Development of a Calcium Aluminate Cement from steelmaking slag by altering its mineralogical compositions

Strict environmental norms and raising concern to recycle solid wastes generated during ironmaking and steelmaking processes has been the key driving force in developing various technologies. The present study describes a calcium-aluminate clinker prepared from steel ladle slag by modifying its mineral compositions. The slag paste prepared by mixing with water exhibited flash setting behaviour due to the presence of C 12 A 7 and C 3 A phases. In contrast, the slag clinker, developed by sintering a mixture of pre-determined quantity of slag and Al 2 O 3 at 1400°C for 2h and 4h, contained CA, CA 2 , Gehlenite and ‘Q’ phases. Hydration of slag clinker contained stable C 3 AH 6 , AH 3 and stratlingite with preferential growth of calcium-aluminate hydrate prisms along c-axis that provided a well-defined raceme like morphology with interlinked structure. It improved the setting time and crushing strength of the clinkers after 6h and 24h curing at room temperature. Additionally, presence of ‘Q’ phase with lamellar prismatic crystals also helped in enhancing the strength. The developed clinker also exhibited superior crushing strength as compared to commercially available calcium aluminate cement of medium purity. The slag, used as a source of CaO could replace CaCO 3 completely and thus contributed to reduction in CO 2 emission during clinker making process.