Transforming electric arc furnace waste into value added building products

© 2017 Elsevier Ltd Electric Arc Furnace dust is an abundant hazardous by-product of EAF steelmaking which poses significant environmental challenges for disposal given the presence of high concentrations of heavy metals which can leach into groundwater or contaminate soil when landfilled. This study proposes a novel new process to safely transform electric arc furnace dust into value-added building materials by combining it with blue shale to produce high strength lightweight aggregates. Both materials were characterised elementally and thermally by X-ray fluorescence and differential scanning calorimetry-thermal gravimetric analysis. Dilaotmeter study proved that addition of electric arc furnace dust to blue shale resulted into lower softening temperatures and addition of 5 wt% of electric arc furnace was found to be appropriate as 10 wt% addition showed no bloating behaviour. Light weight aggregates with 0 and 5 wt% electric arc furnace dust were sintered to different temperatures for different holding times. The results revealed that increased sintering temperature and holding time resulted in more porous structure in light weight aggregates with electric arc furnace dust, compared to the samples without electric arc furnace dust. This was observed closely via scanning electron microscope images. The study concluded that the sintering of blue shale with 5 wt% electric arc furnace dust at 1150 °C for 5 min Produced the highest compressive strength (8.25 MPa) with a moderately low density (1.76 g/cm3). The resulting light weight aggregate showed negligible leaching of heavy metals when tested, due to their stabilisation in the crystalline ceramic phase during high temperature sintering. Electric arc furnace dust was confirmed as a potentially valuable input in the production of non-toxic, high performance building materials

From waste to surface modification of aluminum bronze using selective surface diffusion process

When corrosion is the dominant failure factor in industrial application and at the same time high mechanical properties are required, aluminum bronze is one of the best candidates. Hence, there is a continuous quest for increasing the lifetime of aluminum bronze alloys through enhancing the abrasion and corrosion resistance. Existing methods are based on modifying the bulk properties of alloy or surface modification which required sophisticated equipment and process control. This approach has limited application for advanced components because of high price and difficulty to apply. In this research, we developed an innovative approach to enhance the corrosion and abrasion resistance of aluminum bronze through selective surface diffusion process. In this process, we have used waste materials as input and the modified surface has formed in a single and green process. New surface structure consists of finely dispersed kappa phase (χ) in uniform alpha (α) solid solution matrix. Results have demonstrated that this uniform diffused modified surface layer has improved hardness of the base material and both corrosion and abrasion resistance has increased. This novel surface modification technique has opened a pathway for using waste materials as input for surface modification of aluminum bronze to meet the needs of industrial applications in a cost effective and environmentally friendly way

Enhancing steel properties through in situ formation of ultrahard ceramic surface

Abrasion and corrosion resistant steel has attracted considerable interest for industrial application as a means of minimising the costs associated with product/component failures and/or short replacement cycles. These classes of steels contain alloying elements that increase their resistance to abrasion and corrosion. Their benefits, however, currently come at a potentially prohibitive cost; such high performance steel products are both more technically challenging and more expensive to produce. Although these methods have proven effective in improving the performance of more expensive, high-grade steel components, they are not economically viable for relatively low cost steel products. New options are needed. In this study, a complex industrial waste stream has been transformed in situ via precisely controlled high temperature reactions to produce an ultrahard ceramic surface on steel. This innovative ultrahard ceramic surface increases both the hardness and compressive strength of the steel. Furthermore, by modifying the composition of the waste input and the processing parameters, the ceramic surface can be effectively customised to match the intended application of the steel. This economical new approach marries industry demands for more cost-effective, durable steel products with global imperatives to address resource depletion and environmental degradation through the recovery of resources from waste