• 한국구조물진단유지관리공학회 논문집
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• 제28권4호
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• pp.48-54
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• 2024

원전 구조물은 냉각수를 사용하기 위해 해안가에 위치하고 있으며, 염해에 의한 철근부식에 노출되어 있다. UAE에 지어지는 원전 구조물의 경우, 해안가의 온도가 높으므로 염화물 이동이 다른 지역에 비하여 빠르게 평가된다. 본 연구에서는 원전 구조물에 사용되어지는 재료와 배합을 이용하여 5,000 psi (35 MPa)설계강도 등급의 시편을 제작하였으며, 온도와 재령을 고려하여 염화물 확산계수를 평가하였다. 재령 28일 및 91일에 강도 평가 및 온도에 따른 확산계수를 평가하여 특성을 분석하였다. 또한 91일 재령 콘크리트에 대하여 20℃~50℃의 범위에서 염화물 확산실험을 수행하였다. 또한 온도에 따른 기울기를 로그함수로 변환하여 활성화에너지를 도출하였으며, 기존의 제안값들과 비교하였다. 제안된 활성화에너지는 온도의존형 염화물 확산계수에 사용하여 합리적인 내구성 설계를 수행할 것으로 평가된다.

• Advances in concrete construction
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• 제9권1호
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• pp.33-41
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• 2020

In this study, polyethylene glycol (PEG) and polyacrylamide (PAM) have been used as self-curing agents to produce self-curing concrete (SC). Compressive strength, ultrasonic pulse velocity (UPV), bulk electrical resistivity, chloride ion penetrability, water permeability, and main microstructural characteristics were examined under different curing regimes, and compared to those of the control concrete mixture with no self-curing agents. One batch of a control mixture and one batch of a SC mixture were air-cured in the lab to act as non-water-cured samples. The water curing regimes for the control mixture included continuous water curing for 3, 7, and 28 days and periodical moist curing using wetted burlap for 3 and 7 days. Curing regimes for the SC mixtures included 3 days of water curing and periodical moist curing for 3 and 7 days. SC mixtures showed better microstructure development and durability performance than those of the air-cured control mixture. A short water curing period of 3 days significantly improved the performance of the SC mixtures similar to that of the control mixture that was water cured for 28 days. SC concrete represents a step towards sustainable construction due to its lower water demand needed for curing and hence can preserve the limited water resources in many parts of the world.

• 한국건설순환자원학회논문집
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• 제11권1호
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• pp.62-69
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• 2023

UAE 지역에 시공되는 원전구조물의 노출환경에서 대기 중의 높은 황산염 이온 및 해안의 높은 염화물 이온에 의한 열화를 고려할 필요가 있다. 본 연구에서는 연평균 38 ℃ 이상의 높은 온도에 따른 확산성과 강도의 영향을 평가하기 위해 두가지 강도 등급(40 MPa 및 27 MPa) 및 두 가지 양생/확산 온도 조건(20 ℃ 및 50 ℃)을 고려하였다. 초기 양생 온도가 높은 경우, 7일 전 초기재령에서는 압축강도가 고온 양생에서 크게 발현하였으나, 28일 재령에서는 20 ℃ 양생 온도 조건에서 압축강도가 약간 증가하였다. 염화물 확산의 경우, 강도 평가결과와 다르게 28일 재령에서 초기 양생 온도가 높은 경우, 40 MPa 및 27 MPa 에서 모두 확산계수가 감소하였다. 91일 재령의 경우, 온도의 증가에 따른 확산성의 증가와 재령 효과에 의한 확산성의 감소가 동시에 발생하였다. 재령 28일에 20 ℃로 양생 및 확산 실험을 한 결과에 비하여, 재령 91일에 50 ℃로 양생 및 확산 실험을 한 경우, 재령의 증가에 따라 40 MPa에서는 76.2 % 수준으로, 27 MPa 에서는 85.4 % 수준으로 확산계수가 감소하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.9-14
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• 2005

The Burj Dubai Project will be the tallest structure ever built by man; when completed the tower will be more than 700 meter tall and more than 160 floors. The early integration of aerodynamic shaping and wind engineering considerations played a major role in the architectural massing and design of this residential tower, where mitigating and taming the dynamic wind effects was one of the most important design criteria. This paper presents a brief overview of the structural system development and considerations of the tower and discusses the construction planning of the key structural components of the tower.

