## 2 Debonding Mechanisms and Reduction of Debonding Risk
Smaller slabs make it difficult to keep wheel paths away from joints, thereby incrementing the risk of flexural debonding due to vertical traffic loads [27]. Moreover, bigger slabs can rest a higher number of wheels on them, which increases shear stresses in the interface due to horizontal traffic loads [13]. Since stresses produced by uniform length changes are concentrated on the vicinity of discontinuities, size has no significant impact on them [28; 29; 30]. Nevertheless, interfacial stresses due to non-uniform length changes and subsequent curling and warping are lower in shorter slabs [31]. Joint properties determine load transfer between adjacent slabs and water penetration towards the interface. Load transfer between two adjacent slabs [32] is produced by both the effect of aggregate interlocking and continuity of the bottom layer of the pavement [10; 33]. Fibers also contribute to improving the load transmission by limiting joint and cracks opening and generating a dowel bar effect [34]. Proper load transfer reduces the magnitude of normal debonding stress on the unloaded slab [10]. Water penetration towards the interface through the joints should be avoided because it might reduce interfacial bond strength. In addition, in the case of whitetoppings, the impact of water is more drastic since it can cause asphalt stripping and raveling [35]. To avoid this, joints must be sealed with hot-poured asphalt sealant and the use of backer rod should be avoided [15]. Interfacial treatment plays a crucial role in the mechanisms of interfacial debonding since the magnitude of the interfacial strength depends on it [36]. The most frequently used treatments relate to increasing the roughness of the interface, either by milling (for whitetoppings) or by shotblasting (for overlays) [15]. At the laboratory level, interface grooving has also shown good behavior [16]. Bonding agents should be employed very carefully because their coefficient of thermal expansion is usually very different from that of concrete [14] and weak planes might be generated at the interface [8]. Finally, the concrete mix also influences the mechanisms of both bond strength and stresses in the interface since compounds regulate the mechanical and physico-chemical properties of the overlay. For instance, high-performance concrete might not require additional treatment to the interface [37], the addition of fibers could also improve the adherence [38; 39; 40] and reduce the deterioration of joints and cracks [41]. Meanwhile, stronger aggregates and greater aggregate top size can also increase the load transfer in joints [32]. To reduce stresses produced by vertical and horizontal traffic loads, increasing the elastic modulus would be desirable [13; 42]. In case of stresses due to variations in length, the mix can be optimized for reducing differential deformations between layers due to temperature, drying shrinkage, and autogenous shrinkage. Although the phenomena behind these change lengths are complex and involve many variables, a careful selection of as materials, mix proportion, pavement geometry, or degree of restraint can help in their minimization.