The substitution of ordinary Portland cement (OPC) with sustainable limestone calcined clay cements (LC3) has represented a major innovation in the building industry over the last 20 years, though some challenges require to be addressed still (Sharma et al. Limestone calcined clay cement and concrete: a state-of-the-art review. Cem. Concr. Res. 149, 2021). Most importantly, LC3’s lower calcination temperature than OPC (750–850 and 1450 °C, respectively), despite being environmentally benign, triggers a higher water and admixture demand. In this work, several superplasticizers were investigated to assess which are the most promising to be used with LC3 cements and the key physicochemical properties required for that purpose. The binder used for this investigation is based on a calcined clay from the Technical Research Center (TRC) for LC3 in India, a representative calcined clay that could be used in the construction sector in the near future. Kinetic profiles on LC3 proved to be similar to those on parent OPC material, indicating a similar interaction mechanism between admixture and binders. Nevertheless, the adsorption equilibrium value was considerably higher for LC3, which was correlated to its higher surface area. Adsorption on LC3’s individual components (i.e., calcined clay, OPC, limestone, gypsum) confirmed that differences in adsorption behaviour must be ascribed to calcined clay’s unique properties. Thanks to adsorption isotherms, a Langmuir–Hinshelwood adsorption mechanism was observed; most importantly, surface coverage at optimal dosage proved to be the lowest for the most dosage efficient admixtures, which are also characterized by the highest Langmuir equilibrium constant.