ABSTRACT
This chapter discusses the additions contribute to the hydration reactions, the Portland cement and additions together are generally known as the binder, and aims to the binder content and water: binder ratio when discussing mix proportions. Additions are defined as ‘finely divided materials used in concrete in order to improve certain properties or to achieve special properties’. The former case allows choice of the rate of addition, but means that an extra material must be handled at the batching plant; a pre-blended mixture overcomes the handling problem but means that the rate of addition is fixed. The incorporation of additions leads to a rethink about the definition of cement content and water: cement ratio. Higher additions are also used in some types of concrete, most notably self-compacting concrete in which high powder contents are required for stability and fluidity of the fresh concrete.
