NEW ASPECTS OF BLAST FURNACE SLAG CEMENT HYDRATION

摘要

Blast furnace slag cements are qualified for applications in nearly all fields of construction. Their properties are similar to pure Portland cements and often beyond this. Anyhow, these cements still meets resistance, because of their reputation for requiring an extended curing duration. Due to the self commitment of the German cement industry to lower its fuel energy consumption, the share of blast furnace slag cements in production will increase. As a logical consequence, the application of blast furnace slag cements will be intensified in fields of construction, which were reserved for Portland cement up to now. The purpose of this work is to describe the course of hydration of blast furnace slag cement for varying slag contents. The specimens were exposed to different relative humidities. The content of non-evaporable water, relative to that in a fully hydrated paste of the same cement, was used as a measure of the degree of hydration. The content of non-evaporable water was analysed by the Carbon-Water-Method. The results so far indicate that the late hydration has been underestimated up to now. With growing slag content, a considerable hydration occurs after the 28th day. This happens regardless of the preceding moisture conditions. Thereby, a much higher degree of hydration was reached than could have been expected from blast furnace slag cements.