Kira Weise describes blast furnace slag as a material for use in construction and presents a method for assessing reactivity using thermogravimetric analysis techniques. The focus is on examining blast furnace slag as an additive in cement-bound systems. The reaction mechanisms of Portland cement and blast furnace slag are considered separately, and internationally published modeling approaches regarding the interaction of both materials are reviewed. The author proposes a simple model for predicting the calcium hydroxide content in binder samples. Her goal is to establish a foundation for concrete designs based on the chemical reactivities of the raw materials used. This innovative approach aims to enable a more efficient and resource-saving use of materials.