2013 Session: 467

• Use of Moisture-Induced Stress Testing to Evaluate Stripping Potential of Hot-Mix Asphalt
  Abstract: Stripping of hot mix asphalt (HMA) in the field is an ongoing issue for many Departments of Transportation (DOTs). A leading cause of stripping is hydraulic scouring. The Moisture Induced Stress Tester (MIST) is a recently developed technology that applies alternating pressure and vacuum cycles to submerged asphalt samples to mimic hydraulic scouring. The objective of this study was to differentiate six HMA mixes used by Maine DOT in terms of their moisture susceptibility using the latest MIST technology and field cores. Half of the field cores were conditioned in the MIST. Before and after conditioning visual observations were made, and the bulk specific gravity and resilient modulus were determined using the CoreLok and ASTM D4123, respectively. All conditioned and unconditioned samples were tested for indirect tensile strength (ITS) in accordance with ASTM D 6931. Values from before and after conditioning were compared by HMA mix. It was determined that the MIST conditioning process does cause moisture damage to the samples in a manner that mimics hydraulic scouring. It is recommended that further research be carried out to investigate the effect of the MIST on HMA cores, and that parameters be developed for characterizing the results of the MIST conditioning process. These results would also help in the development of standard specifications for the use of MIST
  Authors: Pinkham, Rudy; Cote, Sarah Ann; Mallick, Rajib B.; Tao, Mingjiang; Bradbury, Richard L.; Regimand, Ali
  Authors: Pinkham, Rudy; Cote, Sarah Ann; Mallick, Rajib B.; Tao, Mingjiang; Bradbury, Richard L.; Regimand, Ali
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 467
  Paper Number: 13-4538
• Effect of Warm-Mix Technologies and Testing Protocol on Moisture Susceptibility of Asphalt Mixtures
  Abstract: Moisture susceptibility of asphalt mixtures is a commonly addressed concern in mixture designs. As the industry shifts toward the use of warm mix asphalt (WMA) technology from the traditional hot mix asphalt (HMA) there has been increased concern regarding the performance of WMA technology in regards to moisture susceptibility. This concern is primarily driven by the decrease in required production temperatures of the asphalt mixtures which may result in aggregates that have not been dried thoroughly prior to being coated with asphalt binder. To assess this concern, 87 mixtures were evaluated for their resistance to moisture damage using the most common laboratory tests for assessing such damage: AASHTO T 283 and AASHTO T 324. In addition to WMA moisture susceptibility performance, the acceptability of the standard test protocols for moisture testing of asphalt mixtures were evaluated by comparing laboratory performance thresholds to the field performance of the mixtures. As a result of this study, it was determined that there was no statistical difference between field compacted specimens versus laboratory reheated specimens for TSR and HWTD results. WMA consistently showed statistically lower TSR and SIP compared to HMA control mixtures. The current specification criteria for HWTD may need to be adjusted assessing moisture susceptibility of WMA since several mixtures failed in the lab but showed good performance in the field.
  Authors: Leatherman, Kristoffer; Willis, James Richard
  Authors: Leatherman, Kristoffer; Willis, James Richard
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 467
  Paper Number: 13-4673
• Ranking of HMA Moisture Sensitivity Tests in Iowa
  Abstract: Several agencies specify AASHTO T283 as the primary test for field acceptance of moisture susceptibility in hot mix asphalt. When used in this application, logistical difficulties challenge its practicality, while repeatability is routinely scrutinized by contractors. An alternative test is needed which can effectively demonstrate the ability to screen mixtures based on expected performance. The ideal replacement can be validated with field performance, is repeatable, and allows for prompt reporting of results. Dynamic modulus, flow number, AASHTO T283, Hamburg wheel tracking device (HWTD), and the moisture induced sensitivity test (MIST) were performed on plant produced surface mixes in Iowa. Follow-up distress surveys were used to rank the mixes by their performance. The rankings indicate both the quantity of swelling from MIST conditioning and submersed flow number matched the performance ranking of all but one mixture. Hamburg testing parameters also appear effective, namely the stripping inflection point and the ratio between stripping slope and the creep slope. Dynamic modulus testing was ineffective, followed by AASHTO T283 and ratios produced from flow number results of conditioned samples.
  Authors: Schram, Scott Alan; Williams, Ronald Christopher
  Authors: Schram, Scott Alan; Williams, Ronald Christopher
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 467
  Paper Number: 13-4750
• Continuum-Coupled Moisture-Mechanical Damage Model for Asphalt Concrete
  Abstract: Despite the detrimental effects of moisture damage, few macro-scale models exist that are capable of modeling moisture-induced damage in asphalt concrete. These models neither account for the irreversibility of moisture-induced damage nor for time-dependency of moisture damage. In this study, a continuum moisture damage model based on the continuum damage mechanics (CDM) is presented. Both adhesive and cohesive moisture damage phenomena are modeled independently, which allows one to introduce fundamental mechanical properties for each process and model the transition between adhesive and cohesive damage. 2D and 3D simulations are performed and the results of the simulations presented to demonstrate the applicability and utility of these micromechanical computational models. Though the constitutive model presented here is developed to model asphalt concretes as a continua, it is shown that it is well-suited to asphalt mastic, which exhibits time-dependent recoverable and irrecoverable deformations, and degrades with loading and moisture exposure.
  Authors: Shakiba, Maryam; Abu Al-Rub, Rashid K.; Darabi, Masoud K.; You, Taesun; Masad, Eyad A.; Little, Dallas N.
  Authors: Shakiba, Maryam; Abu Al-Rub, Rashid K.; Darabi, Masoud K.; You, Taesun; Masad, Eyad A.; Little, Dallas N.
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 467
  Paper Number: 13-4763
• Effect of Warm-Mix Technologies and Testing Protocol on Moisture Susceptibility of Asphalt Mixtures
  Authors: Willis, James
  Authors: Willis, James
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 467
  Paper Number: 13-4673
• Continuum-Coupled Moisture-Mechanical Damage Model for Asphalt Concrete
  Authors: Shakiba, Maryam
  Authors: Shakiba, Maryam
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 467
  Paper Number: 13-4763
• Use of Moisture-Induced Stress Testing to Evaluate Stripping Potential of Hot-Mix Asphalt
  Authors: Pinkham, Rudy
  Authors: Pinkham, Rudy
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 467
  Paper Number: 13-4538
• Ranking of HMA Moisture Sensitivity Tests in Iowa
  Authors: Schram, Scott
  Authors: Schram, Scott
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 467
  Paper Number: 13-4750