Field Performance Evaluation of High Polymer-Modified Asphalt Concrete Overlays

The objective of this paper was to assess the viability of using high polymer (HP) modified asphalt concrete (AC) mixtures in Virginia as a reflective crack mitigation technique or when deemed appropriate as a tool for increased crack resistance on higher volume facilities. This was achieved by compiling and evaluating routine distress survey data against pre-paving distress survey data for relevant in-service HP pavements constructed between 2015 and 2018 and comparing them with several control in-service conventional polymer-modified asphalt (PMA) pavements. This is the first effort in North America to provide a detailed field performance of HP AC mixtures. In general, none of the evaluated mixtures (HP or PMA) was able to prevent reflective cracking completely. The HP sections showed the most promising performance 5 years after construction regardless of traffic level and the pre-existing pavement conditions. The pavement management system data for the reviewed sections indicated a potential controlling effect of the joint condition of the underlying jointed concrete pavement layer regardless of the asphalt mixture type employed (PMA or HP). Moreover, performance evaluations using the network-level pavement management data were conducted to estimate the life expectancy of HP AC overlays. Two different approaches and three levels of analysis were undertaken. Overall, PMA and HP AC overlays had an average predicted service life of 6.2 and 8.3 years, respectively, indicating a 34% extension of performance life of the AC overlays with high polymer modification.

High-Temperature Property Evaluation and Index Research of Modified Asphalt before and After Aging

In order to better evaluate the composite modified asphalt of composite modified asphalt, this study through dynamic shear rheological (DSR) test, the three kinds of polymer modified asphalt before and after ageing: the compound modified asphalt (CCR), rubber powder modified asphalt (CR) and composite modified asphalt of SBS modified asphalt (SBS) analysis, to explore suitable for composite modified asphalt of modified asphalt evaluation index. The results show that: Compared with G*/sinδ, G*/(sinδ)9 has higher accuracy for evaluating the composite modified asphalt of polymer modified asphalt and is more sensitive to changes in phase angle. The critical temperature of anti-rutting factor TG*/sinδ9 is significantly higher than that of TG*/sinδ, especially for composite modified asphalt. This has an important impact on the PG classification in the Superpave asphalt binder specification. G*/sinδ underestimates the high temperature grade of the modified asphalt. The equivalent viscosity measured with η’ = sinδ-4.8628 G*/ω has the best correlation with the anti-rutting factor G*/(sinδ)9, and the highest correlation coefficient is 0.999, which is more suitable as a high-temperature property evaluation index of modified asphalt.

Multi-Level Laboratory Performance Evaluation of Conventional and High Polymer-Modified Asphalt Mixtures

Asphalt concrete (AC) overlays have been one of the most common treatments used by the Virginia Department of Transportation (VDOT) for maintaining/rehabilitating pavements. However, when the overlay is placed on existing composite pavements or cracked AC pavements, differential movements across any cracks or joints can result in physical tearing of the AC overlay. Thus, the long-term performance of many AC overlays will highly depend on their ability to resist cracking. The purpose of this study was to assess the viability of using high polymer-modified (HP) AC mixtures in Virginia as a crack mitigation technique or when deemed appropriate as a tool for increased resistance to rutting and cracking on higher volume facilities. Another objective was to assess the ability of various testing protocols to discern the performance of pavements through a comprehensive evaluation of three conventional polymer-modified (PMA) and five HP field-produced mixtures placed in Virginia. This included laboratory testing at multiple levels of complexity (basic, intermediate, and advanced) on collected asphalt binders, plant-produced asphalt mixtures, and field cores. The performance characteristics of PMA and HP mixes were evaluated in the laboratory in relation to durability and resistance to rutting and cracking. Based on the mixes tested, stone matrix asphalt (SMA) mixes showed better performance than dense-graded surface mixes (SM) regardless of the asphalt binder type. Moreover, HP mixes showed better performance than PMA mixes regardless of the mixture type. Overall, SMA-HP mixes showed the most promising performance among all evaluated mixes.

The Use of Steel Slag as Substitution of Coarse Aggregate on Indirect Tensile Strength and Marshall Properties of AC-WC

High traffic levels on road can causing road damage, especially cases of permanent deformation and fatigue cracking. One solution is to utilize waste of material, such as steel slag as coarse aggregate and polymer modified asphalt as binding material. This paper explores experimental laboratory investigation on the use of steel slag on Marshall characteristics and indirect tensile strength of AC-WC mixture by using Starbit E-60 and Pen 60/70. Laboratory works begin with physical testing of material, then, finding the optimum bitumen content (OBC) for each type of the mixtures. Finally, Marshall Standard and indirect tensile strength (ITS) at OBC were conducted. Results shows that the use of steel slag for AC-WC mixture are proven to improve resistance to permanent deformation as well as fatigue cracking. Substitution of steel slag for coarse aggregates were able to increase Marshall stability, Marshall Quotient and indirect tensile strength (ITS) of the mixtures, however, it slightly decreases the volumetric performance of mixture, such as voids in total mixes become higher and voids filled with asphalt as well as voids in mineral aggregates tend to decrease.