New Progress in Artificial Aggregate Research: Preparation of Phosphogypsum High-Strength Aggregate Through the “Compacting Before Hydration” Process

Abstract

The production method of phosphogypsum high-strength aggregates is explored in this study through the dry powder compaction–fragmentation–grinding–hydration process, which has a good prospect for massive industrial production. Dry powder blocks were first produced using the pressure program and then crushed into small pieces with angular shapes. The aggregate was sharpened and made angular using a grinding machine, and after spraying with water for 1 d, it was soaked in saturated lime water for maintenance to obtain a rough aggregate. After being sheathed, the apparent density and cylinder pressure strength of the phosphogypsum high-strength aggregate in the drying state were up to 2010 kg/m 3 and 23.58 MPa, respectively. These results indicated that the rehydration process after compaction can solve the short board of the low strength of high-doped phosphogypsum products, and the phosphogypsum aggregate at the preparation site has the characteristics of density and high strength. The results of phosphorus and fluoride pollutants in phosphogypsum high-strength aggregates showed that they met the requirements of Class I water. Finally, microscopic analysis, XRD and SEM, respectively, identify the phase type were CaSO 4 and ettringite. Through mercury intrusion porosimetry, the changes in the internal pores of the aggregates in the aggregate maintenance process were explored, further verified the compactness and high strength characteristics of high strength aggregate. The results of this study have a certain significance for the resource utilization of phosphorus gypsum and the development of artificial aggregates.

Keywords: artificial aggregate； phosphogypsum aggregate, hydration after compaction, high density and high strength, ettringite