• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.29 no.6
• /
• pp.315-325
• /
• 2017

This study aims to provide information for the design and use of structural lightweight concrete (SLWC) for floating concrete structures in a marine environment. An experimental program was set up and comprehensive experimental campaign were carried out to determine SLWC mix proportions that can satisfy specified concrete strength, density, and slump values all of them were determined from previous research. Comparisons with previous SLWC mix designs that have been utilized for actual floating concrete structures were made. Key aspects needed to be considered regarding to the use of SLWC for floating marine concrete structures were discussed.

• Journal of the Korea Concrete Institute
• /
• v.26 no.3
• /
• pp.287-297
• /
• 2014

Heat of hydration of mass concrete is one of the most important factors that significantly affect structural quality and construction period. Therefore, appropriate methods to control heat of hydration are essential technologies for mass concrete construction. In this study, probability of thermal cracking was checked by thermal analysis prior to the construction of a turbine foundation in a domestic power plant. Subsequently, changes of concrete mix proportion and an effective curing method were proposed to control heat of hydration of mass concrete structures. Concrete manufactured by slag cement was proposed instead of concrete produced by ordinary Portland cement, and an automated curing method was proposed to improve the curing method using typical moist curing with blanket. The automated curing method maintains the temperature difference between center and surface of concrete below a setting value by temperature monitoring. Concrete with slag cement was used for actual construction. One of two identical turbine foundations was cured by an insulated curing method, and the other was cured by the automated curing method to compare the curing methods. And then, the effects of control of heat of hydration were evaluated based on temperature/strain monitoring and crack investigations.

• Magazine of the Korea Concrete Institute
• /
• v.4 no.2
• /
• pp.83-92
• /
• 1992

본 연구의 목적은 현장에서 구입 가능한 저품질의 재료를 사용한 일련의 실험을 통하여 28일 압축강도와 물\ulcorner시멘트비와 관계를 유출함으로써 고강도 콘크리트의 배합설계식을 얻기 위한 것이다. 목표슬럼프는 고층건물에서의 시공성을 고려하여 15$\pm$2cm로 하였으며 혼화제로는 고성능감수제를 사용하였다. 실험결과로부터 고강도콘크리트의 응력-변형도 특성을 비롯하여 탄성계수, 포아송비, 단위중량 등 고강도 콘크리트의 일반적인 재료성질을 얻었으며 본 연구에서 제안한 고강도콘크리트의 배합설계식은 국내현장조건을 고려한 실용식으로 고강도콘크리트으 설계 및 시공을 위한 기초자료로 사용 가능하다고 판단된다.

• Korean Journal of Construction Engineering and Management
• /
• v.13 no.2
• /
• pp.48-57
• /
• 2012

A variety of studies on concrete have been performed to examine the advantages for structural material, but less attention has been paid to the contribution of concrete to finishing. Due to this matter, specific management guidelines for construction and quality on exposed concrete have not been clearly established despite more construction cost and quality control are required. This study analyzed a impact factors on the quality by survey of the existing research and practice. Field tests were performed using mock-up models to analyze the quality of exposed concrete according to form manufacture method, concrete mix proportion, and concrete placing method. Results indicate that the quality of exposed concrete was determined by concrete mix proportion and construction managements. Guidelines of quality control on exposed concrete in construction stages were proposed.

• Journal of the Korea Concrete Institute
• /
• v.24 no.5
• /
• pp.597-604
• /
• 2012

The present study assessed the $CO_2$ emissions of concrete according to the type and replacement ratio of supplementary cementitious materials (SCM) and concrete compressive strength using a comprehensive database including 2464 cement concrete specimens and 776 cement concrete mixes with different SCMs. The system studied in $CO_2$ assessment of concrete based on Korean lifecycle inventory was from cradle to pre-construction, which includes consistent materials, transportation and production phases. As the performance efficiency indicators, binder and $CO_2$ intensities were analyzed, and simple equations to evaluate the amount of $CO_2$ emission of concrete were then formulated as a function of concrete compressive strength and the replacement ratio of each SCM. Hence, the proposed equations are expected to be practical and useful as a guideline to determine the type and replacement ratio of SCM and unit content of binder in concrete mix design that can satisfy the target compressive strength and $CO_2$ reduction percentage relative to cement concrete.

