Evaluation of climatic effects on moisture variation and performance of unbound pavements with sprayed seals

Abstract

Over 90% of Australia's surfaced roads are unbound pavements with sprayed seals. However, achieving complete impermeability with these seals is challenging, leading to some moisture exchange between pavement layers and the environment. As moisture fluctuations influenced by climatic factors significantly affect the structural performance of particularly unbound granular layers, there is a pressing need to enhance Australian pavement design by incorporating climatic effects to meet better pavement performance. Hence, the current study numerically evaluates the degree of moisture saturation ($${S}_{r})$$ S r ) variations of pavement layers under different Australian climates. This paper reveals how ambient climate impacts the moisture variations of pavement layers based on the results of 126 numerical simulations performed. Results indicated that the annual rainfall is not an appropriate parameter to decide the service moisture condition of the UGM layer, but the ratio between annual rainfall and annual pan evaporation ($$\frac{P}{{\text{PE}}}$$ P PE ) combined with the saturated permeability of the seal ($${K}_{{\text{s}}})$$ K s ) is found to be a better indicator. More importantly, this study develops a novel empirical model to predict the service moisture condition of the UGM layers aiming to advance the current Australian pavement design guide. Furthermore, a correlation between pavement moisture and a widely used climatic index, Thornthwaite Moisture Index ($${\text{TMI}}$$ TMI ) is presented in this study. Furthermore, this paper proposes a novel approach to integrating climatic factors into the current Australian pavement design of unbound pavements with thin seals. This study enhances understanding of the complex relationship between climate and pavement moisture by taking a multi-dimensional approach.