About the research
Automated plate load testing (APLT) was conducted on County Road V-18 in Poweshiek County, Iowa, to assess and compare performance of unbonded concrete overlay sections constructed in 2008–2009. The unbonded overlays on County Road V-18 were constructed in selected areas using an asphalt concrete (AC) interlayer or a non-woven geotextile fabric interlayer. Wiegand et al. (2010) documented the construction techniques and materials used to build the test sections (project TR-600). The results of the study documented here provide a new assessment of the in situ deformation and composite modulus of the test sections.
Test results showed that the core thicknesses varied between 8.8 and 10.2 in. in sections with the geotextile interlayer, and 7.3 and 7.6 in. in sections with the AC interlayer. The geotextile fabric was about 0.1 in. thick and the AC layer was about 0.5 in. thick. Cyclic APLT results indicated that, on average, the composite resilient modulus was 40 percent higher, permanent deformation was lower, and the exponent in the power model that defined number of cycles vs. permanent deformation was lower in the geotextile sections than in the AC layer sections. Because the data set obtained in this study did not include the mechanistic properties of the underlying layers, additional APLT testing is recommended. Future testing should also assess the in situ drainage difference between sections and the ride quality (e.g., international roughness index (IRI) and pavement condition index (PCI)) between different pavement interlayer types.