Characterization of air-quenching steel slag and its utilization as admixture in Portland cement

Steel slag coming from air quenching process is different from slags from other pretreatment processes, such as air cooling process, hot-splashing process, etc. This research investigated the characterization of steel slag producing from the air-quenching process and its utilization in Portland cement. The results showed that the air-quenching steel slag was about <10mm spherical particle and the D 50 particle sizes of the investigated samples were only 0.98 mm and 1.22 mm, respectively. Its main mineralogical compositions were calcium silicate (including dicalcium silicate and tricalcium silicate), dicalcium ferrite, merwinite, RO phase and magnetite, while its minor mineralogical composition was periclase. A little free CaO existed in the steel slag but couldn't be detected by the XRD for its lower content. The study of effects of grinded air-quenching steel slag on the physical performance and hydration process of Portland cement showed that the pozzolanic activity of air-quenching steel slag was lower at early time but increased continually in the future. The air-quenching steel slag wasn't damaged to the volume stability performance of the Portland cement for its lower free CaO and free MgO content in this research. The hydration products of the steel slag-Portland cement were hydrated calcium silicate, portlandite and ettringite.