Cetin, Bora

Post-construction roadside soils often suffer from compaction, low fertility, and poor structure, challenging vegetation establishment and stormwater management. This study evaluates the effectiveness of organic amendments (OAs) and proprietary amendments as alternatives to traditional methods. The study involves greenhouse experiments (pot and mesocosm) and field experiments to evaluate vegetation growth and water quality across different amendment and soil applications. Results show that compost amendments significantly improve vegetation growth, with yard-waste compost outperforming others. Biochar shows early growth potential but requires nutrient supplementation for sustained performance. Proprietary amendments support rapid vegetation establishment, enhanced root density, and reduced nutrient leaching, with Sustane 4-6-4 exhibiting consistent growth across application rates. The field study validates greenhouse findings and shows increased biomass and root density with compost amendments, while proprietary amendments result in high nutrient retention and runoff quality. This study highlights the potential use of OAs and PAs to reduce erosion and support long-term vegetation growth. The findings provide practical guidelines, benefits and implementation steps for managing roadside soils after construction activities.

Base stabilization additives are used to increase the strength and stiffness of road foundations on weak and susceptible soils. The Minnesota Department of Transportation (MnDOT) quantifies the structural contribution of pavement layers by introducing granular equivalency (GE) factors. While numerous additives exist for improving the performance of aggregate base layers, this study focuses on proprietary additives including Base One, Claycrete, EMC SQUARED, PennzSuppress and Roadbond EN1. The laboratory study revealed that EMC SQUARED was the superior stabilizer, with an optimum dosage set 15% higher than the manufacturer recommended dosage (MRD). The long-term performance of proprietary additives was monitored by considering full-scale field implementation with optimum additive dosages obtained from laboratory investigation. Controlled sections without stabilization exhibited higher values in the California Bearing Ratio (CBR) and composite elastic modulus right after construction, while the impact of stabilizers on the increasing strength of the full depth reclaimed (FDR) base was revealed after two years of construction. Falling-Weight Deflectometer (FWD) tests demonstrated a progressive increase in the stiffness of stabilized sections over time, surpassing the control section's stiffness after two years. The economic analysis utilizing Life Cycle Cost Analysis (LCCA) indicated that stabilized sections, particularly those treated with EMC SQUARED, offered lower Equivalent Uniform Annual Cost (EUAC) values across various maintenance scenarios. These findings suggested potential cost savings over a pavement's life cycle with higher GE factors of recycled asphalt pavement base aggregate treated with proprietary additives. The findings will contribute to a comprehensive understanding of the benefits, feasibility, and design considerations associated with using commercial stabilizers in FDR base layers.

It is well-known that longitudinal joint construction quality is critical to flexible pavement life. The maintenance activities caused by longitudinal joint deterioration's direct or indirect effects and raveling problems along the centerline paving joint of asphalt roadways have become challenging for many highway agencies. A poorly constructed joint can lead to premature deterioration of an otherwise sound pavement. Thus, improving the joint’s construction can improve density and decrease permeability. It is probably the single most crucial remedy to enhance pavement performance. A density profiling system (DPS) provides continuous, instead of limited, coverage provided by conventional joint quality evaluation methods. Statistical, probabilistic, and percent-within-limits (PWL) analysis of DPS data suggests avoiding the construction of an unconfined joint. Tapered joints, confined butt joints employing the Maryland method or otherwise, echelon paved, and unconfined butt joints with cut back can produce adequate compaction at the joint.

These appendices pertain to report NRRA202103, Determining Pavement Design Criteria for Recycled Aggregate Base and Large Stone Subbase.

Seasonal freeze-thaw weakening has a significant effect on pavement foundation performance. The seasonal freeze-thaw cycles cause extensive damage to the pavement from frost-related problems such as frost heave, frost boils, thaw weakening, total rutting, and degradation of mechanical properties. Changes in temperature of pavement foundation geomaterials during freeze-thaw cycles can significantly influence the performance of pavement foundation layers. It is crucial to monitor the changes in water content, temperature, and matric suction of aggregate base and subgrade soils to be able to predict the frost depth, freezing and thawing times, and number of freeze-thaw cycles. This project has two main goals: (1) develop a data-driven model to predict the maximum/minimum frozen soil depths and (2) freezing and thawing duration and numbers via use of standard climate data that includes precipitation, shortwave radiation, and air temperature. During this research, a model was developed and validated using the climate and environmental data collected from MnDOT. As a result of this research an Excel tool was developed that can predict frost depth, soil temperature, number of freeze-thaw cycles, and duration of freezing and thawing periods at a given soil depth via use of weather data. The required climate data include air temperature, relative humidity, wind speed, precipitation, and solar radiation.

