Improving the Foundation Layers for Pavements: Field Assessment of Jointed Portland Cement Concrete Pavement with Premature Distresses – Iowa US 34 Field Study - TPF-5(183)

(2016) Improving the Foundation Layers for Pavements: Field Assessment of Jointed Portland Cement Concrete Pavement with Premature Distresses – Iowa US 34 Field Study - TPF-5(183).

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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. The Iowa Department of Transportation (DOT) identified that a few sections of pavement on US Highway 34 near Mount Pleasant, Iowa showed early deterioration in ride quality. The Iowa State University research team conducted a visual survey of the cracked panels and the natural geography of the area and performed in situ falling weight deflectometer testing near center and joint of 140 panels over a span of about 830 m. Of the 140 panels, 25 panels showed distresses. The surface layer consisted of nominal 260 mm (10 in.) thick jointed portland cement concrete pavement (JPCP) placed over 150 to 260 mm (6 to 10 in.) thick subbase layer. Based on the project drawings, grading in the tested span required fills up to 10 m and cuts about to 3 m. Of the 830 m test span, about 480 m consisted of subgrade constructed with fill materials, about 350 m consisted of natural subgrade constructed in cut. FWD tests were conducted to evaluate differences in the deflection basin parameters and the modulus of subgrade reaction (k) values between the cracked and uncracked panels, and cut and fill areas. Statistical t-test analysis was conducted to compare the measurement values obtained on panels with and without cracks and in cut and fill areas. All cracked panels were located in the cut areas. Results showed statistically significant differences in the FWD test results between cracked and uncracked panels, with results on uncracked panels representing better support conditions than on cracked panels. Similarly, values in the fill areas showed support conditions that are better than in the cut areas. The k values were on average about 1.3 times lower under cracked panels than under uncracked panels. The COV of the k values were higher under cracked panels (38%) than under the uncracked panels (23%).