Abstract
Tests were performed on asphalt concrete specimens with (101.6 mm in diameter and 101.6 mm in height), and the results were implemented for calculating permanent deformation and resilient modulus under repeated compressive stress with different levels of stresses (0.068, 0.138 and 0.206) MPa at 40 ºC. Two types of additives namely (carbon black-asphalt) and (SBR-asphalt) were tried as rejuvenators with three percentages of (0.5, 1 and 1.5) % by weight of asphalt cement along with two ratios of AC (1 and 2) % have been implemented as rejuvenator and blended with the reclaimed asphalt concrete. Aged materials were obtained from the site. 100% Reclaimed Asphalt Pavement material from the reclaimed mixture is implemented. A set of (3) specimens were prepared for every mixture; three specimens were tested under (repeated compressive stress) at each level of stress. The objective of this work was to study the effect of two types of additives (Styrene-Butadiene-Rubber (SBR) and carbon black) on the performance of recycled asphalt concrete mixture. It was concluded that the Resilient modulus (Mr) at (0.138 and 0.206) MPa stress level decreases by (14, 22 and 8) % and (22, 34 and 11) for reclaimed and recycle mixtures with (carbon black-asphalt and SBR-asphalt) respectively when compared with that at 0.068 MPa. Permanent deformation for recycled mixtures with (carbon black-asphalt and SBR-asphalt) increased by (65.9, 4.54) %, (146.6, 27.2) % and (79, 5.5) % at level of stresses (0.068, 0.138 and 0.206) MPa respectively when compared to reclaimed mixture.
Highlights
CHARACTERISTICS OF USED MATERIALS 2.1 Aged Materials The Reclaimed asphalt mixture was obtained by the rubblization of the asphalt concrete from the highway section in The Second Hindiyah Bridge which is located in the city of Tuwerij at Karbala province
The variances between samples were in a slight degree, and the average gradation of the two samples obtained to be the aged aggregate gradation is shown in Table 2 which demonstrates the gradation of job mix formula during construction of highway and reclaimed aggregate for binder layer which falls within Specification limits of Roads and Bridges, (SCRB, 2003)
2.2.1 Asphalt cement blended with carbon black Asphalt cement of penetration grade (40-50) from Al-Dura refinery was mixed with 1.5% of carbon black which was obtained from local market
Summary
Asphalt binder loses many of its oil components during construction and service, resulting in a high proportion of asphaltenes in the blend, which leads to increased stiffness and viscosity of the binder and decreases ductility, making the binder more hard and brittle. To recycle this hard and brittle aged pavement, the asphalt must be returned or changed to have the rheological properties of the original asphalt. Asphalt cement was heated to approximately 110oC, and the SBR was added gradually to the asphalt cement with thrilling until homogenous blend was reached, the mixing and thrilling sustained for thirty minutes by a mechanical blender.
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