Description:
The use of deep soil mixing (DSM) technique in deep ground improvement projects has increased over the past decade due to being more cost-effective and easier to implement compared to other techniques such as piling, for structures subject to low to medium loads. Currently, Portland cement, lime and their combination are being used as the most common binders in DSM. However, due to the economic and concerning environmental disadvantages of using these binders, there is a need for new environmentally friendly cementing materials. This research attempts to find a way to use stockpiles of industrial by-products, such as fly ash (FA) and slag (S), as new green binders; consequently, reducing the carbon footprint in ground improvement projects. Different contents of FA and S, activated by liquid alkaline activator (L), were added to a soft marine soil to evaluate the changes in its behaviour as well as its microstructure. In addition, mixtures with cement (C), lime (Li) and their combination were prepared and tested for comparison. Binders were added at contents of 10, 20 and 30%, by dry soil mass, and samples were cured for 7 days. The results revealed that these new binders significantly increased the strength and stiffness of the soft soil, and they can be a suitable replacement for C and Li. The optimum mixture was found to be CIS+5% FA+15% S, within the range of binder, L and water content studied in this research. Moreover, recycling FA and S would substantially limit the expansion of landfill sites.
Description:
The use of deep soil mixing (DSM) technique in deep ground improvement projects has increased over the past decade due to being more cost-effective and easier to implement compared to other techniques such as piling, for structures subject to low to medium loads. Currently, Portland cement, lime and their combination are being used as the most common binders in DSM. However, due to the economic and concerning environmental disadvantages of using these binders, there is a need for new environmentally friendly cementing materials. This research attempts to find a way to use stockpiles of industrial by-products, such as fly ash (FA) and slag (S), as new green binders; consequently, reducing the carbon footprint in ground improvement projects. Different contents of FA and S, activated by liquid alkaline activator (L), were added to a soft marine soil to evaluate the changes in its behaviour as well as its microstructure. In addition, mixtures with cement (C), lime (Li) and their combination were prepared and tested for comparison. Binders were added at contents of 10, 20 and 30%, by dry soil mass, and samples were cured for 7 days. The results revealed that these new binders significantly increased the strength and stiffness of the soft soil, and they can be a suitable replacement for C and Li. The optimum mixture was found to be CIS+5% FA+15% S, within the range of binder, L and water content studied in this research. Moreover, recycling FA and S would substantially limit the expansion of landfill sites.