Detection of Reclaimed Asphalt Pavement Presence in Asphalt Mixtures Using a Method of Successive Asphalt Binder Extraction

The work deals with the detection of presence of RAP (reclaimed asphalt pavement) in asphalt mixtures. Information about the presence of RAP in an asphalt layer can be technically advantageous, for example, when planning further recycling of the layer. The method described in the paper can also be used to verify the success of a treatment of an aged binder in RAP, which is dosed in the production of new asphalt mixtures. The asphalt binder was obtained by a method of successive extraction from asphalt mixtures with different RAP content. Basic empirical tests of the asphalt binder (needle penetration and softening point) were chosen to detect the presence of RAP. The complex shear modulus G* was further determined on the extracted binders using a dynamic shear rheometer (DSR).

Quantification of the Effect of Binder Source on Flexibility of Long-Term Aged Asphalt Concrete

Asphalt concrete (AC) aging reduces the resistance of flexible pavements to fatigue, thermal, and block cracking. Therefore, it is critical to understand the effects of AC aging on flexible pavement serviceability. Binder source has a significant effect on AC long-term aging. Therefore, it is necessary to develop a reliable, practical, and systematic method to quantify the effect of binder source on AC cracking resistance. Seven laboratory mixes were designed and produced at three asphalt binder replacement (ABR) levels using various binders, but same binder performance grade (PG). The AC mixes were tested using the Illinois Flexibility Index Test (I-FIT) under unaged and long-term aged conditions. Standard Superpave tests and temperature-frequency sweep tests, were conducted on virgin binders under various aging conditions. By comparing the binder rheological parameters and flexibility index (FI) of long-term aged AC specimens, the [Formula: see text] and m-value after 40-h of aging using a pressure aging vessel (PAV) were identified as valid indicators to reflect the effects of the binder source on AC long-term flexibility. A minimum [Formula: see text] of -8°C and m-value of 0.280 were proposed as the preliminary thresholds. A new parameter, [Formula: see text], which is defined as the m-value of 20-h PAV-aged binder minus the m-value of a 40-h PAV-aged binder, correlates well with the aging rate of AC. A binder with a high [Formula: see text] may induce an excessive drop in flexibility after long-term aging.

Influence of Antistripping Additives and Rejuvenators on Healing Performance of Moisture-Damaged HMA

This study aims to evaluate the effect of different rejuvenators and antistripping agents on the healing performance of hot mix asphalt (HMA). Two damage HMA series (e.g., moisture damage and aged damage) were subjected to either induction or microwave heating. A PG64-22 virgin and aged binder were used and modified with several additives. Three long-term aged binders (e.g., PAV5, PAV15, and PAV20) were conducted by pressure aging vessel (PAV) test. The moisture damage series fabricating with a new binder was further categorized into four different freeze-thaw (FT) cycles (e.g., 0FT, 1FT, 3FT, and 5FT). Also, the aged series was fabricated with three different aged binders. A total of eight damage-healing cycles were applied to all asphalt mixtures, examined by the three-point bending test. The moisture resistance of modified asphalt mixture was examined by indirect tensile strength test. Overall, asphalt mixtures modified with either antistripping additives or rejuvenators not only obtained higher moisture resistance but also gained better healing performance under moisture damage. In addition, the study showed a probable correlation between moisture damage and long-term aging in terms of healing performance, such as PAV15 and 3FT cycles and PAV20 and 5FT cycles.

Variability of Reclaimed Asphalt Pavement (RAP) Properties within a State and Its Effects on RAP Specifications

Reclaimed Asphalt Pavement (RAP) is a highly recyclable material that provides a source of aggregates and asphalt binder to be re-utilized in new paving mixtures. State transportation agencies in the U.S. have constructed their specifications to allow for the use of RAP in new paving mixtures, but with conditions so that suitably performing mixtures are developed. These conditions are imposed because of concerns that the aged binder contained within the RAP may negatively impact the resultant mixtures performances. Many state transportation agencies have constructed their specifications with respect to the AASHTO guidance on utilizing RAP in Superpave mixtures. Questions remain as to the accuracy of these methods, especially if the RAP stockpiles’ properties vary greatly. The purpose of this study was to characterize and compare the properties of the RAP stockpiles being used throughout Massachusetts and to determine the impacts that these properties have on the currently utilized specifications for RAP. The properties of the RAP stockpiles within Massachusetts varied greatly. No geographical or regionalization of RAP properties could be made. By default, the current specifications for using RAP makes no distinction between RAP stockpile properties, especially at smaller percentages like <15% or at low RAP binder ratios (RAPBR). The data from this study demonstrated that this could lead to mixtures without the appropriate virgin binder grade and therefore they could exhibit subpar performance. Specifications should be revised to require more thorough testing of RAP for each mixture design, regardless of the allowable percentage or RAPBR, to ensure adequate mixture performance is maintained.