Volumetric and Performance Comparison of Field Produced Lab Compacted and Laboratory Produced Lab Compacted Hot Mix Asphalt Mixtures: A Case Study On Three Road Projects In Addis Ababa
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Date
2024-05
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Addis Ababa University
Abstract
The aim of this study was to compare the mixture volumetric and performance of lab produced lab compacted and field produced lab compacted asphalt mixtures in terms of Marshal flow and stability (for Marshal samples), rutting and moisture sensitivity together with checking bitumen and aggregate qualities. In doing so, loose asphalt mixtures ready to be paved was collected from selected road sites in Addis Ababa and taken in to the laboratory. Raw materials like aggregate, filler and bitumen were also collected from their respective quarry sites and batching plants in order to produce laboratory control samples. In addition the batching plants of the study areas were assessed for age and capacity. The bitumen and aggregate were all found qualified with regard to design specifications on the case study areas. Those raw materials were then mixed in the laboratory by keeping the projects‘ aggregate gradation and optimum binder content.
Three road projects were involved in this study, namely Kality-Tuludimtu road project, Entoto-Kotebe Access road project and Imperial Kadisco Intersection project. The first two projects were designed using Marshal method and third project was designed using the Superpave method. The field and laboratory produced Marshal mixtures were compacted with Marshal compaction in accordance with design traffic level and the Superpave samples were compacted to Nin, Ndes and Nmax by a SGC machine according to field traffic level.
Understanding the performance and volumetric difference among field produced and lab produced Marshal and Superpave samples is used to mitigate the economic impact on the paving industry and take further implementations. Marshal samples were evaluated with indirect tensile strength, stability and flow. The Superpave samples were evaluated with indirect tensile strength and wheel-tracking test. On the way to these tests, the mix volumetric of both Superpave and Marshal samples were determined. The result of this assessment shows that, field produced Marshal samples show an average increment of 3.7% in bulk and theoretical maximum specific gravities while field Superpave samples found 0.2 times more than lab produced samples; which were manifested in the mix volumetric variation. The Marshal flow and stability test results also proven the difference between lab and field samples. Indirect tensile strength test results for Marshal laboratory mixtures were found 1.6 and 2.15 times more in accordance with field samples. The field Superpave samples, however show an improvement on indirect tensile strength test. The wheel-tracking test was also applied to Superpave samples to evaluate the rutting performance of the field and lab samples. The laboratory samples protected their structural integrity during the wheel loading duration and gave 24% lesser maximum rut depth than field samples. With the entire assessments of this study, laboratory samples of Marshal and Superpave samples proven better performance than field samples.
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Bitumen and aggregate physical properties, field and lab produced Marshal and Superpave samples, mix volumetric, performance measures