Improving the Foundation Layers for Concrete Pavements: Pavement Foundation Layer Reconstruction – Pennsylvania US 22 Field Study - TPF-5(183)

(2016) Improving the Foundation Layers for Concrete Pavements: Pavement Foundation Layer Reconstruction – Pennsylvania US 22 Field Study - TPF-5(183). Transportation, Department of

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Abstract

This report is one of the field project reports developed as part of the TPF-5(183) and FHWA DTFH 61-06-H-00011:WO18 studies. The project involved constructing a minimum 457.2 mm thick rock cap over general subgrade fill material as subgrade treatment with geosynthetic separation layer at the interface, a 50.8 mm thick class 2A leveling stone subbase, and a minimum 76.2 mm thick cement or asphalt treated base (CTB or ATB), and a 254 mm thick portland cement concrete (PCC) pavement. Field testing was conducted on three test beds with the leveling subbase layer at the surface, and one test bed each with PCC, ATB/CTB, rock cap, and general subgrade fill material at the testing surface. In situ test methods including nuclear gauge, light weight deflectometer, falling weight deflectometer, dynamic cone penetration, air permeability testing, and intelligent compaction monitoring with 100% coverage, were used. Point testing was conducted by spacing the test measurements about 50 to 100 m apart to capture the variability along the road alignment. The length of the test beds varied between 15 m to 620 m. Testing was conducted along the center line and along left and right of the center line with test point spacing of about 5 to 10 m. In addition, dense grid testing with test spacing between 1 and 4 m was also conducted to capture spatial variability of the measurement values over a small area. Geostatistical semivariogram analysis was performed to analyze the point test data from dense grid pattern testing to characterize and quantify spatial non-uniformity of the PCC surface and foundation layer properties. In situ test results were analyzed and compared with the design assumed modulus and drainage coefficient values. Results indicated that the subgrade layer modulus (ESG) determined on the rock cap layer was on average lower in two test beds and higher in one test bed. The reason for lower ESG values in the two test beds is attributed to a likely weaker underlying general fill subgrade layer. The average subbase layer modulus (ESB) determined for the ATB/CTB layers were higher than the design assumed values. The drainage coefficient values were calculated based on the saturated hydraulic conductivity values measured using the air permeability test device, and the pavement geometry, which showed “good” to “excellent” drainage.