Cold In-Place Recycling with Expanded Asphalt Mix (CIREAM)

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Abiodun, Samuel
Cold in-place Recycling , Early Strength , Moisture Resistance , Expanded Asphalt
Cold in-place recycling with expanded asphalt mix (CIREAM) has become an accepted road rehabilitation technique in Ontario and other parts of the world given its advantages over regular cold in-place recycling (CIR) and other methods. Although CIREAM offers early strength advantages and extended paving periods among other benefits, late season CIREAM can be burdened by distresses such as ravelling, potholing and other moisture-induced damage. Limited information on the behaviour and failure mechanisms of CIREAM has also hindered its utilization in spite of the numerous benefits. This research investigated effects of additives on foam properties of roofing asphalt flux (RAF) binder in order to evaluate the suitability of the binder for CIREAM. The study also investigated how mixture variables and test protocols affect performance properties that relate to early strength and moisture resistance of CIREAM versus CIR. Indirect tensile strength testing with moisture conditioning was used to assess the effects of asphalt cement type (80, 300 pen grades and polymer modified asphalt), conditioning time, and additives such as Portland cement, foam stabilizers, polymers and fibers. Uniaxial cyclic compression with partial confinement was used to assess effect of additives on deformation resistance of recycled mixes. Although a siloxane-based stabilizer significantly improved the stability of RAF foam, the binder may not be suitable for CIREAM due to its limited expansion. The optimum binder content was found to be around 2 percent, which is significantly higher than the minimum 1 percent currently used in Ontario. Both Portland cement and the siloxane additive exerted significant positive effects on strength behaviour and moisture resistance of the recycled mixes. In regular CIR mixes, 2 percent binder content gave desirable early strength and strain performance compared to 1 percent. Application of controlled amounts of additives (e.g. Portland cement, foam stabilizers) and case-by-case evaluation can improve the performance properties of CIREAM and address the associated problems. The entire research effort described in this thesis was designed to provide advice on potential improvements in the CIREAM process as it is currently carried out in Ontario, and also help in developing quality control standards in CIREAM and other cold mix processes.
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