Research On Microstructure Of Environmental-friendly Asphalt Concrete Based On Digital Image Processing Technology

In recent years, the microstructure of asphalt concrete has become the focus ofresearch. However, most of them are concerned with the hot mix asphalt. With thedevelopment of economy, the resource on earth is decreasing rapidly. So peopleattach importance to the recycling of materials. In road engineering,environmental-friendly asphalt concrete are Porous Asphalt Concrete (PAC),Reclaimed Asphalt Pavement (RAP) and Dense Graded Asphalt Concrete with BasicOxygen Furnace slag (DGAC(BOF)). Based on the asphalt lab project of civilengineering department in National Cheng Kung University, Taiwan, this paper triesto analyze PAC, RAP and DGAC(BOF) from micro level and establish therelationship between the micro parameters and the macro properties. The maincontents are as follows:1. Research on the relation between and macro propertiesAccording to the formula=10022n(in=1sin2θi)+(in=1cos2θi), iscalculated. It turns out that the rutting depth increases with both for the specimensfrom lab and on the site. It’s because represents the inclination of aggregate. Theless the, the more uniform the aggregate distribution is. The rutting resistance ofPAC and DGAC（BOF）is superior to HMA. Although the rutting depth of RAC（40%）is bigger, it still conforms to the specification. So the application of RAC still makessense.As for the specimens DGAC(NA) and DGAC(BOF) from the site, modulus ofresilience and indirect tensile strength change with, the bigger the, the smallerthese parameters are. Besides, the performance of DGAC(BOF) is superior toDGAC(NA) on these aspects. 2. research on the uniformity of aggregate distributionThe cross sections of the lab specimens are divided into two parts, upper part andlower part. The uniformity is counted by the number of the aggregates in given ofupper part subtracting that of lower part. The result shows that PAC and HMA arerelatively uniform, the standard deviation is small. However, RAC(40%) containsmuch old materials. So its standard deviation is big.3. study of air void distributionImage-Pro Plus6.0is used in this paper to process pictures. But due to thesimilarity in colors between air void and bind, the software can’t deal it well. Socodes are written to extract the air voids. The air void changes with the depth, firstincreases, reach a maximum in middle and then decreases.4. Research on image gradationAccording to the proportion of equivalent diameter in each range, gradationcurve is drawn. The relative error Di is used to assess the difference between theimage gradation and the actual gradation. The result shows that the image gradation ofthe dense graded asphalt concrete is most close to the actual one. However, as forPAC，the average error is relatively big and the effect is not as good as others.This paper aims to analyze the micro structure of these three environmentalfriendly asphalt concrete——PAC，RAC（40%）and DGAC（BOF）, hoping to predictthe macro properties through the micro analysis.