Investigation of mechanical, rheological and workability behaviour of blast furnace slag cement and chemical additive containing mortars

This study provides detailed insights into the effects of chemical admixtures on the performance of more sustainable blast furnace slag (BFS) cement systems, aiming to contribute to the development of environmentally friendly and sustainable construction materials. The research focuses on addressing the disadvantage of low early strength, which hinders the widespread use of BFS cement systems. In this thesis, mortars were prepared using CEM I 42.5 R and BFS-based CEM II A-M (S-L) 42.5 R cements in combination with superplasticizer and set-accelerating chemical admixtures. The workability and mechanical properties of the mortars, as well as the setting times and rheological properties of the cement pastes, were investigated. Chemical admixtures were added to the mortar mixtures in different proportions, and their effects on the fresh and hardened properties of mortars made with BFS cement were examined. Polycarboxylate- and polynaphthalene sulfonate-based superplasticizers were paired with various types of set accelerators and tested together. To evaluate mechanical performance, flexural and compressive strength tests were carried out on the mortars at 2, 7, and 28 days. Additionally, the rheological behavior of the cement pastes and the flow characteristics of the mortars were experimentally analyzed. The study revealed that BFS and chemical admixtures have significant effects on the early and final strength development, rheological properties, and workability of mortars.