This paper describes how the increased performance of polycarboxylate superplasticizers is generally explained by the steric hindrance they are intended to develop between cement particles. In fact, direct evidence of this is relatively scarce. The only direct measurements to date have been made by atomic force microscopy on model surfaces of magnesium oxide. This paper reports very recent measurements using the same technique but on surfaces of calcium silicate hydrate that constitute a more realistic model system. Furthermore, it is shown that the measured interfacial behavior of superplasticizers can be quantified by a scaling law approach borrowed and extended from polymer physics.