Expansive Soils and Clays

Expansive soils are conventionally treated with chemical stabilizers manufactured by energy-intensive processes that significantly contribute to carbon dioxide emissions globally. Geopolymers, which are synthesized from industrial byproducts rich in aluminosilicates, are a viable alternative to conventional treatments, as they are eco-friendly and sustainable. In this study, a metakaolin-based geopolymer was synthesized, and its effects on the strength and volume-change behavior of two native expansive soils from Texas, with a plasticity index over 20 were investigated. This paper elaborates on the geopolymerization process, synthesis of the metakaolin-based geopolymer, specimen preparation, and geopolymer treatment of soils. Comprehensive material testing revealed two clays with a plasticity index over 20. They were each treated with three dosages of the metakaolin-based geopolymer and cured in 100% relative humidity for three different curing periods. The efficiency of geopolymer treatment was determined by testing the control and geopolymer-treated soils for unconfined compressive strength (UCS), one-dimensional swell, and linear shrinkage. Field emission scanning electron microscope (FESEM) imaging was performed on the synthesized geopolymer, as well as on the control and geopolymer-treated soils, to detect microstructural changes caused by geopolymerization. A significant increase in UCS and reduction in swelling and shrinkage were observed for both geopolymer-treated soils, within a curing period of only 7 days. The FESEM imaging provided new insights on the structure of geopolymers and evidence of geopolymer formation in treated soils. In conclusion, the metakaolin-based geopolymer has strong potential as a lower-carbon-footprint alternative to conventional stabilizers for expansive soils.

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Combined effect of mineralogical and chemical parameters on swelling behaviour of expansive soils

Scientific Reports ◽

10.1038/s41598-021-95746-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Bendadi Hanumantha Rao ◽

Peddireddy Sreekanth Reddy ◽

Bijayananda Mohanty ◽

Krishna R. Reddy

Keyword(s):

Expansive Soils ◽

Research Work ◽

Swelling Pressure ◽

Combined Effect ◽

Practical Significance ◽

Chemical Compositions ◽

Chemical Parameters ◽

Swelling Behaviour ◽

Mineral Contents ◽

Swelling Properties

AbstractMicrolevel properties such as mineralogical and chemical compositions greatly control the macro behaviour of expansive soils. In this paper, the combined effect of mineral (i.e. montmorillonite, MMC) and chemical contents (i.e. Ca and Na in their total (T), leachable (L) and exchangeable form (CEC)) on swelling behaviour is investigated in a comprehensive way. Several 3-dimensional (3D) graphs correlating MMC and Ca/Na ratio, together, with swelling property (swelling potential, Sa, and swelling pressure, Sp) are developed. 3D plots, in general, portrayed a non-linear relationship of Sa and Sp with MMC and Ca/Na ratio, together. It is hypothesized that swelling initially is triggered by chemical parameters due to their quick and rapid ionization capability, but the overall swelling phenomenon is largely controlled by MMC. It is importantly found that expansive soils are dominant with divalent Ca++ ions up to MMC of 67% and beyond this percentage, monovalent Na+ ions are prevalent. From the interpretation of results, the maximum Sa of 18% and Sp of 93 kPa is measured at MMC of 43%, (Ca/Na)T of 10–14 and (Ca/Na)L of 2–7. It is concluded from study that total CEC + MMC for determining Sa and (Ca/Na)T + MMC for determining Sp are superior parameters to be considered. The findings of the study also excellently endorsed the results of Foster32, who stated that ionization of Na or Ca depends on the constituent mineral contents. The findings presented herein are unique, interesting and bear very practical significance, as no earlier research work reported such findings by accounting for chemical and mineralogical parameters impact, in tandem, on swelling properties.

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Estimation of swelling characteristics of expansive soils with influence of clay mineralogy

Acta Agriculturae Scandinavica Section B - Soil & Plant Science ◽

10.1080/09064710.2021.1872696 ◽

2021 ◽

pp. 1-6

Author(s):

Kundan Meshram ◽

Nitu Singh ◽

P. K. Jain

Keyword(s):

Expansive Soils ◽

Clay Mineralogy ◽

Swelling Characteristics

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Long-term Field Heave Studies on Various Foundation Techniques in Expansive Soils

Indian Geotechnical Journal ◽

10.1007/s40098-020-00474-8 ◽

2021 ◽

Author(s):

P. Hari Krishna ◽

V. Ramana Murty

Keyword(s):

Expansive Soils ◽

Term Field

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Cotton Wastes Functionalized Biomaterials from Micro to Nano: A Cleaner Approach for a Sustainable Environmental Application

Polymers ◽

10.3390/polym13071006 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1006

Author(s):

Samsul Rizal ◽

Abdul Khalil H. P. H. P. S. ◽

A. A. Oyekanmi ◽

Niyi G. Olaiya ◽

C. K. Abdullah ◽

...

Keyword(s):

Building Materials ◽

Expansive Soils ◽

Research Work ◽

Functional Materials ◽

Extraction Process ◽

Process Conditions ◽

Environmental Application ◽

Isolation Technique ◽

Metals Removal ◽

Combined Pretreatment

The exponential increase in textile cotton wastes generation and the ineffective processing mechanism to mitigate its environmental impact by developing functional materials with unique properties for geotechnical applications, wastewater, packaging, and biomedical engineering have become emerging global concerns among researchers. A comprehensive study of a processed cotton fibres isolation technique and their applications are highlighted in this review. Surface modification of cotton wastes fibre increases the adsorption of dyes and heavy metals removal from wastewater. Cotton wastes fibres have demonstrated high adsorption capacity for the removal of recalcitrant pollutants in wastewater. Cotton wastes fibres have found remarkable application in slope amendments, reinforcement of expansive soils and building materials, and a proven source for isolation of cellulose nanocrystals (CNCs). Several research work on the use of cotton waste for functional application rather than disposal has been done. However, no review study has discussed the potentials of cotton wastes from source (Micro-Nano) to application. This review critically analyses novel isolation techniques of CNC from cotton wastes with an in-depth study of a parameter variation effect on their yield. Different pretreatment techniques and efficiency were discussed. From the analysis, chemical pretreatment is considered the most efficient extraction of CNCs from cotton wastes. The pretreatment strategies can suffer variation in process conditions, resulting in distortion in the extracted cellulose’s crystallinity. Acid hydrolysis using sulfuric acid is the most used extraction process for cotton wastes-based CNC. A combined pretreatment process, such as sonication and hydrolysis, increases the crystallinity of cotton-based CNCs. The improvement of the reinforced matrix interface of textile fibres is required for improved packaging and biomedical applications for the sustainability of cotton-based CNCs.

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