On the Mix Design Advances in Microsurfacing: A Systematic Surface Performance-Oriented Literature Review

Among surface maintenance treatments, microsurfacing (MS) has attracted scientific and practical interest as a preventive solution for pavement maintenance in order to promote road safety, cost-effectiveness, and environmental sustainability. MS is widely recognized for the ability to improve the main functional characteristics of road pavement, which are essential to ensure driving comfort and safety, while extending the pavement service life. Given the excellent surface properties of MS, the present research wants to cover the state-of-the-art gap through a deep literature review focused on skid resistance, surface macrotexture, and noise emissions performance, by including both laboratory and field applications. To give the readers a comprehensive framework on the current advances in MS, the literature analysis combines the surface performance-related information with the improvement in MS mix design, which includes new additives, wastes, or by-products. In addition, this work provides a critical interpretation of the data from a statistical point of view, and a comparison with the threshold values set by an Italian Road Agency. The systematic literature review concluded that MS shows excellent performance of skid resistance and macrotexture: data collected always exceed the threshold values set by the road agency, and more than 70% of the total data are significantly above them. Moreover, the information collected suggests that MS noise emissions are comparable to conventional surface courses (e.g., hot mix asphalt, split mastics asphalt), but the manipulation of the grading curves and the use of sound-absorbing materials can even improve its acoustic features.