Turning waste into treasure: Preparation, physical properties and microstructure of alkali-activated phosphorus tailings-based fully solid waste non-sintered lightweight aggregates

Based on the potential safety risks associated with the buildup of solid waste in Lianyungang City, Jiangsu Province, and the dual challenges of high energy consumption and resource scarcity in conventional building material production. Herein, adhering to the concept of "total solid waste utilization", phosphorus tailings based artificial lightweight aggregates (PT-LWA) were fabricated through multi-component collaborative design, using phosphorus tailings (PT), fly ash (FA), soda residue (SR), and granulated blast furnace slag (GGBS) as the 100 % raw material system. A comprehensive analysis was conducted to assess how varying proportions of raw materials and diverse curing conditions influence physical performance, microstructural features, durability, release characteristics of heavy metals. Additionally, economic costs and economic emissions from PT-LWA were analyzed. The findings showed that the artificial lightweight aggregates exhibited optimal efficiency when fabricated with a raw material ratio of PT: FA: SR: GGBS = 40 %:20 %:30 %:10 % under 80 °C steam curing conditions. Specifically, the bulk density, softening coefficient, and 1-h water absorption of the resultant PT-LWA were 1038 kg/m³, 0.942, and 14.1 %, respectively. Additionally, the cylinder crush strength attained a value of 9.7 MPa, surpassing the performance observed in conventionally cured samples. Microstructural analysis revealed that the dominant hydration phases primarily consisted of C-(A)-S-H gel formations. They are evenly distributed on particle surfaces and form a robust colloidal structure, which further enhances its strength. The concentration values of released heavy metals are well below the thresholds defined by China's hazardous waste identification standards (GB 5085.3-2007), suggesting that PT-LWA will not cause secondary environmental pollution.