SemMaterials

...an economical solution to today's paving problems

The patented SemMaterials Stylink® Technology chemically reacts a Styrene-Butadiene (SB) block copolymer in the base asphalt. The improved physical properties and elastomeric qualities of Stylink® modified HMA cannot be matched by conventional asphalt cement mixtures. What does this mean when deciding how to spend our highway dollars?

The binder costs more, but there is only a small (10-25%) increase in the total cost of the AC mix.
For projects awarded in 1994, Tennessee DOT reported the average per ton cost of in-place conventional AC-20 was $145.20, and that of PMAC was $260.97. This looks like a big difference. But the premium surface mix aggregate costs $20.65 per ton, so the material cost is only 21.5% higher, assuming 5% binder.

The Kentucky Transportation Cabinet reports the 1995 average unit bid price for their standard AK/A premium skid resistant mix used on high volume roads was $31/ton of unmodified placed mix, and $37/ton of polymer modified placed mix, or an increase of 19.4%. For Kentucky's 20/30 Class I surface mix, the unmodified average cost was $41/ton and modified $45/ton, or a difference of only 10%. Typical costs for surface mix in Oklahoma show a 25% higher cost for Stylink over conventional AC.

Polymer Modified AC pays for itself in only 1 to 3 years, but may last 4 to 9 years longer.
Based on the costs of the various mixes in Tennessee, Kentucky and Oklahoma, and based on a predicted 10 year service life of the surface mix, it only takes 1 to 3 years in extended pavement service life for the Stylink to pay for itself.

How much longer will the Stylink last?
A 1989 AAPT paper ("A Mechanistic Evaluation of Mixes Containing Conventional and Polymer Modified (Styrelf) Asphalts", Proceedings, Association of Asphalt Paving Technologists, Volume 58, 1989) by Khosla and Zahran of North Carolina State University reported significantly longer predicted service lives. Using laboratory data on resilient modulus, fatigue life, resistance to rutting, and mitigation of low temperature cracking, Stylink HMA was predicted to last 3.9 to 8.9 years longer than unmodified asphalt, using a Terminal PSI (present serviceability index) of 2.5 and the FHWA VESYS IIIA structural program. In their study, Khosla and Zahran found that mixtures made with Stylink binders were more resistant to rutting and thermal cracking; and the Stylink significantly improved the fatigue life.

Canadian Study Shows Stylink® HMA has 4-6 years Longer Service Life, for an Average Savings of $3,800 per lane-km
John Emery Geotechnical Engineering Limited (JEGEL), did a recent study comparing Stylink sections with conventional AC sections on four field projects constructed between 1987 and 1992, and representing various traffic and climatic conditions in Canada. The exhaustive analysis included a pavement distress survey, laboratory testing of resilient modulus, resistance to fatigue and resistance to permanent deformation. They concluded the Stylink sections had life cycles 4 to 6 years longer than the unmodified sections. Life cycle costing was calculated using a 7.5% interest rate and 4.0% inflation rate to determine the present worth of the construction, maintenance and rehabilitation costs of the pavements.

Stylink HMA Is Cost-Effective Alternative to Portland Cement Concrete for Busy Intersections.
Recently Maryland did an experimental project comparing Stylink HMA to PCC on intersections on busy U.S. Route 40 (29,200 ADT). After 13 months of service, which included the most consecutive days over 90°F in Cecil County history, there was no evidence of rutting, and there has been none for over 10 years. This pavement had rutted at the rate of 1-inch/year prior to this project. The cost of the Stylink section was considerably less than the PCC, the traffic delay during construction was less, and the smoothness as measured by California profilograph was much better. Now, several years later, the Stylink mix intersections are still performing, while the PCC ones were removed and replaced after a couple of years because of severe cracking.

Longer lasting roads, lower life cycle costs. Contact your local SemMaterials Representative to find out more about stretching your paving dollars.