Accelerated mix design of stabilized subgrades
Problems encountered with subgrade failures due to the loss of stabilizer over time, or ineffectiveness of stabilizer in some soils is well documented. In other cases, the amount of stabilizer applied has been found insufficient. If the selected concentration of additives is not adequate to ensure short-term and long-term durability of a pavement layer, the stabilization will be ineffective, and pavement rehabilitations will be necessary, requiring costly repairs and road closures.^ The proper type and concentration of stabilizers are typically determined considering only the plasticity and the gradation of the subgrade. However, a number of other parameters such as the interaction between the mineralogy of the materials and additives in presence or absence of moisture, construction methods and curing processes significantly impact the performance of stabilized subgrades.^ TxDOT currently requires acceptable strength in lieu of most durability tests to select the optimal additive. Strength tests can be conducted more rapidly than durability tests (7 days vs. 1 month). In addition it requires less laboratory equipment and technician training. However, achievement of a specified strength does not always ensure durability. Moreover, the current TxDOT procedures for selecting the optimal additive are time-consuming and the protocols determining the level of moisture conditioning are not currently available. As part of this research, new accelerated testing methods are proposed that could minimize the time required for soil specimen preparation, curing, conditioning and testing to complete the design process. They also address some of the shortcomings that exist in the current protocols to establish whether the stabilizer or stabilization method is deemed to be effective in the field construction projects.^ In order to develop new and accelerated protocols, several soils with different characteristics and different stabilizers were evaluated under different curing and compaction methods. These soils were categorized using traditional methods and in terms of their mineralogical properties. These materials were then evaluated following the current TxDOT specifications and compared with the proposed methods of moisture conditioning, such as back pressure, vacuum, and submergence of specimens. ^ To select the best alternatives, simplicity and applicability of the test were considered as well as their correlation with methods covered in current specifications. For that matter, a protocol that could be performed on stabilized soils within one week was developed to address the effectiveness of stabilization as the main outcome of this research.^
Veisi, Maryam, "Accelerated mix design of stabilized subgrades" (2008). ETD Collection for University of Texas, El Paso. AAI1453855.