13. Investigating the Rheological Behavior of Low Water-to-Cement Concretes Admixed With Superplasticizers and Co-Dispersants and the Underlying Dispersion Mechanism

Principal investigator(s) – PI

    Researcher(s) in-charge- RI

      Associated researcher – AR

        Former members

        • M.Sc. Manuel Ilg
          Technische Universität München (TUM), Lehrstuhl für Bauchemie
        • Dr. Lei Lei
          Technische Universität München (TUM), Lehrstuhl für Bauchemie
        • Professor Dr. Johann Plank
          Technische Universität München (TUM), Lehrstuhl für Bauchemie
        • M.Sc. Dominik Staude
          Technische Universität München (TUM), Lehrstuhl für Bauchemie

        Subject Area

        Construction Material Sciences, Chemistry, Building Physics

        Term

        2017-2021

        Project identifier

        Deutsche Forschungsgemeinschaft (DFG) – Projekt number 387082770

        Project Description

        Concretes formulated at very low w/c ratios (< 0.30) have become increasingly popular. However, applicators often report a honey-like “sticky” consistency for those concretes which creep rather than flow and exhibit a low speed of flow when poured at the job site. Such rheological behavior is highly undesirable for the placement process. The aim of the project was to ascertain the main causes for the stickiness and creeping flow behavior of concretes of low w/c ratios and to provide potential solutions to overcome such unfavorable rheological properties. Regarding this, specific structural motifs for PCE superplasticizers were identified which favor a high speed of flow. Additionally, non-ionic co-dispersants were tested as flow enhancers and the working mechanism underlying this new type of dispersion were investigated in more detail by using different experimental techniques (e.g. dynamic light scattering, critical micelle concentration etc.).The overall goal of this project was to significantly deepen the knowledge on the dispersion mechanisms occurring specifically in low w/c systems, and to interconnect the data obtained for the adsorbed layer thickness, HLB values and structural motifs of individual PCE molecules with key rheological parameters such as yield stress, plastic viscosity and flow speed.

        Conceptual sketch illustrating the working mechanism of the non-adsorbing co-dispersants in cement at low w/c ratios.
        © Technische Universität München

        Conceptual sketch illustrating the working mechanism of the non-adsorbing co-dispersants in cement at low w/c ratios.

        Publications

        Ilg, M., Plank, J. (2020). Effect of non-ionic auxiliary dispersants on the rheological properties of mortars and concretes of low water-to-cement ratio. Construction and Building Materials, 259, 119780.

        Ilg, M., Plank, J. (2020). Non-adsorbing small molecules as auxiliary dispersants for polycarboxylate superplasticizers. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 587, 124307.

        Ilg M., Lei L., Plank J. (2017) “Effect of Non-Ionic Additives on the Dispersing Performance of Polycarboxylate Superplasticizers”, in Chinese in: New Development in Polycarboxylate Superplasticizer and Application Technology – 2017, Proceedings of the 6th National Conference on Polycarboxylate Superplasticizer and Application Technology, Beijing (China), May 23 – 25, 2017, p. 25 – 29.

        Lei, L., Chomyn, C., Schmid, M., Plank, J. (2020). Characterization data of reference industrial polycarboxylate superplasticizers used within Priority Program DFG SPP 2005 “Opus Fluidum Futurum-Rheology of reactive, multiscale, multiphase construction materials”. Data in brief, 106026.

        Staude, D., Plank, J. Phase Analysis and Hydration Behavior of Different Particle Fractions Contained in a Commercial Portland Cement. Cement and Concrete Research, submitted