PURPOSES : In Korea, asphalt overlay has been used as a typical alternative rehabilitation method for deteriorated pavements. However, asphalt overlay has problems due to poor bonding of the asphalt overlay and the old concrete. Recently, concrete overlays, which have advantages such as long-term durability and high structural capacity to carry heavy traffic, have been considered for rehabilitation construction. However, concrete overlays have limitations such as difficulty in opening to traffic and pavement noise. Recently, an appropriate fine-size exposed aggregate concrete pavement technique was reported to solve these problems. Therefore, this study aims to suggest an optimum mixture design of fine-size exposed aggregate concrete overlay (EACO) that can ensure low noise and early strength. METHODS : The optimum mixture design of fine-size EACO is determined to ensure adequate structural performance for early traffic opening and good functional performances such as low noise. Therefore, the optimum mixture proportion is determined based on the optimum design of aggregate content to produce a low-noise pavement texture by controlling the exposed aggregate number (EAN) and mean texture depth (MTD). RESULTS : The water-cement ratio and unit cement ratio were used to determine the mixture designs to achieve workability and adequate strength for early traffic opening. The texture was determined by selecting the maximum size of coarse aggregate smaller than 10 mm with an S/a ratio of less than 30% for low noise. With these mixture proportions, the EAN and MTD were 50±5 / 25cm2 and 1.0±0.2 mm. Respectively, which meet the criteria for EACO. CONCLUSIONS: In this study, an optimum mixture design of EACO for early traffic opening and low noise is suggested by using earlyhigh strength cement, and the pavement texture is implemented considering EAN and MTD. In addition, a pavement surface texture criterion is suggested for the quality control of EACO.

PURPOSES : Exposed aggregate concrete pavements have been adopted in several countries because of their advantages of pavement texture characteristics, which can produce low tire-pavement noise and higher load-carrying capacities. The magnitude of tire-pavement noise greatly depends on the wavelength of pavement texture. The wavelength of exposed aggregate concrete pavement can be controlled with maximum sizing and by controlling the amount of coarse aggregates in the concrete mixture. In this study, the maximum size and the amount of coarse aggregate in the exposed aggregate concrete pavement are investigated to produce equal levels of wavelength in the asphalt pavement. METHODS: A simple method to measure the average wavelength of pavement texture is introduced. Subsequently, the average wavelength of typical asphalt pavement is investigated. A set of mixture designs of exposed aggregate concrete with three maximum-sized coarse aggregates, and three amounts of coarse aggregate are used. The average wavelengths are measured to find the mixture design needed to produce equal levels of wavelength as typical asphalt pavement. RESULTS : With a cement content of 420 kg/m3 and fine aggregate modulus of 30%, the number of exposed aggregates was 48, and the shortest texture depth provided a wavelength of 4.2 mm. According to the number of exposed aggregates, the exposed aggregate concrete pavement could be rendered low-noise, because its wavelength was similar to that of asphalt pavement ranging from 3.9 to 4.4 mm. CONCLUSIONS : Selection of appropriate maximum sizes and the amount of coarse aggregates for exposed aggregate concrete pavement can produce a wavelength texture closely resembling that of asphalt pavement. Therefore, the noise level of exposed aggregate concrete pavement can be reduced with an appropriate maximum size and the amount of coarse aggregates are employed.

