• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.299-305
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• 2012

The objective of this paper is to obtain the basic data in order to develop an eco-friendly concrete through evaluation on the properties of polymer cement mortar and concrete using PVAc (Polyvinyl Acetate), as a kind of water-soluble polymer. For this purpose, the physical properties of cement mortar and concrete which does not contain the PVAc as the control batch were compared and analyzed with those using the PVAc. And then, the replacement amount of the PVAc was 3%, 6%, 9% and 12% by binder, respectively. And also, the properties of concrete using the PVAc were evaluated, by adding an antifoaming agent in order to control the air contents increasing with an increase of amount of polymer usage. As a result, in the case of polymer cement mortar using the PVAc, it presented that the compressive strength reduced, while the performance of flexural strength and drying shrinkage increased. When the replacement of the PVAc was 6% within concrete, the compressive, tensile, flexural strength and elastic modulus were increased.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.101-104
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• 2008

The cost of repairing the deterioration of concrete structures due to corrosion of the reinforcement steel has been the prominent figure in the maintenacne of the reinforced-concrete infrastructures. As an alternative material to steel reinforcement, the use of Fiber Reinforced Polymer (FRP) bar in concrete is being actively studied for the high resistance of chemical environment and high strength to weight ratio properties of FRP. However, there remain various aspects of FRP properties that still need to be studied before the standard design criteria can be established. One of the imminent issues is the bond between FRP and concrete. In this study, the bond-behavior of FRP bars in concrete is investigated via the pullout test with three varying parameters: surface condition of FRP bars, concrete compression strength, and cyclic loading patterns. As a result of experiment, the bond strength of GFRP increased with the concrete compression strength increasing and decreased with applying cyclic load.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.200-207
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• 2021

The purpose of this study is to investigate experimentally the effects of type of superplasticizer on tensile behavior and cracking pattern of alkali-activated slag-based cementless composite. Three mixtures were prepared according to type of superplasticizer, and the compressive strength and tension tests were performed. Test results showed that differences of tensile strength, tensile strain capacity, and toughness of composites were up to 28.1%, 39.1%, and 66.2%, respectively, according to type of superplasticizer, although fiber balling or poor dispersion of fibers in fresh composites was not observed. It was also observed that the type of superplasticizer influenced number of cracks and maximum fiber bridging stress.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.258-265
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• 2001

Compression and bending test have been conducted to evaluate the mechanical performance of CFRC at several different temperature up to $2000^{\circ}C$ . Tools and several grips for the test at high temperature were designed to obtain mechanical properties of CFRP. A major cause of increasing strength according to increasing the density and the temperature were analyzed. SEM method was utilized to find out the damage and the fracture mechanism. The new simple equation for the L(span length)/h(beam height) of specimens and for the failure criterion on the 4 point bending were proposed.

• Journal of Conservation Science
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• v.31 no.4
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• pp.373-386
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• 2015

This study identified degradation properties by temperature stress with Araldite$^{(R)}$ AY103-1/HY956 used for ceramics. Tensile and compressive strength of durability increased for 6,480 hours at temperature of $34{\sim}45^{\circ}C$. In stability of external stress and temperature, compressive strength is superior to tensile strength, it requires conservation plans considering strength properties and stress of restoration materials. The tensile shear strength of adhesion properties decreased for 4,320 hours at temperature of $40{\sim}60^{\circ}C$. In ceramics with porosity, environments under isothermal-isohumidity are important because interfacial properties of adherend are concerned with performance variation. Glossiness decreased for 6,480 hours at temperature of $34{\sim}45^{\circ}C$ and color difference increased. Gloss stability was superior and color stability was weak, which requires improvement of optical properties. In artifacts on display in museums, there is concern about temperature rise on restoration materials by lighting therefore, it needs to minimize change in physical properties by exposure environments.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.513-521
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• 2003

Existing tests results have shown that confining the concrete compression region with closed stirrups improves the ductility and load-carrying capacity of beams. However, only few researchers have attempted to utilize the beneficial effects of the presence of these stirrups in design. This paper presents the result of experimental studies on the load-deflection behavior and the strengthening effect of laterally confined structural high-strength concrete beam members in which confinement stirrups have been introduced into the compression regions. Fifteen tests were conducted on full-scale beam specimens having concrete compressive strength of 41 MPa and 61 MPa. Different spacing of stirrups(0.25∼1.0d) and amount of tension steel($0.55{\sim}0.7{\rho}_b$) as major variables were investigated. And also, this study present an appropriate shear equation for decision of ultimate failure modes of high-strength concrete beams according to stirrup spacing. The equation is based on interaction between shear strength and displacement ductility. Prediction of failure mode from presented method and comparison with test results are also presenteded

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.365-373
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• 2016

