• 한국농공학회지
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• 제44권2호
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• pp.117-126
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• 2002

Concrete containing discontinuous discrete steel fiber in a normal concrete is called steel fiber reinforced concrete(SFRC). Tensile as well as flexural strengths of concrete could be substantially increased by introducing closely spaced fibers which delay the onset of tension cracks and increase the tension strength of cracks. However, many properties of SFRC have not been investigated, especially properties on repeated loadings. Thus, the purposes of this dissertation is to study the flexural fatigue characteristics of SFRC considering cumulative damage. A series of experimental tests such as compressive strength, splitting tensile strength, flexural strength, flexural fatigue, and two steps stress level fatigue were conducted to clarify the basic properties and fatigue-related properties of SFRC. The main experimental variables were steel fiber fraction (0, 0.4, 0.7, 1, 1.5%), aspect ratio (60, 83). The principal results obtained through this study are as follows: The results of flexural fatigue tests showed that the flexural fatigue life of SFRC is approxmately 65% of ultimate strength, while that of plain is less than 58%. Especially, the behavior of flexural fatigue life shows excellent performance at 1.0% of steel-fiber volume fraction. The cumulative damage test of high-low two stress levels is within the value of 0.6 ∼ 1.1, while that of low-high stress steps is within the value of 2.4 ∼ 4.0.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.239-244
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• 2001

Opens the construction market recently, the construction industry of Korea has faced up to the barrier of globalism, and has been enforced to follow the various global standards in many aspects. Accordingly, it is expected that the test method related to the cement and concrete will be changed to conform to the international standards in Korea. Therefore, in this study, the strength tests are executed for the cement mortars, made by KS and ISO standards respectively, and then obtains such results. 1) The flow of the cement mortar according to ISO is about 8% higher ,than that of KS. 2) The flexural strength of the cement mortar according to ISO is about 10~20% higher than that of KS, and the compressive strength is about 30% higher. 3) The compressive strength relation between the cement mortars of KS and ISO may be expressed in the first-order recurrence formula as follows: Y = 1.33X - 8 In which X is the compressive strength(kgf/$\textrm{cm}^2$) of the mortar according to KS and Y is the compressive strength(kgf/$\textrm{cm}^2$) of the mortar according to ISO.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.308-311
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• 2004

Many researchers have reported that adding steel fiber to concrete improved its tensile and flexural strength significantly, but relatively few studies have been made on the compressive behavior of SFRC(steel fiber reinforced concrete). It is still less in case of high strength SFRC. The main objective of this research is to examine the effect of adding steel fiber on the compressive strength of high strength SFRC using fiber reinforcing index$(RI,\;V_f(l/d))$. It was found from the study that compressive strength was noticeably increased in proportion to RI.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.757-762
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• 2002

This study focused on the investigation of durability of latex modified concrete in the points of surface scaling resistance as cement types variated and latex content variated such as 5%, 10%, 15%, and 20%. An increasing the amount of latex produced concrete with increased flexural strength, but with slightly lower compressive strength. The increase in flexural strength might be attributed to the latex films between the hydrated cement and aggregates, and the decrease in compressive strength to the flexibility of the latex component named by Butadiene. The surface scaling resistance test was used to evaluate the durability of latex-modified concretes and rapid setting latex-modified concretes. The surface scaling resistance of LMC was quite good comparing to conventional concrete. Further, surface scaling resistance of RSLMC was improved with increasing the latex content.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 추계 학술논문 발표대회
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• pp.109-110
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• 2015

In this study, fresh state properties and mechanical properties of low slump concrete which is applied to road pavement have been evaluated by mixing modified sulfur. As results, influence of mixing modified sulfur on the workability was low. Also, compressive strength, and flexural strength tend to decrese with increasing addition rate of modified sulfur. However compressive strength, and flexural strength of modified sulfur concrete were equivalent with that of plain concrete.

