• Advances in concrete construction
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• v.14 no.2
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• pp.93-102
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• 2022

In this study, limestone powder (LS) and fly ash (FA) were used as powder materials in self-compacting concrete (SCC) in increasing quantities in addition to cement, so that the two powders commonly used in the production of SCC could be compared in the same study. Considering the reduction of the maximum aggregate size in SCC, 10 mm or 16 mm was selected as the coarse aggregate size. The properties of fresh concrete were determined by slump flow (including T₅₀₀ time), V-funnel and J-ring experiments. The experimental results showed that as the amount of both LS and FA increased, the slump flow also increased. The increase in powder material had a negative effect on V-funnel flow times, causing it to increase; however, the increase in FA concretes was smaller compared to LS ones. The increase in the powder content reduced the amount of blockage in the J-ring test for both aggregate sizes. As the hardened concrete properties, the compressive and splitting strengths as well as the modulus of elasticity were determined. Longitudinal and transverse deformations were measured by attaching a special frame to the cylindrical specimens and the values of Poisson's ratio, initiation and critical stresses were obtained. Despite having a similar W/C ratio, all SCC exhibited higher compressive strength than NVC. Compressive strength increased with increasing powder content for both LS and FA; however, the increase of the FA was higher than the LS due to the pozzolanic effect. SCC with a coarse aggregate size of 16 mm showed higher strength than 10 mm for both powders. Similarly, the modulus of elasticity increased with the amount of powder material. Inelastic properties, which are rarely found in the literature for SCC, were determined by measuring the initial and critical stresses. Crack formation in SCC begins under lower stresses (corresponding to lower initial stresses) than in normal concretes, while critical stresses indicate a more brittle behavior by taking higher values.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.437-440
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• 2003

This study has focused on the possibility for recycling of tailings from the Sangdong tungsten mine as powder of self-compacting concrete(SCC). The experimental tests for slump-flow, reaching time to the slump-flow of 500mm, V-funnel and U-box were carried out in accordance with the specified by the Japanese Society of Civil Engineering(JSCE). The result of this study, in case of SCC mixed with tailings, slump-flow was decreased with increasing mixing ratio. But reaching time slump-flow of 500mm, V-funnel and U-box were satisfied a prescribed range. The mechanical properties including compressive strength, splitting tensile strength and static modulus of elasticity were checked with the requirements specified by Korean Industrial Standard(KS). The compressive strength of SCC was decreased with increasing replacement, splitting tensile strength and static modulus were similar to those of normal concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.640-643
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• 2004

Synthetic lightweight aggregates are manufactured with recycled plastic and fly ash with 12 percent carbon. Nominal maximum-size aggregates of 9.5mm were produced with fly ash contents of 0 percent, 35 percent, and 80 percent by total mass of the aggregate. An expanded day lightweight aggregate and a normal-weight aggregate were used as comparison. Mechanical properties of the concrete determined included density, compressive strength, elastic modulus, and splitting tensile strength. Compressive and tensile strengths were lower for the synthetic aggregates; however, comparable fracture properties were obtained. Relatively low compressive modulus of elasticity was found for concretes with the synthetic lightweight aggregate, although high ductility was also obtained. As fly ash content of the synthetic lightweight aggregate increased, all properties of the concrete were improved.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.119-122
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• 1999

In this paper, the properties of concrete used recycled aggregate are analyzed. The specimens are manufactured for the compressive strength of 210㎏/㎠ with recycled aggaregate ratio of 0%, 20%, 40%, 60%, 80%, 100%, respectivey. At curing 28days, compressive strength, tensile strength, flexural strength, dry-shrinkage, static modulus of elasticity and poission's ratio have been tested according to replacement ratio of recycled aggregate.

