Pavement design features such as joint spacing, base types, and pavement mixture design are typically set by practice and policy. However, this design strategy often results in over-designed concrete pavements or poor performance. The session's learning outcomes will be how pavement design features and materials can be optimized to reduce initial costs and CO2 emissions, as well as life cycle costs and lifetime CO2 emissions. The session would benefit the industry, departments of transportation, and academia.
(1) Review where large environmental impacts are for concrete pavements;
(2) Reference where opportunities are to cut down greenhouse gas emissions for concrete pavements;
(3) Discuss how to enhance the sustainability of concrete pavements through engineering design;
(4) Discuss how to enhance the sustainability of concrete pavements through concrete mixture design;
(5) Identify design tools and optimization strategies for concrete pavements sustainability.
Trade-off Analysis to Improve Concrete Pavement Sustainability by Optimizing Designs
Presented By: James Mack
Description: Historically concrete pavement designs are based on an engineering analysis where the pavement thickness is chosen to meet the traffic, environmental, and subgrade conditions for the project, and the other features, such as joint spacing, base types, etc., are set by practice and policy. If these other features are evaluated, it is assumed that all the designs will perform similarly. This is not a reasonable assumption. Furthermore, this often results in over-designed concrete pavements, leading to higher economic costs and environmental impacts. This presentation will show how pavement engineers can optimize pavement designs by accounting for the performance differences between pavements with different design features; and using a trade-off analysis to create pavement structures with low initial costs and initial CO2 emissions, as well as low life cycle costs and lifetime CO2 emissions.
Concrete Pavement Design Optimization Provides Cost-Effective Pavement with Improved Long-Term Performance
Presented By: Juan Pablo Covarrubias
Affiliation: TCPavements Ltda
Description: The evolution of concrete pavement design has progressed significantly in recent years, more specifically with the advent of mechanistic-empirical (ME) pavement design methods. These more sophisticated design methods highlight the importance of holistically considering all factors that influence concrete pavement performance. Including loading & design life, subgrade support, flexural strength, thickness & joint spacing, edge support & joint stability, and humidity & ambient effects, all of which cannot be considered independently of each other. This presentation will discuss the evolution of concrete pavement design and how optimized designs can provide cost-effective pavement with improved long-term performance using ME design procedures.
Impact of Concrete Pavement Mixture Design Choices on Pavement Sustainability using Caltrans eLCAP Software
Presented By: Ali Butt
Affiliation: University of California Pavement Research Center
Description: Supplementary cementitious materials (SCMs) reduce clinker content in concrete and thus have the promise of reducing the overall greenhouse gas emissions of concrete. However, traditional SCMs such as fly ash and slag are increasingly imported or transported from certain locations in the US; thus, long-distance shipping and transportation adds to the overall GHG emissions of concrete. In this presentation, we present the use of locally available alternative SCMs in California, such as agricultural ashes (rice hull ash) and biomass ashes and natural pozzolans (volcanic ash, perlite, diatomaceous earth, etc.) and compare the global warming potential over the complete life cycle of the concrete pavement.
Optimizing Paving Concrete Mixtures for Improved Durability and Sustainability
Presented By: Milena Rangelov
Affiliation: Federal Highway Administration- NRC
Description: Multiple recent initiatives advocate for reducing embodied carbon, i.e., greenhouse gas emissions, associated with concrete production. Even though readily implementable strategies exist, practitioners are concerned that embodied carbon reductions may adversely affect concrete performance and durability, resulting in detrimental effects from a life cycle perspective. To address such concerns, this study investigates the correlations between embodied carbon of concrete mixtures, mixture design parameters, and experimentally measured mechanical and durability properties. The analyzed dataset included 145 mixtures, featuring a variety of mixture designs from laboratory and field studies. The results indicate that the cement content is the most significant predictor of GWP and that considerable savings can be achieved with cement reduction and replacement without compromising performance. Clear correlations of GWP with compressive strength were not identified, while the results demonstrated that reduced GWP and increased surface electrical resistivity (the utilized durability indicator) often occur in synergy. The study also provides the tie between Performance Engineered Mixtures and embodied carbon and thereby provides practical insights into mixture design optimization that includes both sustainability and durability.