Study of the influence of superplasticizers on the hydration of cement paste using nuclear magnetic resonance and X-ray diffraction techniques

Melamine and naphthalene-based superplasticizers have been used, over the past few decades, in order to improve the workability of concrete. Recently, more efficient copolymer formulations have been introduced for the same purpose. However, the influence of these chemical admixtures on the microstructure of the hardened concrete and, consequently, on its properties still needs to be extensively evaluated. Accordingly, the present work analyzes the hydration characteristics of cement pastes with naphthalene, melamine and copolymer-based superplasticizers, using the techniques of X-ray diffraction (XRD) and nuclear magnetic resonance (NMR), up to the age of 28 days. The results indicate a significant influence of the superplasticizer on the growth rates of the hydrates and on the state of polymerization of the silicates.