Amorphous Steel Fibers Research Articles

고온에 노출된 비정질 강섬유 보강 고강도 콘크리트의 역학적 특성

고온에 노출된 비정질 강섬유 보강 고강도 콘크리트의 역학적 특성

Y-Ray Shielding Performance and Mechanical Properties of Mortar Strengthened by Amorphous Alloy Fibers

The γ-ray shielding performance of the mortar reinforced by zirconium-based amorphous alloy fibers was studied. Meanwhile, the mechanical properties of mortar blocks with two kinds of reinforcement addition phases, i.e. amorphous alloy fibers and steel fibers were tested. The results show that the linear attenuation coefficient to γ-ray increases and the thickness of half-value layer (HVL) decreases with the increasing of volume fraction of reinforcing fibers. The shielding results were simulated by Xcom software, and proven consistent with the experimental results. The compressive strength of mortar block reinforce with fibers of 0.4% volume fraction is 5% higher than that of pure mortar, the flexural strength of mortar block reinforced with fibers of 1.2% volume fraction is 57% higher than that of pure mortar, and 33.4% higher than that of mortar block added with steel fibers.

Effect of embedment length on pullout behavior of amorphous steel fiber in Portland cement composites

For using amorphous steel fibers (ASF) in Portland cement composites, the performance of ASF was evaluated by a pullout test and compared to that of a hooked-end steel fiber (HSF). The embedment length of the fiber (5.0, 8.0, and 12.5mm), compressive strength of the mortar, and number of fibers were considered the test variables. The results showed that a single ASF had a greater maximum applied load (Pmax) than a single HSF; however, at a mortar compressive strength of 30–42MPa, its bond strength (τmax) and pullout energy (Ef) decreased by 40.9–55.8% and 16.9–79.7%, respectively, compared to those of a single HSF. Furthermore, in the pullout failure mode, the Ef of 4 ASFs, which have a volume fraction equivalent to a single HSF, was 2.10–3.04 times higher than that of a single HSF. Based on the Ef of ASFs, an embedment length of 5–8mm is recommended to provide the most effective ASF reinforcement effect to a mortar with a compressive strength of up to 40MPa.

비정질 붕소강 섬유를 혼입한 콘크리트의 역학적 성능 및 중성자 차폐성능 평가

본 연구에서 비정질 붕소강 섬유를 혼입한 콘크리트의 역학적 성능 및 중성자 차폐성능을 평가하였다. 비정질 붕소강 섬유를 콘크리트 체적 대비 0.25%에서 1.0%까지 혼입하여 굳지 않은 콘크리트의 공기량과 슬럼프값, 경화된 콘크리트의 압축강도, 휨강도, 휨인성 및 중성자 차폐성능을 평가하였다. 실험결과, 비정질 붕소강 섬유의 혼입량이 증가할수록 콘크리트의 휨인성 및 중성자 차폐성능이 향상되는 것으로 나타났다. 이를 통해 비정질 붕소강 섬유의 혼입이 중성자 차폐성능 뿐만 아니라 역학적 성능을 효과적으로 개선시켜 줄 것이라고 기대된다. Mechanical properties and neutron shielding performance of concrete with amorphous boron steel fiber have been investigated in this study. The measurement of this investigation includes air contents, slump loss, compressive strength, flexural strength, flexural toughness and neutron shielding rate. Four different fiber volume fractions were selected ranging from 0.25% to 1.0% by volume for the amorphous boron steel fibers. The testing results showed that the flexural toughness and the neutron shielding rate were increase with the increase of volume fraction for amorphous boron steel fiber. Based on the result, it is concluded that the concrete with the amorphous boron steel fiber can be effectively applied to shield the neutron and to improve mechanical properties.

Workability and Mechanical Properties of Hybrid Fiber Reinforced Concrete Using Amorphous Steel Fiber and Polyamide Fiber

Many studies have been performed on hybrid fiber reinforced concrete for years, which is to improve some of the weak material properties of concrete. Studies on characteristics of hybrid fiber reinforced concrete using amorphous steel fiber and polyamide fiber, however, yet remain to be done. The purpose of this experimental research is to evaluate the workability and mechanical properties of hybrid fiber reinforced concrete using amorphous steel fiber and polyamide fiber. For this purpose, the hybrid fiber reinforced concrete containing amorphous steel fiber(ASF) and polyamide fiber(PAF) were made according to their total volume fraction of 0.5 % for water-binder ratio of 33 %, and then the mechanical properties such as the compressive strength, direct tensile strength, flexural strength, and flexural toughness of those were estimated. It was observed from the test results that the compressive strength was slightly decreased with increasing ASF and decreasing PAF and the effect of fiber combination on the flexural strength was not much but the flexural toughness was relatively largely increased with decreasing ASF and increasing PAF.

