• 한국도로학회논문집
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• 제16권6호
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• pp.1-8
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• 2014

PURPOSES : Analysis and design of asphalt concrete (AC) and continuously reinforced concrete (CRC) composite pavements. METHODS : In this study, the service life of the AC/CRC composite pavements was determined based on the probabilistic method in the mechanistic-empirical pavement design guide(MEPDG). Typical pavement design was provided with respect to heavy truck traffic volume of highways. RESULTS : The service life of the composite pavements based on IRI was shorter than that based on rutting at lower traffic volume, but this trend was switched at higher traffic volume. CONCLUSIONS : It is concluded that the main distress affecting the service life of the composite pavements was longitudinal roughness and rutting. Roughness became lower, but rut depth became greater as the stiffness of the CRC increased.

• 대한토목학회논문집
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• 제42권4호
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• pp.537-548
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• 2022

중하중의 교통하중은 포장체에 과도한 응력과 변형을 발생시키므로 이에 대응할 수 있는 포장 단면 설계가 중요하다. 항만 배후도로와 산업도로는 일반도로에 비해 중하중 교통의 비율이 높아 포장의 조기 파손으로 인한 문제가 다수 발생되고 있다. 국외의 경우 중차량의 통행이 많은 도로의 포장설계는 복합포장을 많이 적용하고 있다. 복합포장은 기존 포장의 설계수명을 2배 이상 증대시켜 보수비용 및 사용자 비용을 절감할 수 있는 경제적 포장 형식으로 인식되고 있다. 본 연구에서는 중하중 교통의 비율이 높은 산업도로와 항만 배후도로의 포장 장기 공용성을 확보할 수 있도록 롤러전압콘크리트 기층을 활용한 복합포장의 두께 설계 방안을 제안하고자 한다. 3차원 유한요소해석을 이용하여 포장의 재료물성 변화에 따른 역학적 거동과 장기 공용성을 검토하였으며, 계절별 컨테이너 트레일러에 의해 발생되는 롤러전압콘크리트 기층의 누적피로손상도을 고려하여 사용자가 쉽게 사용할 수 있는 카탈로그 설계를 제안하였다.

• 한국도로학회논문집
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• 제19권1호
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• pp.45-52
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• 2017

PURPOSES : The main purpose of this study is to develop a high elastic modulus and low-shrinkage roller-compacted concrete base (RCCB) in order to prevent fatigue cracking and reflective cracking in the asphalt surface layer of composite pavement. Using a rigid base material with low shrinkage can be a solution to this problem. Moreover, a strong rigid base with high elastic modulus is able to shift the location of critical tensile strain from the bottom of the asphalt layer to the bottom of the rigid base layer, which can prevent fatigue cracking in the asphalt layer. METHODS : Sensitivity analysis of composite pavement via numerical methods is implemented to determine an appropriate range of elastic modulus of the rigid base that would eliminate fatigue cracking. Various asphalt thicknesses and elastic moduli of the rigid base are used in the analysis to study their respective influences on fatigue cracking. Low-shrinkage RCC mixture, as determined via laboratory testing with various amounts of a CSA expansion agent (0%, 7%, and 10%), is found to achieve an appropriate low-shrinkage level. Shrinkage of RCC is measured according to KS F 2424. RESULTS : This study shows that composite pavements comprising asphalt thicknesses of (h1) 2 in. with E2 > 19 GPa, 4 in. with E2 > 15 GPa, and 6 in. with E2 > 11 GPa are able to eliminate tensile strain in the asphalt layer, which is the cause of fatigue cracking in this layer. Shrinkage test results demonstrate that a 10% CSA RCC mixture can reduce shrinkage by 84% and 93% as compared to conventional RCC and PCC, respectively. CONCLUSIONS : According to the results of numerical analyses using various design inputs, composite pavements are shown to be able to eliminate fatigue cracking in composite pavement. Additionally, an RCC mixture with 10% CSA admixture is able to reduce or eliminate reflective cracking in asphalt surfaces as a result of the significant shrinkage reduction in the RCC base. Thus, this low-shrinkage base material can be used as an alternative solution to distresses in composite pavement.

• 한국도로학회논문집
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• 제14권2호
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• pp.1-10
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• 2012

고속도로에서 재령이 20년이 넘는 노후 콘크리트가 늘어남에 따라 콘크리트 포장의 보수/보강이 중요한 이슈로 대두되고 있다. 노후 콘크리트 포장의 보강 대안으로서 아스팔트 덧씌우기가 많이 사용되고 있으나 반사균열 및 포트홀 등 체류수로 인한 문제가 심각하게 대두되고 있다. 본 연구는 반사균열 및 체류수의 문제를 최소화하기 위해 고안된 접착식 방수층을 소개하였으며 포장가속시험을 통해 일반 택코팅을 적용한 합성단면포장과 비교평가를 실시하였다. 실험은 강우를 모사하기 위해 물을 뿌리면서 진행하였고 덧씌우기 포장체의 거동 및 수분 저항 특성을 분석하였다. 연구결과 접착식 방수층은 아스팔트 포장과 콘크리트 포장이 일체로 거동하는 것을 도와주기 때문에 아스팔트 포장체에 발생하는 거동이 일반 택코팅 구간과 완전히 다른 것으로 나타났다. 또 수분의 유입을 최소화하므로 결과적으로 반사균열의 발생을 약 70% 지연시키는 것으로 나타났으며, 체류수로 인한 손상도 줄여주는 것으로 나타났다.

