Laboratory Evaluation of Friction Loss and Compactability of Asphalt Mixtures
Emad Kassem, Eyad Masad, Ahmed Awed and Dallas Little, Texas A&M University, April 2012, 97 pp. (476660-00025-1)
This study aimed to develop prediction models for friction loss and laboratory compaction of asphalt mixtures. In addition, the study evaluated the effect of compaction level and compaction method of skid resistance and the internal structure of asphalt mixtures. The predictive model for friction loss was developed based on parameters that describe aggregate texture and angularity before and after polishing, aggregate gradation, and polishing cycles in the laboratory. Squared-shape slabs of asphalt mixtures were prepared in the laboratory using a linear kneading compactor and polished using a wheel-polishing device. The frictional characteristics were measured after different intervals of polishing cycles. Mixtures with coarser aggregate gradation were found to have better skid resistance than those with fine aggregate gradation. The friction loss model was found to correlate very well with the experimental measurements.
The predictive model for laboratory compaction of asphalt mixtures was developed based on parameters that describe aggregate shape characteristics, aggregate gradation, binder content, and binder properties at compaction temperatures. The researchers executed intensive laboratory experiments to quantify the effect of these parameters on the compaction of asphalt mixture in the laboratory. Two models that describe slope and intercept of the laboratory compaction curves of asphalt mixtures were developed. These models showed strong correlations between the predicted values and the measured ones. These models provide essential inputs to quantify the compaction effort needed to compact asphalt mixtures.
In the last phase of this study, the researchers evaluated the effect of compaction level and compaction method on skid resistance and internal structure of asphalt pavements. The vibratory roller was found to yield a smoother surface than the static roller. In addition, the results confirmed that the vibratory roller was more effective in reducing the air voids than the static roller. Moreover, the test sections compacted using the vibratory roller had more uniform air void distribution compared to the test sections compacted using the static roller.
Keywords: Asphalt Mixtures, Skid, Friction, Compaction, Texture, Angularity, Micro-Deval, AIMS, Abrasion, Polishing, X-Ray CT
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