Title:
Effect of Superplasticizer on Water Availability and Rheological Properties of Cement Paste Containing Calcined Clay
Author(s):
L. Ferrari, V. Bortolotti, N. Mikanovic, M. Ben-Haha, and E. Franzoni
Publication:
Symposium Paper
Volume:
362
Issue:
Appears on pages(s):
976-985
Keywords:
differential scanning calorimetry (DSC), limestone calcined clay cement (LC3), rheology, superplasticizer, time-domain nuclear magnetic resonance (TD-NMR)
DOI:
Date:
6/18/2024
Abstract:
Although limestone calcined clay cement (LC3) is a valid alternative to reduce the carbon footprint of cement production, some of its properties, like workability, still need to be investigated and fully understood. In this work, different cement pastes containing variable amounts of calcined clay with and without superplasticizer were analyzed. Measurements at the rheometer scale were performed to evaluate the superplasticizer’s effect on the samples’ workability. The amount of free water available after 1 hour of hydration in cement pastes was detected by Differential Scanning Calorimetry (DSC). Moreover, the Time-Domain Nuclear Magnetic Resonance (TD-NMR) was used to identify whether this water was contained either in capillary pores or in interhydrate spaces. The results obtained by DSC and TD-NMR revealed that pastes containing superplasticizers show a slightly higher amount of available free water, with a direct positive consequence on rheological properties. However, the amount of calcined clay (CC) in cement impacts both aspects: superplasticizer dosage to reach the target fluidity of pastes and workability retention over 60 minutes. Moreover, the confirmation of the exponential correlation between yield stress and the solid content of cementitious particles is possible when considering the detected capillary water as an indicator of the normalized concentration of solid particles.