The effect of a sustainable material as partially replacement of cement on the geotechnical properties of sandy soil

The deserts in Iraq need to be utilized due to the population growing and cities expansion. More than one third of Iraq's land covered with deserts. Deserts soils have some issues that makes their improvement mandatory. Examples of the issues of soils of deserts are the low bearing capacity, high permeability, high collapsibility potential, and low durability. These issues are because of the uniform particles size distributions of these soils and the lack of edges of the particles. For that, soil improvement is required to modify and fix these issues. Cement is considered one of the most efficient additive to be used for soil stabilization. However, it has some environment issues since it is considered one of the most CO2 emissions sources and energy consumption and also it changes the behavior of soil to be more brittle. In this study, a supplementary cementitious material, calcined shale, is used as partially replacement of cement to improve the geotechnical properties of sandy soil as a more sustainable material. The maximum dry density of cement treated soil reduced by approximately 2.6% when calcined shale content increased from 0 to 70%. The unconfined compressive strength increased when calcined shale is added and reached the maximum increasing rate, 12%, when 30% of cement is partially replaced with calcined shale and then drops by 49% when calcined shale increased to 70%. For the durability, the samples treated with calcined shale exhibit slightly lower performance compared to the samples treated solely with cement. However, these samples successfully completed the 12 cycles of wetting and drying. The results revealed that the calcined shale has the most effect on the unconfined compressive strength of cement stabilized sandy soil when 30% is used as partially replacement.