Presentation on theme: "AAR-410 02/13/031 FAA Airport Pavement Technology Program u Testing and preliminary data analysis from flexible pavements on low-strength subgrade (Construction."— Presentation transcript:
AAR-410 02/13/031 FAA Airport Pavement Technology Program u Testing and preliminary data analysis from flexible pavements on low-strength subgrade (Construction Cycle Three (CC3)). u Current work and plans for next rigid pavement test items.
AAR-410 02/13/032 Low-Strength SG Flexible Replacement – Fall 2002 200 Target Repetitions to Failure 11,0007703,500 Thicknesses are based on 55,000 lb wheel load on 3 CBR subgrade. 5-in thick 8-in thick 43-in (110-cm) thick 34-in (85-cm) thick 24-in (60-cm) thick 16-in (40-cm) thick 6-Wheel 4-Wheel370200011,80036,400 LFC1 LFC2 LFC3 LFC4
AAR-410 02/13/034 Design Methodology u LEDFAA with 2-layer subgrade. u Vary Poisson’s Ratio with subgrade strength: u Poisson’s Ratio = 0.82 – 0.1 * (logE SG /145). u Improve behavior of failure model at low departure levels: u log v = – 2.301 – 0.1607 log C F (Super-Heavy Aircraft Study).
AAR-410 02/13/035 Design Conditions u Reworked subgrade CBR = 3 u Existing subgrade CBR = 5.5 u Wheel load = 55,000 lbs u Dual spacing = 54 inches (4- and 6-wheel) u Tandem spacing = 57 inches (4- and 6- wheel)
AAR-410 02/13/037 Variation of Asphalt Modulus with Temperature (Witczak)
AAR-410 02/13/038 Variation of Pavement Life with Temperature – LFC3, from LEDFAA 350-600 and 1200-2100
AAR-410 02/13/039 Testing Schedule u September 3: started. u September 4: stopped testing on LFC1. u September 6: 990 passes. u September 12: stopped testing on LFC2 at 3,168 passes. u September 13 and 16: 2 test pits in LFC2. u September 17: tried MWHGL wander on LFC3 and 4. u September 18: increased load to 65,000 and continued testing on LFC3 and 4 with old wander. u October 18: stopped at 23,826 passes.
AAR-410 02/13/0320 Failure Criteria for Flexible Design u From MWHGL Report. u A pavement was considered failed when either of the following conditions occurred: u Surface upheaval of the pavement adjacent to the traffic lane reached 1 in. or more. u Surface cracking occurred to the point that the pavement was no longer waterproof.
AAR-410 02/13/0330 Starting Excavation of Trench
AAR-410 02/13/0331 Current Proposal for Rigid Reconstruction (1) u 15 ft x 15 ft (4.5 m x 4.5 m) slabs. u 3-Part optimized mix. u 28-day wet burlap cure. u Transverse joints doweled.
AAR-410 02/13/0332 Current Proposal for Rigid Reconstruction (2) u Looked at decreasing strength and increasing thickness: u Rounded intermediate aggregate, no significant decrease. u 30%, and 50% Class C flyash replacement in a two-part mix (batched 1/13/03), significant decrease at 50%.
AAR-410 02/13/0336 Current Proposal for Rigid Reconstruction (3) u One more batch at 70% flyash replacement. u 15 ft x 15 ft x 11 in thick test slab on existing PCC. Will measure. u Vertical displacement of corners. u Horizontal strains. u Temperature through depth. u Relative humidity through depth.
AAR-410 02/13/0337 Current Proposal for Rigid Reconstruction (4) u Three test items on medium-strength subgrade: u Existing econocrete subbase. u Aggregate subbase. u Slab-on-subgrade. u Rebuilding medium strength subgrade to depth of 3 feet. Target strength is 7 CBR. Half finished.