PURPOSES : The aim of this study is to review freeze-and-thaw testing apparatuses, develop a freeze-and-thaw testing setup with a test protocol, test the freeze-and-thaw properties of soils collected from different parts of South Korea, and suggest an index for frost susceptibility criteria for soils found in South Korea. METHODS : Based on a literature review, a new freeze-thaw testing setup was developed. In addition, a test protocol was developed for freeze-thaw testing. Soils collected from different parts of South Korea and bedding sand used for block pavements were tested to determine whether the measurements from the newly developed test setup could capture important freeze-thaw characteristics of the soils. Finally, to develop local frost susceptibility criteria, a parameter including both the vertical deformation and thermal conductivity characteristics of the soils was suggested. RESULTS : The results from the laboratory experiments indicate that the newly developed freeze-and-thaw setup captures the required parameters to quantify the responses of soils subjected to cyclic freeze-and-thaw testing. In addition, a vertical deformation of up to 2.437 mm is measured. Moreover, seven soils out of the nine tested soils are classified as having a medium frost susceptibility, whereas the remaining two show low frost susceptibility. The bedding sand experiment also shows that there is a possibility of having a frost susceptible condition based on the moisture content. When submerged, the bedding sand is classified as having a medium frost susceptibility. CONCLUSIONS : The "HEART" freeze-thaw testing setup was able to capture the parameters required for evaluating the frost susceptibility of soils. This setup and testing procedure could be further used to test and prepare criteria for classifying the frost susceptibility of soils found in South Korea.

In this study, a mixed resin containing Bis-GMA was developed to produce a light-emitting sign using quantum dots. As a result of measuring the viscosity, color coordinates change, and luminance of the mixed resin, the following conclusions were obtained. The viscosity of the mixed resin decreased as the content of the diluent increased, and viscosity values ​​ranged from 3,627 to 1,349cps showed as a result. The viscosity of the mixed resin decreased as the temperature increased, and the viscosity showed a value of 5,156 to 1,132cps. For the optical properties of InP/GaP/ZnSe/ZnS quantum dots, the absolute quantum efficiency was 91% at 522nm and 90% at 618nm when the gallium was 0.01%. The luminance of the light-emitting sign using the resin mixed with quantum dots was showed 142.6cd/m2 in white and 104.2cd/m2 in the red region.

PURPOSES : Given that large-scale repair works of expressway bridge pavements have high maintenance cost and long traffic blocking time, the thin overlay method that maintains the existing pavement is attracting attention. In this study, because the bridge thin overlay has not been introduced in Korea yet, the basic physical properties of the epoxy thin overlay, which is mainly used for the bridge thin overlay, were investigated, and the skid resistance and bond performance were analyzed. METHODS : Basic physical property tests were performed on each of the epoxy binders, aggregates, and mixtures used in epoxy thin overlay. They were also compared and reviewed against foreign standards. The epoxy binders were tested for viscosity, gel time, and thermal compatibility. The aggregates were tested in terms of water absorption, specific gravity, and gradation. The compressive and flexural strengths of the mixtures were investigated. The epoxy thin overlay has the possibility of detachment of aggregates, so the skid resistance was tested according to the paving phase. In addition, to investigate the bond performance, which is the most important performance of the epoxy thin overlay, the bond strength test was performed by varying the moisture condition and treatment condition of the existing layer surface. RESULTS : The basic physical properties of the materials used in the epoxy thin overlays satisfied foreign standards except for the gradation of aggregates. The skid resistance did not satisfy the standard when the epoxy was exposed, whereas the skid resistance did satisfy the standard when the aggregates were exposed, even after the abrasion test. The bond strength of the epoxy thin overlay satisfied the standard in all cases. The bond strength was the highest when the relative humidity of the existing layer surface was 60%. CONCLUSIONS : The materials of epoxy thin overlay that could be obtained in Korea satisfied the basic physical property standards except for aggregate gradation. Given that the aggregate gradation could be adjusted, it can be concluded that the epoxy thin overlay could be introduced in Korea. In addition, it was confirmed that the skid resistance and bond strength of the epoxy thin overlay were high enough to be used in general road conditions. It was determined that the existing layer surface should maintain an optimal relative humidity of approximately 60% because the moisture condition affects the bond strength.

