Banner passionately believes in being able to present our clients with the most current engineering information, practices, and regulations, as technology and guidelines are continually changing. January of this year, the Dakota Asphalt Pavement Association Annual Meeting was held in Deadwood, SD. The conference was attended by Banner’s Civil Department staff members, Beth Niemeyer, PE and Scott Mohror, PE. The Asphalt Pavement conference includes many informational seminars on new techniques and technology, and updates on current practices and regulations in regards to our roads and highway systems.
Dr. David Timm of Auburn University and a member of the Board of Directors of NCAT (National Center of Asphalt Technology) was a presenter of one of the seminars, "Long Life Pavement - The Road to a Sustainable Future", and shared some very interesting facts about our roadways; something we take for granted but use every day!
Perpetual Pavement is one that has been in service for 35+ years. These pavements have needed minimal structural improvement over their life; have no deep structural distress and have distresses quickly remedied from the surface down. Any distresses that extend through the entire depth of the section are considered a failure; which means starting over.
New pavements designed to be Perpetual Pavements are built with a fatigue resistant HMA material at the base; a durable, high modulus, rut resistant HMA intermediate layer; and a high-quality wear resistant HMA/SMA top layer. This top layer is designed to resist top down cracking and rutting.
An Asphalt Lake?
Pitch Lake, located in southwest Trinidad, is the largest of the world’s three natural asphalt lakes. It is approximately 250 feet deep and has a surface area of 100 acres. The liquid asphalt is black and viscous, but the surface is semisolid, and can be walked on. The asphalt is so soft in some areas that an individual can slowly sink if he or she stands on the surface too long. In some places one can put a stick through the asphalt and remove liquid tar. Although the lake appears quiescent the asphalt still moves with a natural slow "stirring" action. Not only can the flow lines be seen on the surface of the asphalt, but prehistoric trees and other objects have been known in the past to have appeared, disappeared and reappeared.
The lake was created thousands of years ago, by the process of subduction, when the Caribbean continental plate was forced under another plate. This opened fault lines that allowed oil from deep underground deposits to rise to the surface, where it collected in a volcanic crater. The air caused lighter elements of the oil to evaporate, leaving behind the heavy asphalt, a mix of oil, clay and water.
Mining of asphalt from the lake started in 1867 and an estimated 10 million tons of asphalt has been extracted since. The lake is estimated to contain reserves of about 6 million tons, which would last 400 years at the current rate of extraction. Dr. Timm shared that the surface level has not decreased since mining began. The Lake Asphalt of Trinidad & Tobago company mines, processes and exports asphalt around the world.