GEOTECHNICAL ASSESSMENT OF HIGHLY SALINE SOIL STABILIZED WITH FLY ASH

Paper

Pdf Summary

The study evaluated Class C lignite fly ash and Portland cement as stabilizers for highly saline soil collected near Bhavnagar, Gujarat, India. The soil was a low-plasticity silt with an initial electrical conductivity (EC) of 21,500 μS/cm and very low bearing capacity. Mixtures containing 10%, 20%, or 30% fly ash and either 6% or 9% cement were tested for unconfined compressive strength (UCS), soaked California Bearing Ratio (CBR), EC, and durability.<br /><br />Treatment substantially improved strength and pavement performance. CBR rose from 1.62 in untreated soil to as high as 117.26 in a mixture with 30% fly ash and 6% cement. At 28 days, UCS reached 1,588 kPa for the mixture containing 30% fly ash and 9% cement. Stabilized samples also had effective CBR values above the 5% pavement-subgrade threshold, whereas untreated soil did not.<br /><br />Treatment reduced EC to 7,270–8,730 μS/cm, indicating lower measured salinity. Durability depended on cement content: mixtures with 6% cement failed during the first wetting cycle, while those with 9% cement withstood 12 cycles. Of these, the 30% fly ash–9% cement mixture met the specified maximum weight-loss criterion for pavement use. Its strength was also considered suitable for a stabilized sub-base, though not for a base layer.<br /><br />Overall, 30% fly ash combined with 9% cement was identified as the most effective tested formulation, improving strength, stiffness, salinity indicators, and durability. The authors conclude that locally available fly ash and cement offer a practical stabilization option for saline soils in geotechnical and pavement applications.

Keywords

Class C lignite fly ash

Portland cement stabilization

saline soil

unconfined compressive strength

California Bearing Ratio

electrical conductivity

soil stabilization

Bhavnagar Gujarat

pavement subgrade

durability testing