Evaluation of effect of compaction method on the macrostructure of asphalt mixtures through digital image processing under Brazilian conditions

Abstract

For achieving good performance in the field, the asphalt road surfaces compaction must be adequate. The compaction properties and the mechanical performance prediction in the field are previously established from laboratory specimens. Laboratory compaction is carried out through impact, kneading or vibration and these methods differ from compaction in the field. From this, is necessary to establish a comparison between compaction in the laboratory and in the field in terms of the macrostructure (aggregate distribution in the fine aggregate matrix) and air voids distribution. The aim of this study was to determine the laboratory compaction technique which is most representative of compaction in the field, by testing different methods and compactors. Thus, asphalt mixtures were compacted in a gyratory compactor with different gyration angles (0.75°; 1.0°; 1.25; 1.5° and 1.75°). Asphalt mixtures produced with the aid of a Marshall compactor and a French roller compactor were also analyzed. In addition, specimens compacted in the field, were analyzed and evaluated. Analysis of the compaction methods was studied whether digital image analysis using a software application (IPAS-2). The results showed that the Marshall and the gyratory compactors (gyration angles of 0.75°, 1.25°, 1.0°) were the most representative of the compaction in the field, regarding the macrostructural parameters. However, the Marshall compactor presented the greatest variability in the results. As a result, the gyratory compactor, (gyration angle of 1.25°) was best approximates compaction in the field.