CP Tech Center New Publication:
“Automated Plate Load Testing on Concrete Pavement Overlays with Geotextile
and Asphalt Interlayers: Poweshiek County Road V-18”
AND
Transtech Group: “Nonwoven Geotextile Interlayers in Concrete Pavements”
CP Tech Center released a publication titled “Automated Plate Load Testing on Concrete Pavement Overlays with Geotextile and Asphalt Interlayers: Poweshiek County Road V-18”, Principal Investigator Peter Taylor, Director-National Concrete Pavement Technology Center, Iowa State University and Authors David J. White and Peter Taylor.
Automated plate load testing (APLT) was conducted on County Road V-18 in Poweshiek County, Iowa, USA 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 22.5 and 26 cm (8.8 and 10.2 in.) in sections with the geotextile interlayer, and 18.5 and 19.3 cm (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 1.27 cm (0.5 in.) thick. Cyclic APLT results indicated that, on average, the composite resilient modulus (Mr-comp) was 40% higher, permanent deformation (∂p) was lower, and the exponent in the power model (d) that defined number of cycles vs. ∂p 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.
To download a PDF of the full publication titled “Automated Plate Load Testing on Concrete Pavement Overlays with Geotextile and Asphalt Interlayers: Poweshiek County Road V-18”, please click on image above left or go to: http://www.intrans.iastate.edu/research/documents/research-reports/Powashiek_CR_V-18_APL_testing_w_cvr.pdf
Transtech Group: “Nonwoven Geotextile Interlayers in Concrete Pavements”
Improving Pavement in America: Pavement engineers are constantly seeking out proven innovative concepts with the potential to improve pavement performance while reducing costs. An example of such a concept is the use of a nonwoven geotextile as an alternative to hot-mix asphalt (HMA) between cementitious layers. Proven by German engineers to be effective, this concept is not common or widespread in the U.S. However, Implementation of a nonwoven geotextile interlayer was successful in two recent field trials in Missouri and Oklahoma. As part of a recent effort to demonstrate the use of nonwoven geotextile interlayers as concrete pavement interlayers, initial recommendations for materials specifications and better construction practices were developed. The material proved to be cost effective, required minimal training and equipment during construction, and could be placed rapidly. As a result, nonwoven geotextiles have the potential to be a viable alternative to more conventional materials as an interlayer in the U.S. pavements.
Principles:
- Separation – keeps discontinuities (cracks or joints) in the underlying cementitious layer from reflecting to the surface layer. The material is required to possess a degree of compliance that can accommodate the anticipated movements in the base layer.
- Drainage – channels away water that infiltrates into the pavement structure at the surface. Water should drain into the interlayer and then along the (cross-) sloped surface to the pavement edge. Because of this, German practice requires that the geotextile either terminate next to a drainage layer or be daylighted (allowing the egress of water). The drainage function also requires that the geotextile have enough permeability to allow a minimum flow rate in three dimensions.
- Bedding – reduces bearing stresses and the effects of dynamic traffic loads. This function also requires a geotextile material that has some degree of compliance, but not so much that inadequate support stiffness results.
Benefits:
- Cost Savings – lower cost for material and installation.
- Expedited Construction – rapid installation, with firsthand observations revealing installation rates exceeding that of paving.
- Ease of Construction – requiring a minimum of training and equipment
In Germany, nonwoven geotextile interlayers have been used in concrete pavements for more than a quarter of a century. During that time, German engineering has proven nonwoven geotextiles placed between a concrete pavement surface and a cement-treated base (CTB) reduces bonding, facilitates subsurface drainage, and minimizes bearing stresses.
For the Transtech Group information, please go to:
http://www.thetranstecgroup.com/nonwoven-geotextile-interlayers-concrete-pavements/?utm_medium=email&utm_campaign=June%20Newsletter&utm_content=June%20Newsletter+CID_9576711fbdda9782d8800db5db162a11&utm_source=Email%20Campaign%20Monitor&utm_term=Learn%20More