The threat posed by increasing amount of dyes on daily basis, especially on our ecosystem, has brought a serious search for more efficient low-cost adsorbents. Sand is mixed with cement and water to make concrete, used in the manufacture of brick, glass and other materials, and it can also be used as a medium for the filtration of water. Sand, which is ubiquitous, has been used as an adsorbent because of its enormous availability in the local environment. This review reveals that further research must be conducted to bring to the fore the expansive laboratory, industrial and environmental usage of sand materials as dye adsorbents. Consequently, the usage of different types of sand in the field of adsorption science represents a viable and powerful tool, resulting into the superior improvement in pollution control and environmental preservation.

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Adsorption of dyes using different types of clay: a review

This report presents information on the characterization of cementitiously stabilized layers and the properties that influence pavement performance. It also contains recommended performance-related procedures for characterizing these layers and performance-prediction models for incorporation into the mechanistic–empirical pavement analysis methods. Individual chapters highlight pavement distresses of hot-mix asphalt pavements and concrete pavements, laboratory tests and model development, and model calibration. The material contained in the report will be of immediate interest to state materials, pavement, and construction engineers and others involved in the different aspects of pavement design and construction.

Characterization of Cementitiously Stabilized Layers for Use in Pavement Design and Analysis

What controls the mechanical properties of shale rocks? – Part I: Strength and Young's modulus

Foundations on Expansive soils

Expansive soils are problematic due to the performances of their clay mineral constituent, which makes them exhibit the shrink-swell characteristics. The shrink-swell behaviours make expansive soils inappropriate for direct engineering application in their natural form. In an attempt to make them more feasible for construction purposes, numerous materials and techniques have been used to stabilise the soil. In this study, the additives and techniques applied for stabilising expansive soils will be focused on, with respect to their efficiency in improving the engineering properties of the soils. Then we discussed the microstructural interaction, chemical process, economic implication, nanotechnology application, as well as waste reuse and sustainability. Some issues regarding the effective application of the emerging trends in expansive soil stabilisation were presented with three categories, namely geoenvironmental, standardisation and optimisation issues. Techniques like predictive modelling and exploring methods such as reliability-based design optimisation, response surface methodology, dimensional analysis, and artificial intelligence technology were also proposed in order to ensure that expansive soil stabilisation is efficient.

Emerging trends in expansive soil stabilisation: A review

The present study examines the effect of inflow of sodium chloride solutions on the swell–compression behaviour of compacted expansive clays under a range of external loads. Inflow of sodium chlori...

Swell–compression behaviour of compacted clays under chemical gradients

Compacted clay liners in landfills and brine ponds are subject to chemical concentration gradients between the soil water in the clay and the reservoir solution. Soil water is the solution residing in soil pores that is chemically composed of water $(H_2O)$ molecules and dissolved salts molecules (ISSS, 1976). These differences in salt concentration generate an osmotic suction difference: osmotic suction refers to suction arising from the presence of dissolved salts in water (Lu & Likos, 2004). This suction difference is dissipated through the diffusion of salts and flow of H2O molecules (Barbour & Fredlund, 1989). Changes in the dissolved salts concentration of soil water from salt diffusion in response to osmotic suction difference will alter the swell magnitudes of expansive clays, which are strongly influenced by salt concentration (Bolt, 1956; Mesri & Olsen, 1971; Yong & Warkentin, 1975; Mitchell, 1993). Osmotic suction differences between soil water and reservoir solution may thus alter the wetting-induced volume change behaviour of compacted clays used as liners in landfills and brine impoundments.

Swelling of compacted clay under osmotic gradients

Role of direction of salt migration on the swelling behaviour of compacted clays

Unsaturated clays are subject to osmotic suction gradients in geoenvironmental engineering applications and it therefore becomes important to understand the effect of these chemical concentration gradients on soil-water characteristic curves (SWCCs). This paper brings out the influence of induced osmotic suction gradient on the wetting SWCCs of compacted clay specimens inundated with sodium chloride solutions/distilled water at vertical stress of 6.25 kPa in oedometer cells. The experimental results illustrate that variations in initial osmotic suction difference induce different magnitudes of osmotic induced consolidation and osmotic consolidation strains thereby impacting the wetting SWCCs and equilibrium water contents of identically compacted clay specimens. Osmotic suction induced by chemical concentration gradients between reservoir salt solution and soil-water can be treated as an equivalent net stress component, ( pπ ) that decreases the swelling strains of unsaturated specimens from reduction in ...

Influence of Osmotic Suction on the Soil-Water Characteristic Curves of Compacted Expansive Clay

Lime stabilization prevails to be the most widely adopted in situ stabilization method for controlling the swell-shrink potentials of expansive soils despite construction difficulties and its ineffectiveness in certain conditions. In addition to the in situ stabilization methods presently practiced, it is theoretically possible to facilitate in situ precipitation of lime in soil by successive permeation of calcium chloride (CaCl2 ) and sodium hydroxide (NaOH) solutions into the expansive soil. In this laboratory investigation, an attempt is made to study the precipitation of lime in soil by successive mixing of CaCl2 and NaOH solutions with the expansive soil in two different sequences.Experimental results indicated that in situ precipitation of lime in soil by sequential mixing of CaCl2 and NaOH solutions with expansive soil developed strong lime-modification and soil-lime pozzolanic reactions. The lime-modification reactions together with the poorly de-
veloped cementation products controlled the swelling potential, reduced the plasticity index, and increased the unconfined compressive strength of the expansive clay cured for 24 h. Comparatively, both lime-modification reactions and well-developed crystalline cementation products (formed by lime-soil pozzolanic reactions) contributed to the marked increase in the unconfined compressive strength of the ex-pansive soil that was cured for 7–21 days. Results also show that the sequential mixing of expansive soil with CaCl2 solution followed by NaOH solution is more effective than mixing expansive soil with NaOH solution followed by CaCl2 solution. DOI: 10.1061/(ASCE)MT .1943-5533.0000483. © 2012 American Society of Civil Engineers.

T. Thyagaraj

Papers

Swell–compression behaviour of compacted clays under chemical gradients

Swelling of compacted clay under osmotic gradients

Role of direction of salt migration on the swelling behaviour of compacted clays

Influence of Osmotic Suction on the Soil-Water Characteristic Curves of Compacted Expansive Clay

Laboratory Studies on Stabilization of an Expansive Soil by Lime Precipitation Technique