Influence of Silica Fume on the Geotechnical Characteristics of Cemented Sand

Abstract

It is well recognized that the addition of cement to sand is one of the environmental and economic techniques in soil stabilization. However, with respect to silica fume, its impact on the characteristics of cemented sand has not been comprehensively investigated. For this purpose, a series of standard Proctor compaction, unconfined compression, pH and microstructure tests including field emission scanning electron microscope, X-ray diffraction and atomic force microscopy tests were carried out in this research to explore the influence of silica fume on the geotechnical characteristics of cemented sand. Cement in percentages of 3, 5 and 7% and silica fume in percentages of 0, 0.25, 0.5 and 1% by dry weight of sand were utilized. For unconfined compression and pH tests, samples were cured for different curing times of 3, 7, 14, 28, 42 and 56 days. The results indicated that silica fume particles increase maximum dry unit weight of sand–cement mixtures and reduce their optimum moisture content. Moreover, silica fume improves unconfined compressive strength of cemented sand which the impact of this improvement is more obvious for samples with longer curing time. According to the results obtained by unconfined compression and pH tests, it was detected that there are optimum values of curing time and silica fume amount at which strength of silica fume–cemented sand enhances significantly. Furthermore, some relations were proposed between stiffness and unconfined compressive strength of silica fume–cemented sand. Finally, the results of microstructure analysis confirmed the results found through unconfined compression tests.