• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2014년도 추계 학술논문 발표대회
• /
• pp.21-22
• /
• 2014

The purpose of this study is to ascertain strengths and hardening rate of epoxy-modified mortar with wood-tar contents. The polymer-modified mortars (PMMs) using epoxy resin with wood-tar are prepared with various polymer-binder ratios of 1, 3, 5% and wood-tar contents of 0, 5, 10, 15 and 20%. The PMMs using epoxy resin are tested for compressive, flexural and tensile strengths and hardening rate of epoxy resin. As a result, the strengths and hardening rate under polymer-binder ratio 1% and wood-tar content of 5% are more excellent than those of other specimens.

• Advances in nano research
• /
• 제15권6호
• /
• pp.495-511
• /
• 2023

In this research, the impact of micro-silica, nano-silica, and polypropylene fibers on the fracture energy of self-compacting concrete was thoroughly examined. Enhancing the fracture energy is very important to increase the crack propagation resistance. The study focused on evaluating the self-compacting properties of the concrete through various tests, including J-ring, V-funnel, slump flow, and T50 tests. Additionally, the mechanical properties of the concrete, such as compressive and tensile strengths, modulus of elasticity, and fracture parameters were investigated on hardened specimens after 28 days. The results demonstrated that the incorporation of micro-silica and nano-silica not only decreased the rheological aspects of self-compacting concrete but also significantly enhanced its mechanical properties, particularly the compressive strength. On the other hand, the inclusion of polypropylene fibers had a positive impact on fracture parameters, tensile strength, and flexural strength of the specimens. Utilizing the response surface method, the relationship between micro-silica, nano-silica, and fibers was established. The optimal combination for achieving the highest compressive strength was found to be 5% micro-silica, 0.75% nano-silica, and 0.1% fibers. Furthermore, for obtaining the best mixture with superior tensile strength, flexural strength, modulus of elasticity, and fracture energy, the ideal proportion was determined as 5% micro-silica, 0.75% nano-silica, and 0.15% fibers. Compared to the control mixture, the aforementioned parameters showed significant improvements of 26.3%, 30.3%, 34.3%, and 34.3%, respectively. In order to accurately model the tensile cracking of concrete, the authors used softening curves derived from an inverse algorithm proposed by them. This method allowed for a precise and detailed analysis of the concrete under tensile stress. This study explores the effects of micro-silica, nano-silica, and polypropylene fibers on self-compacting concrete and shows their influences on the fracture energy and various mechanical properties of the concrete. The results offer valuable insights for optimizing the concrete mix to achieve desired strength and performance characteristics.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
• /
• pp.53-55
• /
• 2013

Nitrite-Type hydrocalumite (calumite) is a material that can provied a self-corrosion inhibition function to the reinforce concrete. In this study, bisphnol A·F type epoxy-midified mortars without hardner contaning calumite is prepared with various polimer-binder ratios, calumite contents and tow types of curing condition, and tested for flexural and compressive strength tensile strength and corrosion-inhibition. As a result, in the case of wet/dry curing condition, strengths of bisphnol A·F type epoxy-modified mortars without hardener contaning calumite is inclined to decrease with increasing of polymer-binder ratio and calumite content. However, dry cured specimens are slightly improved by using bisphnol A·F type epoxy resin. Finally, regardless of polymer-binder ratios and calumite contents, corrosion-inhibition of bisphnol A·F type epoxy-modified mortars without hardener containing calumite is superior than that of unmodified mortar.

• 한국분말재료학회지
• /
• 제27권1호
• /
• pp.37-43
• /
• 2020

The Fe-22wt.%Cr-6wt.%Al foams were fabricated via the powder alloying process in this study. The structural characteristics, microstructure, and mechanical properties of Fe-Cr-Al foams with different average pore sizes were investigated. Result of the structural analysis shows that the average pore sizes were measured as 474 ㎛ (450 foam) and 1220 ㎛ (1200 foam). Regardless of the pore size, Fe-Cr-Al foams had a Weaire-Phelan bubble structure, and α-ferrite was the major constituent phase. Tensile and compressive tests were conducted with an initial strain rate of 10^-3/s. Tensile yield strengths were 3.4 MPa (450 foam) and 1.4 MPa (1200 foam). Note that the total elongation of 1200 foam was higher than that of 450 foam. Furthermore, their compressive yield strengths were 2.5 MPa (450 foam) and 1.1 MPa (1200 foam), respectively. Different compressive deformation behaviors according to the pore sizes of the Fe-Cr-Al foams were characterized: strain hardening for the 450 foam and constant flow stress after a slight stress drop for the 1200 foam. The effect of structural characteristics on the mechanical properties was also discussed.

