Institute for Transportation

About the research

Base stabilization is crucial for enhancing the structural integrity of roads by improving the strength and stiffness of the base layer, which is vital for mitigating issues with vulnerable soils and increasing the longevity and performance of road foundations. Despite progress in pavement base stabilization using proprietary additives, there is a critical need for further research to fill knowledge gaps and enhance the use of these additives for more sustainable and cost-effective road infrastructure. The existing body of research mainly focuses on non-proprietary stabilizers, with limited exploration of the performance and economic viability of proprietary options.

A study sponsored by the Minnesota Local Road Research Board (LRRB) on entitled, “Base Stabilization Additives – Effect on Granular Equivalency (GE)” evaluated the advantages of proprietary additives in treating full-depth reclaimed (FDR) materials by the estimated GE factors, but it also identified areas needing more investigation. The study’s life cycle cost analysis (LCCA), based on assumed maintenance scenarios, and GE factors, and
derived from two years of data, call for further validation and long-term performance assessment. To address these issues and build on the current findings, a Phase 2 study aims to evaluate the long-term performance and durability of stabilized pavement sections with proprietary additives, validate GE factors through extended field monitoring, and assess the economic feasibility of these additives. This subsequent research seeks to advance the understanding of base stabilization practices and develop guidelines for selecting and optimizing proprietary additives, ensuring structural and cost-saving benefits for pavement design.

About the research

This project will evaluate the performance of a mineral-blended polymeric microsphere powder used to construct concrete pavement test sections at MnRoad. The microsphere concrete mixtures will also be compared with a reference mixture that contains conventional air entrainment and existing mixtures evaluated at MnRoad. Performance will be monitored over a three-year period. The three-fold objectives for evaluating the microsphere mixtures are as follows:

1. Determine the reductions in cement content that can be achieved with typical pavement concrete mixtures in which air-entraining agents are replaced with the microsphere-powder blend.
2. Develop test data on strength and freeze-thaw durability for selected concrete mixtures to support application of the microsphere concrete mixtures in pavement construction.
3. Quantify the sustainability benefits of use of microsphere concrete in lieu of conventional air- entrained concrete mixtures

Laboratory testing on specimens cast during pavement construction will be performed to evaluate strength, modulus of elasticity, resistivity, and freeze-thaw durability. Field data collection will include surface distress surveys, falling weight deflectometer (FWD) testing, ride quality measurements, joint faulting and movement, embedded strain sensor data, ultrasonic tomography (MIRA) testing, curling and warping measurements, and examination of core samples. Results from this project will demonstrate the effectiveness of the mineral-blended polymeric microsphere powder to be used in concrete mixtures to support reductions in cementitious materials content while also supporting freeze-thaw durability. The feasibility of using mineral-blended polymeric microsphere powder in large-scale pavement applications will be evaluated, as well as the impact of use of this material to support both durability performance and reduced environmental impact of concrete. Findings of this work may also support use of mineral-blended polymeric microsphere powder in applications where supplementary cementitious material (SCM) characteristics may cause issues with conventional air-entraining admixtures (e.g., higher carbon fly ash), thus allowing marginal SCMs to be more readily used in concrete.

About the research

While the demand for using good quality aggregate materials for constructing both highway and local road systems has increased, local availability is often found to be insufficient. The use of recycled waste materials has been used in road construction to the maximum economic and practical extent possible with equal or improved performance. Plastic is a significant contributor to waste generation across the United States. The recent ban on imported plastic waste in developing countries is also forcing US cities and states to take issues related to plastic waste more seriously. Consequently, there is an urgent interest and need to transform plastic waste into useful materials to better to deal with it rather than keeping it in landfills. The objectives of this study are to (1) conduct a synthesis on the use of recycled plastics for roads in combination with the literature review results as part of relevant studies conducted on MnROAD by the National Road Research Alliance (NRRA) and National Center for Asphalt Technology (NCAT), (2) evaluate the feasibility of using plastic waste within roadway paving (asphalt and concrete), (3) recommend which applications will be most beneficial and practical, (4) work in partnership with the Minnesota Department of Transportation (MnDOT) to provide a summary of the work being done locally and within the pool–funded studies with NRRA and NCAT, and (5) work with MnDOT/MnROAD to demonstrate the proof–of–concept for the beneficial applications and identify practical challenges when it is fully implemented in Minnesota’s transportation infrastructure system.

About the research

Pedestrian assets, particularly sidewalks, are highly susceptible to aging, adverse weather conditions, and suboptimal construction practices, often leading to rapid deterioration. This deterioration is often ignored due to the widespread misconception that pedestrian assets are low risk, resulting in many deteriorated sidewalks being left untreated or inadequately maintained. A comprehensive deterioration modeling framework that integrates advanced spatial and temporal data sources, advanced data analytics, and predictive modeling would enable infrastructure managers to predict the aging process of pedestrian assets and ultimately prioritize investments, plan maintenance schedules, and allocate budgets efficiently.

This project developed assessment frameworks and deterioration models for pedestrian assets that support reliable and informed decision-making regarding funding needs and asset design and maintenance. Various data sources and modeling and analysis procedures were explored, and a pedestrian asset assessment methodology was developed and evaluated. The research demonstrated a scalable and cost-effective approach to assessing sidewalk conditions, providing actionable insights for proactive maintenance. The quantifiable benefits, including construction savings, improved life-cycle costs, reduced risk, and safety enhancements, position this methodology as a valuable tool for sustainable infrastructure management.