PURPOSES : In Korea, concrete pavements with transverse tining, which have excellent skid resistance, have been mainly constructed to secure road bearing capacity and safety. However, transverse tining has higher noise level of approximately 4-5 dB(A) compared with asphalt pavement. As a method to determine low-noise characteristics of concrete pavements, the fine-size exposed aggregate concrete pavement (EACP) has been studied in Korea and abroad. The surface of EACPs consists of exposed coarse aggregates and 2-3 mm removal surface mortar. EACPs have the advantages of maintaining low-noise and adequate skid-resistance levels during the performance period. Although EACPs have been widely studied to reduce noise, quantitative noise analysis with various paving methods has not been performed owing to differences in mixture proportioning, construction conditions, environmental conditions, and measurement methods. Therefore, the purpose of this study is to investigate the low-noise characteristics of fine-size EACPs by comparing noise with various paving methods, including concrete and asphalt pavements. METHODS: In this study, noise data were collected to quantitatively analyze the low-noise characteristics of EACPs compared with various paving methods such as transverse tining, longitudinal tining, SMA, and HMA. RESULTS: The evaluation of the low-noise characteristics of EACPs compared with transverse tining showed that the relative noise of 13 mm EACP with transverse tining was reduced by approximately 2% at 60 km/h, 4% at 80 km/h, and 5% at 100 km/h. The relative noise of 10 mm EACP with transverse tining was reduced to 3%, 7%, and 8% at 50 km/h, 80 km/h, and 100 km/h, respectively. In addition, it was confirmed that the noise of 10 mm EACP was similar to that of asphalt pavement. CONCLUSIONS : It was confirmed that EACP using 10 mm coarse aggregates generates lower noise than that using 13 mm coarse aggregates. Therefore, the use of coarse aggregates smaller than 10 mm needs to be considered to improve the low-noise effect of EACP.

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, appropriate consistency is required for supporting the compacting machine and minimizing compaction energy. Due to transportation and compaction time, maintaining proper consistency within a period of time is also necessary. Vebe time, a represent parameter of dry concrete consistency, ranged from 30 to 75 seconds is considered appropriate for RCC in pavement application. The purpose of this study is to improve workability of this concrete which consisted of improving its consistency and maintaining it within the working time. It was confirmed that the workable time of a normal RCC is less than one hour. Moreover, it was found that Vebe time drops when water content increases and goes up when sand by aggregate ratio increases. Various admixtures were also employed in this study in order to improve the workability of this concrete. Poly Naphtalene Sulfonate superplasticizer, particularly, was found to be the most effective in term of lowering down Vebe time and maintaining it. With just 0.3% of this admixture, the working time of RCC can be extended up to four hours without affecting its compressive strength.

More Roller-compacted concrete (RCC) is a dry concrete consisted of same materials as conventional concrete with different proportioning which requires compaction effort in order to reach its final form. Thus, both hydration and aggregate interlock play important roles in its strength augmentation. Flexural strength, an important factor in pavement design and fatigue cracking resistance, can be difficult to be obtained at in-situ and may be subjected to high variability. Even though its compressive strength is relatively high compared to conventional concrete with similar binder content, the relationship between compressive strength and flexural or tensile strength were not well defined. The goal of this research is to compare the relationship between compressive strength and flexural strength as well as the relationship between compressive strength and splitting tensile strength of RCC with those of conventional concrete using various equations suggested in other researches and also to determine new regression equations for estimating RCC’s flexural and splitting tensile strength. The positive result of RCC’s flexural strength was found; it was higher than majority of predicted values from conventional concrete for the same compressive strength. In contrast, RCC’s splitting tensile strength was relatively low compared to that of conventional concrete for the same compressive strength. Power equations were learned to be suitable for relationship between compressive and flexural strengths as well as relationship between compressive and splitting tensile strengths.

선형 변단면 부재의 삼차원 공간에서의 해석을 위하여 강도행렬을 유도하였다. 변단면 부재의 구조물을 해석하기 위하여 본 연구에서 유도된 강도행렬을 사용하여 구한 결과와 분할부재를 균일단면 탑 형태로 표현하여 ANSYS에서 구한 결과를 비교하여 본 연구의 결과 효율성 및 정확성이 증진된 것을 확인하였다. 본 연구에서 유도된 강도행렬은 변단면 부재와 균일단면 부재의 해석에 사용할 수 있다.

미세먼지 대응기술이 종전의 관리용이성(PM10, 1차 배출) 중심에서 위해성(PM2.5, 2차 생성) 중심으로 패러다임이 전환된 현시점에서, 입자상 물질뿐만 아니라 초미세먼지 2차 생성 전구물질인 질소산화물(NOx) 제거를 통하여 대기오염을 극복할 수 있는 방안이 사회적으로 요구되고 있는 실정이다. 이에 본 연구에서는 도로이동오염원에서 배출되는 질소 산화물을 효율적으로 제거하기 위한 방안으로 미세먼지 전구체 저감 소재를 도로 및 도로변에 설치되어 있는 기존 콘크리트 구조물에 고정화하기 위한 기초연구를 진행하였다.