Effect of Foaming Agent on the Performance of Phosphogypsum-Based Lightweight Ceramsite

• • Aluminum powder as foaming agent achieves 7-day cylinder compressive strength of 3.8 MPa (100°C drying), outperforming NaHCO3 under identical conditions, enabling lighter aggregates without sacrificing early strength. • • Optimal NaHCO3 formulation (phosphogypsum 47 wt%, slag 32 wt%, fly ash 16 wt%) yields 28-day cylinder compressive strength of 6.5 MPa and bulk density of 1020 kg/m3, meeting lightweight aggregate concrete strength thresholds. • • Aluminum powder reduces bulk density to as low as 765 kg/m3 by forming closed pores, whereas NaHCO3 creates interconnected pores that increase water absorption, compromising durability. • • Excessive foaming agent increases porosity but weakens the ceramsite skeleton; aluminum powder provides better foaming stability, balancing lightweight and strength for structural applications.