Hveem Mix Design and Engineering Properties of Cold In-Place Recycling Mixtures
AuthorAyala Castaneda, Federico
AdvisorSebaaly, Peter E.
Civil and Environmental Engineering
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Nevada DOT has used Cold In-place Recycling (CIR) procedures for more than 20 years. The necessity of a performance-based criteria for CIR mix design is imperative to keep improving the overall conditions of the state roads. This study is part of a research based on developing new criteria for CIR mix design and construction in the state of Nevada. The objectives of this study were: a) analyze the impact of different variables on Hveem mix design of CIR mixtures, b) evaluate the moisture sensitivity of CIR mixtures, c) determine the dynamic modulus (E*) master curves of CIR mixtures, d) evaluate the resistance to permanent deformation of CIR mixtures, and e) conduct a mechanistic-empirical analysis of rutting performance to determine layer coefficients for CIR mixtures.CIR mix designs were performed with the following variables: a) four types of asphalt emulsions including polymer modified and tire rubber asphalt residue; b) two contents of lime slurry (4.5% and 6.0%); and c) two types of gradation, controlled or graded Reclaimed Asphalt Pavement (RAP) meeting Pacific Coast Committee on Asphalt Specifications (PCCAS) and non-graded RAP crushed aggregates. The mix designs were conducted following the Hveem standard method with some modifications and evaluated using Tensile Strength Ratio (TSR) criteria for moisture sensitivity. The results were compared with a previous study using the same materials and designed following Superpave Gyratory method. The type of emulsion and gradation play important roles in the determination of the optimum emulsion content. Dry and wet tensile strengths of the CIR mixtures showed to be higher when using the Hveem mix design than the Superpave method. Performance of CIR mixtures was evaluated by means of dynamic modulus master curves and resistance to permanent deformation using the Repeated Load Triaxial test (RLT). Dynamic modulus tests were conducted using the Asphalt Mixture Performance Tester (AMPT) device and the master curves were built using AASHTO-R84 standard procedure for asphalt mixtures with few modifications. RLT tests were conducted using the Universal Testing Machine (UTM) and the results were used to develop rutting performance models for each CIR mixture. The type of emulsion appeared to be the most critical variable for the stiffness of CIR mixtures. The CIR mixture resulted to have a high rutting-based layer coefficient according to mechanistic-empirical analysis.