The integration of recycled concrete aggregate in paving applications represents a pivotal shift in sustainable infrastructure development, driven by the collaborative efforts of Heidelberg Materials and Ascendant. Washington State's proactive legislation in 2016 encouraged the use of RCA in road construction, prompting the Washington Department of Transportation and the City of Seattle to adopt goals for incorporating RCA in their standard specifications. Notably, the City of Seattle permits up to 30% replacement of coarse aggregate with RCA in concrete paving, while WSDOT recently increased the allowable RCA usage to 100% for concrete pavement, sparking ongoing research and development in paving mix designs.
Sterling Frye, Senior Area Production Manager at Heidelberg Materials, emphasizes the company's commitment to sustainability by initiating testing with 30% RCA as a baseline for the City of Seattle. The introduction of RCA, including the Revolve™ line of products, in concrete mixes for paving represents a significant industry advancement. Heidelberg Materials' meticulous laboratory testing of paving application mixes since 2023 aims to gradually increase RCA usage by 10-to-20% monthly until reaching 100% RCA levels, ensuring quality control and performance consistency throughout the testing process.
Heidelberg Materials' strategic rollout plan in the Pacific Northwest builds upon the success of previous testing in 2020 for general purpose mixes, which incorporated 50% RCA in foundational applications. The transition to higher RCA content in paving mixes necessitates meeting stringent requirements for high early strength, air entrainment, and durability against freeze-thaw cycles and weathering. The company's rigorous testing protocols encompass compressive and flexural strength, air content, and real-world truck trials or test pours, enabling contractors to simulate actual field conditions and assess performance under practical scenarios.
In a mutually beneficial partnership, Heidelberg Materials collaborates with Ascendant, a seasoned expert in concrete demolition based in Puyallup, Washington. Ascendant's proficiency in concrete rubble management aligns seamlessly with Heidelberg Materials' goal of sourcing high-quality RCA for concrete production. Ascendant's ongoing demolition projects in the Greater Seattle Area, including the Interstate 405 widening project and City of Seattle renovations, generate substantial concrete demolition materials that are repurposed as RCA at Heidelberg Materials' Redmond Recycle plant, ensuring compliance with WSDOT and City of Seattle specifications for sustainable concrete reuse.
Ascendant's involvement in key demolition projects, such as the May Creek Bridge in Renton and the Lake Washington Boulevard overpass in Seattle, underscores the company's dedication to sustainable practices and circular economy principles. By supplying demolition materials for RCA production, Ascendant contributes to the creation of environmentally friendly concrete mixtures that meet stringent performance criteria, further solidifying the partnership's role in advancing sustainable infrastructure development in the region.
