Research on the ternary system of clinker, granulated blast furnace slag and limestone

with the aim of lowering the proportion of clinker in cement to reduce CO2 emissions in cement production

The research project built on both the results of the concluded project 28790 "Reducing the environmental impact of concrete construction with new types of cement and concrete using sufficiently available source materials" and the future European standardisation of cements.

In research project 28790 it was determined that cements with up to 50 % by mass of limestone as a main constituent can be used to manufacture concretes with durability properties that are similar to standard concretes made using CEM I or CEM II/A-LL cements. To achieve this, it is necessary to significantly reduce the water-cement ratio to w/c = 0.35. In order to ensure practical workability, optimisation of the paste content, precise adjustment of the main cement constituents in the cement work and adjusted use of concrete admixtures are also required. 

It was shown that many durability properties are comparable to those in the selected reference cements, however there is clear potential for optimisation in terms of the normal product portfolio in Germany. The environmental impact can also be improved further. This becomes possible through the use of a limited supply of granulated blast furnace slag as a third main constituent. Accordingly, this research project aimed to investigate a considerably more extensive field of composition within the ternary system of clinker (K) – granulated blast furnace slag (S) – limestone (LL), which, on the one hand, was based on the cements of the current or future European standards and, on the other hand, was limited by the results of the previous research project and the technical limits that it defined. The durability of concretes was to be investigated using the methods that proved to be effective in the previous research project. These were complemented with further testing procedures (rapid carbonation, testing of freeze-thaw resistance with de-icing salt). 

The aim of the investigations was to answer the question as to whether the K-S-LL system can be used to manufacture durable concretes using clinker-efficient cement under framework conditions that still need to be defined. The results of the research project were then evaluated from the point of view of their environmental footprint.