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

Prof. Dr. Johann Plank
Technische Universität München (TUM), Lehrstuhl für Bauchemie

Researcher(s) in-charge – RI

M.Sc. Manuel Ilg
Technische Universität München (TUM), Lehrstuhl für Bauchemie

Associated researcher – AR

Dr. Lei Lei
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

Publications

Interaction of Superplasticizers with Cement from the Point of View of Colloid Chemistry

J. Plank, M. Ilg

in: V. Mechtcherine, K. H. Khayat, E. Secrieru (Eds.), Rheology and Processing of Construction Materials, pp. 134-141 (2019)

Non-adsorbing small molecules as auxiliary dispersants for polycarboxylate superplasticizers

M. Ilg, J. Plank

Colloids and Surfaces A: Physicochemical and Engineering Aspects 587 (2019)

Characterization data of reference cement CEM I 42.5 R used for priority program DFG SPP 2005 “Opus Fluidum Futurum – Rheology of reactive, multiscale, multiphase construction materials”

Z. Lu, M. Haist, D. Ivanov, C. Jakob, D. Jansen, S. Leinitz, J. Link, V. Mechtcherine, J. Neubauer, J. Plank, W. Schmidt, C. Schilde, C. Schröfl, T. Sowoidnich, D. Stephan

Data in Brief 27 (2019)

Dispersing performance of different kinds of polycarboxylate (PCE) superplasticizers in cement blended with a calcined clay

M. Schmid, J. Plank

Construction and Building Materials 258 (2020)

Effect of non-ionic auxiliary dispersants on the rheological properties of mortars and concretes of low water-to-cement ratio

M. Ilg, J. Plank

Construction and Building Materials 259 (2020)

Characterization data of reference cement CEM III/A 42.5N used for priority program DFG SPP 2005 “Opus Fluidum Futurum – Rheology of reactive, multiscale, multiphase construction materials”

Z. Lu, M. Haist, D. Ivanov, C. Jakob, D. Jansen, P.A. Kißling, S. Leinitz, J. Link, V. Mechtcherine, J. Neubauer, J. Plank, W. Schmidt, C. Schilde, C. Schröfl, T. Sowoidnich, D. Stephan

Data in Brief 30 (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”

L. Lei, C. Chomyn, M. Schmid, J. Plank

Data in Brief 31 (2020)