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.

ABSTRACT
1. 서론
2. 소입경 골재노출 콘크리트 포장의 특성
    2.1. 도로포장의 노면조직과 소음의 관계
    2.2. 소입경 골재노출 콘크리트 포장의 저소음과 품질관리기준 검토
    2.3. 국내 및 국외의 골재노출기법 연구사례
3. 최적 노출방안 도출을 위한 실험적 연구
    3.1. 응결지연제 성능평가 및 실험결과
    3.2. 골재노출 장비를 이용한 최적 노출기법 선정 연구 및 실험결과
4. 최적 노출시기 선정을 위한 ExposingTime Window 검토
5. 결론
REFERENCES

• 김재훈(강릉원주대학교 토목공학과) | Kim Jae Hoon
• 이승우(강릉원주대학교 토목공학과) | Lee Seung Woo (Department of Civil Engineering, Gangneung-Wonju National University) 교신저자