Effect of Selective Demolition and Recycling Method on Properties of Recycled Concrete Aggregates
摘要
Recycled concrete aggregates are rarely used in infrastructure projects for high-grade applications. Specifically, in the Netherlands the natural coarse aggregates may be partially replaced by recycled concrete aggregates (RCA) up to a maximum replacement percentage of 30% (by volume) in high strength concrete ≥ C40/50 and in environmental classes XD, XF and XS. The Dutch Ministry of Infrastructure, Rijkswaterstaat (RWS), initiated a framework “Proeftuin Recyclaat” where pilot studies are conducted to understand the impact of parent concrete quality and use of advanced recycling techniques on quality of RCA generated in RWS demolition projects. These combined efforts are expected to increase the allowable replacement percentages of natural aggregates with RCA, not only for coarse aggregates but also to support the use of high-quality fine RCA. In this context, “high-quality” means that RCA can be used in future high-performance structural concrete with a required lifespan of 100 years. In the present study, RCA resulting from selective demolition of known quality of parent concrete was characterized. The test materials were selectively produced from demolished T-prestressed girders, columns, abutments, and foundations, all from one viaduct. The concrete rubble was recycled using two advanced recycling techniques Smart Liberator and Mangeler (0–0.125 mm, 0.125–4 mm, 4–22 mm), as well as a traditional rotor/impact technique (0–4 mm, 4–22 mm). Aggregate quality is measured in terms of product physical and chemical properties. Special attention was paid to the properties of RCA such as chemical composition, increased aggregate recovery, water absorption, and the Los Angeles coefficient. A systematic valorization of all particle size fractions was suggested based on the quality of the RCA used. The high potential to develop high-quality structural concrete using RCA as a total replacement for natural aggregates was outlined.