Steel slag is a major by-product of the steel industry, with a production of nearly 300 kg for every tonne of steel produced. It has been conventionally used as an aggregate in road base construction, but this use has been limited due to the high free lime content, which causes volume expansion problems. This thesis explores the feasibility of using CO2 activation to eliminate free lime and develop strength for a steel slag-based building product. The CO2 activated steel slag has the potential to be used as cementing material to replace Ordinary Portland Cement (OPC) and to sequester carbon dioxide through activation. The technology can show numerous technical and environmental benefits, while minimizing the embodied energy in the final products.;Compressive strength and carbon uptake of compacts made of KOBM1, KOBM2, ladle and GGBF slag were evaluated in comparison with counterpart OPC compacts. KOBM slag showed the greatest potential, with compressive strength and carbon uptake values comparable to OPC. The microstructural change of carbon dioxide activated KOBM slag was assessed in detail by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Its durability was also measured by the means of an accelerated water softening test. The wallboard made of KOBM slag bonded with sawdust was fabricated, and its mechanical performance was found to be competitive to commercial cement-based wall-boards. The research demonstrates that certain types of steel slags can be successfully activated by carbon dioxide in the production of commercial products to replace OPC.
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