Preparation of eco-friendly and high-strength ceramsite by granite scraps, granite fine mud, and phosphogypsum: Response surface methodology optimization, environmental safety assessment

Granite scraps (GS), Granite fine mud (GFM), and phosphogypsum (PG) are solid wastes containing harmful substances produced during the processing of granite and the production of phosphate fertilizer. Their resourceful and harmless utilization holds great significance in reducing environmental pollution. This study explores the preparation of eco-friendly and high-strength ceramsite using GS as the primary material, GFM as the binder, and PG as the regulator. The performance of ceramsite was studied by conducting single-factor experiments to examine the impact of the GS, GFM, and PG mass ratios. The Box-Behnken response surface methodology was utilized to optimize the effect of sintering conditions on the strength of ceramsite. The results suggested that the properties of the ceramsite are affected by the material ratios. The sintering temperature and keeping time notably influence the strength of ceramsite. Under optimal preparation conditions, the ceramsite achieved a bulk density of 1085.40 kg/m³, apparent density of 2253.63 kg/m³, 1-h water absorption of 0.13 %, hydrochloric acid soluble rate of 0.016 %, and compressive strength of 34.52 MPa. Importantly, high-temperature sintering plays an essential role in fixing heavy metals and reducing the ecological risk level of heavy metals in ceramsite, which ensures excellent environmental performance and application prospects for ceramsite.