Development of an estimative model for the optimal tack coat dosage based on aggregate gradation of hot mix asphalt pavements

• Aggregate larger than 8 mm is directly related to macro-texture.
• The Gompertz model represents the higher increase of macro-texture on AC22 mixes.
• Shear strength is influenced more by aggregate gradation than tack coat dosage.
• Absorption of on site test decreases when % of aggregates larger than 8 mm increases.

In this work the performance of tack coats on asphalt pavement layers is analysed. Adjustment models based on experimental measurements were implemented, relating surface layer macro-texture and aggregate content larger than 8 mm. The best fits were obtained with a Gompertz model, which follows the expected physical macro-texture changes outside the test range. Shear strength was analysed, through prediction curves of each evaluated tack coat dosage, with an optimum tack coat performance for aggregate contents larger than 8 mm between 45% and 50%, and no relevant influence of the tack coat dosage used.

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