Cement-stabilized phosphogypsum (CSPG) mixtures are demonstrated to have sufficient strength at the modified Proctor compaction level to satisfy the Louisiana Department of Transportation and Development design unconfined compressive strength (UCS) criteria of 1.7 MPa at 7 days for stabilized base material. With 8-12 percent cement, at 95 percent of modified Proctor maximum dry unit weight, CSPG had greater resilient modulus and UCS values than the commonly used river silt. Life estimates for a prototype road were highly dependent on the bearing capacity of the subgrade soil. The CSPG base produced acceptable estimated design lives for secondary roads at an attractive cost compared with conventional limestone aggregate.

More than 35 million metric tons of phosphogypsum (PG), a solid by-product of phosphoric acid production, are generated annually in the United States. The combination of environmental concern associated with disposal and the increasing cost to stockpile the material has prompted a search for the commercial use of PG. To prove that PG has a use as a. road pavement material, prototype pavements need to be developed and demonstrated. A laboratory evaluation was made of a prototype road with a CSPG base, including estimates of its potential design life in equivalent standard axle loadings (ESALs) and life-cycle costs compared with conventional limestone bases. The resilient modulus studies showed that a typical CSPG mix will theoretically provide an adequate design life at a life-cycle cost less than conventional materials.