INSTRUMENTATION AND EVALUATION OF PRESTRESSED PAVEMENT, U.S. 220, BLAIR COUNTY, PENNSYLVANIA. FINAL REPORT

A major study has been performed to monitor performance of a prestressed post-tensioned concrete pavement constructed in November-December 1988 in Blair County, Pennsylvania. The 7-in. thick pavement was placed over a lean concrete base. Prestressed pavement slab length between active joints was 400 ft. Instrumentation was installed to monitor interior pavement strain changes attributable to application of post-tensioning stressing, drying shrinkage, concrete creep, strand relaxation, and subgrade friction associated restraints occurring with daily temperature associated concrete slab movements. Movements of slab ends at joints were monitored as well as slab edge curling. Load tests with single axle and tandem axle trucks were conducted during August 1989. Analysis was made of pavement length changes, prestress levels for cross sections for a range of distances from slab ends, and load-stress response of the pavement. During the load testing done in August 1989, pavement stresses were determined from measured pavement strains at prestressed slab edges and inward from edges. Slab stresses were also evaluated using the JSLAB finite element computer program. Stresses of the prestressed pavement as determined from strain measurements were less than those predicted using the finite element analysis. Inspections of pavements were made during construction and subsequent to construction to monitor visual indicators of pavement performance. Transverse cracks in some prestressed slabs were observed to occur after installation of tied shoulders.