# Bonding Evaluation of Asphalt Emulsions used as Tack Coats through Shear Testing
## 1 Introduction
Finally, a study of adhesion using the LCB (Laboratorio de Caminos de Barcelona) shear test was performed by [PERSON] [14] to characterize adhesion in ultra-thin whitetopping reinforcements, while [PERSON] [15] and [PERSON], [PERSON] and [PERSON] [9] analyzed the adhesion of an asphalt concrete-geosynthetic interface. Based on previous works, reducing those structural conditions [16; 17] affirmed that one of the most influential factors in the service life and maintenance of pavements was appropriate bonding between layers, which is obtained by the correct application and surveillance of asphalt emulsion procedures during road construction. This process allows the pavement to act as one element to properly distribute strains, thus reducing the presence of cracks and deformations. This research is focused on complementing the idea that a low-viscosity asphalt emulsion can perform better than a normal emulsion because it can cover the entire surface and fill imperfections in the layers we are bonding. This process results in an improved interlock between layers (as sustained in reference [18]) and seeks to reinforce the perception of asphalt emulsions. Because emulsions are most commonly used for bonding layers due to their low-temperature application capability and low asphalt content, their use is a sustainable method. For this reason, in this article, the adherence of asphalt emulsions was evaluated and used as tack coats through LCB Shear Testing. [PERSON], et al. [19] maintain that during recent years, the study of tack coats in pavements has gained importance in Europe; as a consequence, many researchers have studied the behavior of bonding layers through the analysis of torque, tensile, and shear tests, where some factors with high relevance for asphalt emulsion performance, such as the dosage, asphalt content, type of asphalt mix, contact surface characteristics, compaction load, and application temperature, have been identified [20]. Considering the methodology of the Leutner test model, [PERSON], et al. [21] performed complementary studies to analyze the bonding layers. However, the asphalt emulsion behavior over time has only been studied in a limited way. [PERSON], et al. [22] concluded in their experiments that the bonding improved after a period of days; additionally, the investigation by [PERSON] and [PERSON] [8] showed the long-term performance interactions between asphalt layers and the tack coat. The asphalt emulsion effectiveness when applied as a tack coat between pavement layers was analyzed in terms of the dose and setting time [20]. Considering the dose and setting time of the asphalt emulsion, [PERSON] [23] demonstrated that the best performance was achieved when using doses of 0.45 L/m\({}^{2}\) instead of 0.18 L/m\({}^{2}\) and when using a setting time of 30 to 60 min before compaction of the asphalt layer. Therefore, the objective of this research was to evaluate the mechanical behavior (fracture energy and maximum load) of cationic slow (SS) and rapid (RS) setting asphalt emulsions with different asphalt contents, dosages, and cure times through LCB shear testing at a temperature of 25 \({}^{\circ}\)C. These tests produced displacement-load curves of the asphalt mix specimens. Furthermore, the relationships between the emulsion dosage, asphalt content, and curing time and the maximum applied load and fracture energy were found.