Evaluation of Mixtures and Pavement Performance for Rehabilitation Methods

About 75% of 3R pavement rehabilitation practices in Nebraska is by milling old 4-in. asphalt surface and placing a new 4-in. layer. Another 10% is a deeper replacement such as 5-in. mill/fill or 6-in. mill/fill. Traditionally, Nebraska Department of Transportation (NDOT) has used one mix for the 4-in. strategy; previously 4-in. of the SP4 mix, now 4-in. of the SPR mix. For deeper rehabilitation, NDOT has been using a combination of SRM with SPR or SLX. SRM usually allows 35-65% RAP (reclaimed asphalt pavement) with a coarser mix gradation so that high stiffness can be achieved. The incorporation of high-RAP brings cost savings and the preservation of the environment and natural resources (due to more recycling). SLX is a thin-lift overlay that enables fast construction and provides various functional features, such as riding quality, smoothness, skid resistance, silence, and the drainage capability of the asphalt wearing course for about 8-10 years of service. NDOT is interested in investigating if a combination of 3-in. SRM and 1-in. SLX or 2.5-in. SRM and 1.5-in. SPR can be used for the 4-in. rehabilitation practice in addition to deeper rehabilitation strategies using SRM. To improve pavement engineering practices in Nebraska, there is a clear need to look into the feasibility and potential applications of overlay configurations with more economical mixes such as SRM in the State, and this requires research efforts. The research objective is to test several different mixtures and use mixture properties to investigate pavement performance and LCC analysis when they are used in different rehabilitation practices in Nebraska.