Low-Carbon Concrete Initiative
The City of Portland’s 2016 Sustainable Supply Chain Analysis identified construction services as the top spend category contributing to the City’s supply chain greenhouse gas (GHG) emissions. Within construction services, concrete is one of the most GHG-intensive materials typically used on City construction projects. As a result, in 2019, after gathering both internal and external stakeholder input, the City established its Low-Carbon Concrete Initiative to reduce the overall carbon intensity of the concrete mixes used on City projects. From 2019 to early 2022, the Initiative involved: 1) establishing a product-specific Environmental Product Declaration (EPD) requirement for concrete mixes used on City projects; 2) conducting pilot tests of lower-embodied carbon concrete mixes; and 3) defining Global Warming Potential (GWP) Thresholds for concrete mixes.
For questions related to the Low-Carbon Concrete Initiative, contact Josh Huber, Materials Quality Compliance Specialist, Portland Bureau of Transportation, joshua.huber@portlandoregon.gov
Lower-Embodied Carbon Concrete Pilot Projects
In order to understand how lower-carbon concrete mixes perform compared to traditional 100% cement mixes, the City has been conducting pilot tests of different lower-carbon concrete mixes. The following case studies provide summaries of the pilot tests conducted to date.
Pilot Project Case Study Reports
| Concrete Application | Location | Mix Description | Month/Year Poured | Associated Case Study |
|---|---|---|---|---|
| ADA ramp/sidewalk | N Michigan & N Fremont NE Corner | Type I/II Cement w/30% Slag | April 2020 | Sidewalk Pilot Project 2020 |
| ADA ramp/sidewalk | N Michigan & N Failing SE Corner | Type I/II Cement w/40% Slag | April 2020 | Sidewalk Pilot Project 2020 |
| ADA ramp/sidewalk | N Michigan & N Fremont SE Corner | Type I/II Cement w/30% Slag + Carbon Cure | April 2020 | Sidewalk Pilot Project 2020 |
| ADA ramp/sidewalk | N Michigan & N Failing NW Corner | Type I/II Cement w/30% Slag + Carbon Cure | April 2020 | Sidewalk Pilot Project 2020 |
| ADA ramp/sidewalk | N Michigan & N Webster NE Corner | Type I/II Cement w/50% Slag | May 2020 | Sidewalk Pilot Project 2020 |
| ADA ramp/sidewalk | N Michigan & N Webster NW Corner | Type I/II Cement w/35% Slag | May 2020 | Sidewalk Pilot Project 2020 |
| Pole footing & surrounding sidewalk/refuge | NE Glisan & NE 128th, North end of crosswalk | Type I/II Cement w/50% Slag | March 2021 | Pole Footings Pilot Project 2021 |
| ADA ramp/sidewalk | N Liberty St & N Oatman Ave | Type 1L Cement w/30% Slag | October 2021 | Type 1L Cement Pilot Project 2021 |
| Concrete pavement | N Liberty St & N Oatman Ave | Type 1L Cement w/30% Slag | November 2021 | Type 1L Cement Pilot Project 2021 |
| Driveway | SW Naito Pkwy, between SW Clay & Market St, East Side of Street | Type I/II Cement w/50% Slag | June 2021 | Set Time & Early Strength Case Study 2022 |
| Driveway | 1720 SW Naito Pkwy | Type I/II Cement w/50% Slag | December 2021 | Set Time & Early Strength Case Study 2022 |
| Sidewalk | NE Corner of SW Naito & Harrison | Type I/II Cement w/50% Slag w/accelerator (0.5%) | January 2022 | Set Time & Early Strength Case Study 2022 |
| Sidewalk | NE Grand & NE Davis (on NE Davis - North Side) | Type I/II Cement w/50% Slag w/accelerator (2%) | January 2022 | Set Time & Early Strength Case Study 2022 |
| Sidewalk | NE MLK Blvd & NE Davis (on MLK - East Side) | Type 1L Cement w/30% Slag | March 2022 | Set Time & Early Strength Case Study 2022 |
| Footings | Gabriel Park, wall footings - playground improvements | Type 1L Cement w/30% Slag | June & July 2021 | Park Infrastructure Case Study 2022 |
| Retaining Wall | Gabriel Park, playground improvements | Type 1L Cement w/30% Slag | August 2021 | Park Infrastructure Case Study 2022 |
| Concrete Stairs | Gabriel Park, playground improvements | Type 1L Cement w/30% Slag | October 2021 | Park Infrastructure Case Study 2022 |
| Bike/Pedestrian Path & Bench Pads | Gabriel Park, playground improvements | Type 1L Cement w/30% Slag | February 2022 | Park Infrastructure Case Study 2022 |
Portland Area Mobile Mix EPD
The Sustainable Procurement Program also funded the development of a Portland-area average EPD for mobile mix producers. Four mobile mix producers in the Portland area contributed to the EPD. A copy of the EPD can be found on the ASTM EPD website. Compared to the cost of an EPD for a stationary plant that may produce over 100 mixes, the cost per mix of an EPD for a mobile mix producer is significantly higher. Thus, the Sustainable Procurement Program pursued a local industry-average approach and invited any mobile mix producer supplying the Portland area to participate.
Embodied Carbon Thresholds for Concrete Mixes on City Projects
In May 2022 the City announced its maximum Embodied Carbon Thresholds for concrete mixes used on City construction projects which will go into effect January 2023 (see below for a copy of the announcement). These Thresholds were based on recommendations from a multi-stakeholder workgroup convened to advise the City on establishing such thresholds. Background on the Low-Embodied Carbon Concrete Threshold Committee and their recommendations development process is provided below.
Related Links
- Carbon Leadership Forum: Great hub of resources for reducing carbon within the built environment
- RMI Concrete Solutions Guide: Six Actions to Lower the Embodied Carbon of Concrete
Clean Air Construction Regional Initiative
To improve the air quality in Portland Metro area, the City of Portland, Multnomah County, Port of Portland, Metro, Washington County, TriMet, and Portland Community College are working together to include Clean Air Construction Requirements in their construction contracts. You can find more information on the Clean Air Construction Regional Program website.
Sustainably-Sourced Wood
In 2022, the Sustainable Procurement Program began sponsoring pilot projects with bureaus whereby a construction project's design team works with a consultant who is a subject-matter expert in local/regional markets of sustainably-harvested/sourced wood to identify sustainably-sourced options for the project's wood package. For these pilot projects, the City is utilizing elements of the Cities4Forests' Sustainable Wood for Cities Guide and its eight pathways for sourcing sustainable wood products. In doing so, the pilot projects will look to support local/regional forestries, indigenous-tribe-owned forestries, small landowners, urban reuse, recycled wood, minority/women-owned businesses, and more. As the pilot projects evolve, the Sustainable Procurement Program plans to publish case studies about this work.
Sweatshop Free Apparel
The City's Sustainable Procurement Policy requires the City to purchase apparel products from manufacturers that comply with the City's Code of Conduct for Apparel Contractors [Attachment 1 of the Sustainable Procurement Policy]. The Code of Conduct requires that contractors, and their supply chain partners utilized to supply apparel to the City, comply with labor and health & safety standards that ensure workers are not subjected to sweatshop conditions.
Sweatshop Free Forms for Apparel Contractors
The City discloses the "cut and sew" factory locations where apparel items on City contracts are made. This information is available via the Sweatfree LinkUp database.