Title: Studying The Influence of the Filler Effect of SCMs on the Sulfate Requirement of Blended Cements

Author(s): Franco Zunino and Karen L. Scrivener

Publication: Symposium Paper

Volume: 349

Issue:

Appears on pages(s): 117-124

Keywords: gypsum, ettringite, kinetics, hydration, aluminates, C-S-H, adsorption

DOI: 10.14359/51732743

Date: 4/22/2021

Abstract:
It has been well stablished by several studies that LC3 requires an additional amount of gypsum on top of the normal dosage contained in OPC. In this manner, the second (aluminate) peak do not overlap with the first (alite) peak. This required increase of the sulfate content is attributed to the additional aluminate phases introduced to the system by the addition of calcined clay. However, a correlation between metakaolin (alumininosilicate phase) content and the amount of additional gypsum required for proper sulfation has not been found, and the relationship between these parameters and the position of the aluminate peak is not clear. This study explored in depth this issue in order to further understand the driving mechanism controlling the sulfate demand in LC3. Our results show that there is no direct link between the aluminate phase content and the gypsum demand. On the contrary, the driving mechanism is linked to the specific surface area that the mineral additions (calcined clay and limestone) introduce to the system, interaction commonly referred as filler effect.