Perpetual Pavement is defined as an asphalt concrete pavement that is built to last for 50 years or longer without any maintenance other than occasional replacement of the thin but durable wearing course. This reduces user delays and rehabilitation costs, offsetting the higher initial cost of installation. The removed surface layer can also be recycled, saving material resources.
The main focus of the perpetual pavement concept is to eliminate bottom-up fatigue cracking while still providing a durable product. When pavements undergo cyclic traffic loading, the bottom layer of the pavement structure becomes fatigued from induced strain, cracks begin to develop at the bottom and then propagate into the upper layers, eventually making their way to the surface. To combat this problem, perpetual pavement uses a mix that is resistant to rutting and thermal cracking to create a pavement designed to be strong enough that traffic-induced strains will remain at or below a threshold value (typically 60-70με) known as the "endurance limit", so that cracking of the asphalt will never occur. Perpetual pavement is typically designed in layers using Mechanistic-Empirical (ME) design principles. From surface to base, these layers consist of a thin durable surface course, an intermediate layer, a thick high-modulus asphalt layer, and a fatigue-resistant course which is placed on top of an aggregate base (in this case the rubbilized preexisting PCC pavement) over the subgrade. The top layer absorbs damage due to traffic and environmental factors over the life of the pavement and may be ground off and replaced from time to time to rejuvenate the surface. In this project, the main difference between conventional HMA (control section) and the perpetual pavement is a thicker bottom layer of the HMA. It is designed to a thickness where the endurance limit is never exceeded. Proper design and preparation of the road foundation is also crucial for the durability of perpetual pavement.
ORITE has tested the perpetual pavement concept in Ohio on the WAY-30 test road (on westbound lanes, the eastbound lanes used a special long-lived Portland cement concrete (PCC) design), Interstate 77 in Canton, and on selected sections of the SHRP test road on US Route 23 in Delaware County. ORITE has also tested perpetual pavements in the Accelerated Pavement Load Facility. ORITE also monitored the first perpetual pavement designed and built in New York on its I-86 test road near Angelica.