• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.103-107
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• 1995

The intention of this study is to reduce the drying shrinkage of the cement mortar using the shrinkage reducing agent and the inorganic admixture. In this experiment the drying shrinkage strain, rate of weight loss and strength have been measured depending on age using the motar specimen. The result show that the usage of shrinkage reducing agent up to 1.5% will give an effect of approximately 30% without loss of strength, and the efficiency will increase together with the inorganic admixture. Also, as the amount of shrinkage reducing agent increases, the rate of weight loss increases. Drying shrinkage reduces at the same rate of weight loss.

• Cement
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• s.189
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• pp.41-48
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• 2011

고로시멘트는 포틀랜드시멘트와 고로슬래그의 혼합시멘트로, 최근에는 특히 저탄소 녹색성장 환경에 우수한 시멘트로서 관심이 모아지고 있다. 1824년 영국의 연와공 조셉 아스프딘(Joseph Aspdin)에 의해 발명된 포틀랜드시멘트는 약 184년의 역사를 가지고 있는 반면에, 일본의 슬래그시멘트 역사는 작년이 탄생부터 정확히 100년이 되기 때문에, 잠시 그 역사의 일부를 돌이켜 생각해 보고자 한다. 최근 슬래그시멘트는 건설시장에서 보통포틀랜드시멘트와 경쟁하기 위하여 발열억제를 위한 저발열고로시멘트를 개발하고, 강도경쟁에 의한 품질안정을 위하여 분리분쇄 추진, 고로슬래그에 적합한 클링커를 개발하고, 자기 수축 저감 등을 위한 연구도 병행하고 있다. 날로 심화되는 건설환경에서 살아 남기 위한 여러 방법들이 강구되고 있는 것이다. 고로시멘트는 보통포틀랜드시멘트와 비교해서 중성화, 강도발현을 위한 충분한 습윤양생 등 몇 가지 약점도 있지만, 슬래그시멘트 본연의 고유의 특성을 잘 나타내는 내해수성, 내염성, ASR 등의 장점들도 않고 "환경에 뛰어난" 시멘트로 각인된 만큼, 갖고 있는 특징들을 충분히 잘 활용하고, 개선 보완 시켜나가면 21세기의 최상의 재료로 평가 받을 수 있다고 기대해 본다. 끝으로, 본 자료는 신일철고로시멘트(주)단(檀)이 기고한 (콘크리트공학 2010년 10월호) 논문을 요약 발췌한 것이다.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.291-292
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• 2010

In this study, high-strength concrete mixtures were made with blast-furnace slag of 50% and 70% replacement level to evaluate material properties including compressive strength development, adiabatic temperature rise, autogenous shrinkage and chloride-ion migration coefficient. Test results showed that the use of high percentage blast-furnace slag in high-strength concrete can reduce heat of hydration and chloride-ion migration coefficient, result in control thermal cracking and improve durability performance especially under high corrosive environment.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.120-121
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• 2017

Generally, slump of plain concrete slab is about 120~150mm and slump loss is easy to occur. So, water is added to concrete because this method is convenient for Placing. In order to solve this problem, performance evaluation of concrete using improvement type PC admixture was carried out. Target slump is 210mm and compressive strength is 18MPa. As a result, slump reference value was satisfied 60 minutes after placing and 7-day compressive strength was 21~25MPa.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.501-504
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• 2005

This paper discusses the development of drying shrinkage reducing type superplasticizer(DSRS) by varying dosage of polycarboxylic based superplasticizer, liquid type expansive admixture and antifoaming agent. Adequate mixture proportion of each admixture is fixed at 0.3$\%$ of superplasticizer, 0.15$\%$ of liquidtype expansive admixture and 0.0005$\%$ of antifoaming agent to insure the improvement in drying shrinkage as well as comparable to the slump and air content of conventional concrete. With this mixture proportion, compressive strength of concrete using DSRS is comparable to that of conventional concrete. The use of DSRS studied by the authors has a favorable effect on reducing drying shrinkage due to the effect of water content and expansion by expansive admixture.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.393-396
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• 2005

