A new empirical diffusion model for solvents in sprayed seals based on evaporation measurements

ABSTRACT

Prediction of solvent diffusion and evaporation rate in the initial days after construction of a sprayed seal is of special concern for pavement performance assessment. It is still a major challenge as solvent evaporation is a very complicated process. In this study, laboratory tests were conducted on bitumen-solvent binder films, under different experimental conditions and varying solvent properties. A solution of Fick’s diffusion equation was then used to calculate solvent diffusion coefficient (D) values for the initial 7 days. While a strong correlation was found between D and solvent viscosity as well as D and solvent distillation range, no relationship was found between D and solvent aniline point nor aromatic content. These findings were utilised in developing a multiple linear regression (MLR) diffusion model for the initial 7 days of evaporation. The evaluation of the model indicated close agreement between the predictions and experimental values (R²= 0.95). The model enables road agencies to predict solvent diffusion and residual solvent for the early life of a sprayed seal without needing to conduct extensive experiments thereby saving time and labour cost. Accurate prediction of residual solvent via the developed model will further ensure long-term performance of sprayed seals.

KEYWORDS:

• Sprayed seal
• chip seal
• diffusion
• evaporation
• residual solvent
• performance prediction and evaluation

Acknowledgements

The authors are grateful for the financial support of the Australian Research Council and Austroads in conducting this study. The authors acknowledge Australian Road Research Board (ARRB) for the opportunity to conduct the experiments in their laboratory. The authors also acknowledge the suppliers of the materials: Puma Energy Australia Pty Ltd, Viva Energy Australia Pty Ltd, IOR Energy Australia Pty Ltd, and Recochem Inc.

Disclosure statement

No potential conflict of interest was reported by the author(s).