Carlson A, Jensen T, Lund AF, Dave EV, Saftner DA. MS projects from partnership with city government, in ASEE Annual Conference and Exposition, Conference Proceedings. Indianapolis, IN, United states ; 2014 :Dassault Systemes (DS); et al.; Kaplan; National Instruments; NCEES; Quanser -.Abstract
The availability of mineral aggregates for pavement construction is continuously depleting. The aggregate manufacturing process requires significant amounts of energy, which ranges from 10 to 30 MJ/ton. The process also produces 5 kg/ton of carbon dioxide (CO<sub>2</sub>), which causes significant amounts of greenhouse gas emissions. With the annual consumption of approximately 1.2 billion tons of aggregates in the United States, the environmental impact is significant. More than 125 million tons of fine-grained, crushed siliceous material is generated annually through iron ore mining in northern Minnesota. Typically, this material is referred to as "taconite tailings" and usually ends up as landfill near mining operations. This paper describes a moisture damage evaluation of asphalt mixes that contained significant fractions of aggregate as taconite tailings. The evaluation was conducted with the use of the conventional AASHTO T 283 test procedure as well as an approach with a fracture energy basis. The paper presents comparative results for two mixes: one made with taconite tailings and the other with conventional granite aggregates. The results indicated that a mix that contained taconite had acceptable moisture-damage resistance. The results also pointed out the limitations of the AASHTO T 283 procedure, especially the process of moisture conditioning. The fracture energy results indicated that, although mixes underwent reduced tensile strength, the overall capability of mix to strain without cracking significantly increased after the AASHTO-recommended moisture conditioning process. The study also included a set of samples that were field-conditioned over the winter and spring months. The mechanical behavior of field-conditioned samples was quite different from the behavior of samples conditioned in the laboratory with the AASHTO procedure.
Significant increases in the cost of asphalt paving and increased awareness of the need for sustainable infrastructure in recent years have in turn increased the use of recycled asphalt pavement (RAP) in the manufacture of hot-mix asphalt (HMA). The use of RAP reduces the overall cost of HMA and provides significant environmental benefits. Experience has shown, however, that the addition of RAP to HMA can have a negative effect on the low-temperature fracture characteristics of the pavement. The purpose of this study was to determine the effects of RAP amounts on the low-temperature cracking performance of asphalt mixtures. Different percentages of RAP material, ranging from 0% to 50%, were studied. The embrittlement temperature of mixtures was determined with the use of an acoustic emissions technique. The disk-shaped compact tension [DC(T)] test was used to determine the fracture energy of asphalt mixtures. DC(T) fracture tests were conducted on two control mixtures with no RAP and mixtures that contained 10%, 20%, 30%, 40%, and 50% RAP. Both control and RAP mixtures were manufactured with PG 64-22 and PG 58-28 as the virgin binders, which brought the total number of mixtures tested to 12. In addition to DC(T) fracture testing, indirect tensile testing was conducted on HMA specimens that contained 20% and 40% RAP. Test results clearly indicated the effects of the presence of RAP materials on the low-temperature performance of mixtures. This study demonstrates the benefit of performing fracture tests before RAP is added to the asphalt mixture, and it demonstrates the use of an acoustic emissions-based testing procedure to screen mixtures susceptible to cracking at low temperatures.
Low temperature or thermal cracking in asphalt concrete pavements is a major cause of pavement deterioration. Fundamental fracture evaluation of asphaltic materials is necessary in order to design pavements that are resistant to thermally induced cracking. At present, stress-strain response of asphalt binders within the linear material behavior range is commonly utilized in criteria for material acceptance. The fracturing of a material is a highly complicated phenomenon, and evaluation of the material beyond the linear response range will help close the gap between experimental results and actual field performance. In recent years it has been well established that at low temperatures asphalt mixtures behave in a quasi-brittle manner. For complete evaluation of asphalt mixture cracking performance, it is necessary to consider mixture response past the peak strength. In the present work, a set of nine mixtures, encompassing a variety of variables, including type of binder modification, presence of recycled asphalt pavement (RAP), and low temperature binder grade, are studied to assess their fracture behavior in light of two new fracture testing techniques. Testing was conducted in two stages; fracture energy measurements were obtained using the disk-shaped compact tension (ASTM D7313) test. Fracture energies were determined at two temperatures, two air void levels and two levels of age conditioning. Fracture energy testing was followed by acoustic emissions (AE) evaluation to characterize low temperature cracking behavior of the asphalt mixtures. The AE testing procedure, which has been demonstrated to successfully capture low temperature behavior of asphalt binders, was extended to include low temperature characterization of asphalt mixtures. Testing results also quantify the effects of RAP on low temperature fracture behavior and provide new insights on the effects of commonly used binder modifiers on mixture fracture behavior.
This paper describes a comprehensive investigation of strain tolerant type reflective crack relief interlayer systems through fundamental laboratory testing, computer aided design, and accelerated pavement testing. One of the widely used methods to control the reflection of cracks from underlying, cracked pavement into a new asphalt overlay involve the use of conventionally paved 'interlayers' that tolerate the very high tensile and shear strain that exists above cracks and joints in the underlying pavement. While these systems often slow down the rate of reflective cracking relative to untreated control sections in the field, when cracks do appear they are often offset from the location of the underlying discontinuity. A recently completed study sponsored by the National Science Foundation led to the development of a new fracture test (ASTM D7313-07b - the Disk-Shaped Compact Tension Test for Asphalt Concrete) and new techniques for finite element modeling of fracture in asphalt overlay systems. After successful validation of these tools on three field projects, it was decided to conduct further validation using the Advanced Transportation Loading System or ATLAS device and to experiment with new overlay configurations. A large experimental matrix was used to select promising interlayer materials and pavement layer and joint configuration details using finit e element analysis. A 500 ft(165 m) test pavement was constructed, instrumented, and tested in the cold of winter in 2008. This paper describes this comprehensive investigation, the new test sections developed, the types of distress observed under accelerated loading, and how the results were used to validate a new mechanistic analysis and design tool. Moreover, significant new insights towards the mechanisms and prevention of reflective cracking were obtained and have been summarized.