Concrete additives are finely ground additives, such as tuff, rock powder (quartz powder/limestone powder), fly ash, silica fume and pigments for colouring the concrete, which influence certain properties of the concrete. These are primarily used to improve the workability of the fresh concrete and the strength and density of the hardened concrete.
In contrast to concrete admixtures, the quantity added is generally so large that it must be considered in the grading curve calculation.
Additives must not impair the hardening of the cement or the strength and durability of the concrete and must not endanger the corrosion protection of the reinforcement.
Additives can be divided into different groups:
- inactive (inert) additives
- pozzolanic additives
- latent hydraulic materials
- organic additives
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