UTC 2022 Funding - Cycle 1 Research Projects

Project No.: CY1-TAMU-UTEP-01
Title: Greenhouse Gas Emissions Reduction and Durability of Sustainable Pavement Recycling and Stabilization Using Novel Materials
Performing Institution: Texas A&M University and University of Texas-El Paso
Principal Investigator: Nripojyoti Biswas, Texas A&M University; Rajib Mallick, University of Texas-El Paso; Anand J Puppala, Texas A&M University; Soheil Nazarian, University of Texas-El Paso
Start and Anticipated Completion Dates: 9/1/2023-8/31/2024
Abstract: Subgrade and base constitute the bulk of structural capacity for most asphalt pavements. Therefore, stabilization of these two layers is an overarching focus for most state departments of transportation (DOTs). There is a need to evaluate the greenhouse gas (GHG) reduction potential of Full Depth Reclamation (FDR) mixes with advanced binders or stabilizers such that DOTs could use them appropriately to construct longer-lasting pavements. Also, the production of commonly used calciumbased stabilizers for subgrade stabilization is associated with generating significant greenhouse gases (such as CO2). Using RCA fines (fRCA), a byproduct of the demolition of concrete structures, as a sustainable co-additive with cement stabilizers could lead to the use of millions of tons of concrete waste that is produced annually and landfilled. Previous studies by the research group at University of Texas at El Paso (UTEP) have demonstrated that combining quarry dust with Reclaimed Asphalt Pavement (RAP) provides cost-effective and durable stabilization. Also, the research group at Texas A&M University (TAMU) has shown the benefits of using silica-rich quarry waste as a potential co-additive for improving the performance of Ca-based treatments. The present study seeks to advance the existing knowledge and develop excellent stabilization of the base course and subgrade layers with a focus on the reduction of CO2. The specific objectives of this project are: (1) To compare the CO2 (primary greenhouse gas) emissions from Full Depth Reclamation (FDR) mixes with a conventional asphalt emulsion, foamed asphalt, and High Yield Emulsion (HYE), through laboratory testing, analysis of data, and to evaluate the durability of optimized HYE mix with accelerated loading and testing; (2) To evaluate the use of recycled concrete aggregate fines (fRCA) as a co-additive with cement stabilizer to treat problematic subgrade soils such as expansive soils through engineering, mineralogical, and chemical testing and embodied carbon analysis. The TAMU team will focus on the use of fRCA as a co-additive for subgrade stabilization. Their tasks include the following: (1) collection of problematic soil; (2) procuring and characterizing fines from recycled concrete aggregate (RCA); (3) determining optimum dosages of stabilizers and co-additives; (4) comparing performance (untreated and treated soils containing fRCA); (5) analyzing mineralogical and chemical components; (6) evaluating sustainability benefits, and (7) comparing treatment alternatives. The UTEP team will evaluate the FDR mixes prepared with three different binders. Their tasks include the following: (1) collection of asphalt and other materials from FDR projects; (2) developing mix designs with different binders; (3) collecting and analyzing fuel data from FDR projects; (4) collecting emission data for binder production; (5) testing the optimized mix for durability, and (6) analyzing data and making recommendations on sustainability and durability, including reduction of CO2. The results from this research will lead to a better understanding of sustainability and durability aspects of novel materials, consisting of FDR binders for base and RCA fines for subgrade stabilization. The observations from experiments will be translated to pavement performance under different environmental conditions, such as temperature and precipitation. The data from this project could be utilized for the modeling and performance prediction of recycled/subgrade-treated pavements under extreme environmental conditions. The results will lead to the implementation of sustainable technology, savings in life cycle cost, rehabilitation of more roads, and enhancement of road safety. Implementation will include new specifications for FDR and the treatment of subgrade soils. Also, the sustainability evaluation framework developed in this study will be available for implementation by the state DOTs in 2 CY1-TAMU-UTEP-01 selecting novel materials. The draft specifications and framework will be prepared for possible inclusion in state or federal specifications, as part of the deliverables. Further, any impediments to the implementation of the specifications/framework and further work, if any, will be provided. The project is aligned with the USDOT’s strategic initiative on climate and sustainability, as it contributes directly toward greater recycling, reduction of the use of virgin materials, reduction in the potential usage of Portland cement, and the resulting reduction of greenhouse gas emissions.
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