In search of a possible size-demarcation between load bearing and suspended aggregates in asphalt mixture – an experimental approach

Abstract

Asphalt mix is composed of aggregates of various sizes. It is generally considered that the large-sized aggregates participate in the load transfer through their contact regions, while the smaller aggregates remain suspended within the asphalt binder. The objective of the present study is to investigate whether such a size-demarcation exists, and if so, what is that size. To seek an answer to this question, studies are conducted on the homogeneity of aggregate arrangement and the distribution of the shortest inter-aggregate distance using cross-sectional images of the asphalt mix samples. Compressive strength test, indirect tensile strength test, creep test are also conducted on incomplete asphalt mixes. These incomplete mixes are obtained by skipping one or more sieve sizes. Based on these studies, it appears that a size of 4.75 mm (for the aggregate gradation with nominal maximum size of 13.2 mm used in the present research) construes such a size demarcation. This size demarcation may be different for mixes with different nominal sizes, and hence more research is indeed needed in this direction. Nevertheless, the present paper proposes a new idea of classifying aggregates as coarse or fine, based on their relative roles in load transfer in the case of an asphalt mix.