The UTexas Seal Coat Design Method using 3D laser technology




El Hachem, Yorguo

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The size of the highway network has grown beyond the manageable capabilities of transportation agencies and stakeholders who are concerned with maintaining their assets using limited funding abilities. For that reason, pavement preservation programs have become very popular because they offer cost-effective spending schemes that maximize the service life of roads. Seal coats are one of the most popular pavement preventative treatments used around the world due to their high durability and low cost compared to other surface treatments. Their performance depends on the adequate computation of the aggregate and binder application rates. Misestimating these rates leads to raveling, bleeding, or other distresses. Accordingly, numerous design methods have been developed and are being implemented worldwide. This research assesses the different design philosophies and considers the assumptions adopted by each. It is challenging to design a seal coat when several design methods recommend different and inconsistent application rates. For the first time, the three-dimensional laser is incorporated in the design of seal coats in order to provide a fast, objective, and reliable approach. A predictive model is developed to determine the adequate aggregate application rate based on the size of the aggregates, i.e. the average least dimension, and their density. This study also assesses the contemporary texture characterization techniques and analyzes the variance of the sand patch test. The findings indicate that the sand patch test is not a reliable estimator of the volume of voids in the surface texture, which negatively affects the calculation of the binder application rate. The study recommends an algorithm that accurately measures the volume of voids in the existing surface texture using 3D surface scans. The outcome enhances the estimation of the binder application rate, and the findings can be applied to the existing design methods to improve the performance of the seal coat. Finally, highway agencies could incorporate the 3D laser within the binder sprayer to measure the surface texture during construction and automatically adjust the rate.


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