United States Department of Transportation
i
Evaluate Recycled Concrete as Hot Mix Asphalt Aggregate
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2011-06-01
[PDF-883.66 KB]
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Abstract:Each year around 200 million tons of demolition waste is produced from aging US infrastructures out of which 100 million tons are Portland cement concrete debris. The lack of landfill areas, environmental regulations and costs have hindered safe disposal of this waste. This led to seeking alternate ways of recycling this demolition waste. Recycling the concrete waste not only reduces the waste disposal problem, but also reduces the amount of quarrying of virgin aggregate. This study evaluated the effects of recycled concrete aggregates on mix design and performance of HMA. It was found that the use of recycled concrete aggregates to replace virgin aggregates increased the asphalt content needed in the mix, due to the high absorption of recycled concrete aggregate. In addition, with the increase of content of recycled concrete aggregate, the resistance to fatigue, rutting, thermal cracking and moisture damage is reduced. Therefore, cautions should be made to use recycled concrete aggregate in HMA, even though the volumetric requirements are met. The Superpave volumetrics-based mix design is not sufficient to capture the performance of mixes and should be supplemented with performance-based tests. The concept of “effective” asphalt content during a mix design might not be accurate. The absorbed asphalt may play a role in the performance of HMA. Further studies are needed to test more sources of recycled concrete aggregates in HMA and to verify the shortcomings of volumetrics-based mix design.
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