Low-Carbon Supplementary Cementitious Materials (SCMs) from Waste Stamp Sands

Addressing the critical challenge of reducing CO₂ emissions in the cement industry involves utilizing waste stamp sands as a sustainable source for supplementary cementitious materials (SCMs). Stamp sands, abundant in Michigan's Upper Peninsula, contain silicate minerals that can be converted into high-performance SCMs, enabling reductions in clinker usage and overall carbon emissions [1].Therefore, this study investigated the potential of waste stamp sands from Lake Superior (Gay, MI) as SCMs through calcination. Compositional analysis revealed that the sands contained silicate minerals such as albite, diopside, and anorthite, making them suitable for pozzolanic activity [2, 3]. Calcination at 800–900°C transformed these crystalline phases into reactive amorphous silica and metastable calcium carbonate, enhancing their reactivity [4, 5]. Mechanical tests demonstrated substantial improvements in mortar strength and hydration when 10–20% calcined stamp sands replaced cement. Hydration studies indicated increased early reactivity, while SEM and EDS analyses confirmed the formation of calcium-silicate-hydrate (C-S-H) phases and refined pore microstructures. XRD and FT-IR results validated structural changes in silicate minerals post-calcination. These findings demonstrated that calcined stamp sands effectively improved the mechanical properties of cementitious materials, offering a low-carbon solution for sustainable construction and reducing environmental impacts from mining waste.