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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korea Concrete Institute
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Journal DOI :
Korea Concrete Institute
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Volume & Issues
Volume 22, Issue 6 - Dec 2010
Volume 22, Issue 5 - Oct 2010
Volume 22, Issue 4 - Aug 2010
Volume 22, Issue 3 - Jun 2010
Volume 22, Issue 2 - Apr 2010
Volume 22, Issue 1 - Feb 2010
Selecting the target year
Behavior of FRP-Concrete Composite Decks with the Mechanical Connection
Kim, Sung-Tae ; Park, Sung-Yong ; Cho, Jeong-Rae ; Kim, Byung-Suk ; Cho, Keun-Hee ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 609~616
DOI : 10.4334/JKCI.2010.22.5.609
FRP-concrete composite deck, an innovative system, is composed of concrete in the top and FRP panel in the bottom. Bottom FRP panel can reduce self weight and improve workability. This system requires strong connection between FRP and concrete. Therefore coarse sand coating was previously applied on FRP to improve the bonding. In this study, concrete wedge method is newly introduced to enhance both vertical bond and fatigue performance. Three FRP-concrete composite deck specimens with the concrete wedges were manufactured, and static and fatigue tests were carried out. The results showed that the new FRP-concrete composite deck satisfied deflection and crack width limits set by the design codes. And the fatigue test showed that the composite deck was capable of two million load cycles under 50% of its static strength. Based on the results, it can be concluded that that this new system has outstanding mechanical and durability performance, and therefore, satisfactorily be used in designing FRP-concrete composite deck.
Effects of Expansive Admixture on the Mechanical Properties of Strain-Hardening Cement Composite (SHCC)
Lee, Young-Oh ; Yun, Hyun-Do ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 617~624
DOI : 10.4334/JKCI.2010.22.5.617
This paper reports on a comprehensive study on the mechanical properties of expansive fiber-reinforced strainhardening cement composite (SHCC) materials containing various replacement levels (0, 8, 10, 12 and 14%) of an expansive admixture and 1.5% polyethylene (PE) fibers volume fraction. A number of experimental tests were conducted to investigate shrinkage, compressive strength, flexural strength, and direct tension behavior. Test results show that as expected, the different replacement levels of an expansive admixture have an important effect on the evolution of the free shrinkage of SHCC with a rich mixture. At the volume fraction of 1.5%, PE fibers in normal SHCC reduce free shrinkage deformation by about 30% in comparison to plain mortar. The replacement of an expansive admixture in SHCC material has led the SHCC to a better initial cracking behavior. Enhanced cracking tendency improved mechanical properties of SHCC materials with rich mixtures. Note that an increase in the replacement of expansive admixture from 10% to 14% does not lead to a significant improvement for mechanical properties; this implies that the replacement of 10% expansive admixture is sufficient.
Application of Impact Resonance Test to the Determination of Elastic Modulus and Damping Ratio of Concrete
Jung, Beom-Seok ; Lee, Jae-Hoan ; Kweon, Gi-Chul ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 625~632
DOI : 10.4334/JKCI.2010.22.5.625
The moduli of concrete has been determined by various testing methods. The impact resonance (IR) method has been shown to be truly a simple nondestructive testing method which produces consistent results. It is possible to determine not only the modulus but also damping ratio from the IR test. However, the values of elastic modulus and damping ratio of concrete from the test is known to be affected by various test conditions including, specimen support condition, impact steel ball size and sampling rate. In this study, the optimum IR test conditions are suggested and validated experimentally. The test results showed that the recommended test conditions yielded a variation of resonant frequency within
and damping ratio
. In addition, the modulus from the IR test was comparable to that from a static test when the effect of strain amplitude was properly taken into account.
A Study on Properties of High Blaine Cement for Shotcrete
Kim, Jae-Young ; Kim, Teuk-Jun ; Lee, Min-Suk ; Ryoo, Dong-Woo ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 633~640
DOI : 10.4334/JKCI.2010.22.5.633
This study was performed to get basic information about properties of high blaine cement for shotcrete use. Particle size distribution, setting time and compressive strength test, analysis like as SEM, DSC thermal analysis, XRD was carried out to investigate principle properties of high blaine cement. Setting time of high blaine cement was shorter and compressive strength was higher than those of ordinary portland cement (OPC). Results of analysis showed early hydration products of high blaine cement is smaller and spread widely due to increased specific surface. From the SEM observation and analysis of DSC and XRD results, it was seen that the aluminates accelerators promoted calcium aluminium hydrates while the alkali free accelerators increased ettringite and monosulfates formation. Strength and setting time measurement of cement paste with aluminate accelerator is more effective than the alkali free accelerator in reducing the setting time and increasing early strength while alkali free accelerator is more effective in increasing the strength after 7 days.
