• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.493-598
• /
• 2000

In the rail facilities, the rail track consists of rail, tie, fastening, accessories and bed. The rail track is largely divided into Ballast Bed Track (BBT) and Concrete Bed Track (CBT) according to the type of bed. In this thesis, among Concrete Bed Track, slab track, which is used for the Japanese high speed railway, is a target of this study. Dynamic analysis by using finite element method are performed where moving train load is periodic function. Then through parametric study, some conclusions are obtained as follows. Cement Asphalt Mortar (CAM) affects contrary mechanical behavior to rail and slab greatly. Therefore, change of CAM spring coefficient should be handled with care. For slab thickness, thin slab is more profitable to reduction of vibration of rail than thick one but mechanical capacity of slab is deteriorated. Improved structural type is proposed, then structural analysis is performed for this one. This type is effective to reduction of vibration of railway system.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.10b
• /
• pp.867-870
• /
• 1998

The reinforced concrete structures have been deteriorated for various causes since it serviced for the long time. If we have to service concrete structure long time, we must repair it using appropriate methods and materials. But the data which evaluate the repair material has not been sufficient. So, the aim of this research is to estimate properties of repair materials and to acquire the data which apply to the concrete structures in field. To accomplish this objective, we have made experiment on compressive strength, bond strength, the coefficient of thermal expansion and setting time. Generally, compressive strength and bond strength are favorable but some products are unfavorable under wet curing. Setting time was faster than ordinary portland cement mortar except one material.

• Computers and Concrete
• /
• v.30 no.6
• /
• pp.409-419
• /
• 2022

The purpose of this study is to examine the effectiveness of biological repairing mortars on restoring the structural performance of a sewage culvert deteriorated by sulfate attack. The biological mortars were developed for protecting concrete structures exposed to sulfate attack based on the block membrane action of the bacterial glycocalyx. The diffusion coefficient of sulfate ions in the biological mortars was determined from the natural diffusion cell tests. The effect of sulfate-attack-induced concrete deterioration on the structural performance of culverts was examined by using the moment-curvature relationship predicted based on the nonlinear section lamina approach considering the sulfuric-acid-induced degradation of the structure. Typical analytical assessments showed that biological mortars were quite effective in increasing the sulfate-resistant service life of sewage culverts.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.5 no.2
• /
• pp.152-159
• /
• 2017

In marine environment, the durability of concrete and reinforcing steel is known to be deteriorate by the permeation of chloride ion into concrete. In this study the conductive photocatalyst was used to improve the seawater corrosion resistance of the concrete and steel. Mortar and concrete samples were prepared by mixing with various amounts of conductive active carbon and photocatalytic powder($TiO_2$). The compressive strength of concrete was decreased with the increase of the amount of conductive carbon powders. The samples containing conductive carbon and photocatalytic powders showed the superior seawater corrosion resistance compared with the ordinary sample, which was verified by XRF analysis showing the concentration of chloride ion($Cl^-$) of mortars and concretes. The inhibitive effect of photocatalyst against chloride attack was discussed with the diffusion coefficient of chloride ion into mortar and concrete.

• Journal of the Korea Concrete Institute
• /
• v.15 no.4
• /
• pp.522-528
• /
• 2003

Concrete has been considered as a semi-permanent structural material, because its excellent durability. However, such high durable structure is often attacked by some environmental condition such as chloride diffusion, carbonation and so on. In order to prevent the deterioration behaviors of concrete structures. We estimated durability of concrete when used surface treatment system and coatings by new type inorganic coating materials. Base on the results of chloride ion's diffusion test, the coated cement mortar had smaller transmitted quantity.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.1
• /
• pp.288-295
• /
• 2011

The objective of this study is to develop a proper absorbent-pervious pavement. By using single graded aggregates and SAP, permeability and water absorbability of absorbent-pervious pavement are improved, and also temperature reducing effect is found out. And several tests such as compressive and flexural strength tests, and permeability/water absorption tests of absorbent-pervious pavement are carried out to verify these kind of effects. The compressive and flexural strengths are increased according to decrease of single graded aggregate size, and increase of SAP content. And the volume of water retention and absorbability are increased according to the increase of SAP content and these are also increased in small size of single graded aggregate. And about $20^{\circ}C$ of difference is observed in surface temperature between normal asphalt pavement and absorbent-pervious pavement.