This paper presents the results of drying shrinkage of concrete using shrinkage-reducingadmixture(DSRA) studied by the authors through mock-up test. DSRA is proportioned by expansive admixture and shrinkage reducing agent(SRA). Flowing concrete method is also applied to assist the concrete to reduce drying shrinkage by decreasing water content at the same time. The use of EA and SRA does not affect fluidity, bleeding and setting time. Compressive strength of concrete using EA along with SRA exhibited less than that of plain concrete. However, The compressive strength with combination of EA-SRA along with flowing concrete method shows comparable to that of plain concrete. The application of developed method can contribute to reducing drying shrinkage by as much as 30-40$\%$ compared with that of plain concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.661-664
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• 2006

Recently, various concrete reinforcing fibers have been used to reduce the plastic shrinkage cracking which occurs before the concrete hardens. In this study, the physical properties of nylon fiber reinforced concrete such as slump, air content, compressive strength and tensile strength were investigated. In addition, the performance of nylon fiber in the plastic shrinkage cracking reduction of concrete has been estimated in comparison with polypropylene, poly vinyl alcohol fiber and cellulose fiber. Nylon fiber showed considerable advantages in terms of the workability of concrete and the plastic shrinkage cracking reduction of concrete compared with polypropylene fiber and cellulose fiber.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.161-162
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• 2020

Cracks are caused by drying shrinkage between the upper part of the underground parking lot and the apartment wall. As a result of the investigation, the distance between the apartment and the apartment is more than 45m, and the top slab of the underground parking lot is usually flat when there is not with steps. Therefore, the crack occurs more when the underground parking lot is a PC slab than a RC slab. In this study, the reduction of cracks was conducted by extending the slab, expanding the beam size, increasing the wall thickness, and installing a delay joint on slab. In each case, a finite element analysis was performed to examine the crack reduction method.

• Applied Chemistry for Engineering
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• v.27 no.4
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• pp.380-385
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• 2016

Nanocelluloses, mainly cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC, i.e., defect-free, rod-like crystalline residues after acid hydrolysis of fibers), have been the subject of recent interest. Due to the presence of hydroxyl groups on the surface of nanocelluloses, their surfaces are reactive, making them suitable candidates for reinforcing materials for manufacturing polymer composites. In this study, CNF was used as a reinforcing material for manufacturing cement composites. CNF was prepared by TEMPO (2,2,6,6,-tetramethyl piperidine-1-oxyl radical) oxidation procedure combined with extensive homogenization and ultrasonication. Transmission electron microscopy (TEM) analysis of the suspension showed the width of CNF between 10 and 15 nm. The compressive strength of cement composites containing 0.5% CNF was comparable to that of conventional cement composites. On the other hand, the tensile and flexural strength were improved by 49.7% and 38.8%, respectively, compared to those of conventional cement composites. Also, at an ambient condition, the degree of self-shrinkage reduction reached to 18.9% in one day, followed by 5.9% in 28 days after molding.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.789-795
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• 1999

In this study, carbon fiber reinforced cement composites(CFRCs) reinforced with short noncircular type carbon fibers were fabricated and properties(drying shrinkage, resistance to freezing and thawing, and fracture toughness) were compared with those of the CFRCs reinforced with circular type carbon fibers. It was found that these properties greatly depended on the shape and length of carbon fibers. The drying shrinkage of CFRCs reinforced with C-type carbon fiber was superior to other CFRCs. This effect was increased with a high aspect ratio of fiber. The resistance to freezing and thawing was increased with the fiber length and fiber volume percent, but there was on remarkable effect to fiber shape. Fracture toughness and resistance to crack propagation of CFRCs reinforced with C-CFs were improved compared with other CFRCs. It was believed that the more absorption of fracture energy into the larger interface caused an increase in fracture toughness and resistance to crack propagation.