Investigation of the suitability of cold recycled asphalt concrete for patching potholes in Uganda
Otim, Emmy Kilara
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This study investigated the suitability of cold recycled asphalt concrete as a potential material for pothole patching in Uganda with the aim of reducing on the energy and time used, costs incurred, and environmental pollution resulting from using Hot Mix Asphalt (HMA) as a primary material for patching potholes especially in a highly populated area like Kampala City. The Recycled Asphalt Pavement (RAP) material was collected from the Northern by-pass that is currently being reconstructed by Mota-Engil Construction Company. The RAP material was subjected to laboratory tests and relevant properties were obtained. Some of these properties include: Aggregate Impact Value (AIV) of 10.6%, Aggregate Crushing Value (ACV) of 7.4%, Los Angeles Abrasion value (LAA) of 28.6% and bitumen content of 5.3%. The bitumen emulsion K1-60 was acquired from Stirling Civil Engineers batching plant in Mukono (Mbalala). The bitumen emulsion was tested and the pertinent results include: positively charged, 60% bitumen content, 40% water content, residue on the 710μm sieve as 0.02% (m/m) and density of 0.95 g/cc. AASHTO modified Marshall Mix design was used to prepare the specimens at bitumen contents of 5.5%, 6.0%, and 6.5%. Mix volumetric, Marshall Stability and flow values were obtained from which the optimum bitumen content of the mix was determined as 5.9%. The specimen prepared at 5.9% bitumen content was subjected to conditioned and unconditioned indirect tensile strength tests from a tensile strength ratio (TSR) of 72 % was obtained. The Ministry of Works and Transport (MoWT) specifies a minimum acceptable TSR of 70 %. On this basis, addition of bitumen emulsion and cement to RAP improves the strength and reduces moisture susceptibility of cold recycled asphalt concrete mix making it a potential material for pothole patching in Uganda.