비정질 강섬유 혼입 바닥난방시스템의 열성능 평가

본 연구에서는 비정질 강섬유 혼입 바닥몰탈을 이용한 바닥난방시스템과 일반 몰탈을 사용한 바닥난방시스템의 열성능을 비교 평가하기 위하여 시뮬레이션을 실시하였다. 시뮬레이션은 온수공급온도를 변화시켰으며 다음과 같은 결론을 얻었다. 바닥의 표면온도, 실내의 공기온도 등을 검토 결과 강섬유온돌을 사용할 경우에는 실내공기를 기준으로 하면 강섬유온돌이 일반온돌에 비해 7~9%에 가까운 열효율이 상승되었으며, 바닥의 온도를 기준으로 하면 2~4% 온도상승이 일어나는 것으로 나타났다. The thermal performance of amorphous steel fibers mixed floor heating system was evaluated. Analysis of results, depending on the hot water supply temperature changes, the average temperature of the bottom of the hot water supply temperature is an amorphous steel fiber floor heating system is about 2~4% higher. The average temperature of the floor surface to 1.5m air amorphous steel fiber system is 1~2% higher. The amount of heat supplied to indoor air (1.5m) from the bottom surface of amorphous steel fiber floor heating system is about 7~8% higher

Compressive fatigue performance of fiber-reinforced lightweight concrete with high-volume supplementary cementitious materials

As a part of the fundamental investigation to evaluate the compressive fatigue damage of fiber-reinforced lightweight concrete using high-volume supplementary cementitious materials (SCMs), the stress–strain response of the concrete was examined under cyclic loading within maximum stress levels of 0.9, 0.8, and 0.75 fc’ and a minimum stress level fixed at 0.1 fc’, where fc’ is the concrete compressive strength. To produce a high-volume SCM binder, 20% fly ash and 50% ground granulated blast-furnace slag were used as a partial replacement for cement. Amorphous steel (AS) and polyvinyl acetate (PVA) fibers were added individually or in combination considering their conventionally recommended volume fractions. The fatigue tests were carried out by controlling the load between two limits with a sinusoidal variation at a frequency of 1 Hz. Test results showed that PVA fiber was preferable to AS fiber in enhancing the fatigue life of HVS-LWC, whereas the fatigue damage of the PVA fiber concrete was lower than that of the AS fiber concrete. This trend was more notable under a higher maximum stress level. To improve the fatigue life and fatigue damage of concrete, hybridization of both fibers rather than monolithic use is recommended.

Size effect in normal- and high-strength amorphous metallic and steel fiber reinforced concrete beams

In this study, the size effect on the flexural behavior of amorphous metallic fiber reinforced concrete (AM-FRC) was investigated. For this, several AM-FRC beams having three different sizes were fabricated with different values of water-to-cementitious material (w/cm) ratio and fiber volume fraction. In order to estimate the implication of fiber type on the size effect, steel fiber reinforced concrete (SFRC) having the same mixture proportion as that of the AM-FRC and 0.75% by volume of hooked-end steel fibers were also fabricated and tested. The experimental results showed that lower flexural performance including flexural strength, normalized deflection capacity, and normalized toughness was obtained with an increase in the specimen size, regardless of w/cm ratio and volume content and type of fibers. High-strength concrete was more sensitive to the size effect on flexural strength than normal-strength concrete, whereas less sensitivity to the size effect was observed with an increase in the fiber volume content. The effectiveness of using hooked-end steel fibers in reducing the size effect was greater for high-strength concrete compared to normal-strength concrete, due to the better fiber bond performance.

Workability and Strength Properties of Hybrid Fiber Reinforced Concrete Using Amorphous Steel Fiber and Organic Fiber

The purpose of this experimental research is to evaluate the workability and strength properties of hybrid fiber reinforced concrete containing amorphous steel fiber and organic fiber. For this purpose, the hybrid fiber reinforced concrete containing amorphous steel fiber(ASF) with polyamide(PA) and polyvinyl alcohol(PVA) fiber, respectively were made according to their total volume fraction of 0.5% for water-binder ratio of 33%, and then the characteristics such as the workability, compressive strength, and flexural strength of those were investigated. It was observed from the test results that the workability and compressive strength at 7 and 28 days were decreased and the flexural strength at 7 and 28 days was increased with increasing ASF and decreasing organic fiber.

