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Title |
An Experimental Study on the Required Performances of Roof Concrete Placed in the In-ground LNG Storage Tank
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Keywords |
지붕 기울기 ; 프리스트레싱 ; air support ; 구속수비 ; 단열온도 상승양 roof slope ; pre-stressing ; air support ; confined water ratio ; adiabatic temperature raising test |
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Abstract |
This study is to derive from the required performances and the optimum mix proportion of the roof concrete placed in the in-ground LNG storage tank with a capacity of 200000 m3, and propose the actual data for site concrete work. The concrete placing work without sliding and segregation in the fresh concrete condition is very important because the slope of domed roof is varied in the large range by its curvature. Also the control of hydration heat and the strength development at test ages are classified with massive section about 1.4 m thick and considered to the pre-stressing work and removal of air support after concrete placing work. Considering above condition, slump range is selected 100±25 mm under the slope 20° and 150±25 mm over the slope 20° s until 60 minutes of elapsed time. Also, the roof concrete is satisfied with compressive strength range including design strength at 91 days (30 MPa), pre-stressing work at 7 days (10 MPa), air support removal work at 21 days (14 MPa). Replacement ratio of limestone powder is determined by confined water ratio test and main design factors include water-cement ratio (W/C), sand-aggregate ratio and dosage of admixture. As test results, the optimum mix proportion of the roof concrete used low heat cement is as followings. 1) Replacement ratio of limestone powder 25% by confined water ratio test 2) Water-cement ratio 57.8% 3) Sand-aggregate ratio 42.0%. Also, test results for the adiabatic temperature rising test is satisfied with its criteria and shown the lower value compared to preceding storage tank (TK-13, 14). These required performances and the optimum mix proportion is to apply the actual construction work.
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