PURPOSES : In general, a high-performance concrete construction method is a method of loading mixed cement and other materials on a mobile mixer equipped with a concrete plant. However, the construction cost is high because the unit cost of the mixed cement is very high and the equipment usage fee of the mobile mixer is also high. To compensate for these drawbacks, a cellular spray concrete method was developed. This is a highly functional customized concrete construction method in which admixtures are added to high-flow concrete with cellular (air bubbles) added at the site and constructed through spraying. METHODS : Field workability evaluation using cellular concrete was carried out using a spray method in 2017 and an anti-foaming agent in 2018. The test construction section was set as a new road-pavement construction site. After construction, strength, durability characteristics, and void analysis were performed to compare the construction methods. The results of laboratory tests under optimal conditions were also compared to the on-field results. By comparing the indoor mixing and the on-field results, we analyzed whether there were any problems concerning the performance expression. The economic feasibility at the initial construction stage was analyzed by comparing the existing and the cellular concrete construction methods in terms of material cost and equipment usage fee. RESULTS : In the case of cellular spray concrete, construction through spraying is cumbersome, and the need to additionally use large equipment such as a pump car and compressor constitutes a disadvantage. However, the most relevant feature is that it can be constructed not only on the floor, but also on a slope. In the case of cellular concrete with an antifoaming agent, it was possible to quickly produce high-performance concrete using on-site remixing equipment. By supplying materials to the pouring surface using a conveyor, smooth construction and construction in narrow spaces were also possible. CONCLUSIONS : The cellular concrete method allows the immediate on-site production of high-performance concrete, and it is possible to selectively apply spray construction, antifoaming agent construction, etc.

PURPOSES : The purpose of this study is to measure and analyze the fugitive dust generated by each process through field tests to develop a technology to reduce fugitive dust generated during excavation-restoration work on road pavements. METHODS : The testbed was constructed based on a typical excavation-restoration construction section and comprised five sections for reproducibility and repeated measurements. The excavation-restoration work was divided into pavement cutting, pavement crushing, pavement removal, excavation, and restoration processes and fugitive dust generated by each process was measured. Fugitive dust (TSP, PM10, PM2.5, and PM1) was measured using a GRIMM particle spectrometer, which applies the principle of a light scattering spectrometer and can be measured in real-time. RESULTS : Analyses of the average mass concentration of PM10 generated by the excavation-restoration process are as follows: 1286.3 μg/m³ from pavement cutting, 246.8 μg/m³ from pavement crushing, 697.0 μg/m³ from pavement removal, 747.9 μg/m³ from excavation process, and 350.6 μg/m³ from the restoration process. In addition, the average particle size distribution of the excavationrestoration construction was in the order of PM10~PM2.5 (67 %), PM1 or less (24 %), and PM2.5~PM1 (9 %). The pavement cutting process is characterized by the emission of high concentrations of fugitive dust over a short time, compared to other processes. The pavement crushing process has the characteristic of steadily generating fugitive dust for a long period, although the emission concentration is small. CONCLUSIONS : In this study, it was found that the concentration and characteristics of fugitive dust generated during road pavement excavation-restoration works vary by process and the reduction technology for each process should be developed accordingly.

For form stability of membrane structures, membrane material is required to be in tension. Therefore, in planning and maintenance management, the engineer should consider enough about introduction of stress during construction and re-introduction of stress after completion. Clamping part is an important portion with the function for introducing tension into membrane materials, and the function to transmit stress to boundary structures, such as steel frames. Then, the purpose of this research is to clarify stress condition and stress transfer mechanism including clamping part of membrane structures, and to grasp the changing tendency of membrane structures with the passage of time. In this research, following previous one, we perform well-balanced evaluation by conducting tensile fractured tests of clamping part's specimens, and by measuring individually the amount of displacement of not only overall specimen's length but membrane material and clamping part. Thereby, we consider the influence the difference in the hardness of edge rope and the difference in the direction of thread affect modification and fracture load.

해양생태독성시험의 국제표준시험종 중 생산자에 속하는 대표적인 Skeletonema sp.와 Dunaliella tertiolecta의 생태독성학적 차이점을 알아보기 위해 각 표준시험법(규격)을 비교하였고 환경에 대한 종 적합성과 다양한 시험물질에 대한 민감도를 비교 분석하였다. 그 결과, 시험법의 경우 대부분 동일하였으나 시험 유효성의 기준에서 pH 변화 제한과 초기접종밀도에서 차이가 나타났으며 이는 D. tertiolecta 의 낮은 성장률에 기인된 것으로 추정된다. 적합성에서는 두 종 모두 규격에서 요구하는 유효성의 기준을 연속 만족하여 시험수행의 일관성을 보였고 시험한계 염분범위는 Skeletonema sp.와 D. tertiolecta 각각 20 및 10 psu로 나타났다. 마지막으로 민감도의 경우, 시험규격에서 제시하는 참조물질, 실제 오염 배출수(선박평형수) 및 기타 다양한 화학물질에서 모두 Skeletonema sp.가 D. tertiolecta에 비해 독성 민감도가 상대적으로 높음을 확인하였으며 이는 해양생태독성시험 수행에 있어 생산자를 이용한 시험의 경우 최소 2종 이상의 다른 분류군의 미세 조류를 이용하는 것이 시험결과의 신뢰성과 객관성을 높일 수 있는 방법임을 시사한다.

