• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.609-612
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• 2006

The quality of the concrete compression strength can be determined after the passage of 28 days, but if any defect is found the quality of concrete after that length of time, there can be serious problems in dismantling and repair. Thus, in response to the use of concrete using non sintering cement (NSC), the present study purposed to propose a method of managing the strength of high strength concrete using NSC in comparison with high strength concrete using ordinary Portland cement (OPC) through early strength estimation using microwave, which enables the quick estimation of the strength of high strength concrete using NSC.

• International Journal of Concrete Structures and Materials
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• v.1 no.1
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• pp.3-9
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• 2007

Fiber-reinforced self-compacting concrete (FRSCC) is a new type of concrete mix that can mitigate two opposing weaknesses: poor workability in fiber-reinforced concrete and cracking resistance in plain SCC concrete. This study focused on early-age cracking of FRSCC due to restrained drying shrinkage, one of the most common causes of cracking. In order to investigate the effect of fiber on shrinkage cracking of FRSCC, ring shrinkage tests were performed for polypropylene and steel fiber-reinforced SCC. In addition, finite element analyses for those specimens were carried out considering drying shrinkage based on moisture diffusion, creep, cracking resistance of concrete, and the effect of fiber. The analysis results were verified via a comparison between the measured and calculated crack width. From the test and analysis results, the effectiveness of fiber with respect to reducing cracking was confirmed and some salient features on the shrinkage cracking of FRSCC were obtained.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.39-44
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• 1993

The aim of this study is to develop High Performance Concrete, which can fill in every corner of forms without using any vibrators. In order to place concrete into reinforced members, concrete should have segregation resistance and high flowability. In this study, the binder of concrete, such as Ordinary Portland Cement, fly ash, and blast furnace slag, cement were mixed with the addition of superplasticizers and tested their flowability and segregation resistance using slump flow tester and L type flow tester. As a results, High Performance Concrete can be made using Portland blast furnace slag cement along with superplasticizers but the slump-loss of concrete is so large that measure should be made.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.89-94
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• 2003

In this research, the physical properties of self compacting concrete using ground granulated blast furnace slag and fly ash as a part of cement were investigated. Concrete using ground granulated blast furnace slag and fly ash was prepared with various ground granulated blast furnace slag(30-50 volume %) and fly ash(10-20 volume %) replacement for cement. The effect of each of the materals, which have effects on self compacting concrete made by the basic mix proportion used granulated blast furnace slag and fly ash after hardening, has been checked. The workability, flowing characteristics, resistance of segregation of materals, air content, and compressive strength of concrete using ground granulated blast furnace slag and fly ash were tested and the results were compared with those of ordinary portland cement concrete. In the experiment, we acquired satisfactory results at the point of flowing characteristics and strengths of concrete using ground granulated blast furnace and slag fly ash within the replacement ratio of 65%

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.117-124
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• 1997

In this study, mechanical properties of type V cement concrete with different curing temperature were investigated. The tests for mechancial properties, i.e., compressive strength and modulus of elasticity, were carried out on two kinds of type V cement concrete mixes. concrete cylinders cured at 10, 23, 35 and 50℃ were tested at 1, 3, 7 and 8 days. The 'rate constant model' was used to described the combined effects of time and temperature on compressive strength development. Test results show that concrete subjected to high temperature at early age attains greater strength than concrete to low temperature but eventually attains lower later-age strength than that. With type V cement concrete, the linear and Arrhenius rate constant models both accurately describe the development of relative strength as afunction of the equivalent age.

