• 한국도로학회:학술대회논문집
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• 한국도로학회 2009년도 추계학술대회 논문집
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• pp.97-100
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• 2009

• Structural Engineering and Mechanics
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• 제36권4호
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• pp.401-419
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• 2010

This paper focuses on the development, verification and application of a three-dimensional nite element code for coupled thermal and structural analysis of roller compacted concrete arch dams. The Ostour Arch dam located on Ghezel-Ozan River, Iran, which was originally designed as conventional concrete arch dam, has been taken for the purpose of verication of the nite element code. In this project, RCC technology has been ascertained as an alternative method to reduce the cost of the project and make it competitive. The thermal analysis has been carried out taking into account the simulation of the sequence of construction, environmental temperature changes, and the wind speed. In addition, the variation of elastic modulus with time has been considered in this investigation using Concard's model. An attempt was made to compare the stresses developed in the dam body five years after the completion of the dam with those of end of the construction. It was seen that there is an increase in the tensile stresses after five years over stresses obtained immediately at the end of construction by 61.3%.

• 한국도로학회:학술대회논문집
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• 한국도로학회 2010년 춘계학술대회 논문집
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• pp.217-221
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• 2010

• Structural Engineering and Mechanics
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• 제90권5호
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• pp.467-480
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• 2024

The mechanical properties and durability of concrete pavements may be degraded in extreme situations, resulting in the need for partial repair or total replacement. During the past few decades, there has been a growing body of research on substituting a portion of Portland cement with alternative cementitious materials for improving concrete properties. In this study, two different configurations of powdered and granulated blast furnace slag were implemented, replacing fine aggregates (by 12 wt.%) and Portland cement (by 0, 20, 40, and 60 wt.%) in the making of roller-compacted concrete (RCC) mixes. The specimens were fabricated to investigate the mechanical properties and durability specifications, involving freeze-thaw, salt-scaling, and water absorption resistance. The experimental results indicated that the optimum mechanical properties of RCC mixes could be achieved when 20-40 wt.% of powdered slag was added to concrete mixes containing slag aggregates. Accordingly, the increases in compressive, tensile, and flexural strengths were 45, 50, and 28%, in comparison to the control specimen at the age of 90 days. Also, incorporating 60 wt.% of powdered slag gave rise to the optimum mix plan in terms of freeze-thaw resistance such that a negligible strength degradation was experienced after 300 cycles. In addition, the optimal moisture content of the proposed RCC mixtures was measured to be in the range of 5 to 6.56%. Furthermore, the partial addition of granulated slag was found to be more advantageous than using entirely natural sand in the improvement of the mechanical and durability characteristics of all mixture plans.

• 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.

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.137-160
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• 2015

The one-way (two-way) flexural strength of RCC prisms (circular slabs) reinforced with glass fiber textiles is addressed. To this end, alkaline-resistant glass fiber textiles with three surface weights were used in the composite, the matrix concrete was designed with zero/nonzero slump, and the textiles were used with/without an intermediate layer provided by epoxy resin and sand mortar. Prisms were tested under a four-point loading apparatus and circular slabs were placed on simple supports under a central load. Effects of the amount and geometry of reinforcement, matrix workability, and the intermediate layer on the ultimate load and deflection were investigated. Results revealed that, with a specific reinforcement amount, there is an optimum textile tex for each case, depending on the matrix mix design and the presence of intermediate layer. Similar results were obtained in one-way and two-way bending tests.

• 한국도로학회논문집
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• 제17권3호
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• pp.27-33
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• 2015

PURPOSES : To ensure appropriate RCC properties with sufficient strength development and workability, it is necessary to secure a proper level of consistency. It is also necessary to secure maximum dry density, which is an important factor for increasing the interaction of aggregate interlocking, leading to an augmentation of RCC strength. On the other hand, the dry density of RCC can be changed owing to the compaction conditions, water content, and particle size distribution. A Proctor test and a modified Proctor test were used for determining the optimum water content needed to achieve maximum dry density with different amounts of compaction energy. A Vebe test, on the other hand, was used for checking the level of consistency, which is important for producing a workable mixture. METHODS : To confirm the degree of compaction at various particle sizes, RCC mixtures with different sand/aggregate ratios were evaluated. The Proctor test and modified Proctor test were applied to these mixtures to check the effect of the aggregate gradation and compaction energy on the maximum dry density and optimum water content. During each test, three specimens were produced for all types of water content under each aggregate gradation. A compaction curve and the optimum water content and maximum dry density for each aggregate gradation were then obtained for both tests. The range of water content for the appropriate consistency of each aggregate gradation was determined through a Vebe test. The optimum water content was then evaluated based on this range. RESULTS : The compaction test results show that the modified Proctor test provides a higher maximum dry density and lower optimum water content compared with the standard Proctor test. For the modified Proctor test, two cases of aggregate gradation (s/a = 30% and 70%) had the optimum water contents outside of the appropriate water content range. For the standard Proctor test, on the other hand, none of aggregate gradations provided the optimum water content within the desired range. CONCLUSIONS : The modified Proctor test should be used for an RCC mixture design because it can provide adequacy between maximum dry density and consistency. Moreover, the compaction roller has become highly developed for higher compaction energy.

• 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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• 제17권3호
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• pp.49-58
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• 2015

PURPOSES : The use of environmentally friendly construction methods has been recently encouraged to reduce fuel consumption and the effects of global warming. For this purpose, the roller compacted concrete pavement (RCCP) construction method has been developed. RCCP is more environmentally friendly and economically efficient than general concrete by reducing the amount of CO2 generated through the application of a smaller amount of cement. RCCP has a number of advantages such as an easy construction method, low cost, high structural hydration performance, and aggregate interlocking. However, mix design standards and construction guidelines of RCCP are required for domestic application. In addition, a study on aggregate selection, which has an effect on the characteristics of RCCP, is necessary owing to a limited number of researches. Thus, the aggregate effect on the performance of RCCP in securing the required strength and workability was evaluated in consideration of domestic construction. METHODS : Sand and coarse aggregates of both 19mm and 13mm in maximum size were used in this study. Four types of aggregate gradations (s/a = 30%, 58%, and 70% for the sand and coarse aggregate of 19mm in maximum size, and s/a = 50% for a combination of the three types of aggregates) were set up to investigate the effects of the PCA band on the RCC characteristics. The conditions of s/a = 30% and 70% were evaluated to check the gradation effect outside of the recommended band. The conditions of s/a = 58% and 50% were used because they are the optimum combination of the two and three types of aggregates, respectively. RCCP gradation band was suggested gradation with a proper construction method of RCCP by synthetically comparing and analyzing the correlation of optimum water content, maximum dry density, and strength of requirements through its consistency and compaction test. RESULTS : The lower and upper limit lines are insufficient to secure a relatively strong development and workability compared to an aggregate gradation in the RCCP gradation band region. On the other hand, the line in the RCCP gradation band and the 0.45 power curve in the RCCP gradation band region were satisfactory, ensuring the required strength and workability. CONCLUSIONS : The suitable aggregate gradation on RCCP process should meet the RCCP gradation band area; however, fine particles passing through a #60 sieve do not need to be within the recommended gradation band because the influence of this region on such fine particles is small.