PURPOSES: A methodology using a 3D-engineering technique was developed for implementation in paving Quality Control (QC) practice in bridge overlay paving. METHODS: The as-built surface of a concrete-box-girder bridge tends to exhibit a certain level of undulation or roughness. This is usually caused by the inevitable limitation that camber prediction and construction cannot be perfectly matched. The undulation itself would not be a severe defect in a bridge structure, but it results in a challenge for achieving overlay pavement qualities such as pavement thickness and smoothness. One advantage of the 3D-engineering technique is that it allowed identification in advance, of conditions that will interfere with construction, thus preventing non-conformance qualities from being re-worked. RESULTS : Utilizing this technique, overlay paving was virtually simulated in advance, and insufficient thickness areas and rough sections were visually identified. Paving quantities were automatically computed. Paving level alternatives were correspondingly established based on analysis of the quantitative and 3D visual outputs. CONCLUSIONS: This study showed that this methodology could be successfully utilized for optimizing paving quantity and quality

PURPOSES: The performance of both string line and multi-sonic sensor systems were investigated with respect to achieving smoothness in a 5 cm-thick Stone Mastic Asphalt (SMA) wearing layer. METHODS: String line and multi-sonic sensor systems were applied in the leading and trailing lanes, respectively, with two-lane simultaneous paving. RESULTS: Two systems did not show any significant statistical difference in initial International Roughness Index(IRI). The multi-sonic sensor system produced smoothness similar to that by the string line system. CONCLUSIONS : The string line system was found to be very effective in eliminating roughness below a wavelength of about 2 m, confirming that a string line reference is the best system to obtain a smoother surface. A multi-sonic sensor system evidently demonstrated the capability of replicating a reference level and, partly showed a roughness averaging effect within the system length. It can further be concluded that the effect of smoothness of the underlying layer on the upper layer smoothness cannot be ignored.

PURPOSES: A composite pavement utilizes both an asphalt surface and a concrete base. Typically, a concrete base layer provides structural capacity, while an asphalt surface layer provides smoothness and riding quality. This pavement type can be used in conjunction with rollercompacted concrete (RCC) pavement as a base layer due to its fast construction, economic efficiency, and structural performance. However, the service life and functionality of composite pavement may be reduced due to interfacial bond failure. Therefore, adequate interfacial bonding between the asphalt surface and the concrete base is essential to achieving monolithic behavior. The purpose of this study is to investigate the bond characteristics at the interface between asphalt (HMA; hot-mixed asphalt) and the RCC baseMETHODS: This study was performed to determine the optimal type and application rate of tack coat material for RCC-base composite pavement. In addition, the core size effect, temperature condition, and bonding failure shape were analyzed to investigate the bonding characteristics at the interface between the RCC base and HMA surface. To evaluate the bond strength, a pull-off test was performed using different diameters of specimens such as 50 mm and 100 mm. Tack coat materials such as RSC-4 and BD-Coat were applied in amounts of 0.3, 0.5, 0.7, 0.9, and 1.1ℓ/m2 to determine the optimal application rate. In order to evaluate the bond strength characteristics with temperature changes, a pull-off test was carried out at -15, 0, 20, and 40 °C. In addition, the bond failure shapes were analyzed using an image analysis program after the pull-off tests were completed.RESULTS: The test results indicated that the optimal application rate of RSC-4 and BD-Coat were 0.8ℓ/m2, 0.9 ℓ/m2, respectively. The core size effect was determined to be negligible because the bond strengths were similar in specimens with diameters of 50 mm and 100 mm. The bond strengths of RSC-4 and BD-Coat were found to decrease significantly when the temperature increased. As a result of the bonding failure shape in low-temperature conditions such as -15, 0, and 20 °C, it was found that most of the debonding occurred at the interface between the tack coat and RCC surface. On the other hand, the interface between the HMA and tack coat was weaker than that between the tack coat and RCC at a high temperature of 40 °C.CONCLUSIONS: This study suggested an optimal application rate of tack coat materials to apply to RCC-base composite pavement. The bond strengths at high temperatures were significantly lower than the required bond (tensile) strength of 0.4 MPa. It was known that the temperature was a critical factor affecting the bond strength at the interface of the RCC-base composite pavement.

아스팔트 표층과 콘크리트 기층으로 구성된 복합포장은 강성기층의 높은 지지력과 아스팔트 표층의 소음저감, 평탄성, 미끄럼저항성 등을 확보할 수 있는 장점을 가진 포장이다. 롤러다짐콘크리트(RCC)는 빠른 시공속도와 경제성을 가져 복합포장의 기층으로 활용된다. 그러나 이러한 복합포장의 공용수명 및 성능은 포장 계면의 부착파괴로 인해 저하된다. 그러므로 아스팔트 표층과 콘크리트 기층사이의 적절한 부착은 복합포장의 단일거동(monolithic behavior)을 통한 포장성능 및 공용수명 확보를 위해 필수적이다. 복합포장에 적용되는 아스팔트와 택코트 재료는 역청혼합물을 포함하고 있는 재료로 시간-온도에 의존적인 점탄성 특성을 나타내며 콘크리트는 환경적 조건(온도 등)에 따라 컬링 및 수축·팽창 등이 발생하는 재료적 특성을 가진 재료이다. 복합포장의 역학적 거동은 이러한 각 재료 및 포장계면의 특성에 기반 한다. 그러므로 부착 성능을 평가함에 있어 국내의 계절별 기후에 따른 복합포장 내 온도특성을 반영하여 부착성능이 평가되어야 하며 겨울철 반복적 동결-융해가 발생하는 국내의 기후특성상 이를 고려한 부착내구성 평가 등이 수행되어야 한다. 그러나 국내의 경우 20 ℃의 표준온도만을 적용한 부착성능 평가를 통해 품질관리가 수행되고 있으며 이와 관련된 연구가 미흡한 실정이다. 또한, 복합포장의 경제적 강성기층으로 본 연구에 적용된 롤러다짐콘크리트(RCC)는 적은 단위수량 및 단위시멘트량을 사용하여 시멘트 페이트의 양이 일반콘크리트 포장에 비해 적으며 포설 후 롤러전압다짐이 적용되기 때문에 불규칙한 거친 표면을 형성한다. 그러므로 이러한 특성을 고려한 적정 택코트 재료 및 살포량 선정이 요구된다. 따라서, 본 연구에서는 롤러다짐콘크리트-기층 복합포장에 대한 부착특성을 분석하고자 하였다. RSC-4와 BD-Coat 두 종류의 택코트 재료가 실험되었으며 각 재료의 최적살포량을 선정하고자 0.3, 0.5, 0.7, 0.9, 1.1 ℓ/m2의 살포량이 적용되었다. 추가적으로 100 mm, 50 mm에 대한 core size effect가 고려되었다. 온도 조건에 따른 인장부착특성은 -15, 0, 20 40 ℃의 각 온도 조건에서 실험되었으며 반복적 동결-융해가 발생하는 국내의 기후 특성을 고려하고자 0, 50, 100 Cycle에 대한 부착내구성 실험이 수행되었다. 실험의 각 부착파괴단면은 이미지분석프로그램을 통해 검토 되었으며 검토 내용을 바탕으로 부착특성과 부착파괴단면과의 상관관계가 분석되었다.