• 한국도로학회논문집
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• 제19권6호
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• pp.37-46
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• 2017

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 base. METHODS : 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 $1.1l/m^2$ 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 $40^{\circ}C$. 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 $0.8l/m^2$, $0.9l/m^2$, 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 $20^{\circ}C$, 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 $40^{\circ}C$. 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.

• 한국도로학회논문집
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• 제14권5호
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• pp.21-29
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• 2012

PURPOSES: This study is to investigate the mechanical performance of the fiber reinforced lean concrete with respect to different types of fibers. METHODS: Increased vehicle weight and other causes from the exposed conditions have accelerated the deteriorations of road pavement. A new multi-functional composite pavement system is being developed recently in order to extend service life and upgrade the pavement. A variety of tests were conducted before and after hardening of the concrete. RESULTS: From the test results, it was found that the use of different types of fibers did not affect the compressive strength development. This might be due to the inherent property of the lean concrete. When steel fibers were used relatively greater flexural strength and flexural fracture toughness were developed. Also addition of fly ash by replacing a part of Portland cement the fracture toughness was slightly increased. CONCLUSIONS: It has been known that the addition of fibers and use of mineral admixture can be positively considered in the development of multi-functional composite pavement system as its required mechanical performance is obtained.

• 한국도로학회논문집
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• 제16권6호
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• pp.69-78
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• 2014

PURPOSES : The purpose of this paper is showing that the state of pavement sublayers can be evaluated differently according to direction of FWD. METHODS : The concrete pavement slabs above subgrade without anything, subgrade with cavity, and box culvert were modeled by finite element method(FEM). The modeled pavements were analyzed by changing the direction of falling weight deflectometer(FWD). The deflection results obtained from FEM were used to calculate radius of relative stiffness and composite modulus of subgrade reaction using AREA method. Then, the analyzed results were compared to the results of the test performed at the Korea Expressway Corporation(KEC) test road. RESULTS : The composite modulus of subgrade reaction increased with subgrade elastic modulus, while radius of relative stiffness decreased. The pavement sections of pure earth showed the consistent results regardless of FWD direction. In case there was cavity, the radius of relative stiffness was larger and composite modulus of subgrade reaction was smaller when FWD was leaving the cavity than when approaching the cavity. This pattern became clear when the cavity got larger. In case of the section with box culvert, the pattern was opposite to the case of cavity. When the soil cover depth increased, the effect of box culvert got smaller. When the load was applied far from the cavity and box culvert, the effect was also declined. The test performed at the KEC test road showed identical results to those of finite element analysis. CONCLUSIONS : The direction of FWD should be considered in evaluation of the state of pavement sublayers because it can be evaluated differently even under identical condition.

• 복합신소재구조학회 논문집
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• 제6권4호
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• pp.64-70
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• 2015

A rapid urbanization has increased the portion of paved layer that results in the change of water circulation system. This change leads to frequent events of flooding, drought, and urban heat island. To resolve these issues, permeable pavement system based on Low Impact Development (LID) concept is being applied to international urban areas. Therefore it is necessary to establish a rational design procedure for the permeable pavement system that reflects our environmental conditions. iDue to inherent characteristics of permeable pavement system, water infiltrates thorough the layers so it may reduce the bearing capacity of sub-layers. In this study, an effort was made to investigate the effectiveness of geogrid reinforced crushed stone subbase layer based on field experimental program along with a limited numerical analysis. It reveals that geogrid reinforced sections improve the bearing capacity by close to 20%. In addition, a light weight deflectomenter (LWDT) appears to be promising for the compaction quality control of crushed stone subbase layer in order to construct qualified permeable pavement systems.

• 한국도로학회논문집
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• 제19권6호
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• pp.57-66
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• 2017

PURPOSES : This study develops eco-friendly asphalt reinforcement materials applicable to bridge deck pavement. The main purpose is to ensure highly reliable quality applicable to structures and the possibility of practical application. The main target of the study is to develop materials that are environmentally friendly and capable of improving performance. METHODS : The application of double-reinforcement fiber improves the performance of the road pavement. 1. We use recycled film for application of sheet-typed reinforcement. 2. We use preprocessing fibers to reinforce the properties of composite pavement materials. RESULTS : The developed products may produce materials that fit the purpose of achieving stability and environmental friendliness. Sheet-typed reinforcements use more than 50% recycled resin. The most important type of damage to the asphalt layer is deflection (plastic deformation). These products have a very high deflection resistance of not less than 6,000 cycles/mm. In addition, all performance is excellent. Thus, it will be easier to access the field in the future. CONCLUSIONS : Fiber-reinforced asphalt pavement showed excellent performance. Sheet-typed reinforcements containing 50% recycling resin produced good performance in terms of functionality as well as environmental friendliness. Thus, enhancing the field applicability will enhance the usability of the reinforcements.

• 한국도로학회:학술대회논문집
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• 한국도로학회 2009년도 추계학술대회 논문집
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• pp.525-528
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• 2009