• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.69-84
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• 2017

This paper presents results of an experimental investigation on the behaviour of bond between external glass fibre reinforced polymer reinforcement and concrete exposed to three different environmental conditions, namely, temperature cycles, wet-dry cycles and outdoor environment separately for extended durations. Single shear tests (pull-out test) were conducted to investigate bond strengths (pull-out strengths) of control (unexposed) and exposed specimens. Effect of the exposure conditions on the compressive strength of concrete were also investigated separately to understand the effect of changing concrete compressive strength on the pull-out strength. Based on the comparison of experimental results of exposed specimens to control specimens in terms of bond strengths, failure modes and strain profiles, the most significant degradation of pull-out strength was observed in specimens exposed to outdoor environment, whereas temperature cycles did not cause any deterioration of strength.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.6
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• pp.122-130
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• 1997

An experimental study was conducted to evaluate the bond performance of reinforcing bars embedded in high-strength concrete. Four bond specimens and ten beam splice specimens using concrete with compressive strength of 246kgf/$cm^2$ and 64lkgf/$cm^2$ were tested. The effect of several variables on basic development length and compressive strength of concrete is discussed in splice specimens. The test results showed that the current trend in concrete specification of making the splice length longer to compensate for having smaller cover and spacing may not be an effective approach.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.31-45
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• 2000

Because of the high unit cement content in the concrete mix, major concrete temperature rises are observed in the initial stages of hardening in structural members with large cross-sections made of high-strength concrete. While this temperature rise in the initial stages of hardening contributes to the initial development of the concrete strength, it also causes thermal cracking and obstructs medium to long-term increases of the concrete strength. In the study reports below, investigations were made on the effects of the concrete temperature rise in the initial stages of hardening on the medium to long-term development of the strength of structural concrete between the ages of 28 and 91 days. In the study, comparisons were made, for example, between the compressive strength of a control specimen subjected to standard curing at 28 days and the compressive strength of core specimens taken from structural members, and observations were made on the methods of evaluating the concrete strength in structure, defined here as the compressive strength of core specimens at 91 days. The results obtained indicate that, when the maximum temperature of the concrete is the structure does not exceed $60^{\circ}C$, the concrete strength in structure at the age of long-term will generally be greater than the compressive strength of the standard-curing specimens at 28 days, allowing one to evaluate the strength of the structural concrete in terms of the compressive strength of the 28-days standard-curing specimens. When, on the other hand, the maximum temperature of the concrete in the structure exceeds $60^{\circ}C$, the strength in concrete structure may be smaller than the compressive strength of the 28-days standard-curing specimens, creating risks in the evaluation of the concrete strength in structure by latter.

• International Journal of Concrete Structures and Materials
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• v.2 no.1
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• pp.41-48
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• 2008

This study investigates the spalling properties of high strength concrete designed with various types of mineral admixture and diverse content ratios of polypropylene (PP) fiber. Experimental factors considered in series I are four pozzolan types of mineral admixture and series II consists of three shrinkage reducing types of mineral admixture. PP fiber was added 0.05, 0.10 and 0.15vol. % in each mixture of series I and series II, so that totally 27 specimens including control concretes in each series were prepared. Test results showed that the increase of fiber content decreased the slump flow of fresh concrete and increased or decreased the air content depending on the declining ratio of slump flow. For the properties of compressive strength, all specimens were indicated at around 50 MPa, which is high strength range; especially all specimens in series II were 60 MPa. Fire test was conducted in standard heating curve of ISO 834 with ${\phi}100{\times}200\;mm$ size of cylinder moulds for 1 hour. The specimens incorporating silica fume exhibited severe spalling and most specimens without the silica fume could be protected from the spalling occurrence in only 0.05vol % of PP fiber content. This fire test results demonstrated that the spalling occurrence in high strength concrete was not only affected by concrete strength related to the porosity of microstructure but also, even more influenced by micro pore structure induced by the mineral admixtures.

• Steel and Composite Structures
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• v.28 no.5
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• pp.527-539
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• 2018

The use of reinforced concrete (RC) shear wall with concrete filled steel tube (CFST) columns and steel fiber reinforced concrete (SFRC) shear wall has aroused widespread attention in recent years. A new shear wall, named SFRC shear wall with CFST columns, is proposed in this paper, which makes use of CFST column and SFRC shear wall. Six SFRC shear wall with CFST columns specimens were tested under cyclic loading. The effects of test parameters including steel fiber volume fraction and concrete strength on the failure mode, strength, ductility, rigidity and dissipated energy of shear wall specimens were investigated. The results showed that all tested shear wall specimens exhibited a distinct shear failure mode. Steel fibers could effectively control the crack width and improve the distribution of cracks. The load carrying and energy dissipation capacities of specimens increased with the increase of steel fiber volume fraction and concrete strength, whilst the ductility of specimens increased with the increase of steel fiber volume fraction and the decrease of concrete strength.

