• International Journal of Concrete Structures and Materials
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• 제2권1호
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• pp.9-14
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• 2008

The cracking problem in concrete is widespread and complex. This paper reviews the problem and focuses on those parts of the problem that are more readily solved. Polymer fibers are shown to have promise in several important areas of the cracking problem. To investigate one of these areas of the cracking problem more completely, an experimental research program focusing on the early-age properties of fibers was carried out. This study researched the properties of four polymer fibers; two of the fibers were macrofibers, and two were microfibers. Each fiber was tested at several dosage rates to identify optimum dosage levels. Early-age shrinkage, long-term shrinkage, compressive strength, and tensile strength were investigated. Long-term shrinkage and strength impacts from the polymer fibers were minimal; however, the polymer fibers were shown to have a great impact on early-age shrinkage and a moderate impact on early-age strength.

• 펄프종이기술
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• 제47권4호
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• pp.136-143
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• 2015

It is well known that the use of PCC as a filler for printing paper making brought about the serious deterioration of strength properties of paper, although PCC could be helpful to reduce the energy consumption. The use of modified PCC with NCC was tried to solve and/or reduce the strength deterioration problem. NCC was prepared from SwBKP by the acid hydrolysis. There was no significant changes in chemical properties and crystalline structure. However the cyrstallinity of NCC was higher than those of SwBKP. The different dosage of NCC was applied to modify the properties of PCC. 0.1% of NCC dosage was enough to improve ash retention and paper properties. The use of modified PCC with NCC as a filler improved ash retention, bulk, opacity and formation without the serious deterioration of strength properties. Thus the use of modified PCC with NCC might be helpful for not only reduction of energy consumption but also increase of filler dosage without the significant sacrifice of strength properties by the optimization of retention system.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.94-99
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• 1992

In this study , some factors such as mix proportion, type and dosage of high range water reducing admixture(HRWR) and natural pozzolanas influencing on the slump loss of high strength concrete(H.S.C) using HRWR were investigated for reducing the slump loss. The acquired results indicated that the slump loss of H.S.C was affected according to cement content, sand percentage and type and dosage of HRWR and fly ash was superior to ground granulated blast furance slag in reducing the slump loss of H.S.C.

• 한국도로학회논문집
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• 제15권4호
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• pp.117-125
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• 2013

PURPOSES : The purpose of this study is to evaluate of field application and laboratory performance of warm-mix asphalt (WMA) according to the dosage rate of organic-based WMA additive. METHODS: Three asphalt mixtures, i.e., hot mix asphalt (HMA), WMA with the dosage rate of 1.5%, WMA with the dosage rate of 1.0%, were sampled from the asphalt plant when the field trial project were constructed. With these mixtures, the laboratory testings were performed to evaluate the linear viscoelastic characteristics and the resistance to moisture, rutting and fatigue damage. RESULTS : From the laboratory test results, it was found that the WMA with the reduced dosage rate of additive would be comparable to HMA and WMA with the original dosage rate in terms of the dynamic modulus, tensile strength ratio, rutting resistance. However, the fatigue reisistance of WMA with the reduced dosage rate was slightly worse but it should be noted that the fatigue performance is necessarily predicted by combining the material properties and pavement structure. CONCLUSIONS: Through the field construction and laboratory testings, the dosage rate of organic-based WMA additive could be reduced from 1.5% to 1.0% without the significant decrease of compactability and laboratory performance. The long-term performance of the constructed pavement will be periodically monitored to support the findings from this study.

• 한국화재소방학회논문지
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• 제23권4호
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• pp.7-12
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• 2009

고강도 콘크리트(HSC)는 화재 시 $100^{\circ}C$ 이상에서 부재내부의 수분 증발로 인하여 발생한 수증기가 수밀한 콘크리트에 갇혀 피복이 탈락되는 폭렬현상이 발생한다. 콘크리트의 폭렬을 제어할 수 있는 방안으로는 폴리프로필렌 섬유(PP섬유)를 혼입하는 방법이 가장 효율적인 것으로 보고되었다. 그러나 일정량 이상 PP섬유의 사용은 폭렬저감에 효과가 없으며 특히, 초고강도 콘크리트의 시공성을 저하시킬 것으로 판단된다. 따라서 본 연구에서는 콘크리트 강도 60MPa에서 최적의 PP섬유량을 도출하고 120MPa 초고강도 콘크리트에서 시공성을 확보하기 위하여 PP섬유를 대신하여 PP분말 및 폴리비닐알콜(PVA)섬유를 사용한 기둥실험체의 내화실험 및 잔존강도 실험을 수행하였다. 실험결과 60MPa 실험체에서 PP섬유 함유량이 0%에서 0.2%까지 증가 할수록 잔존 축강도비는 68%에서 85%까지 증가하였으나, PP섬유 함유량이 0.2% 이상에서는 잔존강도의 증가가 거의 나타나지 않았다. 또한, 120Mpa 실험체에서 내화성능과 시공성을 함께 고려할 경우 PVA섬유가 가장 합리적인 것으로 나타났다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.161-162
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• 2023

