• Computational Structural Engineering
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• v.7 no.4
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• pp.4-9
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• 1994

강섬유 보강 콘크리트는 콘크리트 내에 강섬유를 임의로 투입함으로써 취성의 콘크리트 물성을 연성적으로 향상시킴과 동시에 압축, 인장, 휨 강도를 증가시킨 새로운 구조 신소재라고 할 수 있다. 과거 70년대가 SFRC의 재료적 물성에 대한 실험적 시기였던 반면 현재는 현장에 SFRC를 시공하는 응용단계라 할 수 있다. SFRC의 우수성은 선진 외국의 경우 일반적으로 기업, 정부, 계약관계자 등에게 잘 인식되어 있어 이미 많은 시공현장에서 응용되고 있다. 이로 인하여 외국(미국, 일본, 유럽 등)의 경우 구조적으로 안정되고 경제적인 구조물을 실현하고 있으나 국내의 경우는 안타깝게도 SFRC에 대한 인식이 아직 일반화되어 있지 않으며 시공현장도 매우 드문 실정이다. SFRC에대한 연구는 국.내외 학회에서 꾸준히 연구, 개발하고 있으며 이들 연구결과가 경제적이고 우수한 구조물을 실현하는데 기여할 수 있기를 기대한다.

• Korean Journal of Agricultural Science
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• v.23 no.1
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• pp.39-50
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• 1996

The normal cement concrete is widely used material to build the construction recently, but it has a fault to increase the dead load on account of its unit weight is large compared with strength. So, many engineers are continuously searching for new materials of construction to provide greater performance at lower density. Many studies were carried out on the lightweight aggregate concrete in foreign country in the latter half of the 19th century, therefore lightweight aggregate concrete has been used successfully for many years for structural members. The main purpose of the work described in this paper were to establish its physical and mechanical properties of no-fines lightweight concrete using synthetic lightweight coarse aggregates. Test results are summarized as follows ; The water-cement ratio was shown less than 33% in use synthetic lightweight coarse aggregates, unit weights of synthetic lightweight concrete was shown less than $1,800kg/m^3$ and compressive strength was higher than $200kg/m^2$. And the pulse velocity was more than 3,000m/sec. The relationship of compressive strength between unit weight and pulse velocity was shown to be approximately linear.

• Journal of the Korea Institute of Building Construction
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• v.20 no.5
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• pp.391-397
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• 2020

This study is to compare and analyze the strength, drying shrinkage and carbonation properties of lightweight aggregate mortar using recycling water as prewetting water and mixing water. The flow, compressive strength, split tensile strength, drying shrinkage and carbonation depth of lightweight aggregate mortar with recycling water were measured. As test results, the mortar flow was similar in all mixes regardless of the recycling water content. The compresseive strength of the RW5 mix with 5% recycling water as prewetting water and mixing water was the highest value, about 53.9 MPa after 28 days. In addition, the tensile strength of lightweight mortar was about 3.4 to 3.8 MPa, indicating 7 to 9% of the compressive strength value regardless of recycling water content. In the case of drying shrinkage, the RW2.5 mix using 2.5% recycling water showed the lowest shrinkage rate as about 0.107% at 56 days. The drying shrinkage of the plain mix without recycling water was relatively higher than the RW2.5 and RW5 mix. The RW5 mix showed lowest carbonation depth compared to other mixes. In this study, the RW5 lightweight aggregate mortar with 5% recycling water exhibits excellent compressive strength and carbonation resistance. Therefore, it is considered that if the recycling water, a by-product of the concrete industry, is properly used as prewetting water and mixing water of lightweight mortar and concrete, it will be possible to increase the recycling rate of the by-product and contribute to improve the property of lightweitht aggregate mortar and concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.2
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• pp.49-59
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• 2016

According to KS and Standard Specifications for Concrete, the compressive strength of concrete containing recycled aggregate is limited to 27 MPa and thereafter there are little research on concrete containing recycled aggregate of its compressive strength of greater than 27 MPa. Therefore, to expand the applicability of concrete recycled coarse aggregate(RCA), this paper concerns the mechanical properties of concrete containing RCA with compressive strength ranging from 30 to 60 MPa. The experimental parameters were water-cement ratio and replacement ratio of RCA. Water-cement ratio(w/c) was 0.36, 0.46 and 0.53, and replacement ratio of RCA was 30, 50, 70 and 100%. The experimental results were discussed about compressive strength, elastic modulus, split tensile strength and modulus of rupture. Test results of elastic modulus were compared to the design code predictions. Experimental elastic modulus for concrete with w/c=0.53 decreased by greater than 10% compared with that for concrete with w/c=0.36. The design code predictions for elastic modulus overestimated the experimental results. Whereas, the design code predictions for modulus of rupture underestimated the measured values.

