材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
高強度コンクリートの諸特性と耐久性について
近藤 時夫小柳 洽児玉 和巳
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1975 年 24 巻 260 号 p. 432-440

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Experimental studies were conducted on the strength and deformation properties and durability of high strength concrete having more than 800kg/cm2 strength, which was fabricated by five different mixing proportions and cured under four different conditions including steam and autoclaved curing. In addition to natural sand and crushed stones, cement clinker was also used as a concrete aggregate. High strength concrete containing various level of entrained air was also examined. The compressive, flexural and tensile strengths as well as static and dynamic moduli of elasticity and Poisson's ratio of the test specimens were obtained periodically up to the age of one year.
The following experimental results were obtained: in order to produce a certain level of compressive strength and workability, the clinker aggregate concrete required a considerably less unit water level, consequently reducing the unit cement level, than that of the natural aggregate concrete. While the air entrained concrete required a large unit water level, consequently increasing the unit cement requirement.
All the concrete specimens cured under various conditions increased their strength as they were aged. However, the rate of strength increase between the age of 28 days and one year was about 20 percent for the fog room cured concrete and only few percent for the autoclaved concrete.
The modulus of brittleness, i.e., the ratio of compressive strength to tensile strength, of high strength concrete fall between 14 and 18 and was larger than that of ordinary concrete.
The freezing and thawing resistance test indicated that the durability of autoclaved concrete without entrained air was poor, while the durability of fog room cured concrete without entrained air and autoclaved air entrained concrete was excellent. Air entrainment in high strength concrete has potential usage because it yields good durability and easier handling properties in field, although the air entrainment causes negative effect on the strength of the products.
Modulus of elasticity of autoclaved concrete was smaller than that of the concrete cured under other conditions.

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