Resource utilization of metallurgical steel slag and copper slag for the preparation of cementitious materials: performance differences and microstructural mechanisms

Steel slag (SS) and copper slag (CS), the two most typical types of iron-rich solid wastes, have garnered attention for their potential use in construction materials; however, their low cementitious activity significantly hinders practical engineering applications. This study incorporated triethanolamine (TEA) during mechanical grinding to enhance grinding efficiency, examining the activation effects on SS and CS by analysing the relationship between specific surface area and compressive strength, while employing multiple microscopic experiments to elucidate the reaction mechanisms. Experimental results reveal that SS exhibits higher grinding efficiency than CS under the influence of TEA, primarily due to the well-defined crystalline structure of SS, which is more readily ground compared to the amorphous glassy phase in CS. However, the compressive strength of alkali-activated steel slag (AASS) prepared from finer SS particles is lower than that of alkali-activated copper slag (AACS). ICP testing data indicate that the CS releases a greater amount of Si elements in NaOH solution than SS, and DG/TGA results further confirm a significantly higher yield of hydration products in AACS compared to AASS. Combined with SEM-EDS analysis, AACS forms a denser gel structure with higher Si content. These factors contribute to the superior mechanical performance of AACS over AASS.