Laboratory testing methods for evaluating the moisture damage on the aggregate-asphalt system

Abstract

The durability of the bitumen-aggregate system is a critical factor affecting the performance of asphalt pavements. It is achieved by a careful selection of the materials based on the analysis of their compatibility and their water sensitivity. Currently, a variety of analytical test methods are used to evaluate the power of the binder to adhere to various aggregates and their susceptibility to moisture. Many of these methods are time consuming and/or require sophisticated and expensive instrumentation. The most common procedure, the indirect tensile strength (ITS) test, has been questioned by many researchers and simpler testing procedures, such as the rolling bottle test, are considered to be an indicative measure. Several studies have introduced a new test procedure, the binder bond strength (BBS) test. The test, based on the pull-off strength of the bond between asphalt and aggregate measured before after water conditioning, has shown good repeatability, reliability and the ability to determine the effects of different aggregate type, conditioning time and moisture on the aggregate-asphalt system. This paper explores the potential of the BBS test by correlating the results of test methods presently used to evaluate the strength of the bond of the asphalt-aggregate system measured with the BBS test. Four different aggregate types and a traditional bitumen were tested according to the respective European standard, including type, length and temperature of conditioning. However, the different aspects of the mixture considered in each test method determine a poor agreement of the results. Comparable levels of moisture resistance are observable only in the long term.