Cement Science and Concrete Technology
Online ISSN : 2187-3313
Print ISSN : 0916-3182
ISSN-L : 0916-3182
Cement Chemistry
EVALUATION OF PROTECTED PASTE VOLUMES USING THE RECORD OF LINEAR TRAVERSE MEASUREMENT AND DIRICHLET TESSELLATION OF CEMENT PASTE REGIONS AROUND AIR VOIDS AS A PLANAR POINT PROCESS
Shin-ichi IGARASHISoshi YAMASHITAKeigo YUGAMI
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JOURNAL FREE ACCESS

2021 Volume 75 Issue 1 Pages 66-73

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Abstract

The surface density of air voids was evaluated from the records of linear traverse measurement. The entire volume of the protected paste region was estimated by the product of the surface density and the assumed thickness of the protection from the surface of air voids. The volume fraction of the protected volume to the entire cement paste matrix was defined as the coverage ratio. If the thickness of the protected volume is assumed 0.2mm, which has been generally recognized as an upper limit of the spacing factor for moderate exposure of concrete, the coverage ratio is greater than 80% in the concrete with adequate air contents. The protected paste region was also evaluated using 2D images of air voids. The distribution of those air voids identified in the images was considered as planar point processes. The paste region including the points was divided according to the algorithm for Dirichlet tessellation. Each polygonal tile surrounding a point representing air void was regarded as an area to be protected by the void. A histogram of the areas of those tiles was obtained, and the sizes of the tiles were compared with the protected area fraction estimated from the assumed thickness of protection and the surface density. If the thickness was assumed 0.2mm for the protected area, most of the tiles were covered with the protected areas provided by air voids. The sizes of protected paste volume inferred from the Dirichlet tessellation were comparable with that estimated by the surface density of air voids. In other words, when a distance comparable with the allowable spacing factor is assumed, the cement paste matrix around random air voids is almost covered with the protected region.

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