Evaluation of Shrinkage Cracking Characteristics and Degree of Restraint for Ultra-High-Strength Concrete
Yoo, Doo-Yeol ; Min, Kyung-Hwan ; Yang, Jun-Mo ; Yoon, Young-Soo ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 641~650
DOI : 10.4334/JKCI.2010.22.5.641
The concrete cracking from the restrained stress caused by the shrinkage may play significant cause of deterioration of concrete structures by allowing the permeation of sulphate and chloride ions which in turn triggers corrosion of steel reinforcement. In particular, the cracking becomes more critical as water binder ratio (W/B) is reduced and concrete strength increases. Therefore, it needs to evaluate correctly the comprehensive shrinkage behavior of concrete with high strength: high-strength concrete (HSC), ultra-highstrength concrete (UHSC). The unrestrained shrinkage tests, however, cannot estimate the net shrinkage effectively which affects cracking after full development of strength and stiffness because it does not consider the degree of restraint, strength development, stress relaxation, and so on. Therefore, in this study, both free and restrained shrinkage tests with variables of W/B (W/B of 30, 25 and 16%) and admixtures (fly ash (FA) and granulated blast-furnace slag (BFS)) for HSC, very-high-strength concrete (VHSC) and UHSC were performed. The test results indicated that the autogenous shrinkage and total shrinkage at drying condition were reduced as W/B increased and FA, BFS were added, and the cracking behavior was suppressed as W/B increased and FA was added.
Slump and Mechanical Properties of Hybrid Steel-PVA Fiber Reinforced Concrete
Yang, Keun-Hyeok ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 651~658
DOI : 10.4334/JKCI.2010.22.5.651
Sixteen concrete mixes reinforced with hybrid steel-polybinyl alcohol (PVA) fibers and a control concrete mix with no fiber were tested in order to examine the effect of the micro and macro fibers on the slump and different mechanical properties of concrete. Main variables investigated were length and volume fraction of steel and PVA fibers. The measured mechanical properties of hybrid fiber reinforced concrete were analyzed using the fiber reinforcing index and compared with those recorded from monolithic steel or PVA fiber reinforced concrete. The initial slump of hybrid fiber reinforced concrete decreased with the increase of the aspect ratio and the volume fraction of fibers. In addition, splitting tensile strength, modui of rupture and elasticity, and flexural toughness index of concrete increased with the increase of the fiber reinforcement index. Modulus of rupture and flexural toughness index of hybrid fiber reinforced concrete were higher than those of monolithic fiber reinforced concrete, though the total volume fraction of hybrid fibers was lower than that of monolithic fiber. For enhancing the flexural toughness index of hybrid fiber reinforced concrete, using the steel fiber of 60 mm length was more effective than using the steel fibers combined with 60 mm and 30 mm lengths.
Capacity and Length of Compression Lap Splice in Unconfined Concrete of 100MPa and Less Compressive Strength
Chun, Sung-Chul ; Lee, Sung-Ho ; Oh, Bo-Hwan ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 659~666
DOI : 10.4334/JKCI.2010.22.5.659
Although the compression splice needs not be longer than the tension slice due to existence of end bearing, current design codes impose a longer compression lap splice than a tension lap splice in high strength concrete. Hence, new criteria for the compression lap splice including the effects of concrete strength need to be sought for economical design involving ultra-high strength concrete. An experimental study has been conducted with column specimens in concrete strength of 80 and 100 MPa. Test results show that the splice strength can be evaluated to be proportional to square root of compressive strength of concrete. Bar stress developed by end bearing is not affected by splice length and is expressed with a function of the square root of concrete strength. Mean value of stresses developed by end bearing is 16.5 square root of
. The stresses developed by bond in compression splices are nearly identical to those in tension splices and, therefore, strength increment of compression splices is attributed to end bearing only. From regression analysis of 58 tests, a design equation is proposed for compression lap splice in 40 to 100 MPa of compressive strength of concrete. By the proposed equation, the anomaly of lap lengths in tension and compression is got rid of. In addition, the equation has a reliability equivalent to those of the specified strengths of materials.
