• International Journal of Highway Engineering
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• v.6 no.4 s.22
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• pp.101-108
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• 2004

Asphalt overlay method is a general method to extend the of life old concrete pavements. However, reflection cracks are the typical problem of the AC overlay on distressed concrete pavement. Joint sealing, stress absorbtion layer have been used to prevent reflection cracks however partial success of to delay the timing of reflection cracking was recognized. Reflection crack problem can be eliminated by using rubblization method, which crush concrete pavement slab into piece of aggregate size that can be used base material. Previous research on rubblization method indicated that the size of rubblized PCC ranged 40-70mm at upper layer, and more than 100mm at lower layer. In this study, the adequate depth of rubblized PCC that ran prevent reflection cracking of AC overlay is estimated base on the simulation test of reflection cracking with 0, 10, 20cm rubblized PCC base.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.6
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• pp.1109-1116
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• 2016

There are various test methods for evaluating the reflective cracking resistance of asphalt concrete pavement. Repeated direct tensile test is cheap and simple compared to the other traditional experimental methods. Determination of failure criteria is needed to apply a repeated direct tensile test. Various methods were used to determine the number of failure of repeated direct tensile test. The number of failure was defined as the time to reach 10% of the initial load, this method can be satisfied with specified tolerance of 10%. When the thickness of specimen is increased to 50 mm from 30 mm, the failure number is increased by 13.6 times. Thus, this result shows that the thickness of pavement is a big influence on the reflective cracking resistance. Reflective cracking resistance of asphalt concrete is decreased according to the increase in opening displacement. The repeated direct tensile test can be used as a reflective cracking resistance factor in pavement design, because it can evaluate the reflective cracking resistance according to the pavement thickness, opening displacement, material properties etc.

• International Journal of Highway Engineering
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• v.5 no.3 s.17
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• pp.1-9
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• 2003

This study was performed to evaluate the effect of various joint sealant on reducing the reflection cracking of asphalt concrete overlay on cement concrete pavement. The test method used was an accelerated reflection cracking test in shear mode, which was developed for evaluation of reflection cracking resistance of overlaid asphalt concrete in laboratory. The test results showed that use of joint sealants resulted in a significant reduction of reflection cracking. When sealant E was used, the fatigue life was the highest, with relatively larger horizontal deformation. When Sealant B was used, the dynamic stability was the highest with the smallest horizontal deformation. In general, the greater the tensile strength of sealant, the better the crack resistance of the mixture.

• International Journal of Highway Engineering
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• v.2 no.4 s.6
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• pp.101-109
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• 2000

This study was performed to estimate fatigue life of polymer-modified and reinforced overlay asphalt mixtures with respect to reflection cracking in asphalt overlay pavement. In order to achieve the goal, the expedited reflection cracking test method was developed and applied to various mixtures and the results were compared one another with respect to the resistant characteristics of reflection cracking. The theoretical prediction equation of fatigue life for each mixture was suggested based on statistical analysis of experimental test results in the flexural failure mode. Since coefficients of correlation between estimated values and measured values were very high ($r^2=0.95$ or higher), the prediction model can be used for relative comparison of various pavement overlay choices to be used in the field.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.315-316
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• 2003

차량의 통행이 빈번한 기존 아스팔트 도로는 연속적인 차량의 하중에 의한 스트레스로 하중을 받을 때마다 아스팔트도로 층의 강도와 안정성이 떨어지면서 균열이 발생하고 이 균열이 아스팔트 도로 상층부까지 전달되는 반사균열이 발생한고, 열팽창과 수축의 반복에 기인하는 상부의 아스팔트 층의 피로에 의한 균열이 발생한다. 따라서 아스팔트 도로의 반사균열을 억제하고, 아스팔트의 소성변형에 의한 rutting현상을 억제하여 아스팔트의 도로보수 주기를 연장하여 도로상에서의 잦은 보수에 의한 자동차의 정체현상을 줄이고 도로유지에 소요되는 비용을 절감하기 위해서 아스팔트 도로를 설치할 때 아스팔트를 보강시켜주는 geogrid의 사용이 보편화 되고 있다. (중략)

• International Journal of Highway Engineering
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• v.7 no.2 s.24
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• pp.1-12
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• 2005

This study was conducted to evaluate effect of geogrid and fabric, which are used underneath the overlaid asphalt pavement for retarding reflection cracking by simulated laboratory test. In this study, an interlayer at the interface between old concrete pavement surface and overlaid asphalt mixture, and polymer-modifier were used as an effort of retarding reflection crack initiation and for strengthening mixture. Five products were used in preparation of asphalt concrete beam specimen which was tack coated on top of jointed concrete block. Simulated Mode I and II fracture test were conducted under wheel loading and results were compared among those products. From the test results, several material and reinforcement combinations were observed to have a significant retardation effect against reflection cracking. The most effectively strengthened pavement against reflection cracking was found to be the LDPE-modifier asphalt mixture with a grid reinforcement at the bottom.

