1993 Fiscal Year Final Research Report Summary
Effects of Curing of Winter Concreting on the Freeze-Thaw Resistance of Concrete
| Project/Area Number |
04650417
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
コンクリート工学・土木材料・施工
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| Research Institution | University of Tsukuba |
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Principal Investigator |
YAMAMOTO Yasuhiko University of Tsukuba, Inst.of Eng.Mechanics, Professor, 構造工学系, 教授 (40061220)
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| Project Period (FY) |
1992 – 1993
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| Keywords | cold weather concreting / frost damage / water content / slow freeze-thaw test / freeze-thaw durability / curing / compressive strength / water-cement ratio |
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| Research Abstract |
The followings are main findings in this research.
(1) The procedure of allowing moderate water-evaporation from concrete for 1 or 2 days immediately after placing of concrete, and, then, providing sufficient moist curing is an effective and practical way of remakably increasing the freeze-thaw durability of concrete without impairing its strength development.
(2) The required compressive strength of concrete at the end of curing may be decreased as the water-cement ratio is decreased.
(3) Even within the range of usual water-cement ratio, say, 45 to 65 %, the required periods of curing in cold weather concreting can be greatly shortened by lowering the ratio.
(4) The inner deteriorations caused by an action of slow freezethaw cycles such as that under the natural weather conditions are considered to be isolated and minute ones, which can be remedied easily by the hydaration products of cement if a sufficient amount of unhydrated cement remains in the concrete.
(5) Lowering water-cement ratio enhances the benefit of improving the freeze-thaw durability of concrete through such effects as the increased capability of remedying inner frost damge, increased resistance against deteriorating actions due to atrength increse after curing, decreased degree of water-saturation due to the continued cement hydration after curing.
(6) The freeze-thaw resistance of fully saturated concrete with water is dependent entirely on its compressive strength, and satisfactory freeze-thaw durability can be obtainted only when its compressive exceeds about 230 kgf/cm^2.
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