Use of air-cooled blast furnace slag in cement production – a contribution to the reduction of CO₂ emissions

Using substitute raw materials alongside the traditionally used limestone, clay, and marl to produce Portland cement clinker saves natural resources and achieves the recycling of waste in a new value-added process. Additionally, certain substitute raw materials also have the great advantage that they release no or very little CO2 during the burning process. This represents a significant contribution to achieving climate neutrality. The aim of this research project was to evaluate the recyclability of air-cooled blast furnace slag [ACBFS] as a substitute raw material in the clinker burning process of cement production. Over a course of several weeks, air-cooled blast furnace slag was added in varying quantities to the raw materials for clinker production in an Austrian cement plant. After assessing the influence on grindability and grinding energy consumption, the produced cements underwent a series of mortar and concrete tests, including the determination of solidification times, water requirement, fresh concrete parameters, compressive strength, and carbonation resistance. The results obtained allow for a better understanding of the basic usefulness of waste slag in cement production technology and the amount of slag that can be added without losing the quality of cement.