• KIEAE Journal
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• v.8 no.5
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• pp.55-60
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• 2008

The purpose of this study is to increase the use of Hwangto and examine the strength according to what it is compounded with. Hwangto-concrete containing Hwanto without cement nor organic chemical products were compared to the traditional cement concrete through some durability experiments. We expect to gain more knowledge on the potentials of Hwangto-concrete as an architectural source. 1) As Hwangto binder amount rises, the value of slump increases too. The reason is that the increase of the quantity of cement causes the increase of the amount of material and the decrease of the amount of aggregate. 2) When the mixed component into Hwangto-concrete remains at 2%, the compress strength is generally dispersed high along the per unit fission, in case the amount of which is at $400(g/m^3)$. The highest compress strength is 39MPa. It means that it can be applied to common structures and we need to conduct a basic property test to ensure the strength and fluidness. 3) Hwangto-concrete is expected to be highly used in the ocean structure and chemical industry because it has better resistance to sulfuric acid and to hydrochloric acid than the cement-concrete has. The result of this study is as follows. It is expected that Hwangto-concrete will be widely applied and further research on its durability and tests for its basic substantial characteristics based on future component added to it.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.165-171
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• 2004

Latex modification of concrete provides the material with higher flexural strength, as well as high bond strength and reduced water permeability. However, If the thermal expansion properties of overlay concrete (latex-modified concretes) are big different from that of substrate (ordinary portland cement concrete), these would cause a big interfacial stresses and result in premature failure. Therefore, the purposes of this study were to investigate thermal expansion characteristics of latex-modified concrete with cement types. The result of thermal expansion showed the coefficient of thermal expansion of concretes increased with latex inclusion. The coefficient of thermal expansion of RSLMC was a little smaller than that of LMC, which might be due to the finer cement grain, compacter internal, and stiffer properties of concrete. However, the coefficients of LMC and RSLMC were quite similar to that of ordinary cement concrete. Thus, this would not cause an interfacial stresses and will enable to ensure long-term performance of concrete bridge deck overlays.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.505-508
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• 2008

In this study, temperature increase and strength development of concretes with different types of cement were investigated to construct dam drop spillway. For this purpose, boxes of 1${\times}$1${\times}$1m size with 4 different concrete mixtures were made. The types of concrete were Type I cement concrete, fly ash cement concrete and two type concrete with ternary cement, respectively. The temperature at each point were monitored in these boxes. Based on the Box test, hydration analysis of slab of 2.0m thickness was carried out. This paper presents these experimental and analytical results.

• Advances in concrete construction
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• v.8 no.4
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• pp.305-309
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• 2019

Pervious concrete pavements are the need of the day to avoid urban flooding and to facilitate ground water recharge. However, the strength of pervious or porous concrete is considerably less compared to conventional concrete. In this experimental investigation, an effort is made to improve the strength of pervious concrete by adopting fibres and a small amount of fine aggregate. A porous concrete with cement to aggregate ratio of 1:5 and a water-powder ratio of 0.4 is adopted. 30% of the cement is replaced by cementitious material ground granulated blast furnace slag (GGBS) for better strength and workability. Recron fibres at a dosage of 0.5, 1.0 and 1.5% by weight of cement were included to improve the impact strength. Since concrete pavements are subjected to impact loads, the impact strength was also calculated by "Drop ball method" in addition to compressive strength. The effect of fine aggregate and recron fibres on workability, porosity, compressive and impact strength was studied. The investigations have shown that 20% inclusion of fine aggregate and 1.5% recron fibres by weight of cement give better strength with an acceptable range of porosity.

• Advances in concrete construction
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• v.11 no.2
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• pp.151-161
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• 2021

The major shortcoming of concrete in most of the applications is its high self-weight and thermal conductivity. The emerging trend to overcome these shortcomings is the use of foam-concrete, which is a lightweight concrete consisting of cement, filler, water and a foaming agent. This study aims at the development of a cost-effective high-volume fly-ash foam-concrete insulation wall cladding for existing buildings using natural fiber like rice straw in different proportions. The paper reports the results of systematic studies on various mechanical, acoustic, thermal and durability properties of foam-concrete with and without replacement of cement by fly-ash. Fly-ash replaces 60 percent by weight of cement in foam-concrete. The water-solid ratio of 0.3, the filler ratio of 1:1 by weight, and the density of 1100 kg/㎥ (approx.) are fixed for all the mixes. Rice straw at 1%, 3% and 5% by weight of cement was added to improve the thermal and acoustic efficiency. From the investigations, it was inferred that the strength properties were increased with fly-ash replacement up to 1% rice straw addition. In furtherance, addition of rice straw and fly-ash resulted in improved acoustic and thermal properties.