The use of gabbro dust in the cold recycling of asphalt paving mixes with foamed bitumen

Abstract

Abstract Mineral fines are a waste product of aggregate production in quarries and asphalt mixing plants. The incorporation of mineral gabbro dust into foam bitumen causes developing of a mesh reinforcement in the recycled base mixture. This mesh reinforcement, observed in a recycled base structure, induces an increase in stiffness modulus, where its elastic part of complex modulus dominates over the imaginary part. Therefore, it is possible to create a recycled mixture with a lower susceptibility to loading time/temperature. In result, the presence of gabbro dust in recycled mixture limits the magnitude of strains induced by the traffic load. This paper presents the results of the tests carried out on the mineral dusts derived from gabbro rock. Structural and functional properties of the fines were determined to prepare their characteristics. Then, the cold recycled mixtures for the road base were designed with the 5–20% mineral fines content. The mixtures were prepared in cold recycling technology with foamed bitumen. Further tests involved determining mechanical and physical properties of the recycled mixes, including air voids content, Marshall stability, Marshall quotient (stiffness), indirect tensile strength and stiffness modulus at 20°C). The results indicated a positive influence of the gabbro dusts on the investigated parameters. With the use of ANOVA tests, the significance of the influence of the gabbro dust and foamed bitumen on these properties was evaluated. Harrington’s multicriteria method was employed to establish gabbro dust and foamed bitumen amounts, the addition of which would guarantee optimal properties of the recycled base mixture.