Understanding cementitious materials in fresh state: A nano-scale study on the effect of the mixing time

► Effects of mixing time of mortar in changes both in fresh and hardened state. ► Adsorption, micro-electroforetic, electroosmotic and EIS measurements. ► Different binders and superplasticizers. ► Parameterization of the effect of the agitation. ► Consequences for handling of the fresh material and on their hardened properties. The appropriate mix of cement, water, sand and aggregates produces the material called concrete, which results to be much more complex than it seems at first sight. In the last decade, the chapter concerning special uses of concrete has gained much more relevance being the nowadays challenge to produce tailored concretes for special uses. When mixing a cementitious material, it behaves like a fluid, having a transition phase until it becomes a solid. A good approximation to the rheology of the concrete in this phase is represented by the Binghan model of fluid mechanics, being this period very influenced by the different chemical admixtures and additions used to be able to manage the mix. An understanding of how individual colloids interact with each other is crucial as long as agglomeration, segregation or right dispersion of the mixes is concerned. In this paper, for different binders and PCE and SNF superplasticizers, adsorption, micro-electroforetic, electroosmotic and electrochemical impedance spectroscopy measurements have been carried out on the plain binders and on fresh state cement pastes both mixed during the standard regime and during longer time, and the results have been compared and critically analyzed with the traditional characterization techniques for fresh state concrete, deriving important practical consequences not only for the handling of the fresh material but also for their hardened properties.