• Advances in concrete construction
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• 제7권1호
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• pp.31-37
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• 2019

This paper evaluates the workability and hardened properties of self-compacting concrete (SCC) containing silica fume as the partial replacement of cement. SCC mixtures with 0, 2, 4, 6, 8 and 10% silica fume were tested for fresh and hardened properties. Slump flow with $T_{500}$ time, L-box and V-funnel tests were performed for evaluating the workability properties of SCC mixtures. Compressive strength, splitting tensile strength and modulus of rupture were performed on hardened SCC mixtures. Experiments revealed that replacement of cement by silica fume equal to and more than 4% reduced the slump flow diameter and increased the $T_{500}$ and V-funnel time linearly. Compressive strength, splitting tensile strength and modulus of rupture increased with increasing the replacement level of cement by silica fume and were found to be maximum for SCC mixture with 10% silica fume. Further, residual hardened properties of SCC mixture yielding maximum strengths (i.e., SCC with 10% silica fume) were determined experimentally after heating the concrete samples up to 200, 400, 600 and $800^{\circ}C$. Reductions in hardened properties up to $200^{\circ}C$ were found to be very close to normal vibrated concrete (NVC). For 400 and $600^{\circ}C$ reductions in hardened properties of SCC were found to be more than NVC of the same strength. Explosive spalling occurred in concrete specimens before reaching $800^{\circ}C$.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.198-201
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• 1996

The purpose of this study is to analyze the properties of high fluidity concrete using the viscosity agent of a cellulose system with W/C of 35~50% in hardened state. It is proven that properties of high fluidity concrete in hardened state is nearly the same with normal concrete in the same W/C and no strength difference by tamping method do not appeared. Therefore, no tamping method is thought to be reguired in high fluidity concrete.

• Advances in concrete construction
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• 제10권5호
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• pp.369-379
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• 2020

Reduction of disposal of waste materials due to construction demolition has become a great concern in recent decades. The research work presents the hardened properties of concrete where the partial substitution of recycled coarse aggregate with natural aggregate in amount of 0%, 10%, 30% and 50%. By using different mixed proportions, fresh and hardened properties of concrete were conducted for this investigation. These properties were compared with control concrete. It can be seen that all of the hardened properties of concrete were decreased with the increasing percentage of recycled aggregate in concrete mixes. It was noticed that up to 30% recycled aggregate replacement can be yielded the optimum strength when it used in normal concrete. Finally, it can be said that disposed recycled concrete utilizing as a partial replacement in natural aggregate is a great way to reuse and reduce environmental hazards which achieve sustainability approach in the construction industry.

• 한국구조물진단유지관리공학회 논문집
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• 제16권4호
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• pp.44-51
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• 2012

본 연구에서는 황토에 시멘트나 유기계 접착제를 첨가하지 않은 천연재료 황토결합재를 사용하여 황토경화체를 제작하고, 배합조건에 따른 강도성상을 평가하였다. 황토와 석회의 결합재에 천연재료를 첨가할 경우 사용한 천연재료는 모두 물리적 성능을 개선하는 효과가 있었다. 천연재료 중에서 석회는 황토경화체의 물성을 증가시키는데 가장 큰 영향을 미치고 있다. 황토경화체의 물리적 특성은 적용한 배합비 중에서 W/B 45%, 단위수량 $285kg/m^3$, 석회첨가율 60%일 때 가장 우수하게 나타나고 있다.

• Structural Monitoring and Maintenance
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• 제11권1호
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• pp.1-18
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• 2024

Self-compacting concrete is widely used around the globe today due to its special and unique properties. This study examines the effect of natural and crushed gravel combinations in different percentages in short-and long-term properties of concrete. The best utilized sand had a fineness modulus of 2.7. In the mentioned mix designs, silica fume was used with 0 and 7% of the weight of the cement. In order to check the properties of fresh and hardened concrete, 9 and 5 test types were performed, respectively. The carried out tests were slump flow, V-funnel, J-ring, L-box, U-box and column segregation for fresh concrete, and compressive, tensile and flexural strengths for hardened concrete. A mix with only 100% natural gravel was considered as the control mix. According to the results, the control mix design and the one containing 100% crushed gravel with silica fume were the best in fresh and hardened concrete tests, respectively. Finally, using the optimization method, a mix design with 25% natural gravel, 75% crushed gravel and silica fume was introduced as the best mix in terms of the results of both fresh and hardened concrete tests.

