Blending of dry binders and mortars

While on the industrial scale at least the calcium sulfate is interground when producing a portland cement, different powders often need to be blended in laboratory studies in order to obtain a homogeneous mix. Such a mix could be either a binder or a dry mix mortar. Blending is extensively treated in textbooks related to particle technology, and the reader can be 

In principle there are two different ways of blending the individual components when producing a fresh paste, mortar or concrete, as it is possible to (1) make a premix of the dry materials, which is later mixed with water and eventually aggregates to obtain the paste or the mortar, or (2) prepare directly the paste or the mortar from the individual ingredients. 

The second case - mixing the individual components with water - requires a thorough mixing process of the fresh paste or mortar see Section 1.6.1 for details. 

Admixtures might be either added in a dry mix or dissolved in the mixing water. The first case is relevant for dry mix mortars, whereas in concrete production the admixtures generally are added in liquid form. In case the admixture is added to the dry mix, a good homogenisation needs to be ensured. In addition, it has to be kept in mind that there is a difference between adding the admixture as a solid and adding it dissolved in water, as the dry admixture needs to be dissolved first before it can interact with 

Very fine particles such as microsilica are difficult to incorporate both in dry mixes and in fresh pastes, mortars or concretes. Further information and suggestions on how to treat such material are given in Section 1.6.1. 

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