• Computers and Concrete
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• 제13권5호
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• pp.649-657
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• 2014

In this paper, effects of magnetic water on different properties of cement paste including fluidity, compressive strength, time of setting and etc, has been studied in concrete laboratory of Sahand University of Technology. For production of magnetic water, three devices including an AFM called device(made in UAE), a device marked AC(made in Germany) and finally a device was designed and made in Concrete Laboratory of Sahand University of Technology) have been used. The results show that, intensity and direction of magnetic field, velocity and time of water passing through magnetic device, and amount and type of Colloidal particles have direct effects on properties of magnetic water and using such a water in making cement paste, increases its fluidity and compressive strength up to 10%.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.445-448
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• 2006

Mix design of C80A which is applied to the vertical members of The Burj Dubai Tower, the tallest building of the world, was performed so as to meet the requirements of rheological property, mechanical properties & construction sequences based on material analysis in Dubai, UAE. Experimental investigations were carried out to evaluate & optimize the quantities of total binders, the proportions of Micro Silica, Dune Sand & PFA, changes of S/a and the comparison of chemical admixture, etc. Approximately $65,000m^3$ of C80A concrete has been poured to the vertical members since 16-Apr-2006. In the actual application, it was showed that C80A has proper early strength achievement, excellent mechanical properties and satisfactory flowability & workability. The results of extensive site testing can be summarized that the average compressive strength at 28days is 98.8MPa, the average elastic modulus at 28days is 47.8GPa, the flow of concrete after pumping at the height of 250m (L72) was over 500mm.

• 국제초고층학회논문집
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• 제11권1호
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• pp.61-68
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• 2022

The Address Jumeirah Resort is a mixed-use 77-story tower reaching a height of 301 meters with a slenderness ratio of 13.5:1. The development is situated in the Jumeirah Beach District and accommodates 217 key five-star hotel suites, 478 residential apartments, 444 serviced-branded apartments, retail shops, ballrooms and entertainment facilities around the premises. The building has over 242,000 m2 of usable area. The project is an award-winning development that broke multiple Guinness records. The focus of the paper is to present the challenges faced in the structural design and construction of the super tall tower and the highest occupiable skybridge in the world.

• Advances in concrete construction
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• 제8권1호
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• pp.65-76
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• 2019

This paper investigates the effect of recycled glass powder (RGP) on flowing properties of self-compacting mortars (SCMs) containing different ratios of fillers and superplasticizer dosages. Fly ash (FA), nano-silica (NS), micro-silica (MS), metakaolin (MK) and rice husk ash (RHA) are used as fillers and their synergistic effect with RFP is studied. The effects of fillers and high-range water reducer (HRWR) on flowing ability of mortars are primarily determined by slump flow and V-funnel flow time tests. The results showed that for composites with a higher RGP content, the mortar flowing ability increased but tended to decrease when the composites containing 10% MK or 5% RHA. However, the flowing ability of samples incorporating 5% RGP and 10% SF or 25% FA showed an opposite result that their slump flow spread decreased and then increased with increasing RGP content. For specimens with 3% NS, the influence of RGP content on flowing properties was not significant. Except RHA and MS, the fillers studied in this paper could reduce the dosage of HRWR required for achieving the same followability. Also, the mixture parameters were determined and indicated that the flowability of mixtures was also affected by the content of sand and specific surface area of cement materials. It is believed that excess fine particles provided ball-bearing effect, which could facilitate the movement of coarse particles and alleviate the interlocking action among particles. Also, it can be concluded that using fillers in conjunction with RGP as cementitious materials can reduce the material costs of SCM significantly.