An Approach to Quantitative Image Analysis for Cement Pastes

Abstract

Cement paste microstructure as revealed in backscatter SEM presents a number of inherent difficulties that interfere with implementing quantitative image analysis. An approach to overcoming these difficulties is presented, involving gray scale segmentation coupled with application of a hole filling algorithm. Using this approach it is possible to isolate the unhydrated and hydrated portions of phenograins separately, and to combine them for analysis of combined phenograins. Pores and coarse calcium hydroxide masses may also be isolated for feature analysis. Results are reported on mature cement pastes prepared at two water:cement ratios (w:c 0.45 and w:c 0.30) and with and without superplasticizer. It was found that superplasticizer greatly reduced the content and the average size of “visible pores” and increased the content and the average size of coarse CH particles compared to corresponding plain pastes. The area per hydrated phenograin was much smaller in the lower w:c ratio pastes and higher in superplasticized pastes. Among the solid features measured, unhydrated cement particles had the smallest circularity values (at about 2.7) and were the most circular features; Hydrated phenograins had the largest circularity values (at 3.5) and were the most elongated features.