currently known. It has been adopted or is about to be adopted in the majority of the U.S. states, and it has strong support from the industry, as it is a robust, simple and no-nonsense specification. The Ontario Ministry of Transportation (MTO) has temporarily adopted the recovery portion of the MSCR as a test for indirectly specifying polymer modification for grades requiring enhanced performance, but is currently not considering the adoption of the full MSCR specification. It has, instead, temporarily adopted the DENT as a full test within the current PG Specification, with an acceptance criterion. ExBBR continues to be tested by the MTO as a “for information only” during the last couple of years, but is not used for acceptance. What are the implications of these changes? While these new tests (ExBBR and DENT) represent an interesting direction of research, industry is of the opinion that their adoption as part of acceptance specifications by the MTO is premature. Firstly, AN AECON COMPANY 50 OHMPA | ASPHALTOPICS YOUR ROAD TO SUCCESS IS PAVED WITH OUR INNOVATIVE SOLUTIONS AME Materials Engineering knows the road. When it comes to pavement engineering and design solutions, we offer a full range of analysis, consulting and testing services to ensure cost-effective strategies for all your infrastructure expansion and maintenance needs. Whether the job calls for new construction, rehabilitation or pavement preservation, our proven expertise and focus on green energy technologies are here to support your success. AME…AS INNOVATIVE AS THE ROAD IS LONG. CALEDON 905 840 5914 ame@amecorp.ca OTTAWA 613 726 3039 ame.ottawa@amecorp.com these tests haven’t shown a very good correlation with pavement performance in the reported MTO trials. Secondly, the test methods are long and complex and the testing variability so far has been very high, especially for the DENT test. This will open the possibility of extensive disputes and disagreements between parties regarding the quality of the materials. Thirdly, there is a lack of agreement in the scientific community that these tests represent the best protocols for capturing the material properties in question. Serious technical disputes about the DENT test exist, especially around the concept of extensional rheology. Such tests have been proven in the past to have high variability and to be difficult to be accurately conducted in a QA/QC laboratory environment (the Direct Tension, originally part of the PG specification, but now practically dropped, is the best example). Also, because of their failure mechanism, some researchers believe extensional tests don’t actually model fatigue fracture very well. The adoption of the PG specification has no doubt been a major step forward in improving the quality of our pavements. We almost never see rutting anymore, our transverse cracking is all but eliminated, and the general state of our pavements is good. Fatigue in pavements is currently the distress which still needs our attention, as it is the least successful to be modeled by the current PG specification. Fatigue, however, has to be addressed primarily at mix level, as modeling HMA fatigue through binder testing has not been very successful in the past. Our current RAP usage in mixes is higher than in the in the past and, at the same time, our binder content is significantly lower than during the utilization of Marshall mixes. More so, today we tend to use higher dosages of RAP or RAS without adjusting the virgin AC grades down accordingly. All these factors contribute to a poorer fatigue resistance of our mixes in Ontario today. While PG specification development represented a major step ahead, we are today in another period of attempting to move our AC specifications forward. Owners are once again searching for better performance. Through validated research and best practices, it is our industry’s mission to stay ahead. Tony Kucharek is Director, Technical Services of McAsphalt Industries
We asked our columnists and article contributors to send in photos of themselves from 1974. Can you guess who’s who? Answers below. 1 2 3 4 5 6 7 8 9 1. Bentley Ehgoetz 2. Gerald Huber 3. Abigail Wright Pereira 4. Ed DeToro 5. Adam Draper (+ 14 years) 6. Sandy Brown 7. Stephen Erwin 8. Doug Duke 9. John D’Angelo FALL <strong>2014</strong> 51
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