of low-cost bentonite adsorbents—A review
Published in Particulate Science and Technology, 2019
Jock Asanja Alexander, Muhammad Abbas Ahmad Zaini, Abdulsalam Surajudeen, El-Nafaty Usman Aliyu, Aroke Umar Omeiza
Bentonite is a clay material of volcanic ashes altered in shallow sea and lagoons areas. It generally composed predominantly of smectite group. The main smectite minerals are sodium, calcium montmorillonite, saponite (magnesium montmorillonite), nontronite (iron montmorillonite), hectorite (lithium montmorillonite), and beidellite (aluminum montmorillonite). Smectite minerals are composed of two silica tetrahedral sheets with a central octahedral sheet designated as a 2:1 layer with water molecules and cations occupying the space between the layers (Guerra et al. 2013). The octahedral layer in which all three octahedral positions are filled is called trioctahedral, while when two-thirds of the possible positions are filled is called dioctahedral. Saponite is an example of trioctahedral smectite when Mg2+ fills all the octahedral positions, while beidellite is dioctahedral smectite when Al3+ fills only two out of the three octahedral positions. The most common ones are calcium and sodium montmorillonites. Calcium bentonite can be found in many parts of the world, while sodium based is relatively rare in occurrence (Viana et al. 2004). Saponite occurs in few areas of the world, while hectorite, beidellite, and nontronite are rare. Nontronite occurs mainly in iron-rich soil.