Can calcium aluminates activate ternesite hydration?

Abstract

Aluminium hydroxide (AH 3) has recently been shown to be able to activate hydration in ternesite, a phase found in some calcium sulfoaluminate (CSA) cements. This study explored the capacity of a number of calcium aluminates (C 3 A, C 12 A 7 , CA and C 4 A 3) to activate ternesite hydraulic reactivity. After laboratory synthesis, the aluminates were blended with ternesite at a ratio of 1:2 and their hydration was monitored with isothermal conduction calorimetry for 7 days at 25 ºC. The resulting pastes were analysed with XRD, FTIR and DTA. The presence of ternesite in the pastes altered the aluminate heat flow curves, shortening the induction period and bringing the reaction peak forward, an indication of hastened hydration. Ternesite also altered the reaction products, which included calcium monosulfoaluminate hydrate and strätlingite.

Recent progress in low-carbon binders

“…According to Ben Haha et al [377], aluminum hydroxide can be used to activate ternesite to form ettringite, strätlingite and C-S-H in different proportions, depending on the reactivity and reaction degree. Work by Montes et al [378], focusing on how other calcium aluminates activate the hydration of ternesite, has also been published recently. Synthetic C3A, C12A7, CA and C4A3 (ye'elimite) phases were blended with ternesite separately, then the hydration reactions of the blends were studied through various techniques.…”

Producing cement clinker assemblages in the system: CaO-SiO2-Al2O3-SO3-CaCl2-MgO

“…In fact, ternesite formation is known to be enhanced in sealed or controlled systems that have a higher local partial pressure of SO3 and O2 [47][48][49]. Considering the improved hydraulic properties of ternesite produced in the presence of MgO [50] and its enhanced hydration in presence of mayenite [51], the clinker phase assemblages (containing ternesite and chlormayenite) produced in S1b and S2b are potentially interesting low-energy clinkers. The results presented in the previous sections showed improved alinite and ye'elimite formation at 1250 and 1300°C; therefore, these temperatures were also tested to assess their co-existence at those conditions.…”

Effect of Colloidal Silica on the Hydration Behavior of Calcium Aluminate Cement

“…The sharp absorption band at 1117 cm −1 is the bending vibration of Si-O-Si. The bands at 1013 and 719 cm −1 are attributed to the bonds vibration of C 2 ASH 8 [ 28 ]. The signals at about 680 and 640 cm −1 are assigned to AlO 6 vibrations.…”