The volume stability of modern steelmaking slags

Abstract

Most processes of steel manufacture necessarily generate a substantial proportion of slag. Often much of this is landfilled, and at many plants it will be the main item (by tonnage) that is dumped. This rock-like material can be used as an aggregate, but the main obstacle to widespread use is concern over the volume stability. The main cause of volume instability is hydration of free lime, although hydration of free magnesia may also contribute in some cases. There are three key steps to effective use of this abundant secondary aggregate. First, some pretreatment of the slag is usually necessary (such as weathering). Second, a test is necessary that reliably predicts the behaviour in use, within a reasonable time. This is commonly an expansion test. Third, calibration of the test is necessary so that test results can provide a useful distinction between material which is suitable and that which is not; this is normally achieved by linking laboratory tests to road trials. Subject to these three steps, steelmaking slag can make a valuable contribution to the need for secondary aggregates.

Soil Modification by the Application of Steel Slag

“…Exposures of steel slag to weather for 6 -12 months have been identified [9] to reduce these oxides and consequently its expansive nature. Consequently, black cobblesized steel slag samples, collected from a stockpile adjacent to Justrite Supermarket along Idiroko Road in Ota, that had been exposed to weather for eight months and air-dried in the laboratory for another four months were utilized during this research.…”

Laboratory Treatments of EAF Slag for its Use in Construction

“…The rate of hydration for free MgO is usually lower than free CaO [7]. A long weathering period is then required to avoid impact of MgO hydration on volume stability of the slag containing more than 5% of MgO.…”

“…Fe 2 O 3 can stabilize β -C 2 S phase [5]. Both Fe 2 O 3 and Fe 3 O 4 can react with CaO, decreasing amount of CaO available for C 2 S formation, as well as content of free CaO in the slag [6,7]. Table 6, making it possible to form compounds rich in Ca, Si, Fe and Al.…”

Recovery of Steelmaking Slag and Granite Waste in the Production of Rock Wool

“…The volume instability can be solved by submitting the steelmaking slag to a vitrification process 22 . Table 1 also provides the chemical analysis of the waste from granite cuttings.…”