Improving the Foundation Layers for Pavements: Pavement Foundation Layer Reconstruction – Michigan I-94 Field Study-TPF-5(183)

(2016) Improving the Foundation Layers for Pavements: Pavement Foundation Layer Reconstruction – Michigan I-94 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 280 mm thick jointed PCC pavement by undercutting the existing foundation layers to a depth of about 690 mm and placing an open-graded drainage course (OGDC) layer composed of recycled steel slag over the subgrade with a geotextile separation layer at the subgrade/OGDC layer interface. Field testing was conducted on two test sections with OGDC base layer and one test section with the existing pavement system. Point test methods including nuclear gauge, light-weight deflectometer, falling weight deflectometer, dynamic cone penetration (DCP), gas permeability testing, and plate load testing, and roller-integrated 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. Testing was also conducted in a dense grid pattern (with 0.6 to 1.5 m spacing) to capture spatial variability over a small area. Geostatistical semivariogram analysis was performed to analyze field point test data from the dense grid pattern testing to characterize and quantify spatial non-uniformity of the PCC surface and foundation layer properties. The composite modulus of subgrade reaction (kcomp) measured from field plate load test was about 34 kPa/mm, which was about 2.5 times lower than the design target of 84 kPa/mm (310 pci). But the kcomp values estimated from empirical relationships with DCP measurements and from laboratory measurements were about 1.1 to 2 times higher than the design kcomp. The field permeability measurements confirmed that the coefficient of drainage (Cd) values assumed in design were met in the field. Laboratory testing conducted to assess permanent deformation of the recycled slag indicated very low permanent strains (< 1%) after 100,000 cycles with negligible particle degradation. Comparing resilient modulus (Mr) of homogenous and layered composite test results revealed that the average Mr of composite sample is about 1.7 times lower than the average Mr of a homogenous OGDC sample at a similar density. This reduction in Mr in the layered composite sample is attributed to the weaker subgrade layer.