Laboratory characterization of cementitiously treated/stabilized very weak subgrade soil under cyclic loading

This research study was performed to examine the appropriate treatment/stabilization schemes for very weak subgrade soils at high water contents, and to evaluate the corresponding performance-related properties [e.g., resilient modulus and permanent deformation] for use in the design and analysis of pavement structures. Five different soil types, that represent the typical range in subgrade soils in Louisiana, were collected and considered in this study. Three different moisture contents (at the wet side of optimum), producing a raw soil strength of 172 kPa (25 psi) or less, were selected for treatment/stabilization. The percentage of cementitious stabilizer (lime or cement) was determined to achieve a target 7-day strength value of 345 kPa (50 psi), as treatment for working table applications, and 1034 kPa (150 psi), as stabilization for subbase applications. Repeated load triaxial (RLT) tests were performed on the laboratory-molded treated/stabilized specimens in order to evaluate their resilient modulus and to study their deformation behavior under cyclic loading. A good correlation was observed between the water/cement ratio and both the resilient modulus and the permanent deformation of the specimens. The soil specimens were compacted at low water/cement ratios and showed better performances than those compacted at high water/cement ratios. The test results also showed that the use of a direct correlation between the unconfined compressive strength (UCS) and the resilient modulus for cementitiously stabilized soil can be misleading. In the case of heavily treated/stabilized subgrade soils for subbase applications, the permanent deformation of this layer can be ignored in pavement design.