• International Journal of Highway Engineering
• /
• v.11 no.3
• /
• pp.41-49
• /
• 2009

Cement concrete pavement has become more common in Korean highway systems. However, as its service period increases, there are some technical problems occurs and no clear solution is available primarily due to the lack of active researches. This research, hence, aims to develop a new mix proportion that may provide better strength and durability with extended service life. Based on a variety of literature reviews, the experimental variables were determined as unit cement content, S/a ratio and W/C ratio. From the experimental works, it is recommended to increase the unit cement content up to 375kg/$m^3$, 400kg/$m^3$ and 425kg/$m^3$. The target slump and air content were set 40mm and 5%, respectively. The maximum size of coarse aggregate was decided to be 25mm because of the easiness of supply in the field. The reduction of W/C ratio was necessarily required and decreased to 0.4 which was proven not to cause any mixing problem with the increased unit cement contents along with polycarbon-based high range water reducing agent. In addition, it was known that the S/a ratio could be reduced to 0.34. The lowered S/a might be possible because of the increased cement paste and hence increased cohesiveness and workability.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.3
• /
• pp.22-29
• /
• 2015

In this study, we tested to develop and apply structural insulation performance improvement concrete to field, which had compressive strength in 24 MPa and thermal conductivity twice as much as normal concrete. After experiment about slump and air contents, combination product of Plain and calcined diatomite powder showed reduction of slump and air contents and combination product with micro foam cell admixture, we cannot find result of slump and air contents reduction. Unit weight of combination product with insulation performance improvement materials decreased more than that of Plain. In the test of compressive strength, compressive strength of insulation performance improvement concrete decreased more than that of Plain but was content with 24 MPa. thermal conductivity of insulation performance improvement concrete tended to decrease. Freezing and thawing resistance of insulation performance improvement concrete was similar to that of Plain. In carbonation resistance test, combination product with calcined diatomite powder showed the result which was similar to that of Plain. In carbonation resistance test, combination product with micro foam cell admixture showed a increase compared to that of Plain and length variation of combination product generally increased.

• Proceedings of the Korean Institute of Industrial Safety Conference
• /
• 2002.05a
• /
• pp.257-261
• /
• 2002

산업폐기물인 철녹을 콘크리트에 배합하여 그 강도특성을 밝힌 후에 다시 장기적으로 계절적 변화에 따라 노출된 구조 요소인 재료의 전기적 특성을 밝히는 것은 새로운 재료연구에 중요한 일이라 하겠다. 여기서 전기적 특성은 철의 본 성질을 기대할 수 없는 것으로 폐기물로서도 사용할 수 없는 것이기 때문이다. 본 연구에서는 일반콘크리트와 비교해서 전기적으로 특성이 개선될 수 있음을 기대하고 이에 대한 실험으로 사실확인을 하고 적용하는 요소에 따라 전기적 특성을 증진하는 배합요소를 찾고자 한다.(중략)

• Journal of the Korea Institute of Building Construction
• /
• v.18 no.2
• /
• pp.133-140
• /
• 2018

The objective of this study is to propose a reliable mixing design procedure of concrete using artificial lightweight aggregate produced from expanded bottom ash and dredged soil. Based on test results obtained from 25 mixes, empirical equations to determine water-to-cement ratio, unit cement content, and replacement level of lightweight fine aggregates were formulated with regard to the targeted performance (compressive strength, dry density, initial slump, and air content) of lightweight aggregate concrete. From the proposed equations and absolute volume mixing concept, unit weight of each ingredient was calculated. The proposed mix design procedure limits the fine aggregate-to-total aggregate ratio by considering the replacement level of lightweight fine aggregates, different to previous approach for expanded fly ash and clay-based lightweight aggregate concrete. Thus, it is expected that the proposed procedure is effectively applied for determining the first trial mixing proportions for the designed requirements of concrete.

• Journal of the Korea Concrete Institute
• /
• v.21 no.6
• /
• pp.745-752
• /
• 2009

This paper presents the optimized mixing design of lightweight aerated concrete using hydrogen peroxide. Design of experiments in order to the optimized mixing design was applied and commercial program (MINITAB) was used. Statistical analysis was used to Box-Behnken (B-B) method in response surface analysis. The influencing factors of experimental are unit cement content, water ratio and hydrogen peroxide ratio. According to the analysis of variance, at the hardened state, water ratio and hydrogen peroxide ratio affects on dried density, compressive strength and bending strength of lightweight aerated concrete, but unit cement content affects on only dried density. In the results of response surface analysis, to obtain goal performance, the optimized mixing design for lightweight aerated concrete using hydrogen peroxide were unit cement content of 800 kg/$m^3$, water ratio of 44.33% and hydrogen peroxide ratio of 10%.