## 1 Introduction  
Cracks in the road pavement cause the acceleration of damage due to a decrease in durability. In addition, the penetration of water into the lower layer through the cracks causes additional damage, due to the decrease in the adhesion and shear resistance of each pavement layer. In Korea, the application of composite pavement that applies asphalt surface overlay has recently increased to repair damaged concrete pavement [1; 2]. However, composite pavement has a disadvantage, in that it is vulnerable to reflective cracking in the joints or cracks of the existing concrete pavement. Once reflective cracking occurs, water penetrates, and the deterioration of the existing concrete is accelerated, which in turn significantly reduces the service life of the entire pavement system. A stress relief layer is an excellent alternative for suppressing these reflective cracks [2; 3]. According to various studies related to reflective cracking, it has been reported that the stress concentration phenomenon occurring at the crack tip increases the crack propagation speed [4; 5; 6]. In addition, it has reported that the load transfer efficiency of the stress relief layer reduces the reflective cracks occurring in the existing cracks or joints [7; 8; 9; 10]. As a result of investigating the performance of the stress relief layer under various environmental conditions, it has been reported that the performance of the stress relief pavement structure in a warm area is superior to that in a cold area [7; 11; 12; 13; 14; 15]. On the other hand, research by [PERSON] et al. and others [16; 17; 18; 19; 4; 6; 7; 11] has reported that the stress relief layer increases the life of pavement by 2-5 years, but does not completely suppress the reflective cracking. A study by [PERSON] et al. [20] reported that the stress relief method using a chip seal delayed reflective cracking by 3-5 years. In the study of [PERSON] et al. [13], it was reported that the stress relief method using a chip seal has a strong effect of preventing water penetration. [PERSON] et al. [21] conducted a wheel tracking test and a fatigue crack test to investigate the effect of the fiber-asphalt composite stress relief layer in overlaid asphalt pavement. As a result of the experiment, it was reported that when the stress relief layer was installed at the bottom of the overlying layer, it showed the greatest effect, reducing permanent deformation by more than 50% and increasing the fatigue crack propagation time 10 times. [PERSON] et al. [22] evaluated that a specimen with a stress relief layer installed at the bottom of the asphalt layer had a life extension effect of about 10 times compared to that of an unreinforced asphalt specimen through a laboratory fatigue cracking test of asphalt specimens. In South Korea, a crack prevention layer using a glass grid has been applied as a rehabilitation method for highway concrete pavements to suppress reflective cracks. In this method, emulsified asphalt is sprayed on the existing pavement surface as an adhesive, and then the glass grid in the form of a roll manufactured in the factory is heated on site and attached to the existing pavement surface. Therefore, the construction speed is slow, and the longitudinal roughness may be degraded due to distortion of the glass grid during the construction of the upper asphalt layer. The F-SAMI (fiber-reinforced, stress-absorbing membrane interlayer) method, using integral continuous construction equipment, has been recently introduced to improve the construction disadvantages of the glass grid method. This method can minimize construction time, because it continuously sprays emulsified asphalt, fiber, and aggregate using integrated equipment. In addition, there is an advantage of reducing construction cost by about 30% by removing the factory manufacturing process of the crack prevention layer by manufacturing and constructing the fiber-asphalt composite layer on site.