PURPOSES: In order to evaluate a crack resistance at cold joint, sealing tape was adopted to apply at cold joint instead of typical tack coat material(RSC-4). The sealing tape was made by hot sealing material. The crack resistance as function of environmental and traffic loading was measured with visual observation. METHODS : In this study, the crack resistance was evaluated as function of environmental and traffic loading. The freeze-thaw method was adopted for environmental loading of asphalt pavement. condition. The damage of cold joint under freeze-thaw action is initiated by ice expansion load and accelerated by the interfacial damage between new and old asphalt pavement. The traffic loading was applied with wheel tracking machine on the cold joint area of the asphalt pavement for 3 hours at 25℃. The evaluation of crack resistance was measured with visual observation. The freeze-thaw results shows that the sealing tape was significantly increased the crack resistance based on. RESULTS : To estimate the crack resistance at cold joint area due to the environmental loading, the Freeze-thaw test was conducted by exposing the product to freezing temperature(approximately -18℃) for 24 hours, and then allowing it to thaw at 60℃ for 24 hours. The tack coat material(RSC-4) was debonded after 21 cycles of the Freeze-thaw test. The first crack was observed after 14 freeze-thaw cycle with RSC-4 material. But, the sealing tape was not debonded after 24 cycle test. Also, the sealing tape shows the better performance of the crack resistance under the traffic loading with wheel track test. The crack was generated the under traffic loading with RSC-4(tack coating), however, the crack was not shown with sealing tape. It indicates that the sealing tape has a strong resistance of tensile stress due to traffic loading. CONCLUSIONS: Based on limited laboratory test result, a performance of crack resistance using the sealing tape is better than that of general tack coat material(RSC-4). It means that the sealing tape is possible to extend a pavement service life because the crack, one of the main pavement distresses, will be delayed. Keywords Sealing Tape, Crack Resistance, Freeze-Thaw, Tensile Adhesion

Asphalt pavement is covered over 90% of Korea road network. There are various causes for damage to asphalt pavement such as crack, stripping, and joints et al. A longitudinal joint occurs in an asphalt pavement when a new batch of hot-mix asphalt (HMA) is laid adjacent to an existing lane for maintenance of asphalt road. It is required to pave the width of a road in multiple lanes because paving the full width of the pavement in a single pass is usually impossible. The durability of longitudinal joints in asphalt pavements is strongly related with the pavement service life. This longitudinal joint is generated attachment sites where the old pavement surface and the new pavement surface are adhered to each other. In the short period of time, early cracks are generated due to the adherence failure of the new and old pavement. Rainwater penetrates into cracks at the time of rainfall. The cracks are enlarged to be connected by labeling and pothole generation, resulting in durability of the pavement deterioration of its service life. Therefore, there is a desperate need for a preventive material that can prevent the expansion of cracks in the longitudinal joint. Compare performance sealing tape with tack coating material, the research team is adopted freeze-thaw and wheel tracking loading test methods. The sealing tape shows the better performance than tack coating material under traffic loading and freeze-thawing test.

이산화탄소 농도가 높은 도심지의 경우 탄산화로 인한 철근부식이 발생하기 쉬우며 이는 콘크리트 구조물의 내구수명을 감소시킨다. 콘크리트 구조물의 경우 다양한 구속조건을 가지며 항상 외부의 재하하중을 받고 있다. 도입된 응력수준은 이산화탄소와 같은 유해인자의 확산을 변화시키며 탄산화 깊이의 변동성을 야기한다. 본 연구에서는 응력재하수준에 따른 탄산화 변동성을 정량화하였으며, 이를 이용하여 탄산화 예측식을 도출하였다. 내구성 설계인자인 피복두께, 이산화탄소 확산계수, 탄산화 반응 수화물, 그리고 외부 이산화탄소 농도를 확률 변수로 정의하였으며, MCS을 통하여 영향인자의 변동성에 따른 내구수명을 도출하였다. 또한 응력수준에 따라 변화하는 내구수명을 도출하였으며, 이를 결정론적인 방법의 결과와 비교하였다. 피복두께 및 내부 수화물 생성이 내구수명 변동성에 가장 큰 영향을 미쳤으며, 응력수준 을 고려한 내구수명평가는 유지관리 우선순위 설정에 합리적으로 적용할 수 있다.

This paper evaluated service life in a RC continuos beam with 2 spans considering loading condition, cold joint, and substitution ratio of GGBFS. Based on the previous test results for 91 and 365 days, changing ratio of diffusion coefficients with applied stress are normalized considering substitution of GGBFS and cold joint. For evaluation of service life in RC continuous beam with 2 spans, non-linear analytical model is adopted. The reduction of service life with cold joint and loading condition should be considered in maintenance even if GGBFS which shows excellent resistance to chloride ingress is used for the RC structures.

In this study, the compressive force is evaluated for the SMA surface reinforcement member which is to improve the bond capacity at cold-joint in PC member. As a result, the total compressive force can be estimated according to the number of wires.

시공지연 등으로 발생한 콜드조인트는 전단력에 취약하며 염화물 침투 및 확산을 촉진시킨다. 본 연구는 압축 및 인장하중과 콜드 조인트 조건을 고려한 1년 양생된 콘크리트의 염화물 확산계수를 분석하였으며 선행연구인 91일 재령의 결과와 비교하였다. 91일 재령결과와 비교할 때, 하중을 재하하지 않은 일반적인 경우에는 건전부에서는 10.7%, 콜드조인트에서는 10.5%로 낮게 평가 되었다. 건전부와 콜드조인 트의 감소율의 차이는 비슷하지만 염화물 확산계수는 콜드조인트에서 크게 발생하였다. 압축력 30%의 경우 건전부는 하중재하시 발생된 공 극압밀로 인하여 확산계수가 감소하였다. 콜드조인트 콘크리트의 경우 365일 재령은 91일 재령보다 압축력 30%일 경우 10.9%, 압축력 60%일 경우 5.8% 확산계수가 낮게 평가되었는데, 이는 장기간 수중양생에 따른 지속적인 수화반응에 의해 확산계수가 낮게 평가되었기 때문이다. 인 장력의 경우 압축부와는 다르게 동일 수준의 인장하중과 재령, 콜드조인트 유·무에 따른 확산계수의 차이가 비교적 크지 않았다. 이는 콘크리 트가 1년 재령임에도 불구하고 인장력에 취약한 재료적 특성인 미세균열이 지배적인 영향으로 작용하였기 때문이다.

