Journal of Thermal Analysis and Calorimetry, Vol. 69 (2002) 179–186
STUDY BY THERMOGRAVIMETRY OF THE
EVOLUTION OF ETTRINGITE PHASE DURING TYPE
II PORTLAND CEMENT HYDRATION
J. Dweck
1*
, P. F. Ferreira da Silva
1
, P. M. Büchler
2
and F. K. Cartledge
3
1
Depto. de Processos Inorgânicos, Escola de Química da Universidade Federal do Rio de Janeiro,
Bloco E do CT, Sala E-206, Cidade Universitária, Rio de Janeiro RJ, Brasil, 21949-900
2
Depto. de Engenharia Química da Escola Politécnica da Universidade de São Paulo, São Paulo
Brasil
3
Chemistry Department, Louisiana State University, Baton Rouge, LA, 70803, USA
Abstract
Thermogravimetry (TG) and derivative thermogravimetry (DTG) have been used by the authors as
very effective tools to study hydration steps of cements used for solidification/stabilization of tan-
ning wastes. The present paper presents a method which was applied to separate the peaks shown by
DTG curves of type II Portland cement pastes, analyzed at different times during the first 4 weeks of
setting. Through a specific software a more detailed study of the evolution of the cement hydration
may be done, which allows the measurement of the amount of hydrated water present in tobermorite
gel as well as in ettringite, which are the main phases formed from the original components of the ce-
ment. The number of moles of water present in the ettringite phase calculated by the method is in
very good agreement with the values found in the literature, validating the method to calculate the
same parameter in tobermorite gel. In the latter case the water content decreases significantly during
the first day of hydration, then remains at a constant value over the rest of the analyzed period.
Keywords: ettringite, hydration, Portland cement, thermogravimetry
Introduction
Thermogravimetry (TG) and derivative thermogravimetry (DTG) are effective tools
to follow the different stages of cement hydration as well as to quantify the different
phases, as shown in previous papers of the authors based on solidification/stabiliza
-
tion of tanning waste and related subjects [1–4]. In this paper a method to separate
overlapped DTG peaks is presented, which allows, as other deconvolution methods
do [5], a greater precision than conventional procedures to quantify the main sub
-
stances and to better understand the hydration process.
The method was applied to the hydration of type II Portland cement, to quantify
the moles of water present in two main substances formed during the hydration pro
-
1418–2874/2002/ $ 5.00
© 2002 Akadémiai Kiadó, Budapest
Akadémiai Kiadó, Budapest
Kluwer Academic Publishers, Dordrecht
* Author for correspondence: E-mail: dweck@eq.ufrj.br; Fax: 55-21-5627567