Raw pyrite tailings as fine aggregate in mortar: performance and potential for architectural surface design

The accumulation of pyrite tailings (PT) poses severe environmental threats, yet its potential as a secondary resource for the construction sector remains underexplored. This study presents a preliminary investigation of raw PT as a partial substitute for fine aggregate in mortar, with particular attention to its short-term material performance and potential relevance to architectural surface design. PT exhibited a measured water absorption of 8.09%, compared with approximately 2.0% for the reference fine aggregate, while their loose bulk densities were 1648.7 and 1615.4 kg/m 3 , respectively. Owing to its similar particle size to sand but with higher water absorption and angularity, PT was used to replace 5–20% of the fine aggregate by mass. The water absorption and loose bulk density of PT and the reference fine aggregate were characterized, while mortar flowability and compressive and flexural strengths at 7 and 28 days were evaluated. Selected mortar mixtures were further examined using scanning electron microscopy and X-ray diffraction. The results indicate that raw PT has preliminary potential as a partial fine-aggregate replacement in mortar within the investigated replacement range. Owing to its mineral-derived coloration and surface texture, PT-containing mortar may also offer opportunities for architectural surface design. However, durability, color stability, environmental safety, and long-term weathering performance must be evaluated before such applications can be recommended.