Stabilizing blended calcium sulfate materials for roadway base construction

Blended calcium sulfate (BCS), a recycled fluorogypsum waste material, has been used in Louisiana as a pavement base layer for more than a decade. Without further chemical stabilization, the major concern of using raw BCS as a pavement structural layer is its moisture resistance. It could cause both short-term construction difficulties and long-term performance problems. In order to improve the moisture susceptibility of BCS, various cementitious agents were used in the laboratory for BCS stabilization. To further verify the efficiency of BCS stabilization schemes obtained from laboratory and assess the field performance for stabilized BCS materials as well as potential cost-benefits, three pavement test sections were constructed and tested using the accelerated loading facility (ALF) device. Both laboratory and field test results indicated that a grade 120 granulated ground blast furnace slag (GGBFS) of 10 vol.% stabilized BCS material possessed a superior performance over raw BCS in terms of water resistance, durability, and good long-term performance. Field test results further demonstrated that the GGBFS stabilized BCS base outperformed both a regular crushed stone base and a fly ash stabilized BCS base by a significantly large margin.A life-cycle cost analysis proved that, besides its outstanding laboratory and field performance, using the GGBFS stabilized BCS can provide a substantial long-term savings over regular crushed stone and fly ash stabilized BCS bases in a 30-year pavement design life period.