Study on the Rheology of Fly Ash Versus Calcined Marl Blended Cements with Polycarboxylate-Based Superplasticizers

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Title: Study on the Rheology of Fly Ash Versus Calcined Marl Blended Cements with Polycarboxylate-Based Superplasticizers

Author(s): Serina Ng and Harald Justnes

Publication: Special Publication

Volume: 302

Issue:

Appears on pages(s): 387-400

Keywords: plasticizers; PCE; fly ash; calcined marl; blended cements

Date: 6/1/2015

Abstract:
The dispersing effectiveness of three polycarboxylate-based superplasticizers (PCE) was investigated in two blended cement systems containing entirely different SCMs; fly ash (FA) and calcined marl (CM) at replacement percentages of 20% and 60%. The methods of investigation employed include rheological studies, hydration profiling up to 24h, and packing density analysis. Generally, replacing clinker phases by FA decreased the dynamic yield stress and delayed hydration of the pastes due to increased PCE to clinker ratios, regardless of PCE type. Little variation except for cement with 60% FA replacement (FA60) was observed on the Bingham viscosity. On the other hand, CM competed with clinkers not only for water, but also for PCEs even in CM20, reducing the fluidity of the paste but maintaining a similar initial rate of hydration of the pastes. PCE possessing intermediate side chain lengths proved to be more effective for CM systems than PCEs possessing long side chains.