Introduction
The National Center for Asphalt Technology (NCAT) is a leading pavement research center located in the southern United States. It features the world’s only high-speed, full-scale accelerated pavement testing facility. When Kraton first developed the HiMA technology, NCAT was the perfect place to demonstrate its capabilities.
Challenge
While it is simple to design a pavement to be either rut resistant or crack resistant, it is not easy to make it resistant to both at the same time. The tradeoff becomes even more challenging to manage when the pavement thickness diminishes. This issue is precisely what we wanted to accomplish with our N7 test section.
Resolution
We built a three-layer pavement over 14 cm (5.5 in) of aggregate base. The 3.2 cm (1.25 in) wearing course was assembled with a 9.5 mm NMAS dense-graded mixture. We paved the base course with two layers, each 5.7 cm (2.25 in) thick and made with a 19 mm NMAS dense-graded mixture. All binder courses featured the HiMA bitumen technology. Overall, the three layers amounted to 14.6 cm (5.75 in) thick pavement. Compared to the control section made with conventional PMB, the HiMA section was 18 percent thinner. HiMA mixes were produced at 174°C (345°F) and compacted at 115-147°C (240-295°F).
After 20 million equivalent single axle load (ESAL) applied to each section over five years, the HiMA section resulted in 70 percent less rutting. It also had no bottom-up fatigue cracking while the control had 18 percent area cracks.
The NCAT experiment proved that it is possible to make a pavement thinner and still make it last longer than the conventional alternative. Since then, HiMA has been successfully implemented in numerous places around the world, bringing along social, economic and environmental benefits.
Resources
- Kluttz et al. Performance modeling of a highly modified asphalt pavement, AMPPP, pp 57-61, April 2018
- Willis et al. Performance of a highly modified asphalt binder test section at the NCAT Pavement Test Track, 95thTRB meeting, Washington DC, January 2016
- Back calculation of asphalt concrete moduli using field measured strain, 93rd TRB meeting, Washington DC, January 2014
- Performance and Rational Design of Thin, Highly Modified Structural Pavements, ICPP conference, Columbus Ohio, October 2014
- David Timm et al., Field and Laboratory Study of High Polymer Mixtures at the NCAT Test Track: Final Report, Auburn, Alabama, February 2013
- Randy West et al., NCAT Phase IV Pavement Test Track Findings Final Report 12-10, Auburn, Alabama, October 2012
- Randy West et al., Phase V (2012-2014) NCAT Test Track Findings Report 16-04, Auburn, Alabama, August 2018
- Timm et al., Pavement Rehabilitation Using High Polymer Asphalt Mix, 91st TRB meeting, Washington DC, January 2012
- Scholten et al., Accelerated loading test results of two NCAT sections with highly modified asphalt, AAPA, Sydney Australia, September 2011