| dc.description.abstract | Construction of pavements and other lightweight structures on expansive soils is a considerable cause of concern for transportation infrastructure practitioners around the globe, including in the state of Texas. Pavement undergoes rutting, cracking, shoulder dropping, and differential heaving during its service life due to non-uniform moisture cycles, and consequently, the long-term durability of the structures is severely impacted. Among the available methods, chemical stabilization using calcium-based stabilizers such as lime is one of the most commonly used techniques, considering the ease of construction and low cost of virgin materials for building the transportation infrastructures. The stabilization of high-plasticity soils with lime results in the formation of pozzolanic reactions products, which binds the soil matrix and imparts the desired engineering properties to the soil subgrade.
However, the pozzolanic reactions being a slow process, need considerable time before the final strength or stiffness is achieved. As a result, it results in significant traffic delays during the construction phase and increases the overall life-cycle cost of the project. Additionally, several expansive soil zones also have a considerable concentration of soluble sulfate minerals. Treatment of such sulfate-rich soils using calcium-based stabilizers could be counterproductive, resulting in the formation of a highly deleterious and expansive mineral, ettringite. Researchers have been extensively working on developing novel treatment techniques to mitigate such problems associated with traditional ground treatment techniques.
To overcome the problems associated with slow pozzolanic reactions, sulfate-related heave distresses and long-term durability of transportation infrastructures, a research study was designed to use novel silica-based co-additives, such as quarry-dust and laboratory-grade nano-silica compounds with lime stabilizer to treat high plasticity soils with different levels of sulfate concentration. The present studies showed that the application of these novel-co-additives with traditional dolomitic-hydrated lime significantly modified the reaction kinetics. Additionally, when used with lime to treat sulfate-rich soils, the presence of the additional silica phases suppressed the precipitation and subsequently swelling from ettringite crystals. The presence of the silica phases also improved the durability and permanency of the chemical stabilizer compared to traditional treatment alone. Overall the application of these new treatment techniques will be of immense help for transportation agencies and would help them to use new and more sustainable soil treatment techniques for improving the long-term performance of the transportation infrastructures. | |
