Experimental Study to Improve the Strength of Expansive Soil in Egypt Using Different Percentage of Bitumen

Abstract Clayey soils naturally shrink and swell, which can have a major impact on buildings due to differential settlements. In semi-arid and arid regions of the world, expansive soils present a significant maintenance challenge for geotechnical practicing engineers. This paper investigates the effect of using six different percentages of bitumen to improve the properties of expansive soils in Egypt. Extensive soil samples were taken from three locations, including the 6th of October (Very high potential expansiveness), El-Mokatam area (High potential expansiveness), Abo-Tartor (El-Kharga, El-Wadi EL- Gedid) (Medium potential expansiveness). Each soil sample set is mixed with bitumen at percentages of 0%, 3%, 6%, 9%, 12%, and 15% by weight to generate six different mixtures. Testing was done on the classification, specific gravity, Atterberge limits, compaction properties, free swell, swelling potential, swell pressure, and compressive strength of the natural and treated soils. The results indicated that, when bitumen content was increased to 15%, the liquid limit decreased by 41.5%, 37.23%, and 35.21% for very high potential expansiveness, high potential expansiveness, and medium potential expansiveness, respectively. Also, free swell, swelling potential, and swell pressure decreased by 68%, 65.5%, and 70% for very high potential expansiveness when bitumen content was increased to 15%. For high potential expansiveness, free swell, swelling potential, and swell pressure decreased by 67.2%, 62.26%, and 45%. In addition, increasing bitumen percentage by 15%, decreased by 33.5%, 55%, and 31.43 for medium potential expansiveness. In this study, the effect of using bitumen on shear strength characteristics, optimum water content, max. dry density, swell limit, shrink limit, and shrink-swell limit for very high, high, medium potential expansiveness have been studied. It was concluded that bitumen stabilization using for improvement the properties of expansive soil in Egypt. Finally, a new set of correlation equations was proposed to estimate the swelling characteristics in relation to the bitumen addition percentage to expansive soil.