An automated technique for characterising foamed bitumen using ultrasonic sensor system

Abstract

ABSTRACT The foam characteristics that are used to assess the quality of foamed bitumen are conventionally measured manually using a dipstick and stopwatch. Considering the related safety concerns in manual measurement and sensitivity of the performance characteristics of foamed bituminous mixes (FBMs) to the foam characteristics, the present study aimed to improve the process of determining the bitumen foam characteristics during the foaming process. Accordingly, an ultrasonic sensor system which is capable of automatic non-contact measurement of foam characteristics was developed. The capability of the proposed method in terms of producing repeatable results was evaluated based on repeatability limit, Analytical Performance Value (APV) and coefficient of variation (CV). The study results indicate that the ultrasonic sensor system is very promising in terms of its ability to provide a detailed history of the change of volume of foamed bitumen with time with high repeatability. Conversely, the repeatability of the manual method of measurement was found to be very low at all most all foaming conditions. In addition, to eliminate any possibility of error in determining the foam characteristics obtained from the ultrasonic sensor system, a data analysis algorithm was recommended to analyse the bitumen foam height profile data collected from the device.