Analysis of the Influence of Materials and Construction Practices on Slurry Seal Performance Using LTPP Data

Abstract

This study investigated the influence of materials and construction practices on the performance of slurry seal treatments that were applied in the long-term pavement performance (LTPP) program. The concept of equivalent effectiveness area under the pavement performance curve was developed to characterize the long-term performance of the treatments. The classification and regression tree (CART), a data mining method, was adopted. The data were divided into subsets based on the weather, traffic, materials, and construction practice factors, and set up the study experiment to quantify the effects of these factors. The application rate of asphalt, application rate of slurry mixture, aggregate type, water ratio, maximum traffic speed during the initial curing period, humidity, pavement temperature, air temperature, pavement surface cleanliness condition, and cracking type for aged pavement were identified as split variables to classify the slurry seal projects, and their effects on slurry seal performance were also quantified. The study determined that pretreatment roughness was the most significant factor of the pavement roughness subsequent to the slurry seal treatment. This study revealed that to ensure sufficiently high friction resistance, the maximum traffic speed allowed during the initial curing period should be 72 km/h, and the optimal asphalt rate was between .97 and 1.4 L/m2. This study found that relatively high pavement surface temperature and low air humidity improved rutting resistance. In addition, sufficient mineral filler content may reduce the risk of fatigue cracking. It was also determined that if the pavement was open to reduced-speed traffic less than 1.7 h after the slurry seal treatment, wheel-path longitudinal cracking tended to be more severe. Also, slurry-sealed pavements with transverse cracking, alligator cracking, or raveling were found to be more likely to have transverse cracks compared to those with edge, block, or longitudinal cracks.