Abstract
To evaluate the physical and rheological properties of rejuvenated styrene-butadiene-styrene-modified asphalt (SBSMA) binders designed for rapid in-place pavement recycling, an aged SBSMA binder was rejuvenated with three rejuvenators (i.e., Types I, II, and III) in different dosages. The physical properties of rejuvenated SBSMA were obtained to determine the optimal type and dosage of rejuvenators for the first and second rejuvenation. Performance grade (PG) tests, multiple stress creep recovery (MSCR) tests, and linear amplitude sweep (LAS) tests were conducted to measure the rheological properties using the dynamic shear rheometer (DSR) and bending beam rheometer (BBR). The results exhibited that the rejuvenators could soften the multiple aged binder and enhance its high- and low-temperature performance. The rejuvenation effect of rejuvenator Type I with the optimal dosage of 6∼8% was the most appropriate for the first rejuvenation. The optimal dosage of the second rejuvenation was 10∼12%. The addition of rejuvenators decreased the rutting factor G∗/sin δ, creep stiffness (S), delta Tc (ΔTc) parameter, recovery response (R), and yield stress of rejuvenated SBSMA. On the other hand, an increase in the rate of relaxation (m-value), nonrecoverable creep compliance (Jnr), and yield strain of rejuvenated SBSMA was recorded. Overall, the study findings indicated an improvement in the elastic properties of rejuvenated SBSMA, which contributes to improving the rutting, thermal, and fatigue cracking resistance of asphalt binder and ultimately the response of asphalt pavements.
Highlights
Asphalt binder, which is a by-product of petroleum, is an essential material used in the construction of flexible pavements [1]
Because of the oxidation of the naphthalene aromatics and the polar aromatics, the ratio of asphaltene to maltene of aged SBSMA tends to increase [5]. e aged asphalt binder usually turns into a gel-type asphalt binder that exhibits low ductility, high stiffness, and high thixotropy [6]. e aging of SBS-modified asphalt binder is a combination of asphalt phase oxidation and polymer phase degradation [7]. e chain scission reaction at polybutadiene (PB) segments plays a primary role in the thermooxidative degradation of SBS polymer [8]. e PB segments containing the unsaturated double carbon bonds (C C) are easy targets to oxygen and degrade rapidly into smaller polymer chains under the effect of heat and ultraviolet light (UV) [9, 10]
(2) e rutting and cracking characteristics of the rejuvenated SBSMA were evaluated using dynamic shear rheometer (DSR) and bending beam rheometer (BBR). e addition of rejuvenator to aged SBSMA was found to decrease the high-temperature rutting resistances (G∗/sin δ) of the rejuvenated SBSMA. e rejuvenated SBSMA exhibited lower creep stiffness (S(t)) and a higher rate of relaxation values compared to aged asphalt binder
Summary
Asphalt binder, which is a by-product of petroleum, is an essential material used in the construction of flexible pavements [1]. Aging and degradation of the SBS-modified asphalt (SBSMA) binders under the actions of oxygen, sunlight, rainfall, and vehicle loading can detrimentally deteriorate the performance of asphalt mixtures and eventually lead to pavement failures [3, 4]. Because of increased modulus due to oxidation and low SBS modification, Advances in Materials Science and Engineering asphalt mixtures tend to be brittle with a high propensity to thermal and fatigue cracking [11, 12]. Because the performance evaluation of rejuvenated asphalt binders is often limited to traditional grading parameters such as viscosity, penetration, and softening point, another aim of this study was to evaluate the rutting and fatigue characteristics of rejuvenated SBSMA through measurement and quantification of their rheological properties using the MSCR and LAS tests
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