The phosphogypsum road base material designed by traditional mineral mixture is difficult to meet the demand of large-scale consumption of phosphogypsum.In order to realize the large-scale utilization of phosphogypsum in road base ma-terial,the mix ratio design of high-volume phosphogypsum road base material was explored with aggregate substitution method to determine the propriate graded gravel ratio(mass ratio of 5～10 mm and 10～25 mm fraction of 39∶61).As a substitute for the phosphogypsum-based cementitious material system,the aggregate with different dosages were employed to reach the opti-mum water content and maximum dry density by compaction.The performance test was carried out with the designed mix ratio to screen the propriate ratio as P85S60.For P85S60,the 28 d compressive strength reached 5.39 MPa,but the volume change rate was low,and the volume growth became stable after 7 days with the ultimate volume change rate as about 0.5%,which was conducive to the application of on-site road construction.The fluorine and phosphorus content in the leaching of all ratios meets the first-level limit of Integrated Wastewater Discharge Standard(GB 8978-1996),and the pH of the leaching solution would not increase additional adverse effects compared with conventional cement stabilized crushed stone materials.According to re-sults from XRD and SEM,it can be found that ettringite and hydrated calcium silicate produced by the hydration of the cemen-titious material wrapped around the unreacted dihydrate gypsum.In addition,needle-shaped ettringite and hydrated calcium sil-icate fill tiny pores,making the overall structure dense to form big strength and volume stability.
road base materialmix ratio designperformance testphosphogypsumcompressive strengthvolume change rate
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