Limestone slag cement is a green and sustainable building material with huge market potential. However, its shortcoming of low early compressive strength needs to be improved. A method of using aluminum sulfate to improve the early strength of ternary mixed mortar was proposed, and its effect and optimal dosage were tested. Macroscopic properties such as mechanical properties and surface electrical resistivity were measured at different dosages (0%, 1%, 2%, 3%). The microstructure and products of the mixtures were tested in detail, including by scanning electron microscopy, thermogravimetric analysis, and X-ray diffraction. The results show aluminum sulfate enhances mechanical properties and significantly increases surface electrical resistivity. The 1% and 2% doses had no adverse effects on the 28-day mechanical properties, while the 3% dose reduced the 28-day strength. Considering the changes in mechanical properties and surface electrical resistivity, 1% aluminum sulfate is the optimal dosage.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 봄 학술발표회 논문집
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• pp.19-22
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• 1992

Properties of concrete has effected on the dosage variation of AE superplasticizer agent, Therefore, this study is designed for analysis of concrete properies according to the dosage variation of AE superplasticizer agent , and is aimed to analyze the effect slump, air content, compressive strength, resistance of freezing-and-thawing and for presenting the reference data on the practical use.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.669-674
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• 2002

This paper describes the properties analysis of concrete using bleeding reduction agent. According to the results, the fluidity and the air content of fresh concrete with increase of bleeding reduction agent show little difference in compare with plain concrete which does not use bleeding reduction agent. The efficiency of bleeding reduction agent is confirmed because in variation of W/C and slump, the increase of bleeding reduction agent dosage reduces bleeding remarkably. And the compressive strength of hardened concrete does not show any differences with increase the dosage of bleeding reduction agent. Bleeding reduction agent does not have bad effect on the quality of concrete such as fluidity, air content and the strength of hardened concrete and so on, the dosage of it can reduce bleeding effectively.

• 콘크리트학회논문집
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• 제28권1호
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• pp.67-74
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• 2016

이 연구에서는 다중벽 탄소나노튜브(Multi-walled CNT) 혼입량을 Binder 중량 대비 0.1, 0.3, 0.5%로 다르게 하여 CNT 혼입량에 따른 CNT 보강 시멘트 복합체의 굳지 않은 상태에서의 유동특성, 강도 및 강도발현 특성 등을 살펴보았다. 유동특성에 대한 실험결과, CNT 혼입량이 증가함에 따라 굳기 전 상태의 작업성이 저하되는 것으로 나타났으며, 레올로지 실험에서는 CNT 혼입량 증가에 따라 소성점도의 감소와 항복응력의 증가를 확인할 수 있었다. 또한 레올로지 실험에서 얻은 흐름곡선에서는 낮은 전단속도에서의 틱소트로피 현상이 높은 CNT 혼입량에서 더욱 뚜렷하게 나타나는 것을 볼 수 있었다. CNT 혼입량 증가에 따른 강도특성 실험결과에서는 압축강도 및 인장강도 모두 CNT 혼입량이 증가함에 따라 향상되는 것으로 나타났으며, 압축강도에 대한 CNT 보강에 따른 강도향상 효과가 인장강도에 비해 더 크게 나타났다. 한편 재령별 강도 측정 결과에 따르면 CNT 혼입이 초기강도 발현에도 효과적인 것을 확인할 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.281-286
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• 2001

The utilization of metakaolin as a pozzolanic material for mortar and concrete has received considerable attention in recent years. This paper estimates the fundamental properties of metakaolin as a pozzolanic material in view of fluidity and compressive strength of cement paste and mortar in comparison of silica fume, fly ash and slag. The results show that in order to obtain the same initial fluidity, metakaolin needs higher dosage of PNS superplasticizer than fly ash and slag, however, less dosage than silica fume. In view of compressive strength of mortar, metakaolin exhibits much higher compressive strength than fly ash and slag, and similar compressive strength with silica-fume when 10 % of cement is replaced with a pozzolanic material.