Influence of additives on the fracture mechanical properties of reactivated cement paste

Since the production of cement is very CO2-intensive alternative binders are on the rise.The reactivation of cement has proven to be possible.Attempts are being made to find out, how it can be used as a binder or clinker supplement.A problem to solve is that, so far, the mechanical strength is not as high as the one of the original binder.Reasons for that are a new chemical composition with a different variety of strength giving phases and the morphology of the reactivated grains.The new powder shows high inner porosity and a much bigger specific surface area.This work aims to increase the mechanical strength of reactivated cement by using two types of additives.First, milling agents that are added during the milling process.In this study ground blast furnace slag (GBFS), copper slag (CuS) and electric arc furnace slags (EOS) were used.Further additives are added during the mixing of cement and water.Microsilica (MS), concrete plasticizer, superplasticizer and retarder have been chosen.Parameters that were tested are compressive strength, porosity and fracture toughness.While GBFS gives the highest compressive strength, chemical admixtures increase the strength of reactivated cement paste as well.The fracture toughness is a stable value whereas porosity and strength vary for reactivated cement.