• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6A
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• pp.449-456
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• 2011

Spacing factor proposed by Power is a concept of averaging air void spacing composed of geometric models. Thus, there's a limitation on simulating actual air void characteristics in concrete. This study presents SDI(spacing distribution index) to overcome the limitation of spacing factor. SDI is also evaluated through comparing SDI with SF(spacing factor). In this study, it was confirmed that SF decreased due to increasing air-entrainer content but SDI increased. This occurs because SDI is the area of spacing distribution curve and SDI increases with increasing the frequency of spacing. SDI is evaluated to have better coverage below $300{\mu}m$ of SF so that determination of critical point of SDI above 80% of durability index can be easily obtained with more reliability. SDI is the area of spacing distribution curve and reflects actual air void characteristics in concrete. A comparative study of SDI and results of freeze-thaw test will be performed later.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.701-709
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• 2011

One of the typical evaluation models of concrete air-void system is spacing factor (SF), which was suggested by Power. Power Spacing Factor (PSF) has a disadvantage of the result being different from the actual case due to the existence of entrapped air, because PSF uses average single spacing factor. Therefore, the Actual Measurement Spacing Factor (AMSF) using actually measured data of air void spacing was developed from this study. PSF and AMSF were compared and evaluated in this study by using the image analysis test result of concrete mixture. This study results showed that PSF and AMSF are generally similar, but AMSF had a larger value when PSF was greater than $400{\mu}m$. The results indicated a possibility of PSF giving false measurement estimation where the measurement is less than the actual value in the concrete mixture containing less air. Also, in the result of PSF and AMSF analysis according to the existence of entrapped air, AMSF showed a larger value in the analysis without entrapped air. But PSF showed a smaller value in the analysis without entrapped air, which was different from the actual case. Because PSF used average single spacing factor, it tended to give a false result. The study results showed that AMSF gave more accurate analysis results.