Investigation of the effect of using preheated aggregate and modified binder on chip seal adhesion properties

Chip seal constructed on a compacted granular base are widely used in Turkey, South Africa, Australia, New Zealand, England, etc. Especially, a significant portion of 40183 km of Turkey's 67333 km road network consists of chip seal roads. Chip seals are also used for deterioration preventive maintenance purposes for bituminous hot mix asphalt. The performance of the chip seal can be affected by numerous factors before and after construction. The adhesion performance of the aggregate in the chip seal is significantly affected by the traffic volume of the road, its location, climate, the nominal size of the applied aggregates and the construction method, etc. In this study, three types of aggregates and two types of bitumens were used. Also, bitumen samples were modified with Poly Phosphoric Acid (PPA) at three different percent (at 0.5%, 1.0 and 1.5% by weight) so totally eight type bitumen samples were used. The effect of using heated aggregates at four different temperatures (80 oC, 90 oC, 100 oC, 120 oC) on the adhesion performance of chip seal was investigated by Vialit adhesion and Nicholson stripping tests. Besides, a benefit/cost (B/C) analysis of the improvement of adhesion due to heating the aggregates and modifying the bitumen with PPA in the chip seal application was performed. It was understood that the heating of the aggregates and the PPA additive played a healing role on the adhesion. It was concluded that the use of preheated aggregates provides a higher B/C value than the use of PPA additives. The most important reason for this is that the unit cost of the PPA additive is higher than the aggregate heating cost and the adhesion performance is as good as the PPA added bitumen.