Effect of wetting and drying cycles on resilient modulus and microstructure characteristics of heterogeneous quicklime-stabilized subgrade

The resilient modulus changes due to post-compaction seasonal variations in weather such as wetting and drying, thus affecting pavement performance. Existing research highlights significant differences in back-calculated resilient modulus test outcomes for compacted quicklime-stabilized subgrades after construction. Nonetheless, limited studies exist on the effect of the wetting and drying cycles considering the variability in the compacted quicklime stabilized composites. By using a Taguchi L 9 orthogonal array, four groups of nine samples varying in dry density and water and quicklime contents were created and subjected to multiple wetting and drying cycles (i.e., 0th, 4th, 8th, and 12th). Resilient modulus testing revealed an initial increase up to the 8th cycle, followed by a decrease, with a more pronounced negative effect on samples with lower quicklime and water contents. Scanning electron microscopy and energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analyses indicated distinct microstructural responses after each cycle, with SEM micrographs showing complex pore structures of low circularity and the average formation factors ranging from 0.301 to 0.356. Canonical correlation coefficient between the pore geometrical properties and resilient modulus is approximately 0.689, the associated Wilks' Lambda value is 0.526, and the eigenvalue is 0.901, thus offering direct relationships between macroscopic and microscopic properties of the materials. The highest calcium content was found in the samples subjected to 0th cycle. This study contributes to a better understanding of the resilient modulus characteristics and microstructural evolution of quick-lime stabilized subgrades, offering valuable insights for engineers and researchers in pavement design and maintenance.