Influence of coarse recycled concrete aggregate on the durability of asphalt mixtures

Abstract

Until recently, coarse recycled concrete aggregate (RCA) has been used for the production of new concrete and soil stabilization, as well as for materials applied in road pavement construction, primarily for unbound base and sub-base layers. This paper presents the results of a study which objective was to assess the possibility of using coarse RCA in asphalt mixtures. The experimental research, shown in this paper, included testing of four asphalt mixtures made with coarse RCA (4/22.4 mm) as a partial substitution of natural aggregate, in the amount of 0% (control mixture), 15%, 30% and 45%, by mass. All asphalt mixtures were designed for the base course. The optimum bitumen content increased from 3.4%, for control and mixture with 15% RCA, to 3.5% for the mixtures with 30% RCA and 45% RCA. The rutting and fatigue resistance of asphalt mixtures with RCA were higher compared with the control mixture. Proportional rutting depth ranged between 3.9% and 4.8% for mixtures with RCA, while 5% was measured for the referent mixture. Estimated strain values for a lifetime of 106 load cycles increased from 124 με, for control mixture, to 129 με, 145.8 με and 137.4 με measured for mixtures with 15, 30 and 45% of RCA, respectively. Two out of three RCA mixtures had higher indirect tensile strength ratios, varying from +3% and +13.7% relative to the referent mixture. The results obtained by water resistance testing of mixture with 30% RCA were 4.7% lower than for the control mixture.