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Engineering Behaviour of Clays: Influence of Mineralogy
Published in C. Di Maio, T. Hueckel, B. Loret, Chemo-Mechanical Coupling in Clays, 2018
The minerals of the smectite group (example, mont-morillonite) have the octahedral sheet sandwiched between two silica sheets. The layers formed in this way are continuous in the a and b directions with bonding between successive layers by van der Waals forces and by cations that may be present to balance charge deficiencies in the structure. The bonds are weak and easily separated by cleavage or adsorption of water or other polar liquids. There is extensive substitution for aluminium and silicon within the lattice by other cations. Because of large amount of unbalanced substitution in the smectite minerals, they exhibit high cation exchange capacities, generally in the range of 80– 150 meq/100g. The specific surface can range from 700 to 840m2/g.
Natural Nanomaterials
Published in M. H. Fulekar, Bhawana Pathak, Environmental Nanotechnology, 2017
Clays have extensive applications in many fields such as polymer nano-composites, catalysts, photochemical reaction fields, ceramics, paper filling and coating, sensors and biosensors and absorbents, due to their high specific surface area, chemical and mechanical stabilities and a variety of surface and structural properties. The widely used clays form the smectite group, which refers to a family of non-metallic clays primarily composed of hydrated sodium calcium aluminium silicate, a group of monoclinic clay-like minerals with formula of (Ca,Na,Al,Mg,Fe,Zn)2 (Si,Al)4O10(OH)2 nH2O. Smectite is a clay mineral having a 2:1 expanding crystal lattice. Its isomorphous substitution gives various types of smectite and causes a net permanent charge balanced by cations in such a manner that water may move between the sheets of the crystal lattice, giving a reversible cation exchange with plastic properties. Smectite group include the dioctahedral minerals montmorillonite, beidellite, nontronite, bentonite and the trioctahedral minerals hectorite (Li-rich), saponite (Mg-rich) and sauconite (Zn-rich). The basic structural unit is a layer consisting of two inward pointing tetrahedral sheets with a central alumina octahedral sheet. The layers are continuous in the length and width directions, but the bond between layers are weak and have excellent cleavage, allowing water and other molecules to enter between the layers causing expansion in the third direction.
Weathered rock and slope stability
Published in Duncan C. Wyllie, Rock Slope Engineering, 2017
Some of the products of these processes are the following three types of common sheet-type clay minerals, some of which have swelling characteristics. The general cause of swelling is the easy penetration of water between adjacent oxygen ions of the silica tetrahedra sheets, causing the individual layers of clay particles to separate and swell. Kaolinite is a very common clay formed from feldspars and micas by leaching of acid, quartz-rich rocks such as granite. Kaolinite is non-swelling.Smectite minerals are also very common, the parent materials for which are rocks high in alkaline earths such as basic and intermediate igneous rocks and volcanic ash; they are formed in arid and semiarid areas where evaporation exceeds precipitation. Common smectites are montmorillonite and vermiculite, both of which are highly expansive, while illite (hydrous mica) is also common, but is non-swelling.Chlorite may form by alteration of smectite where Mg2+ cations are introduced into the lattice structure. Biotite from igneous and metamorphic rocks may alter to form chlorites and mixed layer chlorite–vermiculite. Chlorites are non-swelling.
On shale swelling: the unrecognized role of diffusion osmosis
Published in Geosystem Engineering, 2023
Abdulrahman Sheref, Talal AL-Bazali
Since clay is a major component of shale composition, there is a direct relationship between shale swelling and the amount of clay minerals it contains. Clay minerals are layered minerals classified among phyllosilicates which consist of stacks of negatively charged two-dimensional aluminosilicate layers. This negative charge on clay minerals was gained during a process known as ‘Isomorphic substitution’. Smectite is a type of clay mineral that is considered as highly sensitive clay to water which tends to expand through the adsorption of water between its sheets. Smectite group incorporates a variety of clays including montmorillonite, hectorite, and beidellite. It is considered as a 2:1 (T-O-T) clay which means that its structure consists of one octahedral sheet sandwiched between two tetrahedral sheets. Many studies of clay swelling have focused on 2:1 smectite clays due to their high swelling potential and the frequency they are encountered during drilling operations. Anderson et al. (2010) proposed that the tendency of sodium-saturated smectite to swell is the principal cause of shale instability in oil well drilling operations which can lead to collapse and wellbore failure.
Engineering properties of fine-grained red mud
Published in International Journal of Mining, Reclamation and Environment, 2023
Hua Tian, David J. Williams, Keith Mandisodza, Chenming Zhang, Sebastian Quintero Olaya, Wenqiang Zhang, Chongyi Tang
Many geotechnical soil properties depend on their constituent mineralogy. Significant quantities of iron minerals were found in both red mud and sand, present as haematite (Fe2O3) and goethite (FeO(OH)), respectively, whereas the main mineral composition of bentonite was smectite, followed by quartz. Smectite often referred to as a ‘swelling’ or ‘expansive’ clay mineral contains interlayer spaces and exhibits a high expansion (swelling) capability in the presence of water [50]. Thus, the absence of smectite and other claylike minerals indicates that red mud is similar to ‘sand’ sample, yet it undergoes essentially infinite swelling as the limited expansion of composition occurs with hydration, which has been proven in related literature [10]. Apart from iron minerals, the red mud featured significant quantities of nosean (Na8Al6Si6O24(SO4)), distinguishing it from the ‘sand’ sample wherein large quantities of gibbsite (Al(OH)3) were present.
Effect of soluble gypsum on swell behaviour of lime-treated expansive soil – a micro-level investigation
Published in Geomechanics and Geoengineering, 2022
Arvind Kumar Jha, Vijay Bahadur Singh, Ankush Kumar Jain, M. P. Akhtar
The expansive soil is considered as a problematic soil due to its unpredictable behaviour upon moisture variation (Nelson and Miller 1992). The uncertain swell-shrinkage behaviour leads to the distress of many civil engineering structures built on expansive soil which is governed particularly by the minerals present in it (Chen 1988, Nelson and Miller 1992). The presence of smectite group of minerals such as montmorillonite, illite and their structural compositions affects the moisture holding capacity and strength of expansive soil. The susceptible behaviour of expansive soil is controlled by using different traditional (cement, lime, fly ash, ground granulated blast furnace slag, rice husk etc.) and non-traditional (ammonium chloride, sulphonated oils, enzymes, potassium compounds and polymers) stabilisers (Mitchell 1986, Petry and Little 2002, Bhanumathidas and Kalidas 2005, Higgins 2005, Muntohar 2009, Pal and Ghosh 2013).