철근 콘크리트 구조물의 철근에 대한 부식을 발생시키는 다양한 유해 열화인자 중 염화물 이온(Cl-)은 침투로 인한 확산속도가 빠 르고, 철근에 직접적으로 관여하여 부식을 야기시켜 매우 중요한 열화원인이다. 대형 콘크리트 구조물의 타설에서 불가피하게 발생하는 콜드 조인트는 전단력에 취약하여, 이는 내구적 열화에 대한 피해를 증가시키는 경향을 보인다. 본 연구에서는 콜드조인트를 가진 OPC(Ordinary Portland Cement) 콘크리트와 GGBFS(Ground Granulated Blast Furnace Slag) 염화물 촉진 실험으로 염화물 확산계수를 정량적으로 평가하였 다. GGBFS 콘크리트에서는 6.6×10-12 m2/sec의 확산계수가 측정되었는데. 이는 OPC 콘크리트에 비하여 약 30% 수준의 낮은 확산계수값을 나 타내었으며, 콜드조인트를 가진 콘크리트에서도 비슷한 경향이 관측되었다. OPC 건전부 콘크리트에 비하여 GGBFS 콘크리트의 염화물 확산 계수는 건전부에서 0.30배, 콜드조인트부에서 0.39배 정도의 우수한 염해 저항성을 나타내었다.

본 연구는 고강도 섬유보강 시멘트 복합체(UHSCC) 접착성능을 평가하는 것이 목적이다. Direct shear test를 통해 압축전단접착강 도를 측정한 결과 NC(보통강도콘크리트)+ NC 실험체(150×150×150)에서는 모든 수준에서 유사한 압축전당접착강도를 나타내었고, 반 면 UHSCC+UHSCC에서는 지연타설 30분 후부터 0분에 비해 압축전단접착강도가 낮아지는 것을 확인할 수 있었다. 이를 통한 접착면의 파괴 모드를 분석한 결과 NC+NC 에서는 모든 수준에서 비계면 파괴를 보였고 UHSCC+UHSCC에서는 30분, 60분, 90분 시험체에서 계면파괴가 일 어났다. NC 및 UHSCC의 타설면을 XRD 시험을 통해 분석한 결과 NC 시험체에 비해 UHSCC의 시험체 에서 많은량의 SiO2의 성분이 검출되 는 것을 알 수 있었고 UHSCC에서 나타난 코팅막의 주성분의 대부분은 SiO2로 사료된다. 따라서 본 연구에서 사용된 UHSCC는 지연타설 30분 후 부터는 접착성능의 저하로 구조체로서의 사용이 어렵다고 판단된다. 금후 연구에서는 콜드조인트 발생 부위의 면처리 방법을 통한 접착성 능 향상이 필요하다고 사료된다.

This study is, when we pour the concrete, doing bonding shear performance evaluation to search the influence about an adhesive interface by a generated cold joint with a retardation time. In conclusion, this experiment shows that the higher a compressive strength of the concrete is, the higher a reduction ratio of the bonding shear strength is, and the instance of a none agitation and a compaction with 15 minutes of a retardation time are the lowest influence in a whole of the results; each of the reduction ratio of the bonding shear strength is approximately 4.5%.

This paper presents an quantitative evaluation of loading conditions and its interaction of cold joint on accelerated diffusion coefficient. For the work, various loading conditions are prepared for concrete with cold joint. The mineral admixture of GGBFS (Ground Granulated Blast Furnace Slag) is replaced with 40% of weight ratio. The effect of GGBFS is evaluated to be effective to hinderance of chloride penetration. The compressive loading effect shows rapid enlargement of chloride diffusion after 60% of loading ratio while the tensile loading effect shows initially increased diffusion.

In this paper, it is evaluated for sound and cold joint concrete under compressive load. To evaluate the permeability of the concrete, to prepare a cold joint specimens. And the water permeability evaluated by comparison of the sound and the cold joint concrete. it selected control, 30%, and 60% of the breaking strength. Results of evaluating the permeability of the cold joint concrete under compressive load, and tended to reduce at 30% of load, to increase at 60% of load.

In this study, it was evaluated the permeability of cold joint concrete, to evaluated the permeability considering slag concrete and OPC. In addition, the water permeability was evaluated by comparing the sound and cold joint concrete. As a result, OPC-Joint(3.76×10-10m/s), Slag-Joint(3.36×10-10m/s), OPC(2.65×10-10m/s), Slag(2.36×10-10m/s) was evaluated in this order. The OPC-joint is the most highly evaluated. This is estimated to be because the density of the pore structure.

This study was conducted for investigating effect of retardation time of secondary placement on shear bonding strength. Evaluation experiment on the shear bonding performance of UHPC(180MPa level concrete) was conducted according to retardation time and size of specimen. As a result, the smaller the size of specimen, the weaker the measured bonding performance of specimen. Also, comparing specimen which is o minute occurrence time of cold joint with specimen which is after 15 minutes, it showd 70% lesser shear bonding strength.