This study is to examine experimentally on the engineering properties of fiber reinforced concrete using kenaf(KN) fiber and another organic fibers for comparing test, and propose the usable method of KN fiber as an natural fiber in the concrete industry. It is to select 4 contents(0, 0.3, 0.6 and 0.9 ㎏/㎥) of KN fiber and 4 organic fibers (Jute, Cellulose, Polypropylene and Nylon). For this study, it is to perform various tests including slump, air content, plastic and drying shrinkage, flexural and tensile strength, carbonation depth for the fiber reinforced concrete according to contents of KN fiber and 4 organic fibers. The results of this study are as follows : In case of KN fiber contents 0.6 ㎏/㎥, it shows the effective results from increasing concrete strength including flexural and tensile, from decreasing plastic and drying shrinkage, carbonation depth. Also KN fiber is confirmed having excellent performances by comparing with test results of another organic fibers as same contents 0.6 ㎏/㎥. Therefore, considering concrete test results, cost and environment, KN fiber is proposed as the optimum contents in the range of 0.6 ㎏/㎥ and an effective fiber materials, and needs to keep up these study on the site application.

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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 m 3 , 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.

The purpose of this study is to investigate experimentally the variation factors range having influence on the rheological properties of the combined self-compacting concrete according to materials quality, weighting error and site conditions. Two types cement (blast-furnace slag cement and belite cement), lime stone powder as binder and the optimum mix proportions in the preceded study are selected for this study. Also, variations for sensitivity test are as followings; (1) Concrete temperature 3 cases (2) Surface moisture of sand 5cases (3) Fineness modulus of sand 5cases (4) Specific surface of lime stone powder 3cases (5) Dosage of chemical admixture 5cases. Slump flow (650±50 mm), 500 mm reaching time ((7±3 sec), V-type flowing time (15±5 sec) and U-box height (min. 300 mm) are tested for sensitivity. As test results, the variations range for quality control are as followings. (1) Concrete temperature; 10∼20℃(below 30℃) (2) Surface moisture of sand; base±0.6% (3) Fineness modulus of sand; 2.6±0.2 (4) Dosage of chemical admixture; base±0.2% (5) Specific surface of lime stone powder 6000 cm 2 /g. Compared with two types cement including based belite cement (binary type) and based slag cement (ternary type), the combined self-compacting concrete used belite cement type is most stable in the quality control because of high contents for lime stone powder and C 2 S. It is to propose a control scheme of the combined self-compacting concrete in the actual construction work.

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