Mixing Water and Maturity of Hardened Concrete Using Scanning Electron Microscope Techniques. Part One

摘要

Photographic comparison standards and an analysis procedure for their use have been developed to aid in the determination of the age of hydration and the water-cement ratio of hardened concrete. The standards are sets of nine photographs of concrete at a range of ages and water-cement ratios taken at 1200X magnification using the scanning electron microscope (SEM). Concretes were made at nine different water-cement ratios ranging from 0.40 to 1.20 in increments of 0.10 and hydration was terminated for samples from each water-cement ratio at 1, 3, 7, 14, 28, 60 and 90 days of hydration using controlled non-freezing vacuum drying. An array of 63 sets of nine photographs, one for each age at each water-cement ratio resulted. Analysis of their array resulted in the recognition of nine factors of features of the hydration matrix that can be used by a trained observer to estimate age of hydration and water-cement ratio of an unknown concrete sample for which a set of nine 1200X SEM photographs has been made. A step by step procedure is provided using the age and water-cement ratio distribution of the nine features for the evaluation of unknown concrete samples. Sample photographs illustrating the nine hydration features are provided together with a distribution chart for each feature.