PURPOSES : The purpose of this study is to evaluate the performance of road stone block pavements using APT (Accelerated Pavement Testing), which can evaluate the short-term pavement performance of a pavement structure for a given traffic load. METHODS : The performance of stone block, concrete block, and asphalt (modified SMA) pavements were evaluated according to the cumulative equivalent load by using APT. The FWD (Falling Weight Deflectometer) test was used to analyze the deflection per unit load. In addition, the plastic settlement was analyzed by transverse profile measurement. RESULTS: The results of the APT of about 197,000 ESALs (Equivalent Single Axle Loads) show that there were no damages in the stone block, concrete block, and asphalt pavement, such as breakage of stone or concrete block, cracking of asphalt, deflection, and plastic settlement of the wheel-pass section. It was analyzed that the bearing capacity of each pavement section did not decrease sharply with increase in cumulative ESAL. The results of plastic settlement analysis show that in the case of asphalt pavement, the plastic settlement steadily progressed from the beginning of the APT, and a settlement of about 4.76 mm occurred. In the case of concrete block and stone block pavements, no significant change occurred after the initial stabilization step, and plastic settlement of about 1.01 mm and 0.17 mm occurred for the concrete block and stone block pavements, respectively. CONCLUSIONS : As a result of the analysis of the bearing capacity and plastic settlement after the APT, the performance of stone pavement was found to be similar to that of asphalt pavement and concrete block pavement. Therefore, it is concluded that stone pavements are applicable for the road pavement system.

Composite pavements are constructed by placing a high functional asphalt surface layer on a high performance concrete rigid base layer and provide a more durable, high functional surface to road users. Service life of composite pavements is dependent on the bonding performance of the lower rigid base and the flexible surface layer. Accordingly, it is necessary to place an impermeability layer between the functional surface layer and the rigid base to enhance bonding performance and to prevent moisture penetration into the rigid base and deterioration of pavement. In order to use optimal composite pavement sections, two types were applied to impermeability layer: highly impermeable water-tight SMA and mastic asphalt currently in use. APT (Accelerated Pavement Testing) and experimental construction were carried out to evaluate bond strengths between the rigid base and the impermeability layer depending on the type of impermeability layers. Composite pavement sections for the APT had a 22 cm concrete rigid base layer and a 5cm functional surface, as well as either 5cm of SMA impermeability layer and 5cm of mastic layer. After applying around 8,574,000 ESALs, pull-off test was conducted, which showed that the mastic section outperformed the SMA section. In the experimental construction, three types of rigid base layers, JCP (Jointed Concrete Pavement), CRCP (Continuously Reinforced Concrete Pavement), and RCCP (Roller Compacted Concrete Pavement), were used for composite pavement sections, and as in the APT, two types of impermeability layers, SMA and mastic, were used per rigid base layer of new and deteriorated concrete pavement. Therefore, seven composite pavement sections in total were constructed. We measured the bond strength over one year or so following the construction of these composite pavement sections and found that regardless of the type of rigid base layer and whether it was new or not, those sections with a mastic impermeability layer had high bond strengths.

PURPOSES : So far, aged cement concrete pavement on express highways has been rehabilitated mainly with asphalt concrete inlay. However, potholes were the major problem, and they shortened the life of the inlay mainly owing to the poor drainage of water once it infiltrated the interface of the concrete and asphalt. The purpose of this study is to compare the performance and economic efficiency of asphalt overlay and inlayMETHODS: Overlay and inlay were compared through accelerated pavement testing, and a life-cycle cost analysis was conducted in this study using the CA4PRS program.RESULTS and CONCLUSIONS : It was found from accelerated pavement testing that the overlay exhibited reflective crack resistance that was more than twice as effective as that of inlay. The total cost (construction cost + user cost) within the analysis period (20 years) of the overlay was 37% lower than that of the inlay.

PURPOSES : The objective of this study is to evaluate the effect of size and depth of cavities on the pavement failure using the full-scale accelerated pavement testing. METHODS: A full-scale testbed was constructed by installing the artificial cavities at a depth of 0.3 m and 0.7 m from the pavement surface for accelerated pavement testing. The cavities were made of ice with a dimension of 0.5 m*0.5 m*0.3 m, and the thickness of asphalt and base layer were 0.2 m and 0.3 m, respectively. The ground penetrating radar and endoscope testing were conducted to determine the shape and location of cavities. The falling weight deflectometer testing was also performed on the cavity and intact sections to estimate the difference of structural capacity between the two sections. A wheel loading of 80 kN was applied on the pavement section with a speed of 10 km/h in accelerated pavement testing. The permanent deformation was measured periodically at a given number of repetitions. The correlation between the depth and size of cavities and pavement failure was investigated using the accelerated pavement testing results. RESULTS : It is found from FWD testing that the center deflection of cavity section is 10% greater than that of the intact section, indicating the 25% reduction of modulus in subbase layer due to the occurrence of the cavity. The measured permanent deformation of the intact section is approximately 10 mm at 90,000 load repetitions. However, for a cavity section of 0.7 m depth, a permanent deformation of 30 mm was measured at 90,000 load repetitions, which is three times greater than that of the intact section. At cavity section of 0.3 m, the permanent deformation reached up to approximately 90 mm and an elliptical hole occurred at pavement surface after testing. CONCLUSIONS : This study is aimed at determining the pavement failure mechanism due to the occurrence of cavities under the pavement using accelerated pavement testing. In the future, the accelerated pavement testing will be conducted at a pavement section with different depths and sizes of cavities. Test results will be utilized to establish the criteria of risk in road collapse based on the various conditions.

