Foaming Mechanism of SiC in Steel Slag Foamed Ceramics

Steel slag discharged from steel-making process is a kind of huge secondary resources and hard to be reused. Foamed ceramics are building materials used in the wall insulation and could be a potential goal product for huge amount and high value-added utilization of solid waste. In this paper, foamed ceramics containing 30 wt.% steel slag and using SiC as foaming agent were prepared. The effects of SiC content and sintering temperature on its properties were studied, and the difference of foaming mechanism between in steel slag ceramics and in traditional clay ceramics was discussed. The results showed that the foamed ceramics sintered at 1160°C had a qualified properties with density of 0.50 g/cm3 and flexural strength of 2.6 MPa, and only 0.1 wt.% SiC was added into it, which is an order of magnitude lower than 1–3 wt.% SiC added in traditional clay foamed ceramic. SiO2 formed from oxidation of SiC had reacted with CaO and Fe2O3 component derived from steel slag to generate new minerals, augite and anorthite. The reactions not only significantly promoted reaction rate of oxidation of SiC from 4.9% to 73.5%, but also widened temperature range of the oxidation reaction, contributing to foaming process of ceramics and thereby substantial saving of SiC.