• Elastomers and Composites
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• v.12 no.2
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• pp.157-164
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• 1977

(1) 탄성체(彈性體) MBMA를 가황제(加黃劑)로 사용한 가황체(加黃體)는 MOCA를 가황제(加黃劑)로 한 것 보다 Pot life가 긴 것이 특징(特徵)이다. 물리적(物理的) 특성(特性)에 있어서는 2가지 공(共)히 비승하였으나, 내열성(耐熱性)은 MOCA의 경우가 더 우수(優秀)하였다. 인장강도(引張强度), 신장률(伸張率), 반발탄성(反潑彈性)에 있어서는 MBMA를 사용(使用)한 가황(加黃體)와 MOCA를 사용(使用)한 가황체(加黃體)가 동일(同一)하였으나 압축(壓縮)줄음율은 전자(前者)가 높았다. 인열강도(引裂强度)에 있어서는 10부(部)의 MBMA를 가(加)했을 때 후자(後者)와 동일(同一)하였다. 또 MBIA 가황제(加黃劑)를 사용하였을 경우 인장강도(引張强度), 신장률(伸張率) 그리고 반발탄성등(反潑彈性等)이 MBMA 또는 MOCA의 경우와 거의 동일(同一)하였으나 고무가 부드러운 것이 특징이었다. 다만 100% 모듈러스의 경우 전자(前者)가 후자(後者)들보다 낮은 값이었다. NCO와 OH의 비(比)가 2 : 1인 Prepolymer를 사용한 MBIA가황체(加黃體)(MBIA를 가황제(加黃劑)로 한 가황체(加黃體))는 MBMA 가황체(加黃體) 또는 MOCA 가황체(加黃體)에 비(比)해 인열강도(引裂强度)는 낮았다. 그러므로 인열강도(引裂强度)를 향상(向上)시키기 위하여 NCO와 OH의 비(比)를 2 : 1보다 높은 비율(比率)로 취(取)하면 된다. 내열성(耐熱性)에 있어서 MBIA가황체(加黃體)가 MOCA가황체(加黃體)보다 우수(優秀)하였 고 또 배합작업(配合作業)에 있어서도 MOCA나 MBMA 가황체(加黃體)보다 작업성(作業性)이 용역(容易)하였는 바 이같은 이유(理由)는 전자(前者)의 녹는 점(點)$(70^{\circ}C)$이 후자(後者)들보다 낮기 때문이다. MBIA의 기타(其他) 특성(特性)으로서는 Pot life가 MOCA가황체(加黃體)보다 2.5배(倍) 길었다. 끝으로 MBEHA와 MBCHA가황체(加黃體)의 특징(特徵)은 가황속도(加黃速度)가 MBIA가황체(加黃體)보다 느림과 동시(同時)에 고무자체(自體)가 부드러웠을 뿐만 아니라 물리적(物理的) 특성(特性)도 좋지 않았다. (2) 미세구조용(微細構造用) 포옴라버 미세구조용((微細構造用) 포옴라버를 제조(製造)할 경우 이때까지 사용(使用)해온 MOCA가황제(加黃劑) 대신(代身) MBMA를 가황제(加黃劑)로 대체사용(代替使用)이 가능(可能)한 바, 이를 사용(使用)하였을 때의 물리적(物理的) 특성(特性)은 MOCA를 사용(使用)하였을 때 보다 인열강도(引裂强度), 신장률(伸張率) 그리고 열안정성등(熱安定性等)은 월등(越等)히 우수(優秀)하였다.

