Designing Alternative Binders Utilizing Synergistic Reactions


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Title: Designing Alternative Binders Utilizing Synergistic Reactions

Author(s): Harald Justnes and Tone Anita Østnor

Publication: Special Publication

Volume: 303


Appears on pages(s): 191-204

Keywords: Alternative binders; Accelerators; Calcined clay; calcium carbonate; SCM; Synergy

Date: 6/1/2015

Alternative binders are defined as binders without portland cement. Two synergy principles have been described for making improved binders based on slaked lime and pozzolanic SCMs. One showing how neutral salts may accelerate by forming strong alkaline solutions in situ and another showing how calcium carbonate can play a role when alumina containing SCMs are used by leading to an even higher conversion of liquid water into solid hydrates, which subsequently leads to lower porosity and higher strength. Examples are given when the SCMs are calcined kaoline clay contaminated with feldspar and calcined smectite rich marl, respectively. Mortar strengths exceeding 25 MPa (3626 psi) when cured at ambient temperature for 28 days were achieved. Predicted phases in the microstructure, such as calcium monocarboaluminate hydrate, were confirmed by X-ray diffraction. Other details of the microstructure were studied by capillary suction of water, thermal analysis and scanning electron microscopy.