• 한국건축시공학회지
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• 제15권5호
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• pp.451-456
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• 2015

본 연구는 시멘트계 바탕 바름재에 사용되는 바닷모래를 대체하기 위한 재료로서 현무암 가공과정에서 발생되는 현무암 석분슬러지를 재활용하기 위해 현무암 석분슬러지를 사용한 경화모르타르의 특성(연도변화, 응결경화, 흡수계수, 건조수축, 그리고 부착강도 실험)을 평가하였다. 현무암 석분슬러지를 사용한 경화모르타르는 콘크리트 바탕 바름재에 사용되는 기존의 보통모르타르의 특성과 유사하거나 좀 더 향상된 성능을 보였다. 그러나, 현무암 석분슬러지를 사용한 경화모르타르는 보통 모르타르보다 재령 8~9일 이후 건조수축이 증가되었고 부착강도는 감소되었다. 그러나 현무암 석분슬러지를 사용한 경우, KS F 4716 '시멘트계 바탕 바름재'에서 요구하는 최소 품질 규준은 만족하였다.

• International Journal of Concrete Structures and Materials
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• 제10권3호
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• pp.337-353
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• 2016

The successful completion of the present research would be achieved using ground waste glass (GWG) microparticles in self-consolidating concrete (SCC). Here, the influences of GWG microparticles as cementing material on mechanical and durability response properties of SCC are investigated. The aim of this study is to investigate the hardened mechanical properties, percentage of water absorption, free drying shrinkage, unit weight and Alkali Silica Reaction (ASR) of binary blended concrete with partial replacement of cement by 5, 10, 15, 20, 25 and 30 wt% of GWG microparticles. Besides, slump flow, V-funnel, L-box, J-ring, GTM screen stability, visual stability index (VSI), setting time and air content tests were also performed as workability of fresh concrete indicators. The results show that the workability of fresh concrete was increased by increasing the content of GWG microparticles. The results showed that using GWG microparticles up to maximum replacement of 15 % produces concrete with improved hardened strengths. From the results, when the amount of GWG increased there was a gradual decrease in ASR expansion. Results showed that it is possible to successfully produce SCC with GWG as cementing material in terms of workability, durability and hardened properties.

• 한국주조공학회지
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• 제28권6호
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• pp.273-281
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• 2008

Effects of alloying elements on the mechanical properties of hardened and austempered 3.60wt%C - 2.50wt%C ductile cast iron were investigated. Strength and hardness were increased and ductility was decreased as the amount of alloying element increased. The increasing effect of copper addition on the strength was the most pronounced. The strength and hardness were greatly increased and ductility was decreased by hardening. The effect of alloying element on the mechanical properties of the hardened ductile cast iron was not so pronounced due to the high contents of C and Si. The strength and hardness of austempered ductile cast iron were greatly increased, meanwhile the difference of strength from that of hardened one was not so big. The ductility of the former was higher than that of the latter. The strength and ductility of austempered ductile cast iron with 0.25%Mn were the maximum of all Mn added ones. The maximum strength of that was obtained with the addition of 0.80wt%Cu or 2.00wt%Ni along with this amount of Mn added.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1989년도 가을 학술발표회 논문집
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• pp.21-24
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• 1989

The effect of superplasticizing agents on the mechanical properties in hardened concrete have been analyzed and investigated under various mix proportions of water cement ratio of 0.40, 0.50, 0.60 and 0.70, Superplasticizing agents of NL-4000, and Rheobuild-716, and addition rate of sp. agents of 0.0, 0.5, 1.0, 1.5 and 2.0 in the practical range. It is the aim of this study to provide the fundamental data on the compressive strength, dynamic and static modulus of elasticity, stress and strain curve of hardened concrete comparing with base concrete and conventional concrete for the practical use and research data accumulation of superplasticized concrete in the side of development of concrete construction technology and management.

• Advances in Computational Design
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• 제7권1호
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• pp.57-68
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• 2022

A simulation study of the distribution of magnetic flux induced by a U-shaped electromagnet into a two-layer massive object with variations in the depth and properties of the surface layer has been carried out. It has been established that the hardened surface layer "pushes" the magnetic flux into the bulk of the magnetized object and the magnetic flux penetration depth monotonically increases with increasing thickness of the hardened layer. A change in the thickness and magnetic properties of the surface layer leads to a redistribution of magnetic fluxes passing between the poles of the electromagnet along with the layer and the bulk of the steel object. In this case, the change in the layer thickness significantly affects the magnitude of the tangential component of the field on the surface of the object in the interpolar space, and the change in the properties of the layer affects the magnitude of the magnetic flux in the magnetic "transducer-object" circuit. This difference in magnetic parameters can be used for selective testing of the surface hardening quality. It has been shown that the hardened layer pushes the magnetic flux into the depth of the magnetized object. The nominal depth of penetration of the flow monotonically increases with an increase in the thickness of the hardened layer.