• International Journal of Highway Engineering
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• v.1 no.1
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• pp.85-96
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• 1999

This study was performed to evaluate performance of polymer-modified asphalt mixtures and specially designed reinforcement techniques against reflection cracking of the asphalt pavement overlay. Selected polymers were used for asphalt modification and polyester fiber, a polypropylene film (vinyl) and a grid were used for mixture reinforcement. Using the asphalt mixture with optimum asphalt content, a slab was made and cut into two pieces of specimen. A layer of grid or vinyl was placed at the bottom of specimen to strengthen the pavement layer against crack. A repeated loading was applied to the asphalt mixture specimen which is Placed on a cement concrete with a pseudo-crack. Crack propagation under repeated loading was monitored and effectiveness of the devised crack retarding techniques was evaluated. From the test results. a significant retardation of mode I crack progress was monitored from some of the modified and reinforced asphalt mixtures.

• The Journal of the Acoustical Society of Korea
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• v.12 no.3
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• pp.5-12
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• 1993

볼트와 너트에 대한 초음파비파괴검사는 종파와 사각 횡파 기술을 사용하고 있는데 작은 결함신호는 자사산의 신호와 크기가 비슷해 구분이 되지 않는다. 본 논문에서는 나사산의 다중반사신호로부터 결함신호를 구분할 수 있는 방법을 제시한다. 종파를 사용하였을 경우 균열의 선단신호와 코너에서 반사되는 신호는 진행시간이 거의 같아 중첩되어 나타나지만 균열로 인한 Rayleigh파는 균열의 선단신호와 코너에서 반사되는 신호다음에 결함길이에 따른 미세한 진행시간을 가지고 나타난다. 이와는 다르게 횡파를 사용하였을때의 균열의 선단신호는 코너에서 반사되는 신호보다 앞에 나타난다. 이러한 나사산에 존재하는 결함의 선단신호를 기준으로 순방향 또는 역방향으로 반사되는 신호로부터 작은 결함신호도 구분할 수 있고 그 크기를 정량적으로 계산할 수 있다.

• International Journal of Highway Engineering
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• v.1 no.1
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• pp.97-106
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• 1999

This study was conducted to develop a test system for evaluating resistance against reflection cracking in shear mode caused by wheel load in asphalt concrete overlaid on the deteriorated cement concrete pavement. Reflection cracking resistance of selected polymer modified asphalt(PMA) mixtures with and without reinforcement was evaluated using this test system. It was shown that the test results accounted for the effectiveness of materials and reinforcement characteristics in terms of the difference in the resistance against reflection cracking. A shear failure life of a certain mixture was estimated with a high coefficient of determination. when the test results were used in a well known prediction model. Therefore, it seemed to be possible to use this technique for predicting a relative service life of on overlay.

• International Journal of Highway Engineering
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• v.14 no.2
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• pp.1-10
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• 2012

As old concrete pavements of over 20years in age are increasing in expressways, the repair and rehabilitation of concrete pavement have become an important issue. Although asphalt overlay is widely used as an alternative to rehabilitate the old concrete pavement, problems due to infiltrated water such as reflection crack and pothole are imposing a very serious threat to its performance. This study proposes waterproof membrane as a solution to minimize the damage due to reflection crack and infiltrated water, and accelerated pavement testing was carried out for the performance comparison of composite pavement with waterproof membrane and ordinary tack coating. The experiment used water spraying to simulate rainfall, and the behavior and moisture resistance characteristics of overlay pavement were analyzed. The experimental result indicated that the strain pattern of waterproof membrane section differed from ordinary tack coating section because waterproof membrane caused the asphalt pavement and concrete pavement to move together. Additionally, since waterproof membrane minimized the infiltration of water and delayed the occurrence of reflection crack by about 70% in comparison to ordinary tack coating method. Moreover, the damage due to infiltrated water also decreased.