contents and determining the geotextile air entry value. The researchers measured the resilient modulus of the aggregate base at 2% increments over moisture contents ranging between 0% and 12%. All samples were initially compacted at the optimum moisture content of 8.5% to ensure that each specimen had the same microstructure. Specimens were then either dried or hydrated to the target moisture content and tested. Resilient modulus testing was conducted according to AASHTO T307-99. Results of the resilient modulus testing showed that a 2% increase in moisture content of the base course aggregate from optimum caused a 60% decrease in resilient modulus and a fivefold increase in permanent deformation (Figure 9). Conversely, a 2% reduction of the moisture content from optimum by the ELDG results in a 200% increase in resilient modulus and a 40% reduction in permanent deformation (Figure 10). The benefit of the ELDG in reducing moisture levels at or below optimum are clearly shown in this research. Instrumented test using ELDG in expansive clays: University of Texas at Austin (2015) The development of longitudinal cracks associated with the presence of expansive clay subgrade soils is a moisturerelated pavement distress. These environmentally induced longitudinal cracks develop toward the pavement shoulders because of moisture content variations in the subgrade. Environmental moisture variations such as wet or dry periods have higher changes in moisture content at the shoulder of the pavement compared to the center of a pavement. Consequently, the edges of the pavement will shrink and swell more significantly during dry and wet periods respectively. During particularly dry seasons, the flexion of the FIGURE 9 Resilient modulus vs. moisture content at confining pressure of 20 psi FIGURE 10 Deformation vs. moisture content at confining pressure of 20 psi pavement will result in tension toward the surface layer, leading to significant longitudinal cracks (Zornberg et al. 2017). A 6-mile (10-km) section of Texas State Highway 21 (SH21), just north of Bastrop, Texas, was constructed on an expansive clay subgrade and in 2013 was rehabilitated by the Texas Department of Transportation (TxDOT). Prior to this rehabilitation, the road had received regular attention from the TxDOT maintenance operations group. Despite this regular maintenance, performance was deemed to be inadequate due to the extensive network of lateral shoulder cracking present. The 2013 www.GeosyntheticsMagazine.com 0620GS_p28-37.indd 33 33 5/20/20 6:15 PMhttp://www.GeosyntheticsMagazine.com