ACE XP Polymer Fiber helps a new pavement design achieve a higher standard in crack prevention

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Taylor County Airport

Taylor County Airport in Kentucky (Photo by Palmer Engineering)

A custom asphalt mix design utilizing ACE XP polymer fibers has given a general aviation airport the long-term solution it sought for a nagging pavement cracking problem. Initial results show the custom design, which combined both a binder layer and a surface layer reinforced with ACE XP, will exceed expectations by greatly reducing cracking potential.

The six-year-old runway pavement at Taylor County Airport in Kentucky was failing. Airport authorities called on Palmer Engineering to provide a desperately needed 15-year-plus solution to the pavement’s micro-cracking problem. Working with Haydon Materials, the team turned to an expert with long-standing experience in designing crack-resistant asphalt pavements.

custom asphalt mix design utilizing ACE XP polymer fibers“Haydon Materials brought in Phil Blankenship from Blankenship Asphalt Tech & Training,” said Joe Dennis, Surface Tech’s chief technology officer for asphalt.

“The airport authorities were concerned that numerous cracks in the existing pavement could lead to failure, a common failure in airport pavements as aging occurs can create FOD — Flying Object Debris — causing a danger to the aircraft and potentially the traveling public.”

No milling was done on the runway pavement prior to re-paving. This meant the existing cracks would be exposed to the bottom of the  binder layer and would ultimately  reflect upward through the new pavement. The solution called for an inordinately crack resistant and resilient binder layer that either needed to be custom-designed, or an expensive two-dimensional geosynthetic rolled interlayer product.

“As a member of Surface-Tech’s Technical Advisory Committee, Phil is well versed on the capabilities of ACE XP, and he set about designing a completely new binder layer asphalt mix using it.”

Blankenship was able to deliver a design that Haydon could produce in its plant and pave with existing paving equipment. Using ACE XP in the new binder layer design gave Haydon Materials an effective crack resistant solution, while maintaining cost control for this demanding application.

The customized ACE XP mix achieved a new level of flexibility for the binder layer. The new binder layer design — a finely graded, highly asphalted crack resistant mixture — greatly reduced the potential for cracks to reflect upward from the base through the new pavement.

An  ACE XP reinforced surface mix was also designed utilizing a higher-than-normal asphalt content to provide even greater crack resistance than a typical FAA asphalt mix design,

“The development of this unique combination of mix designs for the binder and surface layer is an exciting advancement for the paving industry that holds great promise for dramatically improving crack prevention,” said Dennis.

“With this new approach, contractors can also control the quality in both production and installation, as the new mix design is simply incorporated into the contractor’s production processes, thus eliminating third party contractors to install the 2-dimentional geosynthetic rolled interlayer product.”

For more information on ACE XP  crack resistant designs, contact us.

custom asphalt mix design utilizing ACE XP polymer fibers

New and improved MD3+

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More accurate than ever  — just in time for the asphalt season

MD3+ dosing system for asphaltLast July, Surface Tech introduced the MD3+, the latest version of its Micro Doser system that can handle both 19mm or 38mm sizes of ACE XP polymer fibers. This year, the MD3+ comes with added improvements to the computer interface, which tracks the total weight used and average dosage rate right on the home screen to ensure the accurate dosing of 4.2 ounces of ACE XP into each ton of produced asphalt.

“We are proud to announce that we’ve succeeded in making some programming enhancements that improve the dosing accuracy even more —MD3+ can now dose to within 2 percent of the dosage rate. This is well under Surface Tech’s suggested 5 percent in our product and dosage specifications,” said Joe Dennis, vice president & chief technical officer.

Additionally, Surface Tech has ramped up the availability of the MD3+. The company will be stocking a fleet of more than 20  MD3+ systems strategically around the country and making them available just in time for the spring asphalt season.

To find out how to add the MD3+ and Surface Tech’s revolutionary ACE XP polymer fibers to your next asphalt project, Contact Surface Tech today. We make asphalt stronger than steel, with a life cycle that can go the distance.

Technical review of Indirect Tensile Strength testing advises caution in relying on results

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ACE XP Polymer Fiber
Alternative tests, plus a balanced mix design, can improve predictions of asphalt performance

The indirect tensile strength (ITS) test has been utilized for more than 40 years as a definitive method for predicting the performance of asphalt mixtures. But the test, at 25°C, can render misleading results, according to a recently released technical brief by Phil Blankenship, P.E.

indirect tensile strength (ITS) test“While the indirect tensile strength test at 25°C is sensitive to changes in mixture properties such as air voids, asphalt binder content, binder grade, aggregate properties (angularity, texture, etc.), the resulting indirect tensile strength does not always equate to positive field results,” he writes. “In other words, high tensile strength alone does not always relate to improved cracking resistance.”

The author discusses various developments taken over the past 10 to 15 years in ITS testing to achieve more predictive results for top down cracking. However, differences in testing temperatures and loading rates may not, in reality, conform to ASTM D 6931 standards.

Blankenship presents data from various experiments that show a weak correlation between strength (at 25° C) and ALF cycles to failure. Various results of other tests also show that indirect tensile strength testing alone (at 25°C) can be misleading.

Instead, Blankenship advises that other cracking tests produce good correlations to field performance, and the types of tests and standards are provided within the paper. The author further explores taking a “balanced mix design” approach, or performance-based testing.

To explore the various testing methods for yourself, click here.

