Project Manager: Steven Tritsch, Associate Director-Concrete Pavement Technology Center, Iowa State University (CP Tech Center, ISU)
Authors: David White, Peter Taylor, Pavana Vennapusa, Tom Cackler, and Yifeng Ling
Since 2008, around 1,000 unbonded concrete overlays have been placed on roadways across the United States of America (USA). However, long-term performance questions remain, including the following:
- If the separation layer/bond breaker used is a nonwoven geotextile instead of 1 to 2 inches of asphalt, how does this impact slab migration and vertical deflection?
- If the geotextile used is white vs. black or thin vs. thick, does this impact heat transfer within the concrete overlay?
A research team including (among others) David White, Ingios Geotechnics, Inc. and Peter Taylor, Director-CP Tech Center, recently investigated these geotextile questions. Final Report titled “In Situ Cyclic Loading of Concrete Pavement Overlays Supported on Geotextile and Asphalt Interlayers: Buchanan County Road D-16”, was compete in February 2022. While the research team’s report recommends long-term monitoring, a year after construction, the team found the geotextile interlayer sections demonstrated better structural capacity than the control asphalt interlayer sections.
Geotextile fabrics have been used by pavement engineers for many years as a separation layer between full-depth concrete pavements and stiff cement-treated bases. Because of that success, pavement engineers have recently been evaluating nonwoven geotextiles as an alternative to hot-mix asphalt (HMA) separation layers in unbonded concrete overlay applications. After nearly 10 years of positive project performance, it was found that nonwoven geotextile fabric separation layers work very well when used on existing pavements that have received the appropriate level of pre-overlay repairs.
After nearly 10 years of positive project performance, it was found that nonwoven geotextile fabric separation layers work very well:
• when used on existing pavements that have received the appropriate level of pre-overlay repairs
• acts as a separation material to prevent cracks and other distresses in the underlying pavement from compromising the performance of new unbonded jointed concrete overlays placed over existing jointed
• on continuously reinforced concrete pavements (CRCP)
• provide sufficient drainage to unbonded concrete overlay systems
• can provide significant cost
• can provide significant time savings
State highway agencies are engaged in continuing research efforts to optimize the use of geotextile fabric separation layers.
ABSTRACT:
Automated plate load tests (APLTs) were conducted on County Road (CR) D-16 in Buchanan County, Iowa, to assess and compare the performance of unbonded concrete overlay test sections with three different geotextile fabric interlayers. The pavement was constructed in 2020. Field testing was performed on the asphaltic cement concrete (ACC) pavement prior to construction and then on the unbonded concrete overlay 2 months after construction and 1 year after construction. Cyclic and static APLTs were performed to assess the composite modulus and permanent deformation.
Test results showed that the permanent deformation decreased by about 50 times after placing the PCC overlay over the ACC, both in sections with and without the geotextile interlayers. The composite resilient modulus values on the overlay increased about 10 times when compared to modulus values on the underlying ACC. Results indicated that the composite resilient modulus was still greater than 200,000 psi be decreased after 1 year along with increased permanent deformation in the control section (no geotextile interlayer). In the sections with a geotextile interlayer, the composite resilient modulus value increased 10% to 30% in two sections and decreased 10% in one section, while the permanent deformations increased by 30% to 60%. Results for the geotextile interlayer sections demonstrated better structural capacity than the control sections and monitoring of the load- deformation response of the pavement structure over time (3, 5, and 10 years after construction) is recommended.
Click to go to REPORT
REPORT “In Situ Cyclic Loading of Concrete Pavement Overlays Supported on Geotextile and Asphalt Interlayers: Buchanan County Road D-16“: https://intrans.iastate.edu/app/uploads/2022/02/Buchanan_CR_D-16_CP_overlays_on_geotextile_and_asphalt_interlayers_w_cvr.pdf?utm_source=CP+Tech+Center&utm_campaign=034cdb912d-RESOURCES+Newsletter+March–April+2021_COPY_01&utm_medium=email&utm_term=0_07a32343e1-034cdb912d-169971045
GEOTEXTILES On CPTech Webpage: Geotextiles and resources—REPORTS, MAP/TECH BRIEFS, SLIDES—developed by the National CP Tech Center and its partners on geotextiles: https://cptechcenter.org/geotextiles/?utm_source=CP+Tech+Center&utm_campaign=034cdb912d-RESOURCES+Newsletter+March–April+2021_COPY_01&utm_medium=email&utm_term=0_07a32343e1-034cdb912d-169971045
NATIONAL CONCRETE OVERLAY EXPLORER: http://overlays.acpa.org/webapps/overlayexplorer/index.html?utm_source=CP+Tech+Center&utm_campaign=034cdb912d-RESOURCES+Newsletter+March–April+2021_COPY_01&utm_medium=email&utm_term=0_07a32343e1-034cdb912d-169971045