Freeze-Thaw Durability of Subgrades Stabilized with Recycled Materials

摘要

The long-term performance of a pavement structure largely depends on the underlying soil foundation. When poor subgrade soils are encountered, many highway agencies employ "remove and replace" or chemical stabilization techniques to strengthen the subgrade. Due to rising cost of good materials and traditional stabilizers such as lime, cement, and asphalt, highway agencies are looking for recycled materials for subgrade stabilization. These materials include cement kiln dust (CKD), lime kiln dust (LKD), fly ash (FA), and concrete fines (CF). etc. Previous studies on these recycled materials have demonstrated the immediate benefit of their usage in building a stable platform for construction of upper pavement layers. However, the long-term durability of subgrades stabilized with recycled materials has not been completely studied. This study is aimed at understanding the freeze-thaw durability of subgrades stabilized with recycled materials. An extensive laboratory study is underway to characterize the freeze-thaw durability of laboratory soil samples stabilized with CKD, LKD, FA, and CFs. Laboratory samples were subjected to different number of freeze-thaw cycles in a laboratory freezer and the unconfined compressive strength (UCS) of those samples were measured after 0, 1,3, 7, and 12 cycles. This paper examines the preliminary results of the short- and long-term benefits and risks of using recycled materials for subgrade stabilization in cold climate areas. Only CKD has shown long-term stabilization benefits from the above materials. However, laboratory freeze-thaw testing of CKD stabilized soils showed significant strength loss after 12 cycles. Field performance of a pavement subgrade stabilized with CKD was also examined during this study and showed retained subgrade strength after 6 years of service life.