Identifying Components of Microsurfacing and Cold In-Place Recycling (CIR) Mixtures
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Authors
Bou Zerdan, Charbel
Issue Date
2023
Type
Thesis
Language
Keywords
Alternative Title
Abstract
Pavement preservation is essential to maintaining viable road infrastructure, microsurfacing is a widely used and cost-effective technique for preserving asphalt concrete pavements. CIR is a major pavement rehabilitation treatment that involves recycling old pavement and using it as a stabilizing agent in place of traditional paving materials, making it an environmentally friendly option. However, there is a need for better quality assurance (QA) tools to ensure compliance with approved job mix formulas for these pavement maintenance applications. This research aimed to devise a comprehensive field sampling procedure for slurry systems and develop a reliable and accurate test method to determine the asphalt residue content present in slurry systems and CIR mixtures. Two field sampling techniques were investigated in this study, sampling from utilities cover and from mixer discharge. To be deemed adequate, sampling techniques must satisfy three main criteria: sufficient amount of sampled mixture to determine asphalt binder content, safety of the sampler must be considered, uniform and consistent collected samples. The utilities cover sampling technique involves placing a non-absorptive material over a utility cover, as the mix spreader applies the mixture, the cover gets coated with a layer of slurry. Four different non-absorptive materials, namely plastic film, steel plate, aluminum plate, and asphalt felt, were tested to determine their adequacy for sampling. This study found that asphalt felt was the most successful material for microsurfacing sample collection from utility covers. This study also provides a recommended sampling procedure to obtain accurate and representative samples using utility covers. Sampling from the mixer discharge involves collecting a sample of the slurry mix dispensed from the truck before it comes into contact with the ground in the spreader box. When using this sampling technique, samples should be collected from the mixer whilst the mixer truck is moving. Furthermore, the mixer should be allowed to adjust before sampling from the discharge to avoid non-representative samples. To determine the asphalt residue content present in slurry systems and CIR mixtures to technique were investigated the Ignition method and the chemical extraction method. The ignition method was better than the chemical extraction method at determining the asphalt residue in microsurfacing mixtures. However, the ignition method was inaccurate in determining the asphalt emulsion residue in CIR mixtures, while the chemical extraction method was accurate but is impractical as a field technique. A hybrid method of both techniques is suggested in this study to determine the asphalt emulsion residue in CIR mixtures accurately.