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

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Concretes formulated at very low w/c ratios (< 0.30) have become increasingly popular. However, applicators often report a honey-like 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 is 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 will be identified which favor a high speed of flow. Additionally, non-ionic co-dispersants will be tested as flow enhancers and the working mechanism underlying this new type of dispersion will be investigated in more detail by using different experimental techniques (e.g. dynamic light scattering, critical micelle concentration etc.).The overall goal of this project is 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.