Evaluation of Cracking Indices for Asphalt Mixtures Using SCB Tests at Different Temperatures and Loading Rates

In recent years, there has been a shift towards implementing performance based pavement specifications (PBPS) to increase reliability of asphalt concrete mixture specifications and enhance service lives of roadways. Several of the performance indices used in PBPS are based on the asphalt mixture fracture tests. There is an increasing need for a better understanding the effects of temperature and loading rate interdependency for fracture properties of asphalt mixtures. The goal of this study is to build upon previous work conducted during a Summer Undergraduate Research Program (SURF) project entitled, “Exploration of Temperature and Loading Rate Interdependency for Fracture Properties of Asphalt Mixtures,” as well as to incorporate ongoing research studies at the University of New Hampshire (UNH). There are many proposed fracture indices including Fracture Energy (Gf), Illinois Flexibility Index (FI), Toughness Index (TI), Nflex, and Fracture Strain Tolerance (FST). The objective of this study is to evaluate different fracture indices and their variations with changes in test temperature and loading rates. Results from Semi-Circular Bend (SCB) fracture tests on five asphalt mixtures (from Vermont and Virginia) are being evaluated. All mixtures represent same aggregate maximum sizes and consist of varying amounts of Reclaimed Asphalt Pavement (RAP). Conclusions will be drawn on the effectiveness of each fracture index to distinguish and appropriately rank mixtures as well as on the variations of these indices with changes in test temperature and loading rates. On basis of this study, use of crack mouth opening displacements for fracture index calculations is recommended obtain better distinction of cracking performances between mixtures

Exploration of Temperature and Loading Rate Interdependency for Fracture Properties of Asphalt Mixtures

The importance of studying asphalt mixture and the effect of temperature on fracture properties to improve cracking performance, service life expectancy, and design effectiveness of roads is critical. The increased use of Reclaimed Asphalt Pavement and other additives in mix design requires greater understanding on the effects of loading rate and temperature on fracture behavior. The objective of this study was to assess interdependence of loading rate (time) and temperature on asphalt fracture properties and evaluate the adequacy of standard testing conditions. Evaluation consisted of 5 mixtures from two regional sources, Vermont and Virginia. Fracture tests were conducted through the Disk-shaped Compact Tension and the Semi-Circular Bending geometries using varying loading rates in an effort to study the applicability of the time-temperature superposition principle (TTSP). Comparisons were made between 4 combinations of temperatures and loading rates. The goal of this effort was to evaluate loading rate adjustments to compensate for changing test temperatures. Results indicated that linear viscoelastic TTSP is valid in the pre-peak region of asphalt fracture behavior. SCB test results at low temperature with an adjusted loading rate were able to match the pre-peak behavior

Realistic Traffic Condition Informed Life Cycle Assessment: Interstate 495 Maintenance and Rehabilitation Case Study

As construction costs continue to rise and adequate amounts of funding continues to be a challenge, the allocation of resources is of critical importance when it comes to the maintenance and rehabilitation (M&R) of highway infrastructure. A Life Cycle Assessment (LCA) methodology is presented here that integrates realistic traffic conditions in the operational phase to compare M&R scenarios over the analysis period of a 26-km stretch of Interstate-495. Pavement International Roughness Index (IRI) were determined using American Association of State Highway and Transportation Officials (AASHTO) PavementME System. Meanwhile, vehicle fuel consumption and emission factors were calculated using a combination of Google Maps®, the United States Environmental Protection Agency (EPA) Motor Vehicle Emission Simulator, the second Strategic Highway Research Program (SHRP2) Naturalistic Driving Study, and MassDOT’s Transportation Data Management System. The evaluation of pavement performance with realistic traffic conditions, varying M&R strategies, and material characteristics was quantified in terms of Life Cycle Cost (LCC), Global Warming Potential (GWP), and Cumulative Energy Demand (CED) for both agencies and users. The inclusion of realistic traffic conditions into the use phase of the LCA resulted in a 6.4% increase in CED and GWP when compared to baseline conditions simulated for a week long operation duration. Results from this study show that optimization of M&R type, material selection, and timing may lead to a 2.72% decrease in operations cost and 47.6% decrease in construction and maintenance costs

Casein degradation and peptide formation in cheeses made with Micrococcus sp. INIA 528 milk cultures and high enzymatic activity curds

The effect of milk inoculation with cultures of Micrococcus sp. INIA 528 and of the addition of high enzymatic activity (HEA) curds prepared with this strain on casein hydrolysis and formation of peptides during cheese ripening was investigated by capillary electrophoresis and reversed-phase HPLC. Milk inoculation at 2% with Micrococcus sp. INIA 528 cultures and addition of HEA curds at 10 or 20% enhanced significantly the degradation of all casein fractions, in particular of β-casein. Also, milk inoculation at 2% with Micrococcus sp. INIA 528 cultures and addition of HEA curds at 10 or 20% increased significantly the formation of both hydrophilic and hydrophobic peptides. However, the addition of HEA curds at 20% resulted in levels of hydrophobic peptides high enough to cause bitter flavour defect. Milk inoculation with Micrococcus sp. INIA 528 cultures at 2% and addition of HEA curds at 10% accelerated cheese proteolysis during ripening without risk of bitterness.Peer reviewe