• 콘크리트학회논문집
• /
• 제14권5호
• /
• pp.638-644
• /
• 2002

본 연구에서는 압축강도 1400 kgf/$\textrm{cm}^2$ 를 갖는 불포화 폴리에스터 폴리머 콘크리트를 이용하여 제작한 C형 시험체에 대한 편심압축 시험을 통하여 폴리머 콘크리트 휨부재의 응력-변형률 관계를 구명하고 등가직사각형 응력블럭의 파라미터 $\alpha$, $\beta$1, ${\gamma}$를 산출하였다. 아울러 인장철근비를 달리하는 5종의 전단스팬비 4.0인 철근 보강 폴리머 콘크리트 보에 대한 휨시험에서 얻어진 극한모멘트 시험값과 C형 시험체 응력-변형률 곡선에서 산출되는 파라미터 $\alpha$=0.61, $\beta$1=0.73 를 이용하여 계산된 이론적인 극한모멘트 값을 비교하여 보았던 바, 인장철근비가 0.50 $\rho$b 이상일때 시험값과 이론값이 비교적 잘 부합됨을 확인 할 수 있었다. 그러나 폴리머 콘크리트 휨 부재에 대한 보다 정확한 설계기준의 마련을 위해서는 압축강도와 크기를 변수로 하는 C형 시험체에 대한 보다 많은 시험을 통한 파라미터의 체계적인 연구가 필요하다.

• Computers and Concrete
• /
• 제19권2호
• /
• pp.121-126
• /
• 2017

This paper presents the effect of aggregate type on high temperature resistance of self-compacting mortars (SCM) produced with normal and lightweight aggregates like expanded perlite and pumice. Silica fume (SF) and fly ash (FA) were used as mineral additives. Totally 13 different mixtures were designed according to the aggregate rates. Mini slump flow, mini V-funnel and viscometer tests were carried out on the fresh mortar. On the other hand, bulk density, porosity, water absorption and high temperature tests were made on the hardened SCM. After being heated to temperatures of 300, 600 and $900^{\circ}C$, respectively, the tensile strength in bending and compressive strength of mortars determined. As a result of the experiments, the increase in the use of lightweight aggregate increased total water absorption and porosity of mortars. It is observed that, the increment in the usage of lightweight aggregate decreased tensile strength in bending and compressive strengths of mortar specimens exposed to high temperatures but the usage of up to 10% expanded perlite in mortar increased the compressive strength of specimens exposed to $300^{\circ}C$.

• Advances in concrete construction
• /
• 제17권4호
• /
• pp.211-220
• /
• 2024

Concrete, consisting mainly of cement, water and aggregates; is the most used construction material all over the world. Cement manufacturing industry is one of the carbon dioxide producing sources that contributes to global warming. Therefore, in the last few years, there is a growing interest in using waste materials and by-products as cement replacement materials. Using these kinds of materials as a part of cement replacement reduces the air pollution, cost and also enhances some properties of concretes. In the present work, marble dust (MD) was examined as a partial cement replacement material with seven proportions as 0%, 10%, 20%, 30%, 40%, 50%, 60% and glass powder (GP) was used as an additive, 8% by cement weight, in a 0.55 water-binder ratio concrete. In order to evaluate their effects; workability, strength (compressive, flexural and split tensile), alkalinity, sulphate resistance and ultrasonic pulse velocity tests were performed. Experimental results indicated that with MD replacement and GP addition; there is a loss in the workability but improvement in mechanical properties. With 10% replacement of MD compressive, flexural and tensile strengths increased by 10.7%, 6.2% and 5.3% respectively. Moreover, up to 30% replacement of MD reasonable strength values were obtained.

