Title:
Influence of the Polymer Structure on the Rheology of Portland Cement and LC3 Pastes Containing Superplasticizers
Author(s):
Torben Gädt, Simon Nickl
Publication:
Symposium Paper
Volume:
362
Issue:
Appears on pages(s):
240-248
Keywords:
calorimetry; chemical admixtures; LC3; slump flow; superplasticizer
DOI:
10.14359/51740886
Date:
6/5/2024
Abstract:
Calcined clays are a very promising supplementary cementitious material. A remaining challenge for a widespread application is the rheology of calcined clay containing cementitious materials. The water and superplasticizer demand and the viscosity of calcined clay binders are higher than for normal Portland cement (PC) binders. Consequently, there is a need to improve the understanding of the rheological properties of calcined clay-based binders. Here, we report on the rheological characteristics of four polycarboxylate ether superplasticizers in Portland cement and LC3 pastes. The superplasticizer chemistry is controlled through polymer synthesis. We chose simple slump flow tests to characterize the rheology of the pastes at different superplasticizer dosages. Furthermore, we characterize the initial reactivity of the binder using in-situ calorimetry. All four polymers exhibit very similar properties in the LC3 system, while the differences are much more prominent in Portland cement. The dosage efficiency in the LC3 system is lower for all polymers, and the most dosage-efficient superplasticizer in the LC3 system is only ranked third in Portland cement. Finally, the very early heat flow of the suspensions indicates that dissolution and early hydrate phase formation of the PC are promoted in LC3 systems. We propose that the increased PC reactivity is partly responsible for the larger slump loss of LC3 binders.