Evaluation of porphyry copper mine waste rock using TIMA analysis and its manufactured sand properties

Abstract

Non-ferrous metal mines produce around 1.2 billion tons of waste rock annually, leading to land occupation and environmental hazards such as acidic wastewater. Rich in silicon dioxide and aluminum oxide, these wastes are promising raw materials for manufactured sand. In this study, manufactured sand was prepared from porphyry waste of Dexing Copper Mine without impurity removal. The mineral composition, particle size, shape, and elemental distribution were analyzed using the Tescan Integrated Mineral Analyzer (TIMA) to clarify mineral interrelationships and spatial distribution. Crushing was carried out based on the mechanical properties of minerals in porphyry parent rocks, and the gradation curve of waste rock manufactured sand was determined. The effects of minor Fe and Cu impurities were evaluated via alkali-aggregate reaction and MB value tests. Results indicated that the porphyritic needle content was 1.42%, the Methylene Blue (MB) value was 1.1, and the stone powder content was 7%. Physical performance indicators such as solidity (1.0%), crushing index (23%), and porosity (39.1%) met the technical standards of GB14684-2022. Concrete prepared with porphyry manufactured sand exhibited a six-month expansion rate below 0.1% of standard limit, with no alkali-silica reaction risk. The internal and external irradiation indices were 0.23% and 0.58%, respectively. The radioactivity indicators were below the standard limit of 1.0%, indicating no radiation risk. By combining mineralogical characteristics with physical and mechanical properties, this study confirms the feasibility of producing high-quality manufactured sand from copper mine waste. The findings provide guidance for optimizing preparation processes and support sustainable utilization of mining waste while mitigating environmental impacts.