Performance of granular road base and sub-base layers containing recycled concrete aggregate in different ratios

Abstract

In this study, the usability and performance properties of recycled concrete aggregates (RCA) as granular road base (GRB) and granular road subbase (GRSB) material were investigated. A natural aggregate and the RCAs obtained from concretes with three different compressive strength and mixtures created by adding the RCAs to NA at the ratios of 25, 50 and 75% were used. Physical properties, modified Proctor, resilient modulus, permanent deformation, California bearing ratio (CBR), and permeability tests were carried out on all mixtures. Resilient modulus values (M-r) were obtained using three different resilient modulus models. The highest M-r value among pure RCAs was observed for RCA2 (average of 200 MPa). For the mixture samples, the highest M-r values were obtained in the mixtures containing RCA1 (average of 250 MPa). The minimum of permanent deformation value (epsilon (p) ) for the mixtures was obtained when the ratio of the RCA1 in the mixtures was 50% (epsilon (p) = 0.238%). The obtained CBR values were not related to the M-r values, and the highest CBR values were found for the pure RCAs (average of 126%). High permeability coefficient values (average of 9.973x10(-6) m/s) were obtained for the RCAs. As a result, it was more appropriate to blend the RCAs with the natural material rather than to use them in pure form. In general, it was appropriate to use 50% of RCAs in the mixtures. It was observed that if concrete compressive strength is as high as in RCA1 (18.5 MPa), RCA can be used even in the mixture at a ratio of 75%.