The Effect of Silica Fume on Engineering Properties of Collapsible Soil Present in Edfu- Aswan, Egypt.

Abstract

In recent times the population of Egypt went to get out of the narrow valley on the banks of the river Nile to the reconstruction in desert zones, in which problematic soils appeared, among these types was the collapsible soil. The problematic soil has been given a great attention by geotechnical engineers and researchers. In general, all soils, which cause types of damages or difficulty in constructing new structures or utilizing existing structures, could be classified as problematic soils. The soil chosen in this research was extracted from a site in Edfu- Aswan, Egypt. These soils have caused many problems in this region and due to the development in water and sewage lines, which led to settlements and cracks in buildings. The main objective of this study is to investigate the effect of adding silica fume (SF) on the engineering properties of collapsible soils. Silica fume is a mineral composed of ultra – fine solid, amorphous glassy spheres of silicon dioxide (SiO2) obtained from the metallurgical industries company (E.J.S.C.) in Edfu. A series of laboratory experiments have been implemented on samples prepared with different percentage of SF 1%, 3%, 5%, 7%, and 9%. Test results show that the blend could diminish the collapse potential. Liquid limits and Plasticity Index would also decrease with the increasing the silica fume content. The unconfined compression strength increases from 1.57 to 2.37 kg / cm2 when mixing with SF ratios of 0 to 9%, prepared at optimum moisture content at zero days. The increase in the unconfined compression strength continued consistently for curing times of 7, 14, and 28 days. The increase in the unconfined compression strength is attributed to the internal friction of silica fume particles and chemical reaction between silica fume and soil. An increase in silica fume content in soil has made the stabilized soil samples more brittle than the natural soil samples, which is the ductile one as compared to all the stabilized samples. Their maximum dry density would increase from 1.92 to 2.02 gm/ cm3 at an SF ratio 0 to 9% and the corresponding optimum moisture content increased as well from 21.33% to 27.25%. The silica fume works as a filler material fills the voids in the soil matrix. Thus, - results indicated that by blending Silica Fume and collapsible soil together, the engineering properties of collapsible soils can be enhanced.