Heidelberg Materials North America has expanded its portfolio with the introduction of RevolveTM recycled concrete aggregates. It is also assigning specialists within the company to partner directly with departments of transportation and other agencies so that team-wide knowledge and engineering capacity can be developed.
The move follows legislation passed by the state of Washington encouraging the use of recycled concrete aggregate (RCA) in the state’s roadways. Both the Washington Department of Transportation (WSDOT) and the City of Seattle followed this lead by establishing goals for the use of RCA in their standard specifications. According to Heidelberg Materials, the City of Seattle now allows up to 30 per cent replacement of coarse aggregate using RCA in concrete paving, and WSDOT’s specification recently increased the allowable RCA for use as coarse aggregate for concrete pavement to 100 per cent.
“At Heidelberg Materials, we’re starting with 30 per cent RCA as a baseline test for the City of Seattle,” said Sterling Frye, senior area production manager, Northern Washington Recycle, Heidelberg Materials. “Using RCA such as our Revolve line of products to make concrete mixes for paving is a fairly new thing for the industry overall, and at Heidelberg Materials we began laboratory testing of our paving application mix in 2023. We plan to roll out incremental increases of 10-20 per cent on a month-to-month basis, until we have fully tested and are comfortable with RCA at 100 per cent levels.”
Heidelberg Materials’ Pacific Northwest roll-out plan follows the successful procedure established in 2020 when testing general purpose mixes used for foundations, stem walls and interior slab on grade. Currently, Heidelberg Materials’ general purpose mixes incorporate 50 per cent RCA, replacing virgin coarse aggregates. Mixes for paving applications will have to meet more stringent requirements for high, early strength as well as have air entrainment to resist freeze-thaw and prove durable for exposure to weathering.
To meet both City of Seattle and WSDOT specifications, it is vital to test for compressive and flexural strength and air content. In addition to laboratory testing, “truck trials or test pours are often important for paving applications, partly because they are labor-saving. Lab tests are conducted on small batches and are very manual, whereas a test slab can pour a truck load up to 10 cubic yards. An important factor in a test pour is that the contractor will use the actual tools he plans to use in the field on his job site, enabling him to get real world results with the current conditions of temperature and humidity,” added Mr Frye.
