• Cement Symposium
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• s.36
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• pp.170-176
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• 2009

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.41-44
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• 2008

The purposes of this study are to estimate thestrength of concrete and quantify the deterioration of concrete by a unique X-ray technique with a contrast medium. In order to estimate the strength of concrete, specimens with different water-cement ratios were fabricated using non-air-entrained concrete, air-entrained concrete and mortar to determine the relationship between their compressive strength and the transit dose obtained by the X-ray technique. Also, an experiment to quantify deterioration was carried out on specimens that were subjected to freezing and thawing action to different levels of dynamic elastic modulus. As a result of this experiment, estimation of the strength and relative dynamic elastic modulus of deteriorated mortar, concrete and air-entrained concrete was found feasible by measuring the transit dose by the X-ray technique.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.19-26
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• 2016

Floor damping materials used in floating floor system to diminish the floor noise have been made with low density and dynamic stiffness. Owing to this low density and dynamic stiffness, the deflection in these materials under long-term loading and cracking of the floor finishing mortar in the floating floor system may occur. This paper presents the results of long-term loading effects on the deflection of different types of floor damping materials. The experimental program involved the long-term loading tests for 490 days loading period on sixteen specimens. Specimens were classified as DM1(Damping Materials) to DM8, depending upon the four main parameters; types, bottom shapes and densities of floor damping materials and amount of loading. Results indicated that the long-term deflection of all specimens of damping materials remained unchanged after 200 days at all loading amounts, except the specimens made up of Polystrene, in which long-term deflection remained unchanged after 160 days at 250 N load and 100 days 500 N load. In this paper, two types of correlation expressions were shown in the deflection range prior to the range where deflection remained constant; two analyses by ISO 20392 and linear regression. In comparison of two analyses and experimental results on the difference of deflection of 16 specimens, the difference of deflection was below 0.4 mm in those analyses in case of that total deflection was below 10 mm. Restrictively, it was judged that the analysis for the deflection of specimens made up of Polystrene is more appropriate using ISO 20392.

• The Journal of Engineering Geology
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• v.33 no.4
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• pp.599-609
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• 2023

In the seismic retrofitting of harbor breakwaters in Korea, the recovery rate is often uncertain due to site conditions and site conditions, and problems continue to arise. Therefore, in this study, we analyzed the recovery rate and compressive strength of the improved material through drilling survey by grouting confirmation method after applying low-fluidity mortar injection method, and furthermore, we checked the elastic modulus by downhole test and tomography to confirm the reinforcement effect of soft ground after ground improvement. The experimental results showed that the average shear wave velocity of the ground increased from 229 m/s to 288 m/s in BH-1 and BH-3 boreholes to a depth of 28.0 m, and the average shear wave velocity of the ground to a depth of 30.0 m tended to increase from 224 m/s to 282 m/s in the downhole test. This is believed to be a result of the increased stiffness of the ground after reinforcement. The results of the tomographic survey showed that the Vs of the soft ground of the sample at Site 1 increased from 113 m/s to 214 m/s, and the Vs of the sample at Site 2 increased from 120 m/s to 224 m/s. This shows that the stiffness of the ground after seismic reinforcement is reinforced with hard soil, as the Vs value satisfies 180 m/s to 360 m/s in the classification of rock quality according to shear wave velocity.