Roller-compacted concrete or RCC is a dry concrete that requires compaction in order to reach its final form. Its consistency is usually overlooked due to its inconsistency and lack of subjective nature. To work with this concrete, however, proper consistency is necessary for supporting the compacting machine and minimizing compaction energy. Vebe time is used as consistency measurement due to RCC’s dryness. Vebe time ranged from 30 to 75 seconds is considered to be appropriate consistency for RCC in pavement application. The purpose of this study is to determine the effect of aggregate gradation, water content, admixtures and time on RCC’s consistency for pavement application. It was found that Vebe time decreased when water content increased and increased when sand by aggregate ratio or the amount of fine aggregate increased. The workable time of normal RCC mixture (an optimal mixture) was found to be less than 50 minutes. Poly Naphtalene Sulfonate superplatiscizer or PNS was discovered to be very effective in lowering down Vebe time and maintaining it. 0.3% of this admixture was learned to extend the working time up to four hours without influencing RCC’s compressive strength.

The use of roller-compacted concrete pavement or RCCP has increased steadily in the past few decades. It is an economical version of conventional concrete pavement; whereas the construction cost of other types of pavement is constantly rising. In its mixture design, compactibility is an important factor for achieving high strength while workability is an essential factor for providing workable material. However, the satisfaction of both properties is difficult to achieve because of the effect of various factors such as aggregate gradation and water content. Appropriate combination of materials is significant for providing adequate compactibility and workability of this concrete. In this study, twenty-one mixtures of roller-compacted concrete (RCC) with six different water contents for each of four aggregate gradations were evaluated using Modified Proctor and Vebe tests. Dry density was used to characterise compactibility of RCC while Vebe time was used to express its workability. It was found that Vebe time increased as sand/aggregate, or s/a, ratio increased and decreased when water content rose. On the other hand, maximum dry density decreased as s/a increased. The well-graded aggregates, 58 and 50% of s/a, were found to give its maximum dry density with satisfactory workability. Interestingly, it was learned that the range of appropriate water content corresponding to acceptable workability is narrower than that of appropriate water content corresponding to the acceptable dry density which indicated that it is more crucial and difficult to get appropriate workability than acceptable dry density.

Implementation of noise as an additional measure in pavement service evaluation has come forth since noise seriously influences on driver comfort. Due to a considerable amount of time and cost for traditional road-side noise measurement such as pass-by method, evaluation of tire-pavement noise based on MPD (Mean Profile Depth) has been attempted by numerous researchers. MPD is a part of texture characteristics that influences tire-pavement noise and it can be easily measured by Portable Laser Profiler (PLP). In general, macrotexture is a pavement surface characteristic having the significant impact on tire-pavement noise. Generally, it can confirm that tire-pavement noise increases by the increase of texture depth and wavelength. However, the theoretical study showed that the influences of pavement texture characteristics including texture depth and wavelength on tire-pavement noise are insufficient. In this study, the statistical analysis on relationship between tire-pavement noise, MPD, and wavelength for asphalt concrete pavement was performed. The collected data of measured tire-pavement noise, MPD, and wavelength on asphalt pavement sections from Donghae Expressway, and National Highway 35 Line of South Korea, were conducted and analyzed. Based on the multiple regression analysis results, it was found that tire-pavement noise is linearly increased due to the increases of MPD and average wavelength. In addition, multiple regression analysis of tire-pavement noise level, MPD, and average wavelength gave a similar trends compared to the single regression analysis between tire pavement noise with MPD and tire pavement noise with average wavelength. This study also showed that aggregate gradation used in asphalt mixture significantly affect the MPD and average wavelength. Therefore, tire-pavement noise would be affected by aggregation gradation used in asphalt mixture.

In areas of high-volume traffic, such as the proximities of expressways in large urban areas, the amounts of nitrogen oxides (NOx) emitted into the atmosphere significantly contribute to air pollution. As NOx gas is a major cause of smog and acid rain, this pollutant is considered to be particularly harmful, and therefore, increasing attention has been focused worldwide on the elimination of NOx from the air. Titanium dioxide (TiO₂), a photocatalytic reaction material, is particularly effective in the removal of NOx. As the solar photocatalytic reaction of TiO₂ is the mechanism that eliminates NOx, the TiO₂ in concrete road structures needs to be exposed to the ultraviolet rays (UV) of sunlight to be activated. Generally, TiO₂ concrete is produced by replacing a portion of the concrete binder with TiO₂. However, a considerable amount of the TiO₂ in the concrete is not exposed to either the air pollutants or the UV. Therefore, as an alternative method, surface penetration agents are used to add TiO₂ to the surface of the concrete structure. This study aims to evaluate the in-situ NOx removal efficiency of the TiO₂ penetration method in a field application. Accordingly, the TiO₂ penetration method was tested on the retaining wall of the Gyeongbu expressway in Korea. The results of this study indicated that the quantity of sunlight influenced the NOx removal efficiency rate. Furthermore, it was c that the TiO₂ penetration method can be an alternative to the existing TiO₂ concrete, which produced by replacing a portion of the concrete binder with TiO₂, for removing NOx gas from the air.

A tack coat is a thin layer that ensures the bonding between an asphalt overlay and existing pavement. Adequate tack coat bonding is required for the composite pavement structure to behave as a single layer. The adhesion between the layers is significantly reduced at high temperatures, given that tack coat is characterized as a temperature-dependent material. This implies that debonding frequently occurs at elevated temperature during summer season. However, the distresses or failures related to debonding may not be occurred due to the bond strength recovery effects of the tack coat material in the early-age of the composite pavement. This study intended to investigate the bond strength recovery effect of the tack coat at the interface between the asphalt overlay and existing concrete layer based on the pull-off tests. The bond strengths measured between 18 to 20°C were 0.75 MPa and 0.81 MPa for the cationic rapid setting emulsified asphalt and modified rubberized asphalt, respectively. However, the measured bond strengths of all the specimens were 0.08 MPa or less at a high temperature of 38 to 42°C. As a result of testing the possibility of recovering the bond strength to the debonded specimens at high temperature, the bond strength of 75% or more could be recovered at the interface.