Improving the Foundation Layers for Concrete Pavements: Pavement Foundation Layer Reconstruction with Cement Treated Base Underlain by Geotextile – Michigan I-96 Field Study - TPF-5(183)

(2015) Improving the Foundation Layers for Concrete Pavements: Pavement Foundation Layer Reconstruction with Cement Treated Base Underlain by Geotextile – Michigan I-96 Field Study - TPF-5(183). Transportation, Department of

Preview

Text improving_foundation_layers_MI_I-96_w_cvr-1.pdf File Size:20MB

Abstract

This technical project report is one of the field project technical reports developed as part of the TPF-5(183) and FHWA DTFH 61-06-H-00011:WO18 studies. This report presents results and analysis from a field study conducted on an interstate highway I-96 reconstruction project near Lansing, Michigan. The existing I-96 section with portland cement concrete (PCC) pavement was removed and replaced with a twenty-year design life jointed PCC underlain by a cement treated base (CTB) layer consisting of recycled PCC and existing or new sand subbase with a geotextile separator at the CTB/subbase interface. The Iowa State University (ISU) research team conducted field testing on the new pavement foundation layers during construction to compare with the design assumed values. Field testing was conducted by spacing measurements about 50–100 m apart along the alignment and also in a dense grid pattern (spaced at about 0.9 to 3.0 m) to capture spatial variability over a small area. Geostatistical analysis was performed to analyze the test data from the dense grid pattern testing to characterize and quantify spatial non-uniformity of the foundation layer properties. Field measurements indicated composite modulus of subgrade reaction values ranging from 101 kPa/mm (370 pci) to 327 kPa/mm (1200 pci), which were about 0.74 times and 2.4 times the design assumed values. The lower bound value was based on the average in situ 406 mm (16 in.) thick subbase (including CTB base and sand subbase) layer modulus and in situ subgrade layer resilient modulus (Mr) from falling weight deflectometer (FWD) measurements. The upper bound value was based on average subbase layer modulus from FWD and average Mr determined from dynamic cone penetrometer measurements. Both laboratory and field measurements indicated that the quality of the drainage layer can be rated as excellent according to AASHTO (1993), which exceeds the good rating assumed in the design. Laboratory resilient modulus testing was conducted on homogenous and layered composite samples. Results indicated that on average, the resilient modulus of layered composite samples was about 20% lower than that of a homogenous subbase layer sample with similar density, and the reduction is attributed to the weaker subgrade layer. Compressive strength testing of CTB samples indicated that 12 of 13 samples tested (by both ISU and MDOT) met the project specifications.