Abstract:Self-Compacting Concrete is a relatively new type of concrete. Up to now only a few models have been developed to explain its physical behaviour, like the Water Layer Model and the Excess Paste Model. In this paper, the difference between the Water Layer Model and the Excess Paste Model is highlighted, and the validity of the Water Layer Model to Self-Compacting Mortar with different characteristics of the sand is investigated. The results of this investigation show that the Water Layer Model is effective for the determination of the quantity of water. Furthermore the function of water and superplasticizer is explained using this model.