Improving the Foundation Layers for Concrete Pavements: Pavement Foundation Layer Reconstruction – Iowa I-29 Field Study - TPF-5(183)

(2015) Improving the Foundation Layers for Concrete Pavements: Pavement Foundation Layer Reconstruction – Iowa I-29 Field Study - TPF-5(183). Transportation, Department of

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Abstract

This technical project report is one of the field project reports developed as part of the TPF-5(183) and FHWA DTFH 61-06-H00011:WO18 studies. This report presents results and analysis of field and laboratory tests from a field study conducted on the I-29 interstate highway reconstruction project in Monona and Harrison Counties, Iowa. Falling weight deflectometer (FWD) and dynamic cone penetrometer (DCP) testing was conducted on the existing continuously reinforced concrete pavement (CRCP) and its foundation layers and on the newly placed jointed plain concrete pavement (JPCP) and its foundation layers. The results indicated that the modulus of subgrade reaction (k) values under the JPCP were on average about 1.3 to 1.7 times higher than the k values under the CRCP, which indicates improvement in the stiffness of the foundation layers under the new pavement. However, the k values determined from FWD and DCP test results were significantly different. The k values determined from FWD were about the same as the design target value, while the k values determined from correlations with DCP test results were significantly higher than the design target value if treated subgrade values were used and were slightly higher if results of weak subgrade within the top 450 mm were considered. The k value estimated from laboratory thawed California bearing ratio (CBR) values were about 0.4 times the design value and from unthawed CBR was about 2.2 times the design value. Roller integrated compaction monitoring (RICM) used on foundation layers identified “soft” and “stiff” measurements. Those measurements correlated well with light weight deflectometer (LWD) measurements and better than with DCP and nuclear gauge density measurements. Laboratory resilient modulus (Mr) tests conducted on layered composite samples (with both subbase and subgrade) indicated that the average Mr was either similar to the layer with a lower Mr value (i.e., subgrade) or about average of Mr values of the two layers. Frost heave tests on subgrade materials indicated that the material was susceptible to increasing heave with greater freeze-thaw cycles. The subgrade soil was classified to have high potential to frost-heave and very high potential to thaw-weakening.