Abstract: Phosphogypsum is a by-product generated during the wet-process production of phosphoric acid, with enormous annual output. The stockpiling of large quantities of phosphogypsum not only occupies considerable land resources but may also cause environmental and safety issues such as heavy metal leaching, soil salinization-alkalization, and dump collapses. The resource utilization is therefore urgently needed. At present, phosphogypsum is mainly applied in agriculture, industry, and the construction industry. Due to its complex composition, the utilization is challenging owing to the high pretreatment cost. Based on the concept of waste recycling, this study uses phosphogypsum as the main raw material, supplemented by ground granulated blast furnace slag, fly ash, and type II anhydrite. Two foaming agents, sodium bicarbonate and aluminum powder, were adopted to regulate the pore structure, and the effects of different foaming agents on the performance of ceramsites are compared and analyzed. The sample with the highest cylinder compressive strength is further characterized by XRD, SEM, and BET to investigate its micromechanism. The results demonstrate that the type of foaming agent significantly influences the porosity, bulk density, and cylinder compressive strength of ceramsites. Under identical preparation conditions, the 7 d cylinder compressive strength of ceramsites prepared with aluminum powder is higher than that prepared with sodium bicarbonate. With appropriate raw material proportions and a suitable foaming agent, the non-fired ceramsite achieves a maximum cylinder compressive strength of 6.5 MPa, which basically meets the strength requirements for aggregates in lightweight aggregate concrete. This study realizes the green preparation of non-fired ceramsite with favorable environmental and economic benefits, and provides a new way for the large-scale utilization of phosphogypsum.

Key words: phosphogypsum-based non-fired ceramsite, foaming agent, water absorption, bulk density, cylinder compressive strength

摘要： 磷石膏是湿法磷酸生产过程中的副产物，年排放量巨大，其大量堆存不仅占用大量土地资源，更易引发重金属溶出、土壤盐碱化及堆场坍塌等环境与安全问题，亟需实现资源化利用。目前，磷石膏虽已在农业、工业和建筑行业等领域得到应用，但因杂质成分复杂、预处理成本高，导致利用难度较大。基于废弃材料的合理利用理念，本研究以磷石膏为主要原料，添加高炉矿渣粉、粉煤灰和II型无水石膏，选用碳酸氢钠和铝粉两种发泡剂调控孔隙结构，对比分析发泡剂种类对陶粒性能的影响。针对筒压强度最优的陶粒样品，进一步开展XRD, SEM和BET分析，深入研究其微观机理。研究表明，发泡剂种类对陶粒的孔隙率、堆积密度及筒压强度具有显著影响。相同工艺条件下，铝粉制备陶粒的7 d早期筒压强度优于碳酸氢钠制备的陶粒。当原料配比与发泡剂种类适合的情况下，制备的免烧陶粒筒压强度最高可达6.5 MPa，基本满足轻集料混凝土用骨料的强度要求。该工艺不仅为磷石膏的规模化利用提供了新途径，还实现了免烧陶粒的绿色制备，兼具环境效益与经济效益

关键词: 磷石膏基免烧陶粒, 发泡剂, 吸水率, 堆积密度, 筒压强度