Use of grid reinforcement in HMA overlays – a Texas field case study of highway US 59 in Atlanta District

Abstract

One of the common methods to mitigate reflective cracking, in existing cracked pavements, is the use of interlayer grid reinforcements in hot-mix asphalt (HMA) overlay construction during maintenance and/or rehabilitation projects. As a means of sharing the practical experience, lessons learned, and demonstrating the performance benefits of using interlayer grid-reinforcements, this paper presents a field case study where different types of grid reinforcements (namely geosynthetic paving mats) were used in HMA overlay construction to mitigate reflective cracking and thereafter, field performance was monitored and evaluated periodically. Two HMA overlay test sections (denoted as Sec13 and Sec14), reinforced with different grid materials (i.e., geosynthetic paving mats) were constructed in 2011 over an existing cracked HMA pavement (with transverse cracks) on an in-service highway US 59 in the Atlanta District of Texas. Field performance was subsequently monitored/evaluated for a period of over seven years against an adjacent Control section (Sec01), without grid reinforcement, on the same US 59 highway. Under the same pavement structure, traffic loading, and climatic conditions, various performance indices were evaluated semi-annually including reflective cracking, rutting, longitudinal surface profiles, and interlayer bonding. While the rutting performance was indifferent on all the three test sections after 7 years of service, 17% of reflective cracking was measured on the Control section versus 4% on the grid-reinforced test sections – demonstrating that the use of grid reinforcement (namely geosynthetic paving mats) has been effective in mitigating reflective cracking from the existing cracked HMA pavement. Similarly, while coring indicated satisfactory interlayer bonding conditions on all the three test sections, the rate of pavement surface roughness deterioration was also hardly different on all the three test sections – albeit that the Control section (Sec01) exhibited superiority in terms of the profile indices (smoothness/serviceability) than the grid-reinforced test sections (Sec13 and Sec14).