• 한국도로학회:학술대회논문집
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• 2002.10a
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• pp.199-204
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• 2002

• 한국도로학회:학술대회논문집
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• 2006.03a
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• pp.17-22
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• 2006

• 한국도로학회:학술대회논문집
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• 2002.10a
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• pp.205-212
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• 2002

• 한국도로학회:학술대회논문집
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• 2004.10a
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• pp.227-234
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• 2004

• 한국도로학회:학술대회논문집
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• 2005.11a
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• pp.161-166
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• 2005

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5D
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• pp.619-625
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• 2009

Test constructions were performed at 3 sites to investigate ways for maximizing performance of geogrid-reinforced asphalt pavements known to reduce reflection cracking and rutting. Problems during construction operation which can affect bonding shear strength of the geogrid-reinforced asphalt pavements were defined and the construction conditions were intentionally made during the test constructions. Both immediately and 1year after the test constructions, cores were obtained from positions with good and bad construction conditions and then bonding shear strength tests were performed to be compared each other. Rules to be kept at construction sites were suggested to improve performance of the geogrid-reinforced asphalt pavements.

• International Journal of Highway Engineering
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• v.8 no.3 s.29
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• pp.105-114
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• 2006

A popular alternative to extend the life of aged pavement is asphalt overlay. However, it has a very serious and inherent shortcoming in deterring a reflection crack. Although joint-rehabilitation and stress-relief techniques have been applied to deter such reflection cracks in aged pavement, the techniques had a limited success only in slowing down the progress of a reflection crack. Rubblization technique rubblizes the concrete pavement slab in situ and uses the rubblized slab as the base material. Then, pavement overlay is applied to finish off the rehabilitation of aged pavement. This rubblization technique has the advantage of solving the problem of reflection cracking completely. When rubblization technique is applied, the upper layer of aged concrete pavement is rubblized between 40mm-70mm in depth. However, the lower layer is typically rubblized more than 100mm in depth. Nevertheless, it is difficult to turn the entire concrete pavement of more than 30cm in depth into rubblized aggregate of appropriate size. Thus, a simulation experiment was carried out to find the appropriate rubblized depth, which avoids the reflection cracking and still maintains the function of subbase, by varying the depth of rubblized depth in loom increments of 0cm, 10cm, and 20cm. The result indicated the optimum rubblized depth was 10cm (Lee, 2006). Additionally, a small rubblizinge equipment was developed in order to derive the rubblization technique appropriate for thick concrete pavement. This equipment was tested out on an experimental pavement, which was constructed with the same standard and specification for the road in actual use, by varying its rubblizing head shape and energy as well as the effective area of rubblization. This experiment led to a prototype equipment for rubblization of thick concrete pavement. The prototype was put into use on a highway, undergoing a test construction and monitoring afterwards. This entire process was necessary for the validation of the proposed rubblization technique.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.205-219
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• 2008

The polymers, low-density polyethylene (LDPE) and styrene-butadiene-styrene(SBS) -modified asphalt mixtures are advanced asphalt pavement materials in which $3{\sim}6%$ of them, and/or some other additive, by weight of total binder are added. The purpose of modifying asphalt material is to improve typical weakness such as rutting and cracking resistance of normal asphalt mixtures. These materials have been proved to show many advantages and practical applicability in the plant and field. Wet processed PMA binder and/or dry processed asphalt mixtures are developed as field products for many years. The objective of this paper is to show the characteristics of the LDPE and SBS-modified asphalt mixtures by comprehensive evaluation and comparison with those of normal asphalt mixtures.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.6
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• pp.451-458
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• 2005

The effects of fiber orientation on acoustic emission(AE) characteristics have been studied for various composite laminates. Reflection and transmission optical microscopy were used to investigate the damage zone of specimens. AE signals were classified through short time Fourier transform(STFT) as different types: AE signals with a high intensity and high frequency band were due to fiber fracture, while weak AE signals with a low frequency band were due to matrix cracking and/or interfacial cracking. Characteristic feature in the rate of hit-events having high amplitudes showed a procedure of fiber breakages, which expressed the characteristic fracture processes of notched fiber-reinforced plastics with different fiber orientations. As a consequence, the behavior of fracture in the continuous composite laminates could be monitored through nondestructive evaluation(NDE) using the AE technique.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.87-95
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• 2018

PURPOSES : A geo-grid pavement, e.g., a stress-absorbing membrane interlayer (SAMI), can be applied to an asphalt-overlay method on the existing surface-pavement layer for pavement maintenance related to reflection cracking. Reflection cracking can occur when a crack in the existing surface layer influences the overlay pavement. It can reduce the pavement life cycle and adversely affect traffic safety. Moreover, a failed overlay can reduce the economic value. In this regard, the objective of this study is to evaluate the bonding properties between the rigid pavement and a SAMI by using the direct shear test and the pull-off test. The predicted fractural energy functions with the shear stress were determined from a numerical analysis of the moving average method and the polynomial regression method. METHODS : In this research, the shear and pull-off tests were performed to evaluate the properties of mixtures constructed using no interlayer, a tack-coat, and SAMI with fabric and without fabric. The lower mixture parts (describing the existing pavement) were mixed using the 25-40-8 joint cement-concrete standard. The overlay layer was constructed especially using polymer-modified stone mastic asphalt (SMA) pavement. It was composed of an SMA aggregate gradation and applied as the modified agent. The sixth polynomial regression equation and the general moving average method were utilized to estimate the interlayer shear strength. These numerical analysis methods were also used to determine the predictive models for estimating the fracture energy. RESULTS : From the direct shear test and the pull-off test results, the mixture bonded using the tack-coat (applied as the interlayer between the overlay layer and the jointed cement concrete) had the strongest shear resistance and bonding strength. In contrast, the SAMI pavement without fiber has a strong need for fractural energy at failure. CONCLUSIONS : The effects of site-reflection cracking can be determined using the same tests on cored specimens. Further, an empirical-mechanical finite-element method (FEM) must be done to understand the appropriate SAMI application. In this regard, the FEM application analy pavement-design analysis using thesis and bonding property tests using cored specimens from public roads will be conducted in further research.