About the research

Fleet managers are continuously challenged with determining the optimal equipment replacement time based on increasing operation costs and decreasing economic value. In addition, they are challenged with determining if a lease or purchase provides the greatest value. Compounding upon these challenges, new equipment purchases and leases can create a negative perception among the general public. This first phase of this research—which consists of a literature review, survey to Minnesota Local Road Research Board (LRRB) members, and follow–up case studies—is strategically designed to understand existing decision support models and methods, quantitative data, and constraints that agencies have when determining the optimal equipment replacement. The second phase of this research—which consists of tool development, validation, and training—is intended to meet the identified challenges and support life–cycle cost analysis (LCCA). This tool will provide quantifiable support for the decision–making process, enabling agencies to make defensible decisions.

About the research

This study examined the operation of static and dynamic no right turn on red (NRTOR) signs at eight signalized intersections in Minnesota (six dynamic and two static). Driver compliance with the NRTOR indications were measured using video data. Most dynamic NRTOR sign locations were pedestrian-activated, with one location having additional time-of-day activation of the NRTOR indication. Compliance rates were calculated per signal cycle and per vehicle. Per-cycle compliance rates were 60.8% for dynamic and 80.0% for static sign locations, while per-vehicle compliance rates were 87.1% for dynamic and 92.4% for static sign locations. Statistical models were further developed to confirm the statistical significance of the results and to explore the strength of the effect compared to other intersection characteristics. A survey of practitioners was included to identify the installation and maintenance costs of DNRTOR devices. The report concludes with recommendations on uses of DNRTOR.

About the research

The Midwest region of the United States, including Minnesota, has been experiencing an increase in the number of heavy precipitation events. Historical precipitation data confirmed an increasing trend of heavy precipitation in Minnesota in the 21^st century. This study focused on assessing the impact of heavy-precipitation events on moisture levels and stiffness of pavement foundation layers at the MnROAD facility.

A two-step approach was adopted for predicting changes in saturation and for estimating corresponding resilient modulus values using the resilient modulus prediction equation employed in AASHTOWare Pavement Mechanistic-Empirical (ME) design. PLAXIS 3D, a finite element analysis tool, was used to simulate the movement of moisture within the pavement layer under varying heavy rainfall scenarios. Multiple linear regression models were developed from rainfall simulation data of the PLAXIS 3D model to predict base layer saturation based on rainfall characteristics and hydraulic conductivity of the material. ArcGIS Pro was then used to develop a framework to generate a preliminary vulnerability map showing changes in the resilient modulus of the pavement base layer from rain events. Four regression models were developed and used in ArcGIS Pro to predict changes in resilient modulus for distinct aggregate types under heavy rainfall events, revealing significant reductions in the base layer’s resilient modulus. Recycled aggregate (a mix of recycled concrete aggregate and recycled asphalt pavement) emerged as more susceptible, with initial reductions in modulus values higher under heavy rainfall.

About the research

Minnesota Department of Transportation (MnDOT) staff has experienced that pavement markings do not perform well on seal coat and micro surface treated roadways, referred to as “challenging surfaces.” This report serves as a beginning point and organized approach in addressing pavement marking practices on challenging surface roadways.

The project objective was to document existing district practices and issues through several key tasks, which include a literature review, field review, and analysis of existing practice and performance. This effort identified the need for a field trial to provide control in the evaluation of these markings on challenging surfaces. An outline was developed for a future field trial effort, which will evaluate the marking performance of different combinations of pavement marking materials and installation practices.

These project findings will be used in conjunction with the resulting field trial evaluations to improve MnDOT guidance and standard practice that will result in better performance, efficiencies, and roadway safety.

About the research

This project summarizes the development of a scalable, reliable, and practical process for viewing, querying, understanding, and making consistent, objective, and cost effective decisions regarding pavement marking needs, durability, and quality. The research team developed a Web-based pavement marking management system through the development environment of Microsoft Visual Studio 2005 ASP.NET in conjunction with ESRI’s ArcGIS Sever Enterprise 9.2 SP4 functionalities to manage and produce the GIS map resources. The web site hosting itself was done on a Windows based server operating Internet Information Services (IIS). The resulting web based mapping tool provides MnDOT staff the ability to map and query pavement marking retroreflectivity information and serves as a significant resource to both district and central office staff in developing short and long-term pavement marking plans.

About the research

It is becoming increasingly apparent that it is necessary to explore alternative options for cement and concrete production used in public infrastructure to reduce carbon footprint. One possible process is to bubble CO₂ in the fresh concrete during production to sequester CO₂ and possibly to reduce cement content in the concrete without compromising system performance. Concrete with reduced cement content will exhibit reduced shrinkage reducing the risk of early age cracking. Other CO₂ sequestration techniques such as dissolving it in batch water and manufacturing CO2enhanced aggregates also need to be assessed.

Confirming these benefits would be a breakthrough in simultaneously reducing the CO₂ footprint while enhancing concrete performance.

Two questions are therefore raised – how much CO₂ is sequestered, and what are the effects on the performance of the pavement? The goal of this research is to address these questions through testing, measurements, and the observation of concrete made with CarbonCure technology. The work will also include an assessment of the reduction of the CO₂ footprint compared to control mixtures based on determining the amount of CO₂ bound in the mixture as well as potential changes in maintenance needs of the pavement over the life of the pavement under traffic and environmental exposure.