Our experts share their thoughts on asphalt sustainability, innovation, safety and creating a culture of care.

Featured Article: Rubberized Binders for Dense Graded Hot Mix Asphalt

As the Director of Technical Sales at Polyco, I’m excited to share highlights from a recent collaboration with Skip Brown, a seasoned figure in pavement consulting and Dr. Peter Sebaaly, Director of the Western Regional Superpave Center at the University of Nevada, Reno. With a career spanning over four decades in the pavement industry, I’ve been lucky enough to witness uncounted innovations. The article Skip, Dr. Sebaaly and I wrote delves into one of the most groundbreaking — Polyco’s SigmaBond. In the article, we explore the evolution of rubberized binders and how SigmaBond is revolutionizing the landscape. Read on for some of the highlights of the article, which was recently published in a newsletter by the California Pavement Preservation Center (CP2C) of Cal State Chico

Over the past 50 years, California’s pavement industry has witnessed the extraordinary evolution of rubberized asphalt binders. Traditionally, asphalt rubber (AR) methods involved blending ground tire rubber into the base binder at the hot plant. However, advancements have introduced the terminal blend approach, resulting in a rubber-modified binder (RMB). This innovative method allows for greater flexibility and convenience in handling rubberized asphalt.

RMBs like Polyco’s SigmaBond offer key advantages over traditional AR binders, especially for smaller paving jobs. One notable benefit is storability – RMB can be produced at a terminal, stored in tanks and shipped to multiple hot plants. This eliminates the need for special blending equipment at individual plants, making it a cost-effective and efficient solution. RMB formulations are versatile, applicable to both gap-graded and dense-graded hot mix asphalt, and can be customized to meet various performance grades. 

As a sustainable solution, SigmaBond allows high RAP usage while delivering superior cracking resistance. Research from the University of Nevada, Reno (UNR) has validated SigmaBond’s performance in dense-graded rubber-modified hot mix asphalt (RHMA), showing excellent resistance to reflective cracking: 5-6 times better than unmodified mixes. 

Cracking resistance isn’t all SigmaBond offers. The mixes evaluated in the UNR study, containing 25% recycled asphalt pavement (RAP), also demonstrated equivalent or improved moisture resistance, fatigue life and rutting resistance compared to conventional mixtures. These findings support the recommendation of SigmaBond RMB for dense-graded rubberized overlays on projects of all sizes.

Recent projects in California have put SigmaBond to the test, and the results have only reinforced these benefits. Contractors paving 2-inch dense-graded rubberized overlays in Rancho Murieta, Los Lagos and Stockton achieved excellent in-place density, workability and uniform surface textures that outperformed conventional mixes. The photos below show the highly uniform and tight texture of the finished surfaces. 

As a pioneer in sustainable asphalt modifiers, Polyco’s SigmaBond RMB is driving the future of rubberized binders and circular paving practices. SigmaBond’s ability to be easily batched and stored allows its advantages to extend to projects of any size, from major highways to private parking lots. By enabling high recycled material usage while delivering outstanding cracking and aging resistance, Polyco empowers contractors and agencies to construct longer-lasting, lower-maintenance pavements.

SigmaBond is just the beginning of Polyco’s innovative asphalt paving solutions. I encourage you to explore our website, meet with us at conferences and other events and reach out to learn more about all the exciting ways we can shift the asphalt industry from black to green together.