Lignosulfonates in Cementitious Systems Blended with Calcined Clays

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Title: Lignosulfonates in Cementitious Systems Blended with Calcined Clays

Author(s): Ricarda Sposito, Isabel Dürr, and Karl-Christian Thienel

Publication: Special Publication

Volume: 326

Issue:

Appears on pages(s): 10.1-10.10

Keywords: calcined clays, calorimetry, hydration kinetics, lignosulfonates, plasticizer, setting behavior

Date: 8/10/2018

Abstract:
Calcined clays play an important role when it comes to efficient supplementary cementitious materials (SCM) required in future. The substitution of clinker by calcined clays requires the application of water reducing agents to ensure a good workability of concrete due to high specific surface area and water demand of calcined clays. The interaction of two calcined clays with two lignosulfonate-based plasticizers was investigated in cement paste with respect to their dispersing and setting behavior. A good correlation was obtained between higher substitution rates and higher required plasticizer dosages when the same dispersing effects are aimed at as for ordinary Portland cement. These high dosages result in significant retardation effects in hydration behavior. When same dosages are used for all investigated systems and workability effects are disregarded, the retardation impact on cementitious systems with aluminum-rich calcined clays is less than for pure cement paste. If dosages are optimized regarding workability and setting behavior, lignosulfonates are a suitable plasticizer for cementitious systems with calcined clays.