An alternative approach to estimate the W/C ratio of hardened concrete using image analysis
TNO Bouw en Ondergrond
The water cement (w/c) ratio is a typical quality parameter for concrete. The NT Build 361 Nordtest method is a standard for estimating the w/c ratio in hardened concrete and is based on the relationship between the ilc ratio and the capillary porosity in the cement paste. The latter can be estimated using fluorescent light microscopy of concrete thin sections because the capillary porosity is related to the intensity of the fluorescent light in the cement paste. The NT Build 361 method consists of visual comparison of the light intensity in unknown samples with reference samples. The w/c method easily can be automated by image analysis, comparing the fluorescent light intensity histograms of the fluorescent micrographs. However, there are a few problems to be overcome for image analysis to be reliable with respect to wlc ratio. The first limitation is the presence of aggregates and (air) voids, because only the intensity in the cement paste is of interest. A second issue is that the fluorescent light intensity is strongly dependent on the incident light intensity and age of the fluorescent dye. A third issue is the heterogeneity of the cement paste, i.e. local variation of capillary porosity due to local differences in the w/c ratio. In this paper, we propose solutions to these three problems using specific processing methods of the fluorescent images.
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fluorescent light microscopy
I2lh Euroseminar on Microscopy .Applied to Building Materials 15.-19, Seplember 2009, Dorlmund, Germanv, 254-263