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Subgrade treatment has traditionally been achieved using calcium-based cement. However, it does not necessarily enhance sustainable design. Recently, low-carbon alternatives such as portland limestone cement (PLC) have gained attention as substitutes for traditional cement. In addition, recycled concrete aggregate fines (fRCA), a waste product, have shown potential for application in transportation infrastructure because of their enhancements in pavements. This study investigates the effectiveness of PLC and fRCA in improving soil properties under different environmental stressors. Clayey soil was treated with PLC (10% PLC or 10C) and PLC-fRCA mixtures at different ratios (8% PLC/15% fRCA or 8C_15fRCA and 8% PLC/30% fRCA or 8C_30fRCA). Improvements in strength, stiffness, and volumetric changes were evaluated through unconfined compressive strength and repeated load triaxial tests after exposure to various environmental conditioning cycles (0, 6, and 12 cycles of wet–dry or freeze–thaw) in the laboratory. Results indicated that untreated soil collapsed within two cycles of environmental conditioning. In contrast, treated soils exhibited significant improvements in strength and resilience to environmental stressors. Stiffness also improved with treatment, and despite some reduction after exposure to environmental conditioning, treated specimens maintained relatively higher stiffness values. These enhancements are attributed to the formation of strong binding gels from hydration and secondary reactions among PLC, fRCA, and soil, which exhibit strong resistance to moisture intrusion, helping to preserve their engineering properties. Overall, this study provides a comprehensive understanding of the potential of using fRCA as a co-additive to PLC, offering a more sustainable and durable alternative for the long-term performance of transportation infrastructures. 

The long-term monitoring of transportation infrastructure assets at a lower cost and with short mobilization time is of significant interest to both state and federal transportation agencies in the U.S. Because of the significant improvement in spatial and temporal resolution of synthetic aperture radar (SAR) remote sensing systems and a notable reduction in the cost of data acquisition, SAR has now become a viable method to provide economic and rapid condition assessment of transportation assets. A research study was developed and performed to comprehensively perform the inspection and characterization of a pavement surface based on the amplitude of backscattering of an X-band radar. In situ characterization of the test site was first performed using traditional inertial profilers and aerial photogrammetry with unmanned aerial vehicle (UAV) surveys. The results from these in situ methods were compared with the corrected amplitude of the SAR data, which indicated that the distribution of surface roughness values computed from the inertial profiler, UAV, and SAR exhibited similar probability densities at various segmental lengths considered in this study. This suggested that the problematic areas that are evident during in situ characterization can be delineated and quantified based on the normalized radar cross section of the pavement surface. Overall, the outcome of this research exhibits the potential of SAR for future transportation asset management undertakings, and the systematic framework developed as a part of this research could be of significant interest to engineers and transportation practitioners. 

Bridges play a key role in supporting the transportation network in the United States. The 2021 infrastructure report card prepared by ASCE highlighted that more than 40% of bridges in the U.S. are over 50 years old. Some of these bridges are classified as structurally deficient, even though they are safe to travel. To address these challenges, highway agencies are exploring innovative technologies to conduct inspections and realize benefits in relation to access, cost, and safety. Federal and state DOTs have conducted several studies on the application of uncrewed aerial vehicles (UAVs) for bridge health monitoring. This study identified the existing knowledge gap in performing 360° inspection of bridges. In this current research, UAVs were demonstrated for conducting 360° inspections of three different bridges in Alaska. The locations of the aerial images during the inspections were also pictographically represented to provide a holistic idea for the highway agencies and practitioners. Three-dimensional models representing the actual conditions of the bridge were generated and used for comparing the bridge condition assessments with traditional inspection reports. Infrared imagery was also collected to identify the effect of thermal loading in assessing the conditions of the bridge elements. The applicability and recommendation scale for the use of UAVs for different bridge inspections was provided. The approach demonstrated in this study is expected to result in more than 90% savings in storage requirements and contribute to an increase in the applications of UAVs for conducting 360° bridge inspections across the U.S.