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Title |
Effect of Damage Caused by Extracting Cores on Compressive Strength of Concrete
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Authors |
조선두(Seon Doo Jo) ; 권승희(Seung Hee Kwon) ; 김철영(Chul Young Kim) ; 박영석(Young Suk Park) |
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DOI |
https://doi.org/10.4334/JKCI.2019.31.4.397 |
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Keywords |
코어; 손상; 압축강도; 보정계수 core; damage; compressive strength; correction factor |
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Abstract |
Since concrete core is damaged by the high speed rotation of the drill bit when it is taken from the structure, the bond between the aggregate and the surrounding matrix is weakened near the cutting surface of core. The compressive strength of the core may be undervalued compared to the concrete strength of actual structure due to such damage. The purpose of this study was to quantitatively evaluate the effect of damage caused by extracting cores and to find a method to convert core strength to strength of non-damaged concrete. Three mix proportions of concrete were used to make structures for coring, standard curing specimens, and specimens cured under the same conditions as the structures. At age 28, 90, and 180 days of concrete, the compressive strength tests were performed on each specimens of two size 100×200 mm and 150×300 mm. A total of 324 specimens were tested with 108 cores, 108 standard curing specimens and 108 in-suite curing specimens. Through the comparison of the average compressive strengths of the specimens under the same conditions (water-binder ratio, size and type of specimens), the effect of core damage on the core size was quantitatively analyzed. The compressive strength of 100×200 mm and 150×300 mm cores was reduced due to effect of core damage by 11 % and 4 %, respectively. In other words, the smaller the cross section of the core, the greater the effect of core damage. As the compressive strength of concrete increased, the core damage also increased. From the results of this study, it is possible to estimate the compressive strength of the non-damaged concrete from the core.
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