• Resources Recycling
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• v.33 no.1
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• pp.48-57
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• 2024

This study aimed to improve utilization of the Class C vinyl waste generated in rural areas based on a preliminary investigation on the use of eco-powder, generated through pyrolysis, as a raw material for plastic. The efficiency of pre-processing treatments in controlling ash content of the generated eco-powder and its effect on the basic properties of manufactured plastic were evaluated. The basic properties included ash content of the compressed eco-powder at different levels of ash content, impact strength, flexural strength, and tensile strength. The experimental results confirmed that pre-processing improved the separation efficiency of soil particles and vinyl waste through physical impact. The eco-powder with ash content of less than or equal to 26% was found to satisfy the target performance during impact strength, flexural strength, and tensile strength evaluation. Thus, it was confirmed that the Class C vinyl waste, having low utilization and recovery rates, could be effectively utilized as a plastic raw material after optimum thermal treatment and physical processing using the eco-powder.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.203-210
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• 2019

A recent earthquake on the Korean Peninsula caused much damage to masonry buildings, and research on performance evaluation has been underway. A masonry building is generally constructed using wet construction and is affected by temperature, which reduces the efficiency of the construction. In this study, we propose a dry construction technique for assembling concrete blocks without using mortar and evaluated its performance through experimental and analytical research. To evaluate the performance, experiments were carried out for the prismatic compressive strength, direct terminal strength, and diagonal tensile strength of the dry construction wall. The adequacy of the cross section shape was also reviewed through FEM analysis. The results show that the compressive strength and diagonal tensile strength could exert a certain intensity or higher. Furthermore, the H-type module of a key block acted as a shear key for the entire concrete block, which resulted in excellent shear strength performance. In addition, the shape and thickness of the main block have a major effect on the strength performance of each block. Therefore, an optimal shape and the proposed dry construction method could be applied to replace the wet method by studying the construction or seismic performance of the proposed method.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.395-405
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• 2016

The thermal and mechanical properties of fiber-reinforced mortars for thermal energy storage were investigated in this paper. The effect of the combination of different cementitious composite on the thermal and mechanical characteristics of fiber-reinforced mortars was investigated. Experiments were performed to measure mechanical properties including compressive strength before and after thermal cycling and split tensile strength, and to measure thermal properties including thermal conductivity and specific heat. The results showed that the residual compressive strength of mixtures with OPC and graphite was greatest among the mixtures. Thermal conductivity of mixtures with alumina cement was greater than that of mixtures with OPC, indicating favor of alumina cement for charging and discharging in thermal energy storage system. The addition of zirconium into alumina cement increased specific heat of mixtures. Test results of this study could be used to provide information of material properties for thermal energy storage concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.414-420
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• 2017

The thermal characteristics of concrete fabricated with blast furnace slag were investigated in this paper. Test parameters included water-binder ratio and the content of furnace slag. Experimental program were performed to measure mechanical properties including compressive strength and split tensile strength under high-temperature thermal cycling, and to measure thermal properties including thermal conductivity and specific heat. Test results showed that the residual compressive strength of mixtures with blast furnace slag was greater than that of mixture without blast furnace slag. In addition, thermal conductivity of mixtures with blast furnace slag was greater than that of mixtures without blast furnace slag. It indicates that blast furnace slag was favorable for charging and discharging in thermal energy storage system. Test results of this study would be used to design concrete module system of thermal energy storage.

• Tunnel and Underground Space
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• v.21 no.3
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• pp.205-215
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• 2011

In this study, we analyzed physical properties of granites and their correlation with rock mass classification methods. The granite samples were obtained from field survey, in-situ borehole tests and laboratory tests for a design phase of various roads, railways and other civil engineering works in Korea. Among the measured physical properties, the results of unit weight, compressive strength, tensile strength, seismic velocity, cohesion, friction angle, elastic modulus and deformation modulus were introduced. We also correlated these properties with the compressive strength. The results of different rock classification method of RQD, RMR, and Q-system against the granites in Korea were compared with each other, and the correlation equations were proposed in a more simplified form. We also derived RMR values using the compressive strength as well as the RQD values of in-situ drilled cores, and estimated the deformation modulus of in-situ rock mass in terms of the RMR values.