• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.9
• /
• pp.4542-4551
• /
• 2013

Recently, much attention has focused on the study of eco-friendly concrete using recycled by-products for protecting marine ecosystem and durability of concrete exposed to marine condition. This study evaluated the durabilities of 4 different type of concrete mixtures(Control, Marine, Porous, New slag) with the seawater resistance by marine environment exposure experiment and freeze-thaw resistance, resistance to chloride ion penetration considering severe deterioration environment. In this study, we conducted seawater resistance using compressive strength according to the age(7/28/56 days) of specimen and curing conditions(standard(fresh water), tidal, immersion, artificial seawater). The results show that compressive strength of concrete exposed to marine environment exposure condition was lower than those of the standard curing condition. Also, compressive strength of New slag using eco-friendly materials for protecting marine ecosystem was lower than those of other concretes, there is need to improve the performance of New slag. The results for freeze-thaw resistance showed that all mixtures have excellent, but the Porous and New slag were lower than others. Also, the more improved resistance to chloride ion penetration than those of the Marine was measured in the New slag regardless of curing condition.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.34 no.2
• /
• pp.66-72
• /
• 2024

In this study, the applicability of CCMs (Carbondioxide conversion capture materials) manufactured by reacting carbon dioxide gas with DG (Desulfurization gypsum) as a cement substitute for secondary concrete products were evaluated and the basic physical properties of CCMs-mixed mortar and concrete specimens were measured to derive the optimal mixing ratio. The main chemical oxides of CCMs were CaO and SO₃, and the main crystalline phases were CaSO₄·2H₂O, Ca(OH)₂, CaCO₃, and CaSO₄. In addition, by the results of particle size analysis and heavy metal measurement, the applicability of CCMs as a cement substitute for secondary concrete products was confirmed. As a result of measuring the strength behavior using mortar and concrete specimens with CCMs, the compressive and flexural strength decreased as the mix ratio of CCMs increased, but requirements by the standards for interlocking blocks and retaining wall blocks, which are target products in this study, were satisfied up to the optimal mixing ratio of 10 wt.% substitution. Therefore, its applicability as a cement substitute for secondary concrete products was confirmed.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.18 no.1
• /
• pp.45-51
• /
• 2014

This paper investigates experimentally the confinement effect on concrete. For this purpose, outside lateral reinforcement members made of stainless steel and GFRP were employed. Then, uniaxial compressive tests on concrete cylinders incorporating the members were conducted. A total of 30 cylinder specimens, specifically, 6 unconfined specimens, 12 specimens confined by stainless steel and 12 specimens confined by GFRP, were fabricated. The failure patterns of both unconfined and confined specimens were assessed and discussed based on experimental results. The results proved that the maximum stress and corresponding strains of the cylinders confined using the proposed hoops are increased in comparison with those of the unconfined. This supports that the current work can be used for retrofitting concrete members and structures and thus may lead to increased stability of such structures.

• Journal of the Korea Institute of Building Construction
• /
• v.2 no.2
• /
• pp.129-134
• /
• 2002

The strength and durability of concrete are affected by various factors such as the quality of material, mixing ratio, construction, the method of cure, time elapsed. the condition of test and etc., it is very difficult to pre-estimate the strength of concrete with the use of experimental specimen. The domestic standard of specimen cylindrical type and its sizes are both l0cm$\times$20cm and 15cm$\times$30cm, which are prescribed in KS F2405, and the loading speed is prescribed to test with 2~3kgf/$\textrm{cm}^2$ per second. The loading speed should have great effect on the compressive strength, but in reality in the construction site sometimes the loading speed is applied so dubiously that the value of the compressive strength can be unreliable. And the cross sectional area of a specimen should be level and smooth, otherwise it can be broken at a lower stress than the real strength through the eccentric or intensive working of the load. Capping should be carried out in order to measure the strength correctly. And used for capping are various materials such as capping compound, cement glue, plaster, mechanical grinding and etc. In this study, therefore, I have carried out an experiment on the relationship among the loading speed, the ratio of height to diameter of specimen, the method of capping, and the compressive strength, for the efficient quality control of concrete structures. So this study has been purposed to provide some basic data that can be used effectively at construction sites.

• International Journal of Highway Engineering
• /
• v.1 no.1
• /
• pp.85-96
• /
• 1999

This study was performed to evaluate performance of polymer-modified asphalt mixtures and specially designed reinforcement techniques against reflection cracking of the asphalt pavement overlay. Selected polymers were used for asphalt modification and polyester fiber, a polypropylene film (vinyl) and a grid were used for mixture reinforcement. Using the asphalt mixture with optimum asphalt content, a slab was made and cut into two pieces of specimen. A layer of grid or vinyl was placed at the bottom of specimen to strengthen the pavement layer against crack. A repeated loading was applied to the asphalt mixture specimen which is Placed on a cement concrete with a pseudo-crack. Crack propagation under repeated loading was monitored and effectiveness of the devised crack retarding techniques was evaluated. From the test results. a significant retardation of mode I crack progress was monitored from some of the modified and reinforced asphalt mixtures.

