Early-age properties, strength development and heat of hydration of concrete containing various South African slags at different replacement ratios

This research investigated fresh and hardened properties of concretes containing three different types of slag at three different replacement ratios and three different water/binder ratios. The three types of slag include ground granulated blastfurnace slag, ground granulated Corex slag and a ground granulated ferro-manganese arc furnace slag. Different methods for the assessment of slag hydraulic activity are compared, including chemical and physical characterisation of the various binders and binder blends, mortar compressive strength tests and heat of hydration tests, indicating the limitations of the various methods if used in isolation. The test results indicate that the use of the slags under investigation increases concrete workability at high water/binder ratios only. Setting times and 1-day strength values were strongly dependent on the slag replacement ratio. The influence of slag replacement level on compressive strength reduced over time. Strength development characteristics and long-term strength values were considerably different for different types of slag.