• 한국조경학회지
• /
• 제46권6호
• /
• pp.120-126
• /
• 2018

본 연구는 콘크리트에 잔골재와 폴리프로필렌섬유를 혼입한 실험과 화강토와 폴리프로필렌섬유를 혼입한 실험을 하였다. 특히 두 종류의 실험은 폴리프로필렌섬유의 양을 변경하여 슬럼프, 압축강도, 인장강도 등의 역학적 특성에 대하여 실험적으로 규명하였다. 두 종류의 실험 결과를 비교하여 잔골재를 실험 재료로 사용한 경우와 화강토를 사용한 재료를 비교 분석하여 건조 수축 균열로 인한 부분적인 파괴를 예방하고, 가벼워서 사용하기 편한 품질 좋은 조경용 구조물 및 포장재 개발의 기초자료를 수립하는데 목적이 있다. 콘크리트에서 PP 섬유의 양이 증가할수록 PP 섬유의 체적 또한 현저히 증가하게 되므로 슬럼프가 감소해지는 것으로 판단된다. 압축강도의 결과, 화강토콘크리트는 콘크리트 강도의 59%~71% 정도로 측정되었다. PP 섬유의 혼입량이 증가할수록 압축강도는 상대적으로 줄어드는 경향이 나타났다. 인장강도의 결과 화강토 콘크리트는 콘크리트 인장강도의 68%~67% 정도로 나타났다. PP 섬유를 콘크리트나 화강토콘크리트에서 혼입량을 증가시킬수록 압축강도가 감소하는 것으로 나타났다. 그리고 콘크리트와 화강토콘크리트에 폴리프로필렌섬유를 혼입하면 인장강도가 증가하는 것으로 나타났다. 이러한 결과들을 분석해 화강토를 혼입한 콘크리트에 일정량의 PP섬유를 혼입하여 조경분야의 각종 구조물 또는 포장과 관련된 재료에 활용하면 구조물의 취성에 의한 파괴 및 균열로 인한 박리 박락의 방지 개선효과가 있을 것으로 판단된다.

• 한국도로학회논문집
• /
• 제12권1호
• /
• pp.47-54
• /
• 2010

본 연구에서는 콘크리트 포장의 균열, 스폴링 등의 파손문제를 해결하기 위해 국내 시공사례가 없는 이층 포설 공법의 도입 및 기술 경제적 타당성을 검토하고자 하였다. 본 포장공법중 하나인 강섬유 보강 콘크리트(SFRC, Steel Fiber Reinforced Concrete)의 포장 배합 적용성이 검토되었다. 강섬유 함량과 포장 높이가 산정되었으며, 강섬유 보강 콘크리트의 물성 평가를 위해 압축강도, 휨강도, 휨인성 지수, 인장강도, 피로강도를 측정하였다. 슬럼프와 공기량은 대부분이 시방 기준을 만족하였으며, 28일 강도도 교통개방을 할 수준 정도로 발현되었다. 휨강도 실험 결과, 강섬유 보강 콘크리트가 무보강 콘크리트에 비해 휨인성은 증가하였지만 휨강도는 증가하지 않았다. 에너지 흡수능력, 피로 저항성 및 동결 융해저항성은 강섬유 보강 콘크리트가 무보강 콘크리트에 비해 향상되었다. 향후, 시험시공을 통해 강섬유 보강 콘크리트의 현장 적용성 및 공용성을 평가할 것이다.

• 한국세라믹학회지
• /
• 제28권10호
• /
• pp.810-818
• /
• 1991

Fracture responses of Al2O3 tubes were investigated for various loading paths under combined tension/torsion. The fracture criterion did not depend on loading paths. Fracture angles agreed well with the maximum tensile stress criterion. As the loading condition approaches a shear dominant state, the tensile principal stress at fracture increases compared to the uniaxial fracture strength. By using the Weibull modulus obtained from tension and torsion tests, the Weibull statistical fracture strengths were compared with experimental data. This comparison suggests that fracture may occur at the surface of the specimen when tensile stress is dominant, but within the volume of the specimen when shear stress is dominant. The Weibull fracture strength increased as the loading conition approached a shear dominant state, but underestimated compared to experimental data. Finally, a new fracture criterion was proposed by including the effect of compressive principal stress. The proposed criterion agreed well with experimental data of Al2O3 tubes not only at combined tension/torsion but also at balanced biaxial tension.