<p><p><h2>Preferred QC/QA Procedures</h2>The Federal Highway Administration (FHWA) provides QC/QA guidance to assure the strength and serviceability requirements of geosynthetics in pavement separation. It also gives guidance for the proper construction of the pavement system. The documents are summarized below.</p><p><table class='tablepress' id='tablepress-1973'><thead><th><center>Publication Title</th><th><center>Publication
Year
</th><th><center>Publication Number</th><th><center>Available for Download</th></thead><tbody><tr><td ><center>Geotechnical Aspects of Pavements</td><td ><center>2010</td><td ><center>FHWA NHI-10-092</td><td ><center>Yes<sup>1</td></tr><tr><td ><center>Geosynthetic Design & Construction Guidelines – Reference Manual</td><td > <center>2008</td><td > <center>FHWA NHI-07-092</td><td > <center>No<sup>2</td></tr></tbody></table><br><p class="disclaimer"><sup>1</sup><a href="https://www.nhi.fhwa.dot.gov/training/nhistoresearchresults.aspx?get=&a… are many QC/QA procedures necessary to ensure a proper performance of the geosynthetics in separation applications. Verification of material properties and exhumation for property evaluation are used for both quality control and quality assurance while dust collection and rut measurement are used for quality assurance. GPR and FWD testing can evaluate pavement layer thickness, moisture distribution, and/or resilient modulus quickly and inexpensively; therefore, they can be used to confirm the benefit of geosynthetic separation and estimate the remaining service life of pavements. In Addition, they provide guidance to select appropriate maintenance and rehabilitation activities.</p></p>
<p><p><h2>QC/QA Guidelines</h2>The geotextiles and the threads used in joining geotextiles by sewing shall meet the chemical composition requirements. Fibers used in the geotextile and the threads shall consist of long chain synthetic polymers with at least 95% polyolefins or polyesters by weight. The strength and serviceability requirements of the geotextile for separation in pavement systems can be verified per ASSHTO M288 (1997), Holtz et al. (2008), and state guidance based on the subgrade soil properties. Geotextile labeling, shipment, and storage shall follow ASTM D4873. The QC/QA guidance in ASSHTO M288 (1997) and Holtz et al. (2008) ensures proper geotextile placement, overlapping, aggregate placement, and compaction.</p><p>For performance evaluation, the rut measurement is taken directly on the field and an average rut depth is calculated. A linear or nonlinear correlation curve is used to describe the relationship between the development of rutting and cumulative ESALS to predict the service life of the pavement. Although not standard practice, GPR and FWD testing can be used for both quality control and quality assurance. GPR and FWD testing can evaluate pavement layer thickness, moisture distribution, and/or resilient modulus quickly and inexpensively, therefore, they can be used to confirm the benefit of geosynthetic separation, to estimate the remaining service life of pavements, and provide guidance to select appropriate maintenance and rehabilitation activities.</p><p>Exploratory excavations (test pits) can be used to observe the conditions of the pavement layers, ground water, and geosynthetics. Several in-situ tests (pocket penetrometer, Torvane, and nuclear densiometer tests) can be performed to determine the subgrade soil conditions. The samples of base and subgrade soils and geosynthetics are also collected for laboratory tests. The laboratory tests, such as moisture content and particle size distribution on the soil samples, and permittivity and wide-width tensile strength test on the exhumed geotextile, can be performed.</p></p>
<p><p><h2>Reference (s)</h2>AASHTO. (2006). <em>Standard Specifications for Geotextiles - M 288</em>. Standard Specifications for Transportation Materials and Methods of Sampling and Testing, 26th Edition, American Association of State Transportation and Highway Officials, Washington, DC.</p><p>Al-Qadi, I.L. and Appea, A.K. (2003). “Eight-year of field performance of a secondary road incorporating geosynthetics at the subgrade-base interface.” <em>Transportation Research Record</em> No. 1849, 212-220.</p><p>Black, P.J. and Holtz, R.D. (1999). “Performance of geotextile separators five years after installation.” <em>Journal of Geotechnical and Geoenvironmental Engineering</em>, Vol. 125, No.</p><p>Christopher, B.R., Schwartz, C., and Boudreau, R. (2010). “Geotechnical Aspects of Pavements,” FHWA-NHI-10-092, Federal Highway Administration, Washington, DC, 568p.</p><p><a href="https://www.nhi.fhwa.dot.gov/training/nhistoresearchresults.aspx?get=&a…, D., Marienfield, M., and Hayes, C. (1994). “Evaluation of nonwoven geotextile versus line-treated subgrade in Atoka Country, Oklahoma.” <em>Transportation Research Record </em>No. 1439, Washington, DC, pp. 7-12.</p><p>Hayden, S.A., Christopher, B.R., Humphrey, D.N., Fetton, C., and Dunn, P.A. (1998). “Instrumentation of reinforcement, separation and drainage geosynthetic test sections used in the reconstruction of a highway in Maine.” <em>Proceedings of the 9th International Conference on Cold Regions Engineering</em>, 420-433.</p><p>Holtz, R.D., Christopher, B.R., and Berg, R.R. (2008). <em>Geosynthetic Design and Construction Guidelines</em>, U.S. DOT, Federal Highway Administration, Washington, DC, FHWA-HI-07-092, 460p.</p><p>Loulizi, A., Al-Qadi, I.L., Bhutta, S.A., and Flintsch, G.W. (1999). “Evaluation of geosynthetics used as separators.” <em>Transportation Research Record</em> No.1687, 104-111.</p><p><em> </em></p></p>