• Corrosion Science and Technology
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• v.23 no.3
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• pp.195-202
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• 2024

A zinc mesh sacrificial anode cathodic protection method is recently being developed to protect the reinforced concrete structure in a marine environment. However, comprehensive information regarding the cathodic protection technology applied to reinforced concrete test specimens utilizing zinc mesh sacrificial anodes remains limited. Particularly, no research has investigated the effective range of sacrificial anode cathodic protection in a reinforced concrete structure regarding the transmission of protection current from zinc mesh sacrificial anode to the reinforced concrete structure, particularly concerning effects of temperature variations. This study examined the distribution of potential and current using a long single rebar and several segment reinforcing bars inside a horizontal beam. Vertical pile specimens were applied with a zinc mesh sacrificial anode to simulate concrete bridges or harbor structures. To check the effect of cathodic protection, cathodic protection potential and current of the reinforced concrete specimens were measured and 100 mV depolarization criterion test was performed. It was confirmed that effect of cathodic protection varied depending on resistivity and temperature. The cathodic protection test of pile specimens revealed that the maximum reachable range of cathodic protection current was 10 cm from the waterline as observed in the experiment.

• Computers and Concrete
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• v.21 no.1
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• pp.87-94
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• 2018

This paper presents the results of an experimental study to investigate the influences of high temperatures on the mechanical properties of concrete containing recycled fine aggregate. A total of 150 concrete prisms ($100{\times}100{\times}300mm$) and 150 concrete cubes ($100{\times}100{\times}100mm$) are cast and heated under five different temperatures ($20^{\circ}C$, $200^{\circ}C$, $400^{\circ}C$, $600^{\circ}C$, $800^{\circ}C$) for test. The results show that the mass loss, compressive strength, elastic modulus, splitting tensile strength of concrete specimens containing recycled fine aggregate decline significantly as the temperature rise. At the same temperature, the compressive strength, splitting tensile strength, elastic modulus of concrete specimens containing recycled coarse aggregate and recycled fine aggregate (RHC) is lower than that of concrete specimens containing natural coarse aggregate and recycled fine aggregate (RFC). The shape of stress-strain curves of concrete specimens at different temperatures is different, and the shape of that become flatter as the temperature rises. Normal concrete has better energy absorption capacity than concrete containing recycled fine aggregate.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.203-206
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• 2005

Reinforced concrete(RC) column-bent piers represent one of the popular piers used in highway bridges of Korea. Seismic performance of RC column-bent piers under bi-directional seismic loadings was experimentally investigated. Six column bent piers were constructed with two circular supporting columns which were made in 400 mm diameter and 2,000 mm height. Test parameters are different transverse reinforcement ratio and loading pattern. Three specimens were loaded with bi-directional lateral forces which were main cyclic loads in the longitudinal direction and sub-cyclic loads in the transverse direction. Other three specimens were loaded in the opposite way. Test results indicated that lateral strength and ductility of the latter specimens were bigger than those of the former specimens. Plastic hinge was formed with the spall of cover concrete and the fracture of the longitudinal reinforcing steels in the bottom part of two supporting columns for the former three specimens. Similar behavior was observed in the top and bottom parts of two supporting columns for the latter three specimens.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.1-4
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• 2004

RC column bent piers represent one of the most popular piers used in highway bridges. Seismic performance of reinforced concrete (RC) column-bent piers under bidirectional seismic loadings was experimentally investigated. Six column bent piers were constructed with two circular supporting columns. Test parameters are different transverse reinforcement and loading pattern. Three specimens were loaded with bidirectional lateral forces which were main cyclic loads in the longitudinal direction and subcyclic loads in the transverse direction. Other three specimens were loaded in the opposite way. Test results indicated that lateral strength and ductility of the latter specimens were bigger than those of the former specimens. Plastic hinge was formed with the spall of cover concrete and the fracture of the longitudinal reinforcing steels in the bottom part of two supporting columns for the former three specimens. Similar behavior was observed in the top and bottom parts of two supporting columns for the latter three specimens.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.301-305
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• 1994

Experimental research was carried out to investigate the confinement effect of concrete specimens confined by single spirals subjected to the concentric axial compressive load. Main variables are the compressive strength of concrete, the spacing of the spiral reinforcement and the yield strength of the spiral reinforcement. Axial stress-strain curves are reported.