• Smart Structures and Systems
• /
• v.18 no.3
• /
• pp.405-423
• /
• 2016

In this study, the feasibility of using telecommunication single-mode optical fiber (SMF) as a distributed fiber optic strain and crack sensor was evaluated in concrete pavement monitoring. Tensile tests on various sensors indicated that the $SMF-28e^+$ fiber revealed linear elastic behavior to rupture at approximately 26 N load and 2.6% strain. Six full-scale concrete panels were prepared and tested under truck and three-point loads to quantify the performance of sensors with pulse pre-pump Brillouin optical time domain analysis (PPP-BOTDA). The sensors were protected by precast mortar from brutal action during concrete casting. Once air-cured for 2 hours after initial setting, half a mortar cylinder of 12 mm in diameter ensured that the protected sensors remained functional during and after concrete casting. The strains measured from PPP-BOTDA with a sensitivity coefficient of $5.43{\times}10^{-5}GHz/{\mu}{\varepsilon}$ were validated locally by commercial fiber Bragg grating (FBG) sensors. Unlike the point FBG sensors, the distributed PPP-BOTDA sensors can be utilized to effectively locate multiple cracks. Depending on their layout, the distributed sensors can provide one- or two-dimensional strain fields in pavement panels. The width of both micro and major cracks can be linearly related to the peak strain directly measured with the distributed fiber optic sensor.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.10 no.1
• /
• pp.80-91
• /
• 2022

This study is to provide an prediction model of setting time of super retarding mortar based on equivalent age method under various super retarding agent contents, curing temperature, and water-binder ratio (W/B). An equation for predicting setting time using maturity was proposed. Test results indicated that the setting time can be predicted by determining the curing temperature, W/B, and super retarding agent contents and substituting it into the equation proposed in this study. The coefficient of determination of the equation is 0.9 or more, and the reliability was confirmed through the F-test. Finally, using the equation proposed in this paper, reasonable quality control is possible regarding the setting of super retarding concrete in practice.

• International Journal of Highway Engineering
• /
• v.17 no.1
• /
• pp.7-16
• /
• 2015

PURPOSES : This study was performed to determine a systematic approach for measuring the coefficient of thermal expansion (COTE) of concrete specimens. This approach includes the initial calibration of measurement equipment. Test variables include coarse aggregate types such as natural aggregate, job-site produced recycled concrete aggregate, and recycled aggregate processed from an intermediate waste treatment company. METHODS : First, two cylindrical SUS-304 specimens with a known COTE value of $17.3{\times}10^{-6}m/m/^{\circ}C$. were used as reference specimens for the calibration of each measurement system. The well-known AASHTO TP-60 COTE apparatus for concrete measurement was utilized in this study. Four different measurement apparatuses were used with each LVDT installed and a calibration value was determined using each measurement apparatus. RESULTS : In the initial experimental stage, calibration values for each measurement apparatus were assumed to be almost identical. However, using the SUS-304 samples as a reference, the calibration values for the four different measurement apparatuses were found to range from 3.49 to $8.86{\times}10^{-6}m/m/^{\circ}C$. Using different adjusted values for each measurement apparatuses, COTE values for the three different concrete specimens were obtained. The COTE value of concrete made with natural coarse aggregate was $9.91{\times}10^{-6}m/m/^{\circ}C$, that of job-site produced recycled coarse aggregate was $10.45{\times}10^{-6}m/m/^{\circ}C$, and that of recycled aggregate processed from the intermediate waste treatment company was $10.82{\times}10^{-6}m/m/^{\circ}C$. CONCLUSIONS : We observed that the COTE value of concrete made from recycled concrete aggregates (RCA) was higher than that of concrete made from natural coarse aggregate. This difference is due to the fact that the total volumetric mortar proportion in the RCA mix is higher than that in the concrete mix made with natural coarse aggregate.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.2A
• /
• pp.171-179
• /
• 2009

The porosity in porous media like concrete can be considered as a durability index since it may be a routine for the intrusion of harmful ions and room for the keeping moisture. Recently, modeling and analysis techniques for deterioration are provided based on the pore structure with the significance of durability and the relationship between porosity and durability characteristics is an important issue. In this paper, a series of mortar samples with five water to cement ratios are prepared and tests for durability performance are carried out including porosity measurement. The durability test covers those for compressive strength, air permeability, chloride diffusion coefficient, absorption, and moisture diffusion coefficient. They are compared with water to cement ratios and porosity. From the normalized data, when porosity increases to 1.45 times, air permeability, chloride diffusion coefficient, absorption, and moisture diffusion coefficient decrease to 2.3 times, 2.1 times, 5.5 times and 3.7 times, respectively, while compressive strength decreases to 0.6 times. It was evaluated that these are linearly changed with porosity showing high corelation factors. Additionally, intended durability performances are established from the test results and literature studies and a porosity for durable concrete is proposed based on them.