When explaining what concrete is to students, the analogy to baking a fruitcake turns out to be quite useful. Both "materials" contain solid inclusions (aggregates in concrete, versus fruit or nuts in a fruitcake) and a binder (cement versus dough). In both cases, the consistency of the "batter" may be improved by adding water, and as a result, the porosity of the final product is increased. While in the case of fruitcake this porosity may be an advantage, particularly if the recipe calls for soaking the cake with brandy or kirsch after baking, it can prove catastrophic to the durability of concrete. Indeed, it is through the porous network of the cement paste that chemical agents can enter concrete and cause its degradation. Furthermore, increased porosity of the matrix significantly decreases concrete strength.
At first glance, this may suggest that the solution for a more durable concrete is simply to add as little water as possible. However, while the amount of water required for complete hydration is ~25−30% of the cement mass, about twice this amount is needed to achieve sufficient workability. This is where dispersants, referred to in this field as superplasticizers or high-range water-reducing admixtures (HRWRAs) come into play. Indeed, the introduction of such admixtures in concrete has enhanced the durability, increased the strength, and improved the workability to levels that previously were unattainable.