The microstructure of concrete cured at elevated temperatures

Abstract

The temperature and relative humidity pertaining during curing influence the strength development, microstructure, and long term durability of concrete. Optical and electron microscopy techniques have been used to assess the microstructural characteristics of laboratory prepared concrete and case study material cured under a range of temperature and humidity regimes. Microstructural examination of two month old concrete cured at 16 °C, 42 °C and 46 °C has revealed no marked differences in the spatial distribution, morphology, and volume of hydrates and other microstructural features present. A network of microcracks was evident within the matrix of all the concretes, with that cured at 85 °C, and the sample with eighteen years in-service use, showing a higher degree of microcracking. The concretes prepared at temperatures above 46 °C were also found to have significant development of hydrates, particularly ettringite, within pores and microcracks, together with a generally coarser microstructure.