Response Analysis of RC Bridge Pier with Various Superstructure Mass under Near-Fault Ground Motion
Park, Chang-Kyu ; Chung, Young-Soo ; Lee, Dae-Hyung ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 667~673
DOI : 10.4334/JKCI.2010.22.5.667
The near fault ground motion (NFGM) is characterized by a single long period velocity pulse with large magnitude. NFGMs have been observed in recent strong earthquakes, Northridge (1994), Japan Kobe (1995), Turkey Izmit (1999), China Sichuan (2008), Haiti (2010) etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the far field ground motion (FFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this research is to investigate and analyze the seismic response of reinforced concrete bridge piers subjected to near-fault ground motions. The seismic performance of six RC bridge piers depending on three confinement steel ratios and three superstructure mass was investigated on the shaking table. From these experimental results, it was confirmed that the reduction of seismic performance was observed for test specimens with lower confinement steel ratio or more deck weight. The displacement ductility of RC bridge piers in terms of the stiffness degradation is proposed based on test results the shaking table.
Plastic Hinge Length of Reinforced Concrete Columns with Low Height-to-Width Ratio
Park, Jong-Wook ; Woo, Jae-Hyun ; Kim, Byung-Il ; Lee, Jung-Yoon ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 675~684
DOI : 10.4334/JKCI.2010.22.5.675
The reinforced concrete members are designed to fail in flexural to lead ductile fracture. In the building structures, the failure is typically imposed on beams to prevent damages in columns. However, progression of plastic collapse mechanism may ultimately develop, a plastic hinge at the bottem end of the first floor column, which then can be subjected to shear or bond finally due to large axial force and small shear span-to-depth ratio. In this study, 10 RC column specimens failed in shear after flexural yielding was investigated to determine the factors affecting the plastic hinge length. The findings of this study showed that the most effective factor affecting the plastic hinge length was an axial force. As an axial force increase, an axial strain and a ductility ratio were decreased obviously. The test also shows the observed plastic hinge length was about 0.8~1.2d and the this result has difference compared with forward research.
Shear and Bond Strength of Activated Hwangtoh Concrete Beam
Lee, Nam-Kon ; Park, Hong-Gun ; Hwang, Hye-Zoo ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 685~694
DOI : 10.4334/JKCI.2010.22.5.685
As a eco-friendly material, Hwangtoh (red clay) has been studied for complete or partial replacement of portland cement. Most of existing studies focused on the material properties of the Hwangtoh concrete including the compressive strength, drying shringkage, and creep. In the present study, the shear strength of the beams made with the Hwangtoh concrete was tested. Further, bond strength of tension re-bars embedded in the Hwangtoh concrete was tested. One of the concrete tested consisted of activated Hwangtoh replacing 20% of the cement. The other consisted 100% activated. Hwangtoh replacing all the cement. The beam specimens were tested under two point static loading. The test result showed that the shear strength of activated Hwangtoh concrete beams replacing 20% and 100% of cement was equivalent to that of the ordinary portland cement concrete beam. However, the bond strength of activated Hwangtoh concrete replacing 100% of the cement was less than that of the ordinary portland cement concrete.
Flexural Test on Composite Deck Slab Produced with Extruded ECC Panel
Cho, Chang-Geun ; Han, Byung-Chan ; Lee, Jong-Han ; Kim, Yun-Yong ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 695~702
DOI : 10.4334/JKCI.2010.22.5.695
This paper presents a reinforced concrete composite deck slab system newly developed using a high ductile ECC extrusion panel. In the construction practice, the cracking of reinforced concrete slab often becomes a problem especially in parking garages, underground structures, and buildings. The ECC panel manufactured by extrusion process as a precast product has not only a high-quality in control of cracking but also a merit in applying the construction of concrete slab because the use of ECC panel can realize a formless or half-precast construction with cast-in-place concrete. In the newly developed deck slab system, the ECC extrusion panel is located in the bottom of slab with the thickness of 10 mm, reinforcements are assembled and located on the ECC panel, and finally the topping concrete is placed in the field. In order to evaluate the newly developed slab system, experimental works by four point bending test are conducted to compare with the conventional reinforced concrete slab system. From experiment, the developed deck slab system using a ECC panel gives many improved performances both in control of bending cracking and in load-carrying capacities of slabs.
An Experimental Study on the Shear Behavior of Reinforced Concrete Beams Strengthened by Slit Type Steel Plates with Anchor Bolt
Lee, Choon-Ho ; Jeong, Woo-Dong ; Shim, Jong-Seok ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 703~710
DOI : 10.4334/JKCI.2010.22.5.703
Reinforced concrete beams of existing structure often encounter insufficient shear problems for various reasons. Application of steel plates is one of widely used methods for shear strengthening of reinforced concrete beams that are insufficient of shear capacity. This study presents test results on strengthening shear deficient RC beams by external bonding of vertical and diagonal slit type steel plates with anchor bolt. Test parameters are width, interval, angle and length of slits with anchor bolt. The purpose was to evaluate the failure modes and shear capacities for RC beams strengthened by various slit type steel plates with anchor bolt. The results showed that the slit type steel plate specimens strengthened by adhesive bonding and bolting failed in shear fracture modes at maximum load. Flexural crack first occurred on the tension face of beam and then inclined cracks occurred on the shear span. Finally, slit type steel plates strengthened by adhesive bonding and fastening bolts managed to delay abrupt debonding and didn`t detach fully from main body of RC beam.
