Permeability and Compaction Properties of Recycled Concrete Aggregates as Granular Road Base and Sub-Base

Abstract

Recycled concrete aggregates (RCA) can be used as granular road base (GRB) and granular road sub-base (GRSB) in highway constructions. Thus, the use of RCAs which are waste materials contributes to sustainable economy. But RCAs must meet certain requirements for use in GRB and GRSB. Adequate drainage capability, which is one of these conditions, is important for draining surface water. In this study, drainage capabilities of RCAs produced from concrete from 3 different buildings were compared with crushed aggregate (CA) and natural aggregate (NA). In order to carry out the tests, 23 different designs consisting of mixture and pure forms of the materials were established. The permeability tests were carried out with falling head and constant head permeability equipment to evaluate permeability coefficients. The samples were prepared in the permeability molds by compression at maximum dry unit weight (ɣkmax) and optimum moisture content (wopt), which are the compaction parameters obtained from modified Proctor test. For this reason, wopt and ɣkmax were determined by modified Proctor test before conducting the permeability tests. As a result, it was observed that RCAs had higher wopt values and lower ɣkmax values than the NA and CA. It was determined that the permeability coefficients obtained by the permeability tests of the NA were very low and the permeability coefficients of the CA and RCAs were close to each other and higher than the NA. The fact that the RCAs had a permeability coefficient close to the CA indicates that drainage capability can be sufficient if RCAs are used in GRB and GRSB.