Ultra-High-Performance Steel Fiber-Reinforced Concrete (SUPER Concrete) exhibits improved compressive and tensile strengths far superior to those of conventional concrete. These characteristics can significantly reduce the cross sectional area of the member and the anchorage strength of a headed bar is expected to be improved. In this study, the anchorage strengths of headed bars with $4d_b$ or $6d_b$ embedment length were evaluated by simulated exterior beam-column joint tests where the headed bars were used as beam bars and the joints were cast of 120 or 180 MPa SUPER Concrete. In all specimens, the actual yield strengths of the headed bars over 600 MPa were developed. Some headed bars were fractured due to the high anchorage capacity in SUPER Concrete. Therefore, the headed bar with only $4d_b$ embedment length in 120 MPa SUPER Concrete can develop a yield strength of 600 MPa which is the highest design yield strength permitted by the KCI design code. The previous model derived from tests with normal concrete and the current design code underestimate the anchorage capacity of the headed bar anchored in SUPER Concrete. Because the previous model and the current design code do not consider the effects of the high tensile strength of SUPER Concrete. From a regression analysis assuming that the anchorage strength is proportional to $(f_{ck})^{\alpha}$, the model for predicting anchorage strength of headed bars in SUPER Concrete is developed. The average and coefficient of variation of the test-to-prediction values are 1.01 and 5%, respectively.

• Polymer(Korea)
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• v.39 no.1
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• pp.130-135
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• 2015

Cellulose has attracted much attention as potential reinforcements in green composites. In this study, polypropylene (PP)/cellulose composites were prepared by melt-blending followed by compression molding. To improve interfacial bonding between PP and cellulose, maleic anhydride-grafted polypropylene (MAPP) was used. Mechanical properties of the PP/cellulose composites were investigated by UTM and izod impact tester. Thermal properties of the PP/cellulose composites were investigated by TGA and DSC. SEM images for the fracture surfaces of the composites showed that the MAPP was effective in improving PP/cellulose interfacial bonding. Tensile strength and modulus of the composite were maxima when MAPP content, based on cellulose content, was 3 wt%. With increasing cellulose content, the impact strength of the composites decreased but the tensile strength and modulus increased.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.117-124
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• 2015

Currently, Eco-friendly construction materials are widely utilized for reducing $CO_2$ emission in construction. Furthermore various engineering fibers are also added for improving a brittle behavior in concrete. In the paper, concrete specimens with 10% and 20% replacement ratio with RHA (Rice Husk Ash) are prepared, and engineering behaviors in RHA and OPC concrete are evaluated with different addition of coconut fiber from 0.125~0.375% of volume ratio. Several basic tests including compressive strength, tensile strength, flexural strength, impact resistance, and bond strength are performed, and crack width and deflections are also measured in flexural test. RHA is evaluated to be very effective in strength development and 0.125% of fiber addition leads significant improvement in tensile strength, ductility, and crack resistance. RHA and coconut fiber are effective construction material both for reutilization of limited resources and performance improvement in normal concrete.

• Korean Journal of Agricultural Science
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• v.6 no.1
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• pp.45-55
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• 1979

This study made to find the variation of strengths of briquette ash which were hardened into cement. The briquette ash were mixed with the cement, ((cement (90%)+slaked lime (10%)) and ((cement (80%)+fly ash (20%)) in the ratio of 1:2, 1:3, 1:4, 1:5, 1:7 and 1:9, respectively, and these were compared with the one made of cement plus standard sand in the strengths of compression, tension and bending at the ages of 7 days and 28 days. The results from the study conducted preliminary without studying the economical aspects or duration of the products are summarized as follows: 1. The compressive strengths of mortar made of 1 to 2 ratios of cement to briquette ash, (cement+slaked lime) to briquette ash and (cement+fly ash) to briquette ash were 84%, 90% and 75% at the age of 7 days and 84.9%, 73.5% and 69.8%, respectively of those of Korean Standard values. 2. The compressive strength s of mortar made of 1 to 2 ratios of cement to briquette ash, (cement+slaked lime) to briquette ash and (cement+fly ash) to briquette ash were 69.3%, 75.1% and 41.3% at the age of 7 days and 56.4%, 49%, and 46.5% at the age of 28 days, respectively of the mortar made of standard sand. 3. The tension strengths of mortar made of 1 to 2 ratios of cement to briquette ash, (cement+slaked lime) to briquette ash, and (cement+fly ash) to briquette ash were 64.4%, 47.1% and 35.4% at the age of 7days and 69.6%, 64.8%, and 57.3%, respectively of that of the mort ar produced with standard sand. 4. The bending strengths of mortar made of 1 to 2 ratios of cement to briquette ash, (cement+slaked lime) to briquette ash, and (cement+fly ash) to briquette ash were 46.3%, 65.9% and 39.1% at the age of 7 days and 89.9%, 96.7%, and 85.1%, respectively of that of mortar produced with standard sand. 5. The bending strength of the mortar was lower than that of cement mortar, when the briquette ash were harqened into cement. However, the mortar produced by such method seemed to be used as the secondary products of cement or concrete. The additional usefullness of the hardened biquette ash can be found in contributing toward the solving the various pollution problems, the saving the labor costs needed to clean-up waste materials, and the saving the construction materials.