• Computers and Concrete
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• 제20권2호
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• pp.177-184
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• 2017

The characteristics of lightweight aggregate (LWA) with a low specific gravity and high water absorption will significantly change the properties of lightweight aggregate concrete (LWAC). This study aimed at exploring the effect of presoaking degree of LWA on the strength degeneracy of LWAC and flexural behavior of LWAC members exposed to elevated temperatures. The residual mechanical properties of the LWAC subjected to elevated temperatures were first conducted. Then, the residual load tests of LWAC members (beams and slabs) after exposure to elevated temperatures were carried out. The test results showed that with increasing temperature, the decreasing trend of elastic modulus for LWAC was considerably more serious than the compressive strength. Besides, the presoaking degree of LWA had a significant influence on the residual compressive strength and elastic modulus for LWAC after exposure to $800^{\circ}C$. Moreover, owing to different types of heating, the residual load bearing capacity of the slab specimens were significantly different from those of the beam specimens.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표회 논문집(I)
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• pp.157-160
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• 1998

KS F 4419, which is dealt with the Inter-Locking block, states that water to cement ratio for manufacturing inter-locking block should be less than 25% and in KS F4419, the use of admixture is shown to be reluctant to recommend. In this paper, reinvestigation of some regulations in KS F 4419 are carried out. According to the experimental results, as W/C increases, flexural strength and compressive strength are tended to decrease, whereas they increases within certain range, Flexural strength and compressive strength have higher values in 1:2(W/C=35%), 1:4(W/C=45%) and 1:6(W/C=55%) of mix proportions. Moreover they have rather higher values with the containment of high range AE water-reducing agent. The absorption ratios decrease with the increase of W/C and the containment of high range AE water-reducing agent. Therefore, the regulations on the W/C and admixture in KS F 4419 reguire revision.

• 한국농공학회지
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• 제45권6호
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• pp.128-135
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• 2003

This study is performed to examine the physical and mechanical properties of concrete using recycled aggregate and industrial by-products. The test results show that the unit weight, compressive and flexural strength, ultrasonic pulse velocity and dynamic modulus of elasticity are decreased with increasing the content of recycled aggregate. But, the absorption ratio is increased with increasing the content of recycled aggregate. The unit weight is 2,237∼2,307 kg/$\textrm{m}^3$, the absorption ratio is 2.96∼4.12%, the compressive strength is 415∼532 kgf/$\textrm{cm}^2$, the flexural strength is 75∼96 kgf/$\textrm{cm}^2$, the ultrasonic pulse velocity is 4,350∼4,949 m/s and the dynamic modulus of elasticity is $390\times10^3\;∼\;465\times10^3$ kg f/$\textrm{cm}^2$, respectively These recycled aggregate concrete can be used for high strength concrete.

• 한국건설순환자원학회논문집
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• 제2권2호
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• pp.115-127
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• 2014

Addition of fibers in cement or cement concrete may be of current interest, but this is not a new idea or concept. Fibers of any material and shape play an important role in improving the strength and deformation characteristics of the cement matrix in which they are incorporated. The new concept and technology reveal that the engineering advantages of adding fibers in concrete may improve the fracture toughness, fatigue resistance, impact resistance, flexural strength, compressive strength, thermal crack resistance, rebound loss, and so on. The magnitude of the improvement depends upon both the amount and the type of fibers used. In this paper, locally available waste fibers such as coir fibers, sisal fibers and polypropylene fibers have incorporated in concrete with varying percentages and l/d ratio and their effect on compressive, split, flexural, bond and impact resistance have been reported.

• 한국농공학회논문집
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• 제51권1호
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• pp.21-26
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• 2009

This study was performed to evaluate the physical and mechanical properties of concrete using waste activated carbon. Materials used were ordinary portlant cement, crushed coarse aggregate, natural fine aggregate, waste activated carbon, and superplasticizer. The substitution ratios of waste activated carbon were 0,1,2,3,4,5,6,7,8,9 and 10%. The unit weight was decreased and water absorption ratio was increased with increasing the waste activated carbon content, respectively. When the substitution ratio of waste activated carbon was 3%, compressive strength, flexural strength and dynamic modulus of elastisity were more higher than that of the ordinary portland cement (OPC), and it was decreased with increasing the waste activated carbon content, respectively. The most effective contents of waste activated carbon was 2% in performance and 4% in practical use Accordingly, waste activated carbon can be used for concrete material.