AbstractThe main objective of this study was to evaluate the use of glass fibers and cement as stabilizing agents for highly expansive soil. Fibers with two aspect ratios (12 and 30 mm in length) were added as percentages of the soil’s dry weight (0.5%, 0.75%, 1%, and 1.5%), the cement was added in two percentages by dry weight soil (2% and 6%). Sixteen groups of treated soil specimens were prepared and subjected to laboratory tests—unconfined compressive strength (UCS) after curing (0, 7, 14, and 28 days), swelling percentage, and California bearing ratio (CBR). Interactions at the interface between the fiber surface and the soil matrix were analyzed by scanning electron microscopy (SEM). Also evaluated was effect of fibers on the design and performance of cement-stabilized subgrade layers according to the Mechanistic-Empirical Pavement Design Guide (MEPDG) to compare the performance of flexible pavement sections modeled using default values and laboratory-established soil properties for inputs. Results indicated increases in UCS and soaked CBR and decreases in swelling tendency. The 6% cement/1.5% short fiber mixture resulted in a significant improvement in expansive soil properties over other mixtures.