Engineering properties and mechanical behaviour of problematic soil stabilized by bituminous oil shale ash

This paper investigates the viability of stabilizing expansive brown clays in the Northern region of Jordan using a local bituminous oil shale ash from El-Lajjun, Jordan. A comprehensive experimental programme was designed to i. examine the impact of oil shale ash dose by weight on the strength gain. ii. Evaluate oil shale ash stabilized clays' consolidation and volume change behaviour during loading and unloading. Results revealed that adding 20 % bituminous OSA remarkably improved expansive brown clays' engineering properties and mechanical behaviour. An increase of 140 % in the unconfined compressive strength and a reduction of 19.3 % in the permeability coefficient was obtained at 20 % OSA. Also, the Unconfined Compressive Strength tests revealed that the strength of OSA-treated expansive clays is significantly affected by the curing time. Increases of 35.1 % and 65.7 % in the unconfined compressive strength were achieved after 7 days and 21 days of curing, respectively. Furthermore, the addition of OSA showed an effect on compressibility behaviour, reducing settlement. Regarding the consolidation parameters, the inclusion of 20 % OSA reduced the compression index (Cc) and swelling index (Cs) by 42.67 % and 72.6 %, respectively.