1. Evaluation of Recycled Concrete as Aggregate in New Concrete Pavements Research Agencies Haifang Wen David McLean Washington State University Colorado State University Researchers Washington State Department of Transportation Students: Spencer Boyle, Tim Spry and Danny Mjelde

2. Why was the research performed? To evaluate recycled concrete aggregate (RCA) as a replacement for virgin aggregate in new concrete pavements – RCA was used as a replacement of coarse virgin aggregate up to 45% (0, 15, 30 and 45%) With and without fly ash (0 or 20%) Goal: determine if RCA can be used for new concrete pavement construction and what precautions, if any, are necessary

3. Research Performed RCA as an aggregate was tested for properties such as specific gravity, absorption, abrasion, degradation and alkali-silica reactivity Fresh concrete samples were tested for slump, air content and density Hardened concrete samples were tested for compressive strength, modulus of rupture, coefficient of thermal expansion, drying shrinkage and freeze-thaw durability

4. Research Results RCA as an aggregate met all requirements but needs to be processed first – Has higher absorption capacity and lower specific gravity that virgin aggregate Fresh concrete properties can be met while using RCA – RCA had no significant effect on air content Hardened concrete properties can be met while using RCA – Up to 45% replacement of coarse aggregates with no significant drop

5. Research Recommendations RCA can be used as a replacement for coarse virgin aggregate in new concrete pavement Fresh concrete workability can be a problem, but can be overcome with water-reducing admixtures and/or fly ash Alkali-silica reactivity of the RCA needs to be tested following the crushing process and mitigated if necessary More research necessary if greater than 45% RCA used

6. Implementation Status/Strategy WSDOT plans to construct a test section utilizing RCA in a new concrete pavement…when we actually have the money to construct new concrete pavement! – From this, performance criteria and specifications will be developed (if different criteria necessary with RCA)

7. Value of Implementing Research Save scarce natural resources Utilize quality aggregate from demolished concrete pavements as best value possible Save money by utilizing recycled materials All the above and not sacrifice quality of the concrete pavement

8. For more information, contact: Research Manager Kim Willoughby willouk@wsdot.wa.gov (360) 705.7978 Evaluation of Recycled Concrete as Aggregate in New Concrete Pavements (WA-RD 826.1) http://www.wsdot.wa.gov/research/reports/fullreports/826.1.pdf