PURPOSES: The noise problem in concrete pavements has an adverse effect to the road user or nearby residents and is generated by the contact between a tire and the pavement surface. Exposed aggregate concrete pavements have been adopted to solve the tire-pavement noise problem in the United States and Europe. However, the efficiency of the coagulation retarder and exposure equipment used for this kind of pavement has not yet been investigated. Therefore, this study aims to evaluate the ability of the coagulation retarder and exposure equipment in producing the optimum exposed aggregate texture to achieve low pavement noise. A method for the exposure time selection has also been introduced here. METHODS: Sodium gluconate retarders were selected for use in this study. The retarder-water ratios of 1:1, 1:2, and 1:3 were investigated. The retarder was sprayed on a fresh concrete surface with rates of 200 g/m2, 300 g/m2, and 400 g/m2. The aggregates were then exposed to the surface using a steel brush and a water jet. The efficiencies for the low-noise texture, workability, and environmental impact produced by the two exposure devices were estimated. The EAN and the MTD were investigated according to the exposure time. RESULTS : The aggregates were exposed after the retarder was sprayed on the fresh concrete surface; the exposure lasted for 18 h to 26 h each time. The retarder-water ratio of 1:2 and the spraying rate of 300 g/m2 produced an optimum surface texture for low noise. Additionally, the steel brush performed more effectively in exposing aggregate to the surface compared to the water jet. The selected exposure time window (ETW) was 28 h to 35 h. CONCLUSIONS : The optimum retarder was the sodium gluconate retarder with a retarder-water ratio of 1:2 and a spraying rate of 300 g/m2. The steel brush showed a good performance in exposing the aggregates and showing the efficiency of the coagulation retarder in the given environment so as to produce the quality control condition. The ETW was influenced by the construction, mixture design, and construction environment; however, the selected ETW in this study was 26 h~35 h.

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.

This study is a basic study to CGS, which originates from the IGCC, as fine aggregate for concrete. The study measured density, water absorption ratio, solid volume percentage for grain shape, fineness modulus, grading curve of physical properties of fine aggregate. As a result, the density and solid volume percentage for grain sheet were found to be satisfactory in the aggregate for content (KS F 2527).Water evaluation ratio, fitness modulus, and grinding curve did not meet KS standards. Therefore, it is deemed necessary to adjust the grain size through sieving in case of fineness modulus and grinding curve.

This study was examined the variation of unit water content and fine aggregate ratio in concrete for nuclear power structure using a large amoung of crushed sand.

Along with the increased display devices, the supply for LCD waste glass has rapidly increased. However, there is a problem for recycling. In this study, the possibility of using LCD waste glass as a substitutive material of fine aggregate is determined and compared from the test of the compressive strength and split tensile strength. Finally, it is possible to confirm the results of the failure aspect and analysis of this test.

This paper was examined the durability properties of concrete using rapid cooling slag as fine aggregate for concrete. The results of experiments, concrete using rapid cooling slag showed that durability properties was equal to concrete using normal fine aggregate.

This paper was examined the mechanical properties of concrete using rapid cooling slag as fine aggregate for concrete. The results of experiments, concrete using rapid cooling slag showed that mechanical properties was equal to concrete using normal fine aggregate.

본 연구는 강모래와 부순 모래를 일반적인 혼합방법과 아스팔트 골재 혼합에 사용되는 Driscoll 방법으로 각각 혼합하여 그 특성을 알아보고, Driscoll 방법의 콘크리트용 골재에 대한 적용성을 판단하고자 하였다. 이에 따라 일반혼합과 Driscoll 방법으로 혼합한 골재의 조립율 및 입도곡선, 굳지 않은 콘크리트의 특성 중 슬럼프와 공기량 및 굳은 콘크리트의 특성 중 28일 압축강도 시험을 통해 혼합방법의 따른 특성을 알아보고자 하였다. 아스팔트 골재의 혼합에 사용되는 Driscoll 방법을 사용하여 콘크리트 골재를 혼합하였을 때 일반적인 혼합방법과 비교하여 슬럼프, 공기량, 28일 압축강도가 오차수준 정도의 미미한의 차이를 나타내었다. 따라서 아스팔트 골재 혼합에 사용되는 Driscoll 방법은 콘크리트용 잔골재의 혼합에도 적용 가능할 것으로 판단된다.

최근 들어 정부의 환경정책이 폐기물의 발생량을 줄이되 발생되는 산업부산물을 적극적으로 재활용하는 자원순환형 폐기물 관리로 추진됨에 따라 산업 각 부분에서 발생되는 산업부산물의 재활용에 대한 연구 및 적용성이 활발히 진행되고 있다 최근 잔골재의 대체재로 주목 받고 있는 동슬래그는 본격적인 활용이 진행된다면 잔골재 수급에 많은 도움을 줄 것으로 예상되나 천연골재에 비해 높은 비중 및 대체율이 30%를 초과하면 재료분리가 발생하는 등의 단점 또한 지적되고 있다 본 연구에서는 동슬래그의 혼입 시 발생되는 블리딩의 발생을 혼화제의 사용을 통하여 억제하고 압축강도 시험 결과 등의 종합적인 고찰을 통하여 잔골재 대체시의 동슬래그의 적정 혼입률을 도출하고자 하였다