5.1. Study Summary and Significance
The overall result of the study on the reduction of plastic deformation in the intersection of heavy traffic in urban areas is presented here. First, 20 mm WC-5 mixtures should be applied, as its maximum aggregate size is advantageous in reducing plastic deformation among fluid-resistant asphalt mixture conditions. The satisfaction conditions should be fulfilled in the form of an S-Curve avoiding the restriction of the Superpave to the underside of it. First-grade aggregates with less than 10% elongated particles should be used. Second, in WC-5 mixtures, PG 64-22 normal straight asphalt binders showed more than two times the resistance against plastic deformation. However, PG 76-22 modified asphalt binders are recommended as these have more commonality and economic feasibility. Third, in SMA mixtures where the interlocking feature of aggregates was maximized by increasing the use of coarse aggregates, better commonality and economic feasibility could be achieved by using the PG 64-22 normal straight asphalt binder instead of the PG 76-22 modified asphalt. Fourth, by applying fiber grid reinforcements to PG 76-22 SMA mixtures, a 25% higher dynamic stability value than that of PG 64-22 SMA mixtures was observed. However, because of the high construction costs, the economic feasibility was insufficient. Fifth, the prediction of pavement life by the performance analysis resulted in the analysis of net present value economics under the mixing conditions of each fluid-resistant mixture and clade-mastic mixture. The results also showed a WC-5 with a relatively long pavement life and low construction costs during the 35-year analysis period. Sixth, the researchers recommended the application of the fiber grid-reinforced PG76-22 SMA mixture, with the best resistance to plastic deformation for certain sections up to 20–30 m from the vehicle stop line. Finally, when applying tensile strength ratio and dynamic stability as the standard for asphalt mixture performance tests, the specifications and instructions differ from each other. This calls for their reorganization.
Through this study, more objective and efficient ways of reducing plastic deformation were analyzed. In prior studies, theoretical interpretations and experimental results were derived primarily from indoor combination design conditions. Contrarily, through objective experimental results and performance analysis, field engineers may economically and realistically apply this study to construction.
5.2. Suggestions for Reducing Plastic Deformation
The experimental studies in this research objectively analyzed several ways of reducing plastic deformation. However, the interest and willingness of the participants to implement the systematic guideline are more important. Although excellent solutions are provided as guidelines to overcome plastic deformation, the effects of these solutions cannot be guaranteed unless the efforts and practices of participating engineers are applied to the design, construction, and supervision.
Based on the results of this study, the researchers recommend the following improvements in technical skills throughout design, construction, and supervision. First, more realistic traffic conditions and diverse pavement material variables should be considered for applying for road pavement design programs as a design method. Plastic deformation is closely related to the properties of aggregates. An accurate public performance should be analyzed by supplementing the class of aggregates and parameter values of the materials for the pavement of the clade mastic. Next, the most economical method should be selected. When presenting this in the design budget, it is crucial to reflect the most appropriate measures for the entire life cycle from a macro perspective, such as aggregate grades, binder grades, compositional design conditions, etc. Second, quality control in the production and construction process of asphalt mixtures is a key to impact pavement life significantly.
However, most construction sites still rely on hands-on experience to manage their work. The ordering agencies and construction management facilities supervising these actions lack an overall understanding of pavement, thereby leading to a passive stance on reducing plastic deformation. To solve this problem, more facilities specializing in pavement should be founded to supervise the quality control of pavement. Moreover, it is necessary to operate a systematic and regular management program involving those in charge of ordering, construction project management, construction work, and production companies. Third, as a long-term improvement measure, it is necessary to secure appropriate business periods and project costs suitable for the construction technology of the world’s top 10 economies. Thus far, the management system evaluates the lowest price first. Consequently, all construction project costs in Korea are not reflected in the appropriate project price. The construction period also lacks proper reflection of the five-day workweek or legal holidays. Furthermore, this excessive push for construction is leading to poor quality. Finally, institutional improvements based on related consultations will certainly decrease the social costs from the faulty pavement, such as plastic deformation and cracks. In future studies, cracks should also be analyzed since the cost for fixing cracks would be another big part of the financial burden to transportation agencies, decreasing the fatigue life of the pavement.