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Title |
Determination of Removal Time of the Side Form in High Strength Concrete
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Keywords |
고강도콘크리트; 부착강도; 거푸집 제거시기; 적산온도; P형 슈미트해머; high strength concrete; bond strength; removal time of form; maturity; P type schmidt hammer |
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Abstract |
In this paper, method for the determination of removal time of the side forms in high strength concrete are discussed using the estimation model of compressive strength development, the development of bond strength and rebound number of P type Schmidt hammer in order to review the validity of existing regulation as to side form removal and offer effective quality control method. According to the results, as W/B increases by 10%, the setting time is shortened by about 2 hours. In the scope of the paper, required time to gain 8MPa of compressive strength is determined about 17~20 hours of age and 21~25°D·D of maturity. Bond strength between form and concrete shows the highest value around final setting time, but decreases drastically after that. Amount of concrete sticking on the form is large before setting completed, but after that, its amount shows decline tendency. The rebound value test with P type schmidt hammer can be started faster by 2~3 hours than compressive strength test. It is also confirmed that the removal of forms is possible when the rebound value of P type schmidt hammer is more than 32. It is found from the results that existing regulation regarding removal time of the side form of high strength concrete provided in KCI needs no revision because required time to gain the strength provided in KCI has no adverse effect on strength development at early age and surface condition during stripping the side form. Effective procedure to decide the removal time of side form can be performed by applying P type Schmidt hammer.
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