Synergy in Toughness by Incorporating Amorphous Metal and Steel Fibers

A study on the use of amorphous metallic fibers (AMFs) in concrete was undertaken to combine its action with that of hooked-ended steel fibers for improving flexural strength and toughness. Tests on mixtures with various dosages of AMF (10, 20, and 30 kg/m³ [16.9, 33.7, and 50.6 lb/yd³]), and 15 kg/m³ (25.3 lb/yd³) of steel fibers were carried out, along with hybrid mixtures with two dosages of AMF. The results showed a significant increase in the flexural strength of concrete with the addition of AMF, even at low dosages. The performance of concretes with the hybrid combinations is significantly enhanced. For example, the equivalent flexural strength for the concretes with just 10 kg/m³ (16.9 lb/yd³) of AMF and 15 kg/m³ (25.3 lb/yd³) of steel fibers is 35% higher than with only steel fibers and is approximately 3.5 times that obtained with only 10 kg/m³ (16.9 lb/yd³) of AMF. The load-deflection behavior and the toughness parameters clearly indicate a significant synergy in the hybrid combination.

비정질강섬유보강콘크리트의 휨성능 비교분석

상대적으로 제조공정이 짧아 환경 및 경제적 이점을 갖는 비정질강섬유(AF)를 길이 및 혼입률을 변화하여 휨성능을 평가와 더불어 기존의 일반강섬유(HF)와의 비교분석을 실시하였다. 섬유의 길이는 10 mm, 20 mm, 30 mm, 및 혼입률은 0.3%, 0.6%로 변화를 주어 실험을 진행하였다. 비정질강섬유(AF의 경우 비중은 일반강섬유(HF)와 거의 동일한 값을 가지나 겉보기부피는 약 2배정도 커서 같은 혼입률에서 투입되는 섬유의 개수는 훨씬 증가되어 배합설계에서 주의를 할 필요가 있다. 실험결과 휨강도의 영향은 섬유의 길이 및 혼입률이 증가할수록 강도의 증가를 보였으며, 일반강섬유(HF)보다 크게 나타났다. 특히 최대하중부근에서의 에너지소산능력이 뚜렷하게 증가하여 잔류하중단계에서의 급격한 감소에도 불구하고 일반강섬유(HF)와 거의 유사한 잔류강도 및 에너지소산능력을 보여주었다. 콘크리트 균열 후 파괴진행단계에서는 섬유의 인발저항에 의한 균열진행이 아닌 섬유의 파단에 의한 강도의 급격한 감소를 보여준 것으로 판단된다. The flexural performance of amorphous steel fibers having environmental and economy benefits due to relatively short manufacturing process were evaluated as well as that of hooked steel fibers by varing fiber length and volume fraction. Fiber lengths were 10 mm, 20 mm, 30 mm and fiber volume fractions were varied from 0.3% to 1.2%. Test results with flexural performance showed that mixing design needs to be careful because of relatively high volume of amorphous steel fiber compared to hooked steel fibers. High flexural strength was obtained from both longer fiber length and higher volume fraction. Residual strength and toughness of amorphous steel fiber were similar to that of hooked steel fiber, even though rapid dropping of applied load right after concrete matrix breaking. It can be judged that relatively high ability of energy dissipation around first cracking area relatively overcome rapid dropping of loading.

비정질 강섬유로 보강된 철근콘크리트 인장부재의 인장강화효과

이 논문은 비정질 강섬유 및 일반 강섬유로 보강된 철근콘크리트 인장 부재의 인장강화효과에 대해서 직접인장 실험을 통하여 비교ㆍ분석한 것이다. 이를 위하여 피복두께를 변수로 하는 직사각형 단면의 비정질 강섬유 및 일반 강섬유로 보강된 직접인장실험체를 각 6개씩 제작하여 실험을 실시하였다. 실험결과에 따르면 강섬유로 보강된 철근콘크리트 인장부재는 피복두께가 두꺼워질수록 인장강화효과가 증가하였으며, 비정질 강섬유가 일반 강섬유보다 인장강화효과가 더 우수하였다. 강섬유 보강에 따른 쪼갬균열의 발생 및 진행이 크게 감소하였으며, 비정질 강섬유로 보강된 경우는 철근 직경의 2배 이상 피복두께가 확보되면 쪼갬균열이 억제되고 그에 따라서 인장강화효과가 크게 증가하였다. 특히 일반 강섬유와 비교하여 비정질 강섬유로 보강된 철근콘크리트 부재의 경우는 현행 설계기준의 인장강화효과 규정과는 다르게 작용하중에 따라서 인장강화효과가 증가하였는데, 이 결과는 인장강화효과의 크기를 결정하는 인장강성 계수의 분석을 통하여 확인하였다.

