Evaluation of a Laboratory Asphalt Rotary Compactor
Haghighi, Hamed (2009) Evaluation of a Laboratory Asphalt Rotary Compactor. Masters thesis, Universiti Putra Malaysia.
Several studies have shown that Marshall Compactor, California Kneading Compactor and Gyratory Compactor, the most conventional compactors, are not able to produce laboratory specimens that can truly represent the mixtures compacted in the field. However gyratory compactor fairly gives good simulation of the field roller compactor but no universally approved laboratory compactor has been developed to compact slabs for the wheel tracking and fatigue test. Compacting and preparing more than one sample at the same time is another matter of concern which these conventional compactors cannot achieve. Hence, a suitable laboratory compaction procedure is inevitable. Rotary compactor, a laboratory roller compactor was developed by researches from Universiti Putra Malaysia (UPM). This study was conducted to evaluate the performance of rotary compactor as a laboratory asphalt compactor and incorporated three objectives: to establish a laboratory protocol including procedures and standards for using the UPM rotary compactor, to evaluate the consistency of SMA slabs in terms of thickness and frictional resistance properties, and to validate the use of UPM rotary compactor in achieving the SMA mixtures’ requirements for bulk specific gravity, voids, Marshall stability and flow, resilient modulus and resistance to degradation. To compact a rotary slab to the desired thickness of 65 mm and 4% air voids, the applied pressure was recommended to start from 0 bar (as pre compaction) and stop at 1.5 bar with intervals of 0.25 bar. For each value of applied pressure, 6 number of passes (rotations) were needed (3 passes per each direction). The speed of rotation was recommended to be fixed on 10 Hz (3.29 RPM). Based on checking 315 points of three slabs to measure the thickness and the statistical analysis of these three slabs, the overall thickness of the slabs was almost uniform along the slabs. According to analyzing the performance of 132 core specimens it was concluded that rotary compactor was able to produce slabs with uniformly distributed properties such as volumetric properties, Marshall stability, flow and resilient modulus. Finally a degradation study was carried out to check and evaluate whether the aggregate structure was changed during the mixing and compacting. It was found that two aggregate fractions (12.7 mm and 9.5 mm) were affected and crushed during mixing and compacting procedures. To compensate the observed loss percentages a value called weight factor was introduced to provide the loss of materials.
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