The use of recycled materials promotes sustainability in roadway construction by reducing the consumption of energy and emission of greenhouse gases associated with mining and the production of virgin aggregate (VA). Recycled asphalt pavement (RAP) and recycled concrete aggregate (RCA) have comparable characteristics to VA that have been used in roadway base course applications. This study develops a database for RAP and RCA material characteristics, including gradation, compaction, resilient modulus (Mᵣ), California bearing ratio (CBR), and saturated hydraulic conductivity (Kₛₐₜ). In addition, this study summarizes construction specifications provided by several departments of transportation (DOTs) regarding the use of recycled aggregates in pavement systems. The effects of the presence of RAP and RCA in aggregate matrices on the engineering and index properties of aggregates are investigated and some trends are observed. For example, the study finds a higher RAP content reveals a higher summary Mr (SMr), and a higher RCA content causes an increase in optimum moisture content (OMC) and a decrease in maximum dry unit weight (MDU). In addition, a series of AASHTOWare Pavement Mechanistic-Empirical (ME) Design (PMED) analyses are conducted for three traffic volumes [low (1,000 AADTT), medium (7,500 AADTT), and high (25,000 AADTT)] with the material inputs collected for the database to determine whether different values of different characteristics of RCA and RAP can be used in flexible/rigid pavement designs. Results show that Mr has a higher effect on pavement distress predictions compared to gradation and saturated hydraulic conductivity (Kₛₐₜ).

This project was performed to evaluate the performance of recycled aggregates and large stones used in the aggregate base/subbase layers of pavement systems and provide recommendations regarding pavement design and material selection. As part of this project, eleven test cells were built at MnROAD to evaluate the impact of recycled aggregates and large stones on the long-term pavement performance via a series of laboratory [permeability, soil-water characteristic curve (SWCC), stereophotography (image analysis), gyratory compaction, and resilient modulus (MR) tests] and field tests [intelligent compaction (IC), falling weight deflectometer tests (FWD), rutting measurements, international roughness index (IRI) measurements, light weight deflectometer (LWD) tests, and dynamic cone penetrometer (DCP) tests]. In addition, a pavement mechanistic-empirical (ME) design approach was used to provide recommendations for designs of pavement systems containing recycled aggregate base (RAB) and large stone subbase (LSSB) layers. Overall, this project found that finer recycled concrete aggregate (RCA) material would be preferable to coarser RCA material and a blend of RCA and recycled asphalt pavement (RAP) materials would be preferable to natural aggregate for aggregate base layers. RCA materials provided better performance than the blend of RCA and RAP materials, indicating that RCA materials would be preferable to the blend. For LSSB layers, this project found that geosynthetics would be required to successfully construct thinner LSSB layers. Overall, thicker LSSB layers provided better structural support than thinner LSSB layers both in the short term and the long term.

The objective of this project was to provide a better understanding of how various virgin aggregate and recycled asphalt pavement (RAP) mixtures for surface layers affect the performance of gravel or crushed rock roads and; with further analysis; to determine the optimal RAP content for Minnesota gravel roads. This project included a literature review; preliminary laboratory testing; economic and feasibility analysis; and two field studies. Several studies regarding the use of RAP materials for road surfaces were reviewed. Then; laboratory tests on various RAP materials; one virgin aggregate; and mixtures of RAP materials and virgin aggregate were conducted to observe the effect of RAP on the index properties of the materials and the engineering properties of the mixtures. Initially; six test sections were constructed with various surface aggregates in two locations. Virgin RAP-aggregate blends having 15% to 60% RAP contents were placed as surface aggregate. Then; three more test sections were constructed using RAP-aggregate blends having 50%; 70%; and 80% RAP contents. Several field tests; including lightweight deflectometer; dynamic cone penetrometer; scrape; and dustometer tests; were performed to evaluate the test sections. This report provides insights regarding the effect of using RAP material on surface layers to reduce the use of virgin aggregates. It was concluded that the optimal RAP content for unpaved road surfaces changes according to the properties of the materials used; testing methods; and site conditions.

Concrete grinding residue (CGR) is a slurry waste consisting of water and concrete fines generated from diamond grinding operations that is used to smooth a concrete pavement surface. During this process; CGRs are mostly disposed along the roadside; which can influence soils and plant communities along the roadways. To understand the effects of CGR on soil physical and chemical properties and plant growth; a controlled field site at the Kelly Farm in Iowa was used with CGR application rates of 0; 10; 20; and 40 dry ton/acre to test properties of soils and plants before the application and one month; six months and one year after the CGR application. Two roadsides along Interstate 90 in Minnesota where CGR material was applied in the past were investigated as well. Laboratory and field experiments were conducted to measure plant biomass; bulk density; hydraulic conductivity; infiltration; pH; electrical conductivity (EC); alkalinity; metals; cation exchange capacity (CEC); exchangeable sodium percentage (ESP); and percentage base saturation (PBS) of soil samples collected from the test sites. Statistical analyses were conducted to correlate the CGR additions to the properties of soils and plants. The results of statistical analyses from the Kelly Farm indicated that CGR material did not significantly affect soil physical properties and plant biomass but impacted the chemical properties of soil. Changes in some soil properties such as pH and percent base saturation (PBS) due to CGR did not persist after one year. The results from two Minnesota roadsides indicated that the areas receiving CGR applications in the past did not negatively affect soil quality and plant growth.