Acid-Activated Copper Slag as a Cementless Binder: Microstructural Densification and Strength Development

This research project investigates the development of a sustainable, cementless binder synthesized through the acid-induced activation of iron-rich copper slag, a pyrometallurgical industrial by-product. The methodology evaluates the chemical hardening pathway of granulated copper slag treated with hydrochloric acid (HCl) solutions of varying concentrations (0.03 M, 0.3 M, and 3 M) under a curing temperature of 50 °C over a 56-day period. Analytical characterization techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), are utilized to examine the selective dissolution of iron from the silicate matrix and its subsequent reorganization into Fe-O-Si networks. Microstructural densification is assessed via mercury intrusion porosimetry (MIP)

and modeled using the extended Bhattacharjee relationship. The experimental results demonstrate that the 3 M HCl-activated binder achieves a compressive strength of 100.7 MPa at 56 days, driven by significant pore refinement and the recrystallization of secondary iron oxide phases. Due to elevated free chloride levels, this research provides structural design guidance specifically tailored for non-reinforced, plain concrete applications, offering a viable pathway for low-carbon infrastructure materials.

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