Performance Analysis of Fly Ash Stabilized, Highly Saline Expansive Clays: A Case Study-PPT Presentation

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The study evaluates Class F fly ash as a stabilizer for highly saline, unsaturated expansive clay from Bhavnagar, Gujarat, India. The soil’s high plasticity, salinity and free swell make it vulnerable to moisture-related swelling and shrinkage, which can damage structures. Fly ash from the Wanakbori Thermal Power Plant was added at 10%, 15%, 20% and 25% by soil weight.<br /><br />The researchers compared untreated and treated mixes using geotechnical and chemical indicators, including compaction characteristics, free swell index (FSI), Atterberg limits, electrical conductivity, unconfined compressive strength (UCS) and California Bearing Ratio (CBR). Results show that fly ash substantially reduced free swelling: FSI fell from 73% in the untreated soil to 17% at 25% fly ash. Liquid limit and plasticity index also decreased overall, while maximum dry density declined and optimum moisture content generally increased with higher fly ash content.<br /><br />The study identifies 20% fly ash as the optimum dosage based on its compaction analysis. It also reports moderate increases in UCS and CBR as cementation in the soil mixes increased, alongside a significant reduction in electrical conductivity, indicating fewer free saline ions.<br /><br />Overall, fly ash improved the engineering performance of the saline expansive soil and reduced its swelling potential. The authors recommend further investigation of unsaturated soil behavior, especially matric suction and swell pressure, to better understand and assess stabilization performance.

Keywords

Class F fly ash

saline expansive clay

soil stabilization

Bhavnagar Gujarat

free swell index

Atterberg limits

unconfined compressive strength

California Bearing Ratio

electrical conductivity

optimum fly ash dosage