A recently completed NJDOT research study on Innovative Pothole Repair tested several new techniques and materials that could lead to longer lasting roadways throughout the state. The projects, led by Professors Hao Wang and Husam Najm of Rutgers University evaluated new methods on both asphalt and concrete structures. Pothole repair is one of the primary maintenance activities for highway agencies, drawing significant costs and resources. This means that cost-effective pothole repair methods can reduce or eliminate the possibility of re-patching and save future repair costs.
Asphalt Pothole Repair
Asphalt pavement is continuously subjected to vehicular and environmental loading throughout its lifecycle, leading to the inevitable occurrence of distresses such as cracking, rutting, raveling, potholes and so on. Among these distresses, pothole is critical for causing traffic disruption and safety risks,
Pothole repair is a primary maintenance activity for highway agencies. Typically cold mix asphalt is used for emergency repair and hot-mix asphalt (HMA) for traditional repairs. Usual pothole repair methods include throw and go (roll), edge seal, semi-permanent, spray injection, and full depth repair. Among them, throw and go (roll) method using HMA has been adopted by most transportation agencies for surface patching. However, this common practice largely relies on the usage of HMA. Although the quality of the asphalt patch can be ensured, it presents environmental concerns due to the energy consumption and environmental footprint involved in producing new HMA. To mitigate the impact on the environment, reduce cost and conserve energy, recycled asphalt pavement (RAP) has been widely used as a high
ly desirable material. The addition of recycled asphalt pavement (RAP) in asphalt mixtures can bring numerous economic and environmental advantages.
This study aimed to investigate an innovative approach of pothole repair method using HMA with RAP and preheating. The scope of work of this study includes two aspects. First, the performance of HMA with different RAP contents were evaluated through laboratory tests to select the most appropriate content. Second, the in-site strength of pothole repair is evaluated with field cores to quantify the benefits of repair quality due to recycled material and preheating.
Both microwave heating and infrared heating were tested, with varying results. Microwave heating was able to warm both the surface and internal materials of the pavement, however it’s efficiency was low and the rate of temperature increase was insufficient. Conversely, the infrared heater proved adept at heating the top edges and bottom surface of the pothole to high temperatures in a short amount of time, and was used successfully in pothole repair.
Further tests were carried out adding RAP to HMA patching materials. The results showed that abrasion loss, IDT strength, and interface shear strength of patching material were less resistance to moisture as RAP content increased. That said, with the application of preheating, the overall performance of HMA containing 30% RAP was satisfactory, proving, that it is feasible to use RAP material for pothole repair.
Concrete Pothole Repair
Similar to asphalt pavement, concrete structures are prove to deterioration due to vehicles and weathering. Crack can develop which lead to further deterioration due to chloride infiltration. Thus, a good repair is necessary for maintaining concrete structures. An ideal repair material should be easy to work with under different weather conditions, fast setting, and possess good durability. Rapid setting cementitious patch repair materials are popular for repairing small concrete damages and providing a functional repair within few hours.
Based on extensive literature search and several DOT practices, three formulations were chosen as the best performing candidates. Workability, strength, and restrained shrinkage cracking of the formulations were investigated The restraint shrinkage test protocol simulated upper and lower limits of restraint that a repair material undergoes in real applications. The repairs were also cast and placed in external environmental conditions to expose them to 
natural weathering actions. The cracking behavior was evaluated including cracking spacing and maximum crack width
The investigation led to the identification of three formulations that did not crack for a period of 10 months in filed exposure to NJ climate conditions. Typically, rapid set formulations do not shrink after 6 months. The formulations that did crack revealed that addition of 1 percent of PVA fibers could significantly reduce the maximum crack width. The maximum crack widths observed in all the formulations were an order of magnitude less than the maximum allowable crack width specified by NJDOT which is 1/32 in.
These two projects were completed at a time when potholes have again started to get attention across the state. Recently the New Jersey State Senate voted unanimously to advance a bill that is intended to address concerns about pothole damage to roads and bridges across the garden state.
The bill, S862, would require the state DOT to include information about pothole repair projects and their cost in the annual report. The additional information would include the number of repair projects going on around the state and their cost. There would also be a separate provision that would require a lifecycle cost analysis to be conducted.
The information would also be required to be made available to the public on the DOT’s website.
The projects are not only primed to answer the serious legislative issues in Trenton, but are being recognized for the innovation by AASHTO. Every year, the High Value Research Task Force of AASHTO RAC holds a national competition to find four “high value” research projects from each of the four AASHTO regions in the country. In 2024, Innovative Pothole Repair Materials and Techniques was chosen as one of the recipients of the award.
