Strength characteristics of bentonite–lime–gypsum mix reinforced with coir fibres

Abstract

The paper presents the strength characteristics of a reference mix containing bentonite, lime and gypsum and reinforced with coir fibre. The content of lime, gypsum and coir fibre was varied from 0 to 10%, 0 to 10% and 0 to 2%, respectively. The curing period was varied from 3 to 28 days. Cylindrical specimens were prepared for conducting the unconfined compressive strength and unconsolidated undrained triaxial tests. The results reveal that the addition of 8% lime to bentonite increased the deviator stress, friction angle and cohesion. Addition of 4% gypsum to bentonite +8% lime mix increased the deviator stress, decreased the friction angle and increased the cohesion. Further, addition of coir fibres to the reference increased the unconfined compressive strength, deviator stress and cohesion up to a fibre content of 1.5%. The two parameter hyperbolic model can be used for predicting the stress–strain response of bentonite-lime-gypsum-coir fibre mix with appropriate selection of model parameters. The scanning electron micrographs and energy-dispersive X-ray studies confirms the formation of cementing compounds responsible for the improved behaviour. The improved strength characteristics of the reference-coir fibre mix can be used for short term stability related problems.

Keywords:

• bentonite
• lime
• gypsum
• strength characteristics
• constitutive relationship
• SEM–EDAX studies

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Erratum