Rubber Asphalt Roads
| Mahantango Enterprises, Inc. has been supplying crumb rubber for asphalt roads for over twenty years. Over this time many projects were completed, and all were successful due to the expertise and diligent work by Pennsylvania-based asphalt pavement companies and strong support from the Department of Transportation. One extremely durable asphalt pavement currently specified and used in the commonwealth is stone matrix asphalt (SMA). This SMA is used on a variety of roadways including many of Pennsylvania’s most heavily traveled interstate highways. By adding rubber to the SMA the mix gains additional benefits. The crumb rubber adds elasticity to the SMA and also replaces some of the air voids. Air voids, or gaps between the aggregates, are vital to pavement performance. Rubber functions better than these air voids because of its physical properties. Unlike an air void, crumb rubber fills the gap reducing the space for water intrusion. Another valuable property of rubber is its ability to expand when compressed. This is an important property with the over-abundance of rutted roads in Pennsylvania. Crumb rubber pavements resist rutting by pushing back against the pressure created by extreme truck traffic. With all these benefits it would be easy to assume rubber is an expensive solution. But the fact is you get all these crumb rubber benefits at a reduction in cost when compared to SMA without rubber. |
Another application more recently adopted here in Pennsylvania is blending a finer grade of crumb rubber directly into the liquid asphalt at the terminal or right at the blacktop plant. Blending standard asphalt with crumb rubber
increases the Performance Grade (PG) rating of the asphalt oil. This rubber-modified asphalt is an economical method of improving the PG grade.
Photo A is a picture of rubber-modified asphalt blend. This blend is typically about 80% asphalt and 20% fine crumb rubber. The actual mixture can vary, it might be as lean as 90% asphalt and 10% rubber.
In photo B we show the standard 64-22 asphalt, a 76-22 polymer modified asphalt which is a 64-22 asphalt blended with a polymer increasing the PG rate to 76-22. The third sample is a 64-22 asphalt modified with a 20% blend of fine rubber. The resulting product has the PG rating of over 76-22.
Notice the difference in the viscosity of the three samples. The samples are each 20 gram drops of liquid asphalt at room temperature. At warmer temperatures rubber modified asphalt will resist bleeding more than the other two options.
Now let’s take a look at rubber modified asphalt performance in cold temperatures.
Photo C shows the result of an experiment that was performed by Greg Brouse. Greg Brouse is well known as a creative innovator in using crumb rubber in asphalt in the state of Pennsylvania. He has worked in the asphalt industry for over 35 years and with using crumb rubber in asphalt for over twenty years. Click this link to see a webinar presentation Greg did on rubber modified asphalt as used in pavement in Pennsylvania.
In the Drop Test Experiment in photo C three 30 gram samples of the same materials shown in photo B were cooled to approximately 36 degrees. They were then hit with a test hammer. If you notice the standard 64-22 asphalt was broken into many pieces with one drop of the test hammer. The polymer modified 76-22 was also hit with one drop of the test hammer. The results are better than the 64-22 asphalt but there still was significant breakage. And finally take a look at the Asphalt Rubber Blend(ARB) on the right in the photo above. After ten drops of the test hammer the Asphalt Rubber Blend is still intact.This proves that rubber is a stronger, more flexible binder not only in warmer temperatures but in colder temperatures as well. The results show how forgiving an Asphalt Rubber Blend is.
Today with the support of the Department of Transportation and many people working in the asphalt industry like Greg Brouse, rubber modified asphalt has proven to be the premier binder. Rubberized pavements are quieter, decrease rolling resistance while also shortening the stopping distance. Rubberized pavements have less cracking and rutting making the roads last longer. Asphalt Rubber Blend costs less when blended at the blacktop plant as Greg discusses in his webinar.
At a time when Pennsylvania roads are crying out for help, Crumb Rubber is the medic waiting to take the call!
Call for pricing and delivery information.
Click this link to see a rubber modified asphalt webinar presentation by Greg Brouse.
Mahantango Enterprises, Inc. is an approved vendor on PENNDOT’s bulletin 15 as reference number 1994-031.