In this stage, cement particles are rapidly released from the surface
of clinker minerals. The initial hydrolysis of CSA happens
quickly, may be within 10 min after mixing followed by a serial
of fast hydration [21]. It is reported that the reaction of ye’elimite
(C4A3S) and gypsum (CSH2) may play a significant role in this stage
[10,21]. When enough water, C4A3S and CSH2 are available in the
fresh mixture, ettringite (C6AS3H32; AFt) is formed quickly and as
major reaction product, which is detectable using TGA at hydration
age 15 min, as illustrated in Fig. 7: AFt products correspond to the
weight loss at around 50–120 C [8]. Furthermore, a weight loss of
gypsum at around 150 C is distinct [8]. Hydration reactions of this
stage in presence of calcium hydroxide and gypsum may be established
as [22,23]: