Effects of steel cnc milling waste on some geotechnical properties of silty soil

The aim of this study is to investigate the properties of silty soil mixed with steel computer numerical control machine (CNC) milling waste (St-CNC-mw). In this study; laboratory experiments including compaction, California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS), consolidation, swelling permeability and direct shear test have been conducted. Soil and St-CNC-mw mixtures at various rates (5%, 10%, 15%, 20% and 25% by dry weight) were tested at maximum dry density and optimum moisture content values of the mixtures. St-CNC-mw materials are coated by zinc to avoid high corrosion rate (electrogalvanisation) and corrosion rate of steel are reduced more than 100 times after coating. The results have shown that the optimum moisture content decreased and maximum dry density increased by increasing St-CNC-mw. Also the CBR increased and the swelling decreased by increasing St-CNC-mw. Soil with 15% St-CNC-mw has the highest UCS value. In addition, internal friction angle and cohesion increased while the coefficient of permeability (k) decreased by increasing St-CNC-mw. Furthermore, the consolidation tests demonstrated that the initial void ratio (eo), swelling index (cs) and the coefficient of consolidation (cv) of the soil decreased while compression index (cc) increased by adding the amount of St-CNC-mw content in the mixture.