Abstract
Expansive soils exist in large areas around the world, especially in the arid and semi-arid regions. In different areas around Kingdom of Saudi Arabia, this problematic soil exists in form of layers especially in the newly developed regions of the country. Construction activities on such soil requires considering precautionary measures in order to avoid and/or minimize the risks associated with this problematic soil. Different research studies proposed measures to improve construction conditions where expansive soil exists. These measures utilize one of two techniques, either the full replacement of expansive soil layers or mitigating the expansive soil with a wide range of additives. In the current study, a new mitigating agent is introduced to be mixed with expansive soil aiming at improving its geotechnical properties; which shall be reflected in its engineering behavior under construction loads. The mitigating agent is the form of Palm Fronds Ash [PFA].
Palm Fronds [PF] is an agricultural waste that is being hugely produced every year in Saudi Arabia as a byproduct of cultivating millions of palm trees. The typical process of disposing such a waste is through open air burning, which causes serious environmental hazards to Saudi communities. In the current study, the PFA is utilized as a stabilizing agent through mixing it with the expansive soil. Remolded samples of expansive soil samples mixed with 4%, 8% and 12% PFA are prepared and tested in order to assess the improvement, if any, in its geotechnical properties. The results of the experimental program conducted on this soil mixture showed improvement of the geotechnical properties of the expansive soil; Atterberg limits, maximum dry density (MDD), unconfined compressive strength (UCS), and the swelling pressure (SP). This study showed that at a 10% content, by weight, of PFA in the expansive soil samples, the soil Liquid Limit is reduced by almost 40%. The MDD increased by almost 5% and the UCS increased by an average value of almost 26% while the swelling pressure decreased by almost 88%. Moreover, a preliminary empirical equation is presented to estimate the percentage of reduction in swelling pressure as function of the percentage of PFA mixed with the expansive soil.