If the original water-cement ratio of portland cement concrete is low enough and the cement paste cures long enough, hydration products fill all the space and there are no capillary voids. Concrete with no capillary voids has a high strength and low permeability. Until high-range water reducers were developed, it wasn't feasible to produce ready mixed concrete that could hydrate to a zero-capillary void condition. If reducers are also used to permit cement content reductions, finishing may be difficult. Strength cannot be considered apart from performance of the concrete.