높은 포장온도는 아스팔트포장 소성변형의 주요인이나 소성변형을 줄이기 위한 방안으로서 포장온도를 줄이는 측면에서는 아직 많은 연구가 이루어지지 않은 실정이다. 본 연구에서는 소성변형결함을 줄이기 위한 하나의 대안으로, 온도저감 효과가 있는 것으로 알려져 있는 보수성 포장을 배수성 포장의 하부층에 설치한 포장의 공용특성을 연구하였다. 본 연구의 목적은 보수형 배수성 포장의 온도저감효과를 정량화하고, 포장가속시험(Accelerated Pavement Testing)을 이용하여 온도 저감에 따른 소성변형 감소효과를 확인하고, 정량화하는데 있다. 또한 추가적으로 보수성 포장의 상대강도계수를 분석하고, 일반 포장과 비교하여 설계법 적용시 포장두께를 줄일 수 있는지 여부를 알아보고자 하였다. 본 연구를 위해 보수형 배수성포장 2개 단면 및 일반 배수성 포장 1개 단면 등 총 3개 시험구간이 시공되었다. 히팅 및 살수를 일정주기로 실시하였으며 하중조건은 윤하중 8.2ton, 타이어 공기압 7.03kgf/cm2 타이어 접지면적 610cm2이었다. 이 연구에서 포장체 온도저감효과는 중간층의 경우 6.6~7.9℃(평균7.4℃), 표층의 경우 7.9~9.8℃(평균 8.8℃)였으며, 이를 통해 포장표면의 소성변형 발생을 26% 감소시킬 수 있었다. 또한 탄성계수로부터 추정된 보수성 포장의 상대강도계수는 0.173으로 일반 밀입도 포장의 1.2배 정도였으며, 일반배수성 포장 구간에서는 표층, 중간층, 기층 모두 소성변형이 발생한데 반해 보수형 배수성 포장 구간에서는 표층에서 대부분의 소성변형이 발생된 것으로 나타났다.

포장 공용성 모델은 역학적-경험적 포장설계법에서 포장의 수명을 결정하기 위한 가장 중요한 인자이다. 한국 포장연구 프로그램의 일환으로 한국형 포장설계법이 역학적-경험적 방법에 근거하여 현재 개발중에 있다. 본 연구에서는 포장 공용성모델중 아스팔트 혼합물의 영구변형 예측모델을 삼축압축 반복재하시험을 이용하여 개발하였다. 본 시험은 다양한 아스팔트 혼합물에 대하여 온도와 공극률을 변화시켜 하중재하 횟수에 따른 혼합물의 영구변형 특성을 조사하였으며, 본 시험결과를 이용하여 예측모델의 계수값을 결정하였다. 영구변형 예측모델의 계수값은 포장가속시험결과를 토대로 다양한 혼합물에 대한 시험결과를 이용하여 깊이에 따른 전단응력의 변화를 고려한 통합적인 소성변형 모델계수값을 정하는 것보다 혼합물의 종류에 따른 모델계수를 산정하는 것이 보다 정확한 결과를 예측할 것으로 판단된다.

본 논문에서는 포장가속시험기를 이용하여 아스팔트 안정처리층의 피로모형을 개발하여 기존의 실내실험결과와의 상관관계를 분석하였다. 아스팔트 안정처리층의 피로모형은 Miner(1945)의 누적파손(Cumulative Damage)가설을 적용하였다. 포장가속시험에 사용된 아스팔트 안정처리층은 골재최대입경 25mm(BB-3)의 재료를 사용하였다. 포장가속시험결과 피로모형의 변수인 포장하부의 최대인장응력은 하중재하회수가 증가할수록 증가하는 것을 알 수 있었으며 포장층의 탄성계수는 점차 작아지는 것을 알 수 있었다. 아스팔트 피로모형의 기본식에서 변형률계를 통하여 얻은 인장변형률을 통하여 k1=1.29×10-6, k2=3.02의 값을 도출하였으며, 같은 인장변형률에서의 피로수명은 실내실험을 통한 모형보다 크게 나타났다. 또한, 비파괴실험인 FWD를 이용하여 포장의 잔존수명을 추정하는 논리를 개발하였다.

외국의 포장가속시험기는 대부분 아스팔트포장의 시험을 주된 목적으로 개발되었다. 그러나, 국내의 고속도로는 콘크리트포장과 아스팔트포장이 거의 같은 연장을 유지하고 있는 실정으로 콘크리트포장의 활용이 예상되어 콘크리트 포장의 시험을 위한 독자적인 포장가속시험시설의 개발이 요구되고 있다. 따라서 한국의 실정에 알맞은 콘크리트/아스팔트포장 '시험용 포장가속 시험시설'을 개발하기 위하여 1997년부터 1999년 동안의 3년간 연구를 수행하였다. 1차 연도에서는 포장가속시험시설을 제작하는데 필요한 기본적인 사양과 기본 시스템 설계에 관한 기초연구가 이루어 졌고, 2$\sim$3차 년도에는 KALES의 전체구조, 하중작용, 현가장치 및 구동장치 등에 대한 상세설계를 수행하였다. 실모델을 제작하기 전단계로 모형시험기를 만들어 시험을 수행하여 작동성 및 하중분배기구 등을 검토하였다. 피로해석 검토결과 제안된 KALES 시스템은 내구성이 있으며 실제차량을 잘 모사할 수 있는 시험기로 판명되었다.