Role of ternesite on the hydration of C3A in the presence and absence of gypsum

Abstract

Trabajo presentado al 15th International Congress on the Chemistry of Cement (ICCC), celebrado en Praga (República Checa) del 16 al 20 de septiembre de 2019. ; In the search for new eco-cements it has been found that ternesite (2C2S·CaSO4), which has traditionally been regarded as a hydraulically inactive phase, can be activated by aluminum hidroxides (AH3) and some calcium aluminates. This research, in particular, studies the role of ternesite on C3A hydration, with and without gypsum. After laboratory synthesis, C3A was blended with ternesite, gypsum and ternesite+gypsum. The early hydration of those blends was monitored with isothermal conduction calorimetry at 25 °C for 7 days. The resulting pastes were analysed with XRD, FTIR and DTA/TG. Additionally, mixtures of C3AH6 and ternesite in water were prepared in order to study their compatibility. The calorimetric results showed a higher total heat per gram of aluminate in the sample containing gypsum and ternesite than in the sample C3A+ternesite. XRD diffractograms and DTG-TG analysis revealed the presence of AFm in all the samples with gypsum but not in C3A+ternesite which shows no evidence of ternesite activation by C3A. ; Funding from BIA2016-76466-R project as well as the Regional Government of Madrid Community and European Social Fund (Geomaterials Programme2 S2013/MIT-2914) is gratefully acknowledged. Authors thank to Ministerio de Economía y Competitividad the young researcher contract given to Myriam Montes. Financial support for Dr. Paula M. Carmona-Quiroga's participation was provided by the Spanish Ministry of the Economy and Competitiveness under project BIA2015-73237-JIN.