Application of image analysis tools in Matlab to better estimate the degree of binder coverage in rolling bottles test

In asphalt mixture, a strong affinity between binder and aggregates is of prime importance, especially under conditions susceptible to moisture damage. Out of various modifiers/additives used in the literature, the hydrated lime (HL) has been reported as most suitable for improving affinity between binder and aggregates. Therefore, this study attempted to quantify the affinity of HL modified mastics with different aggregates under moist conditions. Further, in order to measure the affinity, the rolling bottle test (RBT) was used, which is also reported as one of the best empirical techniques for assessment of moisture susceptibility. However, in the RBT, the assessment for affinity is generally made through visual inspection by two experienced operators as per a standard procedure which can also be the major drawback of this technique in terms of less reliability and repeatability. Thereby, to reduce this deficiency, the image analysis (with no special setup) was also carried out through the use of the MATLAB program. The results as obtained from image analysis were then compared with the results of visual observation. Both were found to be very similar to each other. Hence, the RBT could be used confidently for the comparison of different binder/aggregate combinations. Also, the RBT results indicated that the HL addition was beneficial with granite, basalt and greywacke aggregates, but it did not have any effect with limestone aggregates. Further, the 10% HL substitution was found to be more efficient than 20% HL substitution as both substitutions showed a similar effect in most of the studied combinations.