AAPT Annual Meeting a good forum for emerging asphalt technologies

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Surface Tech’s asphalt advisor Phil Blankenship to take the President’s role in 2020

Phil BlankenshipFor more than 90 years, the worldwide membership of the Association of Asphalt Paving Technologies has provided a centralized forum for disseminating the latest developments in asphalt paving technology. The organization’s recent annual meeting provided an excellent opportunity for Joe Dennis, Surface Tech’s chief technology officer, and Phil Blankenship, P.E., asphalt advisor to Surface Tech, to explain in depth how ACE XP Polymer Fiber differs from other non-polymer fibers.

“As we all know, no good idea sits idle, and that was largely the response we saw as many of the professionals in attendance gained a better understanding of the capabilities of ACE XP,” said Dennis. “Once the differences are clear, we saw the interest in ACE XP rise dramatically.”

A stellar line-up of presentations on a variety of research projects and material advances filled the three-day event, along with plenty of opportunities to network. Presentations included a wide range of topics, including the impacts of climate change on asphalt, 3-D paving, advances in stress testing, numerical modeling and much more.

“The AAPT Annual Meeting was well attended by a large number of highly educated professionals in our industry,” said Blankenship, who will take on the role of the organization’s president in 2020. “I expect the AAPT to continue to be a significant source of information and technological advancements well into the future.”

To view YouTube videos of the various presentations, visit https://www.youtube.com/channel/UCjWgLqZUstRB_G_zl9gLqLw

IDEAL-CT & Hamburg Wheel Tracker meet the need for crack/rut balanced performance testing in asphalt mixes

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ACE XP shows 30% to 50% improvements in both tests

 Indirect Tensile Cracking Test at Intermediate Temperature (IDEAL-CT)

Figure 1. Indirect Tensile Cracking Test at Intermediate Temperature (IDEAL-CT)

Asphalt pavements need to be stiff enough to minimize rutting, but resilient enough to bend without breaking to prevent cracking. The trend over the last 20 years has been one-sided — fixing the ruts at the expense of the cracks. Many in the industry have begun to recognize the need for a “balanced approach” to developing pavement designs that will perform well in resisting both rutting and cracking.

There are seven key existing performance or index tests for asphalt cracking (see Table 1). These tests vary in complexity and cost, and as a result, the asphalt industry has not traditionally performed cracking performance tests on every project.

Hamburg Wheel Tracker (HWT) Test

Figure 2. Hamburg Wheel Tracker (HWT) Test

For rut testing, the Hamburg Wheel Tracker (HWT) test tends to be the most widely used method. However, many agencies and specifiers, including DOTs, are moving toward adopting performance-based specifications where both mix designs and daily production will need to meet certain minimums in both cracking and rutting parameters in order to be considered.

A new and promising cracking test has recently been developed by Dr. Fujie Zhou and his colleagues at the Texas A&M Transportation Institute. The Indirect Tensile Cracking Test at Intermediate Temperature (IDEAL-CT) is a reduced cost method that provides consistent results to predict field performance in cracking. This test, along with HWT, can be used daily to ensure that asphalt mixes meet both rutting and cracking performance criteria in a balanced manner.

For example, tests utilizing the HWT and IDEAL-CT methods on ACE XP asphalt mixes can be seen in Figures 1 & 2. The results compare mixes with and without ACE XP and show clear performance advantages with ACE XP in both rutting and cracking sample results.

Bottom line: In balanced performance testing, ACE XP Polymer Fiber yields an improvement of 30% to 50% in both rutting and cracking performance. To learn more about ACE XP or how to achieve a balanced approach to testing using the IDEAL-CT method, contact us.

Asphalt crack testing

Fig. 1 - Hamburg Wheel Tracker (HWT) Test Example:

Fig. 1 – Hamburg Wheel Tracker (HWT) Test Example

 

IDEAL-CT Crack Test

Fig. 2 – IDEAL-CT Crack Test Example:

94th Annual AAPT Annual Meeting — we’ll see you there!

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AAPT Annual MeetingThe AAPT annual meeting is just a few weeks away, and our Chef Technical Officer Joe Dennis will be on hand to share the latest updates on ACE XP Polymer Fiber —a product that can make asphalt stronger than steel. The schedule includes several technical presentations on asphalt binders, strength testing techniques and mix designs, plus some social opportunities.

We especially encourage everyone to attend the Leading Edge Workshop on Monday, March 4, at 9:45 a.m. Phil Blankenship, P.E., a leader in the asphalt industry, will preside over the session of Automation in the Paving Industry. This session features two cutting-edge topics of: 3-D Paving: Advances and Limitations and Automation in Testing from the Lab to the Field.  This session will be livestreamed on Youtube.

The line-up of presentations looks both comprehensive and potentially groundbreaking. Check it out here, and plan to join us as we convene in Fort Worth March 3 through 6. To plan a meet-up, contact us.

Surface Tech at WOA — connect with us!

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Innovation drives us to deliver asphalt that’s stronger than steel

World of AsphaltThe 2019 World of Asphalt expo provides opportunities for our industry to share ideas and learn best practices, as well as discover new products and services. It’s a perfect opportunity to investigate Surface Tech’s highly innovative, state-of-the-art ACE XP Polymer Fiber product. To learn how it can deliver outstanding benefits to your next asphalt project, we invite you to connect with Joe Dennis, our vice president & chief technical officer, to find out about an informative networking opportunity with industry specifiers and producers on Tuesday February 12th after WOA hours at the Yard House.

ACE XP is a dry form polymer, making it less expensive, more reliable and easier to adopt than wet polymers. Surface Tech custom-designed its MD3+ machine dosing system to ensure an easy, metered process to introduce ACE XP into any asphalt mixture. The MD3+ requires only compressed air and a 110-volt electric source to operate and will dose both ¾ (19mm) and 1.5-inch (38mm) fibers in U.S. and Metric tonnage rates.