Construction and maintenance of roads requires large volume of aggregates for use as base and subbase
materials. Because of the cost of virgin aggregates, federal and state agencies are encouraging the
recycling of waste materials including materials in old pavements. This study assessed the suitability of
four recycled materials relative to virgin aggregates for use as base and subbase materials. The four
recycled materials were the reclaimed asphalt pavement (RAP), fly ash (FA), reclaimed concrete material
(RCM), and foundry sand (FS). Assessment of these materials was done in terms of their hydraulic,
mechanical, and leaching properties when mixed in with various proportions of virgin aggregates. Except
for slightly higher fine content in some RAP-aggregate mixtures, particle size distribution of all mixtures
was within the Mn/DOT specification band for Class 5 materials. Water retention (pore size distribution),
hydraulic conductivity, resilient modulus, and shear strength measurements were generally similar to that
of 100% aggregates. Exception was the mixtures of FS. Heavy metal concentrations in the leachate were
also generally less than the EPA drinking water standards. We concluded that FA, RAP, and RCM
mixtures will be good substitutes of virgin aggregates as base and subbase materials.
Gupta, Satish; Kang, Dong Hee; Ranaivoson, Andry.
Hydraulic and Mechanical Properties of Recycled Materials.
Minnesota Department of Transportation.
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