In the present work, two common nano-alumina (NA) with different crystal forms (α-NA and γ-NA) are used to research the effects of steel slag-cement composite cementitious materials, which include the hydration properties and mechanical properties. The results show that the NA can enhance the strength of steel slag-cement composite cementitious materials, especially the early strength. Meanwhile, when the addition amount of γ-NA was 1%, the maximum compressive strength and flexural strength at 28 d were 35.43 and 5.21 MPa, respectively; when the addition amount of α-NA was 3%, the maximum compressive strength and flexural strength at 28 d were 36.27 and 4.89 MPa, respectively. In addition, according to the analysis of X-ray diffractometer and differential thermal analysis, it was concluded that the effects of the two types of alumina on the strength were mainly pozzolanic effect and filling effect. The pozzolanic effect of γ-NA was significantly stronger than that of α-NA. However, the large surface area of γ-NA affected the dispersion of the particles and the filling effect. According to scanning electron microscope analysis, compared with α-NA, γ-NA had significantly more hydration products and tighter adhesion. In conclusion, the addition of NA not only improved the properties but further realized the value-added utilization of steel slag.
Keywords: Al2O3; Steel slag; crystal forms; hydration properties; pozzolanic activity.