<p><p><figure id='attachment_3431' style='max-width:627px' class='caption aligncenter'><img class="wp-image-3431 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Plan view of field tests conducted for fiber reinforcement in pavement systems at Texas Transportation Institute." width="627" height="684" /><figcaption class='caption-text'> Field Tests, Texas Transportation Institute, Texas</figcaption></figure></p><p><h2>Project Summary/Scope:</h2>Laboratory and field tests were conducted to evaluate the effect of discrete fibrillated fibers on the life of chemically stabilized sand and clay in pavement layers. The design was a racetrack pattern with a lane width of 4.9 meters (16 feet). The straightway section on each side of the oval was 67 meters (220 feet) long. Each of the 14 sections was 9.4 meters (31 feet) long with the four sections at the ends of the straightaways being slightly longer to provide a transition to the curve. The site was selected to ensure a relatively homogenous subgrade with a very low CBR. The CBR averaged 4.5 % at the top of the subgrade on the test track immediately before traffic. The track had no surface course or seal coat and was designed so that it would fail within approximately 5,000 passes of the loading vehicle.</p><p>After initially surveying the track, the surface root zone was removed and an attempt was made to achieve a uniform density and moisture content at least 150 mm (6 inches) into the subgrade throughout the test track. Then, all materials were mixed in place using a rotary mixer with the exception of sand-cement, which was mixed in a central pugmill plant. After mixing at the pugmill, the sand-cement was delivered to the site and fibers were mixed with the material in place. The lime was mixed in place with the clay, followed by mixing the fibers in place. Visually, it appeared that the fibers opened up better in the clay than in the sand sections during field operations. Approximately 3 weeks was planned for curing of the stabilized material.<br><h2>Complementary Technologies Used:</h2>Cement / Lime Stabilization<br><h2>Performance Monitoring:</h2>Several types of tests were conducted on the materials by different laboratories. Studies included different compaction efforts, confined and unconfined compressive strengths, and basic soil properties of the two soil materials chosen for the study. Measurements were taken perpendicular to the centerline of the tested cross sections to evaluate the performance.</p><p>It was apparent from testing that the fibers enhanced the performance of chemically stabilized materials. The fibers increased the modulus, strength, and strain energy of the sand and clay materials. In certain situations, the use of fibers may allow for a reduction in chemical stabilizer content. Alternatively, the use of fibers may allow reduction in the thickness of the layer in which they were used.<br><h2>Case History Author/Submitter:</h2>Texas Transportation Institute, Texas A&amp;M University, College Station, TX 77845<br><h2>Project Technical Paper:</h2>Crockford, W.W., Grogan, W.P., and Chill, D.S. (1993). “Strength and life of stabilized pavement layers containing fibrillated polypropylene.” Transportation Research Record Vol. 1418, pp. 60-66.<br><h2>Date Case History Prepared:</h2>November 2012</p></p>