보강섬유의 형상과 물성에 따른 인발특성이 콘크리트의 휨거동에 미치는 영향

This study evaluated the bonding property of fiber and flexural behavior of fiber reinforced concrete. Amorphous steel fiber, hooked steel fiber and polyamide fiber was used for evaluation of bonding property and flexural behavior. As a result, the hooked steel fiber was pulled out from matrix when peak stress. However amorphous steel fiber occurred shear failure because bonding strength between fiber and matrix was higher than tensile strength of fiber. Polyamide fibers occurred significantly displacement to peak stress because of elongation of fiber. After that peak stress, fiber was cut off. Amorphous steel fiber reinforced concrete had a greater maximum flexural load compared with hooked steel fiber reinforced concrete because bonding performance between fiber and matrix was high and mixed population of fiber was many. However flexural stress was rapidly reduced in load-deflection curve because of shear failure of fiber. Flexural stress of hooked steel fiber reinforced concrete was slowly reduced because fiber was pulled out from the matrix. In the case of polyamide fiber reinforced concrete, flexural stress was rapidly lowered because of elongation of fiber. However flexural stress was increased again because of bonding property between polyamide fiber and matrix. The pull-out properties of the fiber and matrix has effect on the deformation capacity and flexural strength of fiber reinforced concrete.

비정질 강섬유보강콘크리트의 휨성능 특성

이 연구에서는 ASTM C 1609을 따라서 비정질 강섬유보강콘크리트의 휨실험을 수행하였고, 이를 바탕으로 휨성능을 평가하였다. 비정질 강섬유는 기존의 일반 강섬유와 달리 얇은 두께, 거친 표면의 특성을 가지고 있다. 주요한 실험변수는 섬유종류(비정질 강섬유, 일반 강섬유), 섬유 혼입률(0.25, 0.50, 0.75%) 그리고 콘크리트 압축강도(27, 50 MPa)이다. 실험 결과에 근거하여 비정질 강섬유와 일반 강섬유보강콘크리트의 휨강도와 휨인성을 분석하였고, 그 결과 일반 강섬유보강콘크리트의 경우 주로 휨인성이 증가하였으나 비정질 강섬유보강콘크리트의 경우 휨강도와 인성을 모두 증가하는 것으로 나타났다.

비정질 강섬유로 보강된 철근콘크리트 인장부재의 균열거동

이 논문은 비정질 강섬유 및 일반 강섬유로 보강된 철근콘크리트 인장실험체를 피복두께와 철근 직경의 비에 따라 각 6개씩 제작하여 직접인장실험을 수행하고, 그 결과로부터 강섬유로 보강된 철근콘크리트 인장부재의 균열거동을 분석한 것이다. 실험 결과에 따르면 비정질 강섬유와 일반 강섬유로 보강된 콘크리트 모두 쪼갬균열의 발생과 진행을 제어하는 성능이 양호하며, 특히 비정질 강섬유로 보강된 콘크리트는 피복두께가 철근 직경의 2배 이상이면 쪼갬균열이 발생하지 않았다. 균열간격은 두가지 강섬유로 보강된 실험체 모두에서 피복두께가 두꺼워짐에 따라 증가하였으며, 현행 설계기준에서 규정하는 최대 및 평균 균열간격 식으로 계산한 것보다 비교적 작게 측정되었다. 실험으로부터 측정된 자료로부터 평균균열간격을 이용하여 최대균열 간격 및 최소균열간격을 예측할 수 있는 상관관계식을 제안하였다.

비정질강섬유 보강콘크리트 작업성 및 섬유 분산성 비교분석

비정질강섬유 보강콘크리트 작업성 및 섬유 분산성 비교분석

비정질 강섬유보강콘크리트의 구속건조수축균열 특성

In this study, free and restraint drying shrinkage tests of conventional and amorphous steel fiber-reinforced concrete were performed to investigate the shrinkage characteristics. To consider the effect of restraint condition of concrete on shrinkage cracking, three different test setups were used: ring type restraint test according to ASTM C 1581-04, dumbbell type restraint test according to KS F 2595, and modified dumbbell type restraint test with notches. Crack widths and strain profiles acquired from the tests were compared and investigated. The test results showed that the addition of amorphous steel fibers with 0.2-0.4% volume fraction into concrete resulted in 30% reduction of free drying shrinkage, 3-5 days delay of crack development time, and 20-60% reduction of crack width. Thus, it can be concluded that the amorphous steel fibers can be used for the purpose of crack control of concrete shrinkage cracking.

Tensile and Compressive Creep Behaviors of Amorphous Steel Fiber-Reinforced Concrete

(Received November 29, 2013 / Revised December 19, 2013 / Accepted December 23, 2013)In this study, the creep behaviors of amorphous steel fiber-reinforced concrete were investigated. Two different types of tests were carried out to evaluate the effect of amorphous steel fibers on the creep of concrete: compressive creep test and tensile creep test. Fiber volume fractions used in the test were 0.2% and 0.4% for tensile specimens, and 0.2% and 0.3% for compressive specimens. Basedon the test results, the addition of fiber volume fraction of 0.2% into concrete could significantly reduce both compressive an d tensilecreep. Keywords : Amorphous steel fiber, Tensile and compressive creep, Reinforced concrete* Corresponding author E-mail: kkchoi@ssu.ac.kr