Sustainable Pavement Group Discusses Latest Developments
The FHWA Sustainable Pavements Technical Working Group gathered for its 20th meeting on Monday.
The main focus of the web-based discussion was to allow group members to continue discussions and share examples of how different agencies and organizations are addressing sustainability and related issues.
The meeting was led by Heather Dylla of the FHWA and facilitated by Kurt Smith of ApTech.*
Jim Mack of CEMEX (and past chair of ACPA) presented perspectives on measuring and assessing pavement resilience, noting that pavement resilience should be characterized by three parameters:
A drop in performance induced by the event (which may impact a pavement’s ability to carry loads);
The recovery time to reinstate or improve performance, and
The ability to withstand loading while in a weakened state.
Heather Dylla of the FHWA led a pavement resilience peer exchange aimed at identifying risks posed by climate change and extreme weather events and integrating the risks into planning, operations and program ideas.
The meeting also included a facilitated discussion on the Role of Resilience in Sustainability and Pavement Design by Steve Muench, University of Washington, and Tom Van Dam of NCE.*
On behalf of the concrete pavement community, Leif Wathne commented, “Resilience is quite simply good engineering. We need to recognize as engineers that the pavement design assumptions we have used for decades no longer apply to areas susceptible to inundation.”
“Pavement design in the US is based on compacting the in-place soils and the base layers at or near optimum moisture content,” he says. “We assume that those layers will remain at that moisture (and associated density) in perpetuity. We specifically design the pavement structure with crowns, ditches, drainage layers, etc. to ensure that those assumptions are valid; however, in areas susceptible to inundation, this is simply no longer true. Continuing to design in this way is quite plainly poor engineering.” We have tools at our disposal to account for these new fully saturated conditions under or pavements, and we should use them.
Another opportunity to address the significant threat to our existing pavement network that inundation provides is to embrace “hardening” or retrofit solutions, he says. “You do not have to reconstruct the pavement structure from the bottom to make it resilient to inundation,” he says, noting the stiffness of the pavement structure can be improved from the bottom up (via FDR or deep aggregate layers etc), or via a stiff surface layer (like a concrete overlay). Where this makes sense economically and is functionally a realistic option, it should be embraced.
Joep Meijer of “The Right Environment” presented an update on LCA Pave, an LCA tool under development by FHWA. This Microsoft® Excel-based tool is intended to help agencies assess, benchmark and communicate impacts of materials from cradle to grave. Thus far, the tool has been beta tested and a methodology report review has been completed. The final version of the tool and documentation is being completed, and the tool’s companion resources are currently in FHWA’s publication process.
The concrete pavement industry is somewhat concerned that this LCA tool does not include use-phase impacts, which in some cases (in particular for heavily trafficked pavements) can dominate the overall impacts. It is ACPA’s position that in the spirit of transparency, the tool must in a much more prominent way make it clear to the user the use phase is excluded from the analysis.
LaToya Jackson of FHWA reported on a demonstration project to advance new pavement technology funded through AID-PT. The program is aimed at supporting and showcasing the implementation of innovative pavement technologies, products and processes by state DOTs, as well as levering federal investments with state DOT partnerships. The 5-year project is expected to be funded at $2 million per year by the FHWA and a minimum of $10,000 per state DOT.
FHWA also discussed holding its next meeting prior to the International Symposium on Pavement, Roadway, and Bridge Life Cycle Assessment 2021 (formerly LCA 2020). The event is planned for January 13-15, 2021 in Davis, CA. Click here to see more information.