Microstructure of pretreated steel slag and its influence on mechanical properties of cement stabilized mixture

The reuse of steel slag (SS) is a popular research topic in today's society, and SS is being used gradually to replace gravel in the paving of the pavement base. However, its potential to swell constitutes a major obstacle in its use. In this work, the effects of pretreated SS dosing on the mechanical properties of cement stabilized materials and the changes in the microstructure of pretreated SS were investigated, and a low-cost and field-applicable pretreatment technique was identified that suppresses the swelling of SS effectively. Firstly, fly ash and water at different temperatures were used to treat SS separately, and the swelling rate of the pretreated SS was evaluated. Secondly, the effect of SS on the mechanical properties and durability of cement-stabilized base material was investigated by replacing gravel with pretreated SS at different volume ratios (0, 25, 50, 75%). Finally, the microstructural changes within the SS before and after aging were determined by scanning electron microscopy to clarify the strength formation mechanism. The experimental test results indicated that the addition of 18% fly ash to SS can effectively reduce the swelling rate of SS, and the pretreated SS can replace half of the gravel in cement stabilized material. The volcanic ash reaction between the SS and FA also made some contributions to the mechanical properties and durability of the cement stabilized material. The experimental results will help extend the use of SS and provide a certain extent of theoretical support for its application in pavement base materials. © 2021 Elsevier Ltd