Evaluation of the Maximum Yield Strength of Steel Stirrups and Shear Behavior of RC Beams
Lee, Jung-Yoon ; Choi, Im-Jun ; Kang, Ji-Eun ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 711~718
DOI : 10.4334/JKCI.2010.22.5.711
The requirement of the maximum yield strength of shear reinforcement in the KCI-07 code is quite different to those in the ACI-08 code, EC2-02, CSA-04, and JSCE-04 codes. Eighteen RC beams having high strength shear reinforcement were tested. Test results indicated that even if the yield strength of shear reinforcement in beams was much greater than the maximum yield strength required by the KCI-07 design code, the shear reinforcement of these beams reached their yield strains. Furthermore, the shear strengths of tested beams increased almost linearly with the increase of the amount of shear reinforcement. In addition, larger numbers of diagonal cracks developed in the web of the beam having greater yield strength than the beams having lower yield strength of shear reinforcement. The maximum crack width of the beam having high strength shear reinforcement was approximately the same to the crack with of the beam having normal strength shear reinforcement.
Impact Resistance Evaluation of RC Beams Strengthened with Carbon FRP Sheet and Steel Fiber
Cho, Seong-Hun ; Min, Kyung-Hwan ; Kim, Yun-Ji ; Yoon, Young-Soo ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 719~725
DOI : 10.4334/JKCI.2010.22.5.719
The analysis and experimental program of reinforced concrete (RC) structures for resistance against such extreme loads as earthquake, blast, and impact have been carried by many researchers and designers. Under the extreme loads, a large amount of energy is suddenly exerted to the structure, hence if the structure fails to absorb the impact energy, catastrophic collapse may occur. To prevent catastrophic collapse of structures, reinforced concrete must have adeguate toughness or it needs to be strengthened. The FRP strengthening method and SFRC are studied widely in resistance of impact load because of their high energy absorption capacity. In this study, drop weight impact tests were implemented to evaluate the impact resistance of SFRC and FRP strengthened RC beam while the total steel fiber volume fractions was fixed at 0.75% carbon FRP flexural strengthened RC beams. Futhermore, to prevent the shear-plug cracks when the impact load strikes the beams, additional FRP shear strengthening method are applied. The experimental, results showed that the FRP strengthened RC SFRC beams has high resistance of shear-plug cracks and crack width and SFRC has high resistance of concrete spalling failure compared to normal RC beams. The FRP flexural and shear strengthening RC beams has weakness in the spalling failure because the impact load concentrated the concrete face which is not strengthened with FRP sheets.
Mechanical Properties of Strain Hardening Cement-Based Composite (SHCC) with Recycled Materials
Kim, Sun-Woo ; Cha, Jun-Ho ; Kim, Yun-Yong ; Yun, Hyun-Do ;
Journal of the Korea Concrete Institute, volume 22, issue 5, 2010, Pages 727~736
DOI : 10.4334/JKCI.2010.22.5.727
This paper describes results of an preliminary study to produce strain hardening cement-based composites (SHCCs)with consideration of sustainability for infrastructure applications. The aims of this study are to evaluate the influence of recycled materials on the mechanical characteristics of SHCCs, such as compressive, four-point bending, and direct tensile behaviors, and to give basic data for constitutive model for analyzing and designing infra structures with SHCCs. In this study, silica sand, cement, and PVA fibers, were partially replaced with recycled sand, fly-ash, and FET fibers in the mixture of SHCCs, respectively. Test results indicated that fly-ash could improve both bending and direct tensile performance of SHCCs due to increasing chemical bond strength at the interface between PVA fibers and cement matrices. However, SHCCs replaced with PET fibers showed much lower performance in bending and direct tensile tests due to originally low mechanical properties of own fibers, although compressive behavior is similar to PVA2.0 specimen. Also, it was noted that the recycled sand would increase elastic modulus of SHCCs due to larger grain size compared to silica sand. Based on pre-set target value to maintain the performance of SHCCs, it was concluded that the replacement ratio below 20% of fly-ash or below 50% of recycled sands would be desirable for creating sustainable SHCCs.