• The Journal of the Korea Contents Association
• /
• v.18 no.11
• /
• pp.455-461
• /
• 2018

This paper presents experimental investigations about flexural strength and durability of reinforced concrete beams repaired using ductile fiber reinforced cementitious composite (DFRCC) and carbon fiber sheet through freezing and thawing test. Total 14 RC beams of $100{\times}100{\times}400mm$ size were tested by 3-point bending and freezing and thawing test by KS F 2456. The beams were reinforced using 3D10 steels on both the tensile and compressive sides, and repaired on 3 sides expect on top cycle. Test results showed that the beams repaired using fiber carbon sheet revealed about 15% higher values of flexural strength compared than the cases of DFRCC motar. On the other hand, the results did not showed meaningful differences in the aspect of durability. For further research, consideration of the steel interference effect and real old specimens such as taken from real deteriorated structures are needed to be tested after repairing with DFRCC and carbon fiber sheet.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.6
• /
• pp.197-205
• /
• 2018

Recently, remodeling is increasing due to aging of buildings. Therefore, the importance of quality control of structures has been raised, and interest in safety diagnosis and evaluation of structures has been increasing. In order to accurately diagnose old buildings, a diagnostic evaluation technique is needed to evaluate the defects of structures in advance. In addition, as the safety diagnostic criteria for reconstruction are improved and the weight of structural safety is increased, researches on safety diagnosis techniques of structures that are faster and more reliable are needed. In this study, we tried to estimate the compressive strength by examining the correlation between ultrasonic pulse velocity and compressive strength of a 1 story structure consisting of vertical and horizontal members of reinforced concrete using ultrasonic pulse velocity method, which is one of the nondestructive testing methods. The purpose of this study is to examine the applicability in the field. As a result, the estimated average error rate of the compressive strength of the structure using the ultrasonic pulse velocity method was 28.7%, which confirmed the applicability in the field. However, in order to increase the accuracy of the estimation, the necessity of the reliable diagnostic method using the composite nondestructive testing method was confirmed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.5
• /
• pp.54-59
• /
• 2020

Coarse aggregate is produced in various ways depending on the location and production method. Currently, the construction industry is in need of a stable supply of coarse aggregate and a way to secure standard quality. The purpose of this study is to examine whether the use of coarse aggregate in 3D printing can help solve this problem. ABS filament was selected for use in 3D printing. CATIA was used for the design of the coarse aggregate, and CUBICON Single Plus was used for the production. Six specimens were produced and cured in water for 28 days. Three of them were made with AE agent, and three were made without it. A compressive strength test confirmed that when the AE agent was used, the compressive strength was greater than the lightweight concrete design criterion specified in the concrete standard specification. This suggests that coarse aggregate produced by a 3D printer may be used for lightweight concrete. A mass production system using this method could help to solve the problems facing the construction industry, such as stable supply and demand for coarse aggregate and securing standard quality.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.12
• /
• pp.75-84
• /
• 2008

Recycled-aggregate porous concrete pile (RAPP) which forms a composite ground is one of new ground improvement techniques. In this paper, triaxial compression tests are carried out to investigate the shear strength characteristics of RAPP-Clay composite samples. The main purpose of the tests was to investigate the effects of area replacement ratio ($15%{\sim}100%$) on behaviors of RAPP-Clay samples during shearing. Also, triaxial compression tests using Sand-Clay composite samples were performed to compare with the behaviors of RAPP-Clay samples. The test results showed that the friction angle and cohesion of the RAPP-Clay composite were $18{\sim}34$ degree and $557.0{\sim}588.0\;kPa$, respectively, whereas those of sand-clay composite samples were 26~35 degree of friction angel and $4.0{\sim}18.0\;kPa$.

• Journal of the Korea Concrete Institute
• /
• v.15 no.5
• /
• pp.670-678
• /
• 2003

Recently, since industrial waste and life waste leaped into a pollution source, the building material used now a days is striking the limit. The purpose of this paper is to investigate an application of recycled coal ash using non-sintering method in the construction field. Accordingly, compressive strength, elastic modulus and drying shrinkage were experimentally studied for hardened coal ash using the non-sintering method. Also, Lineweaver and Burk method were applied to the regression analysis of drying shrinkage for the proposal equation. Elastic modulus, compressive strength of material become the basis properties of structural design. And these properties by age for hardened coal ash are important because of change by pozzolan reaction. This hardened coal ash is weak for tensile stress like that of concrete. And drying shrinkage is very important factor to make huge tensile force in early age. In the results, although some differences were shown when comparing coal ash with mortar or concrete, the application as a building material turned out to be possible if further researches were carried out. And the shrinkage characteristic of hardened coal-ash reveals to be similar to that of moderate heat cement.