This study aims at investigating the fracture characteristic according to the shape of the double cantilever beam specimen for mode II with ultra-high strength steel and Mg alloy steel. As the analysis, all three models had the left-hand holes that were constrained by the cylindrical support and the right-hand holes were enforced by the constraint condition of 6mm/min. This study result showed that the shorter the load block of the double envelope test specimen, the higher the safety. The results of this study are thought to be useful for examining the fracture characteristics of specimen for mode II with ultra high strength steel and Mg alloy steel.

This paper aims at investigating the adhesive property at damage analysis according to the shape of the DCB test specimen made of Titanium, Dualumin as the high strength nonferrous metals. In this analysis, all three specimens had the lower holes bound by the cylinder support and the top holes were elongated with the rate of 6mm/min. The study results show that the longer the load block of DCB specimens, the more reliable and durable they are. It is utilized as the basic data at investigating the damage properties of adhesives in DCB specimens made of high strength nonferrous metals.

PURPOSES : This study investigates the abrasion characteristics of coarse aggregate using the Los Angeles (L.A.) abrasion test and the accelerated polishing machine (APM) test. The coarse aggregates are randomly exposed on the surface of asphalt concrete pavements and on exposed aggregate concrete pavements. The exposed aggregates play a very important role in providing skid resistance. Therefore, the adequate abrasion resistance of coarse aggregate must be ensured to maintain the skid resistance during service life. In Korea, the LA abrasion test is conducted according to the KS F 2508 standard for the evaluation of the abrasion resistance of coarse aggregate. However, the road surface abrasion is caused by the friction between the tire and the road surface structure; hence, whether the LA abrasion test, which evaluates the abrasion caused by the impact of coarse aggregates and steel balls, can evaluate the road surface abrasion is questionable. A comparison and an analysis between the APM and LA abrasion tests were conducted herein to evaluate the road abrasion. An analysis was also performed to analyze whether the abrasion characteristics appeared depending on the type of coarse aggregate. METHODS: The results of the APM and LA abrasion tests for various aggregate types were obtained through a series of experiments and literature reviews. The correlation between the LA abrasion loss and the PV data was derived. In addition, the influence of the aggregate type on the abrasion resistance was investigated. RESULTS : An abrasion resistance database was established, and the relationship between the rock types and the abrasion resistance was statistically determined. The results showed that the PV was increased to 0.54 along with a 1% increasing rate of the LA abrasion loss with a 0.67 coefficient of determination. The abrasion resistance was also influenced by the aggregate type, which was found to be statistically significant. CONCLUSIONS: A good relationship between the PV and the LA abrasion loss was obtained, allowing the use of the LA abrasion test (KS F 2508) alone, to reasonably evaluate the abrasion resistance of the exposed aggregate texture. The aggregate types were also found to have an impact on the abrasion resistance.

고준위방사성폐기물의 심지층처분시스템을 이루는 요소인 공학적방벽이 처분환경에서 어떻게 변화할 것인가를 이해하기 위해 In-DEBS 시험이 계획되었고, In-DEBS 시험을 수행할 위치를 선정하기 위하여 심지층처분을 위한 지하연구시설인 KURT 부지 및 확장구간에 대한 지질 및 수리지질학적 자료가 조사, 분석되었다. KURT 부지 및 확장구간에서 조사된 자료를 이용하여 시험을 수행할 수 있다고 판단되는 연구 갤러리를 결정하였고, 연구 갤러리 내에서의 국지적인 특성을 파악하기 위하여 시추공 조사가 이루어졌다. 부지규모 자료의 분석 및 시추공 조사 자료를 이용하여 지하수 유동에 관한 수리지질학적 특징 및 지하수 유입량이 평가되었으며, In-DEBS 시험을 현장에서 준비하고 수행하기 위해 요구되는 조건을 함께 고려하여 In-DEBS 시험에 이용될 대구경 시추공의 위치를 선정하였다. 굴착된 대구경 시추공의 공벽을 조사하여 지하수 유입량을 평가하고 공벽 부근의 수리전도도 분포를 평가하였다. 본 연구를 통해 정리된 수리지질학적 자료는 In-DEBS 시험 현장에서 관측되고 있는 자료를 해석하여 공학적방벽의 변화 과정을 해석할 때에 기초 자료로 활용될 수 있을 것으로 기대된다.