• Magazine of the Korea Concrete Institute
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• v.9 no.4
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• pp.197-205
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• 1997

The shrinkage of polymer concrete overlays to cement concrete causes interface shear, normal and axial stresses in the overlays. These can lead to deterioration of the polymer concrete overlays due to affection of adhesion polymer concrete and cement concrete. The shrinkage stress in the polymer concrete cause it to shorten and the shorting is measured: With the modulus of elasticity of the polymer concrete and strain known the stresses can be calculated. The purpose of this study is to provide the basic data of application of polymer concrete overlays such as bridge decks, highway and airport pavement repair and overlay materials. From the test results. It has been found that depending on the type polymer. overlay thickness, time after curing and temperature. the shrinkage stresses are eliminated by relaxation in time ranging from a few hours to a few days.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.561-564
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• 2006

This study is aimed for investigating the engineering properties of concrete containing fly ash, slag powder and limestone powder. The results of this study are as follows; As limestone powder is incresed, slump, air loss and strength is reduced, variation ratio of length is reduced, dynamic modulus of elasticity and neutralization depth is incresed.

• Advances in nano research
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• v.15 no.6
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• pp.495-511
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• 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.

• Korean Journal of Agricultural Science
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• v.26 no.1
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• pp.65-70
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• 1999

This study is performed to evaluate the engineering properties of rice-straw ash concrete using normal portland cement, natural aggregates and rice-straw ash. The following conclusion are drawn; 1. The dynamic modulus of elasticity is in the range of $289{\times}10^3{\sim}345{\times}10^3kgf/cm^2$, which is showed about the same compared to that of the normal cement concrete. The highest dynamic modulus is showed by 5% rice-straw ash filled rice-straw ash concrete 2. The static modulus of elasticity is in the range of $268{\times}10^3{\sim}335{\times}10^3kgf/cm^2$, which is showed about the same compared to that of the normal cement concrete. The dynamic modulus is increased approximately 3~10% than that of the static modulus. 3. The poisson's number of rice-straw ash concrete is less than that of the normal cement concrete. 4. Accordingly, if we use suitable quantity of rice-straw ash as a replacement of cement, it will greatly improve engineering properties of concrete.

• Computers and Concrete
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• v.20 no.4
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• pp.491-502
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• 2017

In this research, the application of ultrasonic pulse velocity (UPV) test as a nondestructive method for estimating some of the mechanical and dynamic properties of reactive powder concrete (RPC) containing steel and polyvinyl alcohol (PVA) fibers, as well as their combination was explored. In doing so, ten different mix designs were prepared in 19 experimental groups of specimens containing three different volume contents of steel fibers (i.e., 1, 2, and 3 %) and PVA fibers (i.e., 0.25, 0.5, and 0.75 %), as well as hybrid fibers (i.e., 0.25-0.75, 0.5-0.5, and 0.75-0.25 %). The specimens in these groups were prepared under the two curing regimes of normal and heat treatment. Moreover, the UPV test results were employed to estimate the compressive strength, dynamic modulus, shear modulus, and Poisson's ratio of the RPC concrete and to investigate the quality level of the used concrete. At the end, the effect of the specimen shape and in fact the measuring distance length on the UPV results was explored. The results of this research suggest that the steel fiber-containing RPC specimens demonstrate the highest level of ultrasonic pulse velocity as well as the highest values of the mechanical and dynamic properties. Moreover, heat treatment has a positive effect on the density, UPV, dynamic modulus, Poisson's ratio, and compressive strength of the RPC specimens, whereas it leads to a negligible increase or decrease in the shear modulus and static modulus of elasticity. Furthermore, the specimen shape affects the UPV of fiber-lacking specimens while negligibly affecting that of fiber-reinforced specimens.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.237-245
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• 2010

Recently, deflection of the slab during construction periods becoming one of the important issues because of increasing the large-span structures. Early removing the form and support of the slab to achieve the rapid construction cause falling-off in quality of the structures. To reduce these deterioration and make rapid construction, construction of strength and stiffness gain model is needed by the research about the early-age concrete properties. Previous research results indicated that concrete model in existing design codes could not provide the mechanical properties of early age concrete. This paper carried out the concrete compressive strength tests on the curing age at early age stage. Evaluation of the accuracy of compressive strength and modulus of elasticity gain formula in existing various design codes was performed based on this test results, and new design model was proposed. This new model will be useful to develop the new rapid construction methods or prevent the deterioration of the deflection at construction periods. Material tests were performed at 1, 3, 7, 14, 28 curing days, total 159 cylinder style specimens were tested. Based on analyzing the test results, the relationship between compressive strength and modulus of elasticity at early age was proposed.