Improving Geotechnical Properties of Expansive Soil Using Palm Fronds Ash [PFA]

Abstract

Expansive soils exist in large areas around the world, especially in the arid and semi-arid regions. Construction activities on such problematic soil requires considering precautionary measures in order to avoid and/or minimize the risks associated with it. Research studies have proposed several measures to improve construction conditions on such soil. These measures utilize one of two techniques, either the full replacement of expansive soil layers or mitigating the expansive soil with a range of additives to improve its behavior under structures.
In this study, a new mitigating agent is introduced to be mixed with expansive soil aiming at improving its geotechnical properties. The mitigating agent is the Palm Fronds Ash [PFA]. Palm Fronds [PF] is an agricultural waste as a byproduct of cultivating palm trees. In the current study, the PFA is utilized as a stabilizing agent through mixing it with the expansive soil. Remolded samples of expansive soil mixed with 4%, 8% and 12% PFA, by weight, are prepared and tested. The results of the study showed improvement of the geotechnical properties of the tested soil mixtures. At approximately 9% by weight, content of PFA within the expansive soil the Liquid Limit (WLL) decreased by almost 40%, maximum dry density (MDD) increased by almost 5%, the unconfined compression strength (UCS) increased by almost 23%-25%, and the swelling pressure decreased by almost 88%.