Determining the continuous water absorption of unbound granular aggregates utilising hydrostatic weighing approach

Abstract

In most flexible pavement structures, Unbound Granular Materials (UGMs) are exposed to the surrounding environment. Whilst in direct contact with materials, weathering agents can trigger chemical reactions and cause ageing and deterioration of UGMs. In practice, propensity to water absorption can be a principal durability parameter of a road material; however, current testing methodologies fail to suggest a clear understanding of the real-time appetite of aggregate for water. This study devised a Continuous Water Absorption (CWA) testing procedure, based on Archimedes’ principle to gain insight into water-aggregate interactions. The robustness of this method is demonstrated by conducting tests on three replicated samples from two sources of aggregates, Premium and Marginal andesite. Aggregates were tested in various conditions, including three temperatures (5 °C, 20 °C, and 35 °C), and two compositions of the solution (distilled water and tap water). Overall, the CWA results revealed that water absorption of aggregates is highly temperature and solution composition dependent; and the traditional water absorption test methodology generally underestimates the appetite of aggregates to absorb water. In addition, it was proven that the presence of clay minerals in the structure of Marginal aggregates could cause an increase in the propensity of aggregates to absorb water. It is also notable that Premium aggregates indicated higher susceptibility to the testing conditions. In order to reduce the chemical weathering of UGMs, the CWA test results can be used to approximate an effective time to drain water from Unbound Granular Layers (UGLs).