| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1991: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1990: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
The effects of type of aggregate(natural and artificial lightweight aggregate), type of bider(portland cement, flash and powdered blast-furnace slag), water-binder ratio(65, 55 and 45 percent)and the age of concrete to which freeze-thaw cycles are initiated(28 and 3 days)on chloride permeability of concrete deteriorated by freezing and thawing were tested by the method described in the AASHTO Standards T277. Concrete without entrained air and concrete with entrained air of 3.5, 5.5 and 7.5 percent were tested. Grades of deterioration were controlled by the number of cycles of freeze-thaw cycle test.
The followings were revealed from the test results :
1)In case of concrete with natural aggregate, entrainment of air up to around 5 percent is considerably effective to prevent increase of chloride permeability due to deterioration of concrete accompanied by freezing and thawing. Required minimum air contents are approximately, O, 5.5 and 3.5 percent for concrete without admixture, concrete admixed with flyash(30 percent of cement)and concrete admixed with powdered blast-furnace slag(70 percent of, cement), respectively.
2)In case of concrete with artificial lightweight aggregate(in state of completely saturated with water), entrainment of air up to 7.5 percent is not effective to prevent increase of chloride permeability du to deterioration of concrete.
3)Concrete admixed with powdered blast-furnace slag showed remarkably less chloride permeability as compared with ordinary concrete or concrete admixed with flash.
4)Less chloride permeability, in both ordinary and lightweight concrete, was observed in lower water-cement ratio, and in later age of concrete.
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