In the contemporary era, 3D printing technology has become widely utilized across diverse fields, including biomedicine, industrial design, manufacturing, food processing, aerospace, and construction engineering. The inherent advantages of automation, precision, and speed associated with 3D printing have progressively led to its incorporation into road engineering. Asphalt, a temperature-responsive material that softens at high temperatures and solidifies as it cools, presents distinctive challenges and opportunities in this context. For the effective implementation of 3D printing technology in road engineering, 3D printed asphalt (3DPA) must exhibit favorable performance and printability. This requires attributes such as good fluidity, extrudability, and buildability. Furthermore, materials utilizing 3DPA for crack repair should possess high viscosity, elasticity, toughness, superior high-temperature stability, and resistance to low-temperature cracking. These characteristics ultimately contribute to enhancing pavement longevity and ensuring worker safety.

The strength criteria is the acceptable strength for allowable a vehicle start on a concrete pavement at an early age without causing significant damage. The different agencies have provided the strength criteria based on empirical judgement. To make more comprehensive, the ACI specification provided strength criteria by consideration traffic conditions, slab thicknesses, and slab support based on the concept of damage. However, its neglected to consider the damage caused by curling stress due to temperature gradient in concrete pavement. This research aims to provide a strength criteria for opening traffic on concrete pavements while taking into account the damage caused by curling stress and traffic loading. The tensile stress at critical locations was determine due to curling and traffic loads every hour of early age throughout different seasons. The fatigue damage taken throughout early age was assessed. After this procedure, the strength criteria was established as the evaluated damage that did not exceed an acceptable limit. Accordingly, the strength criteria for opening traffic was determined to ensure that the specified damage level existed subject to the construction season, construction period, traffic type, slab thickness, and slab support of concrete pavement.

PURPOSES : The purpose of this study was to improve the performance of concrete pavements by decreasing measurement deviations using an Internet of Things (IoT)-based air content measurement device. METHODS : We calculated the properties of concrete which varied according to the air content. For a low measurement deviation, the concrete pavement performed according to the design standard. To confirm the difference in the performance of the concrete pavement for various air contents, we verified the change in the relative dynamic modulus according to the number of freeze–thaw cycles for each value of the air content. In addition, we analyzed the number of durability cracks according to the freeze–thaw cycles in the field. RESULTS : We confirmed that IoT-based measurement equipment improved the performance of pavements without changing their mixing designs or specifications. We confirmed that the performance of concrete pavements changed even with variations in air content within the range of quality standards. Using IoT-based air content management, we confirmed the reduction in concrete pavement durability cracks without changing the mixing design. CONCLUSIONS : We confirmed that IoT-based air-content management improved pavement performance. The feasibility of extending this concept to manage other concrete properties such as the chloride content should be acknowledged. Future research will require laboratory tests to understand the variation in concrete properties with varying air contents and to consider diverse load conditions.

PURPOSES : This study aims to understand the effect of defective dowel bar installation on jointed concrete pavement (JCP), which can cause joint freezing, spalling, cracking, and faulting and finally shorten the lifespan of the pavement. METHODS : A comprehensive field survey was undertaken at an expressway construction site in South Korea to assess dowel bar installation conditions. In addition, finite element (FE) analysis was used to simulate JCP behavior with both vertical and horizontal dowel misalignments. Different temperature conditions, including a change of -55 °C and gradient of -0.1 °C/mm, were integrated into the FE model to examine horizontal slab contraction and simultaneous slab curling. RESULTS : The analysis revealed pronounced slab behaviors under specific temperature changes, particularly when combined with dowel misalignments. The simultaneous effects of horizontal contraction and slab curling owing to temperature changes and gradients became more evident in the presence of dowel misalignments. CONCLUSIONS : The results confirmed that dowel bar misalignment considerably affected the behavior of the JCP, thereby emphasizing the importance of the proper installation of dowel bars.

PURPOSES : Previously, the expansion state of the concrete pavement in which AAR occurred could not be determined. Because the current situation has not been evaluated, it has been difficult to prepare an appropriate response. In this study, a method for calculating the expansion amount of concrete pavement using the stiffness damage test (SDT) is proposed. METHODS : The SDT method was examined through a literature review. For the laboratory tests, specimens that generated AAR were produced based on the mix design (2018) of the Korea Expressway Corporation. SDT was used to calculate various mechanical properties, and their correlation with the expansion amount was reviewed. RESULTS : Using the SDT, various mechanical properties(elastic modulus, hysteresis area, plastic deformation, plastic deformation index, stiffness damage index, and nonlinear index) were calculated based on the expansion rate of the AAR. The elastic modulus was evaluated as the best predictor of the expansion rate. Thus, if the elastic modulus is calculated using SDT, a prediction equation can be used to calculate the amount of AAR expansion. This equation will need to be supplemented by further research. CONCLUSIONS : SDT was used to confirm that the expansion state due to the AAR of the concrete pavement could be indirectly evaluated. Among the mechanical properties related to SDT, the elastic modulus was found to be the most suitable for predicting the amount of expansion.

PURPOSES : The purpose of this study was to improve the performance of concrete pavements by measuring the unit-water content with an Internet-of-Things (IoT)-based unit-water content measurement device at an increased precision compared with that of existing measuring equipment. METHODS : We calculated the properties of concrete that varied according to variations in the unit-water content. To confirm the change in the performance of concrete pavements, we compared and analyzed the fatigue cracking rate and international roughness index of concrete pavements at the 20-year point of public use according to the changes in properties using the Korea Pavement Research Program(KPRP). RESULTS : We confirmed that IoT-based measurement equipment can improve the performance of pavements without changing their mixing designs or specifications. We confirmed that the performance of the concrete pavements changed significantly, even with unit-water content variations within the range of quality standards. According to IoT-based unit-water content management, we confirmed that the performance of the concrete pavement (fatigue cracking rate and international roughness index) improved without changing the mixing design. CONCLUSIONS : We confirmed that by using IoT-based unit-water content management, pavement performance can be improved. It is necessary to consider whether the application of this concept to other concrete property management items, such as the chloride content, is possible. Considering the changes in concrete properties according to the unit-water content based on laboratory tests and considerations of various load conditions will be necessary for future research.