Stabilization of free CaO in molten BOF slag by addition of silica at high temperature

Abstract

The unstable free CaO (f-CaO) has always been the bottleneck that limits the application of basic oxygen furnace (BOF) slag as a construction material. In this work, silica was regarded as the stabilization addition to make the f-CaO in molten BOF slag stabilized at high temperature. The influences of experimental conditions on the f-CaO stabilization were studied. The results show that the main influential factors on elimination rate of f-CaO are the ratio CaO/SiO2, reaction temperature and stabilization time. In this work setting conditions, with the ratio CaO/SiO2 less than 2.7, the reaction temperature under 1525 °C and the stabilization time over 10 min, the f-CaO content in the stabilized slag falls to the level of less than 3.00%, which can fully meet the Chinese national standard of steel slag powder used for cement and concrete. Additionally, the XRD results indicate that f-CaO is stabilized by silica in forming akermanite phase at high temperature. Moreover, the observation obtained from FESEM indicates that the undissolved lime and precipitated CaO changed into clustered CaO in the stabilized slag with its size ranging from 0.6 µm to 2.5 µm.

Geopolymer Technologies for Stabilization of Basic Oxygen Furnace Slags and Sustainable Application as Construction Materials

“…This must be addressed, employing appropriate treatment to prevent expansion. There are several ways to stabilize BOF slags, such as stabilization in the hot or molten stage [12][13][14], and stabilization by employing a carbonation process [12,15,16]. Singh et al supplemented oxalic acid into cement mortar to improve the densification and mechanical properties of concrete [17], while Ding et al utilized scrubbing attrition and chelating reagent treatment to remove free lime from BOF slags [5].…”

Research Progress on Iron- and Steelmaking Iste Slag-Based Glass-Ceramics: Preparation and GHG Emission Reduction Potentials

“…The f-CaO in steel slag is prone to volume expansion during hydration, resulting in product cracking, which seriously restricts its application in traditional industries (such as cement) [27]. In contrast, in the process of preparing glass-ceramics with steel slag as raw material, this f-CaO limitation could be overcome by acting as a fixed component of glass-ceramics.…”

“…Dai et al [52] developed a novel modifying furnace, consisting of a cyclone furnace (CFu) and modifying chamber (MCh), with which structure the hot ISWS can be transformed efficiently into glass-ceramics, while the iste heat is collected and utilized. Thermal modification is also an effective way to change the mineral composition of steel slag to improve the comprehensive utilization rate, and it is beneficial to improve the iron recovery rate by changing the structure of iron minerals [27]. For example, in situ modification of hot slag by adding silica to induce the formation of anorthite has been investigated to obtain a stable structure that can inhibit the leaching of heavy metals (such as Ba, V, Cr) [12].…”

Profile Features of Emulsified Asphalt Mixture Containing Steel Slag Based on Laser Scanning

“…Outdoor aging is the widely used method to reduce f-CaO content, and slags in this study received 6 months aging treatment [35,36]. Furthermore, some studies altered mineral compositions of slag or added silica at high temperature to control f-CaO [37][38][39].…”