Hydration activation of Alite-Belite-Ye'elimite cements by doping with boron

The hydration behavior of two alite-belite-ye’elimite (ABY) cements has been studied. The production of these materials releases into atmosphere ~17% less CO2 than Portland cement. ABY cement contains alite, β-C2S and yeu0027elimite as main phases while dABY (activated by adding borax) contains these three phases but also α′H-C2S. The role of boron in these systems is two-fold: i) acting as a retarder at early hydration ages, since the precipitation of AH3-gel has been delayed from over 4 hours in ABY to over 24 h in dABY; and ii) as an activator at late hydration ages by stabilizing highly reactive β- and α′H-belites. The degree of hydration of β-C2S in ABY is 42% at 28 days, meanwhile that of β-C2S and α′H-C2S in dABY at the same age is 80 and 88%, respectively. Moreover, the main hydration products in both systems are ettringite and C-S-H gel. The local structure of these hydrated products have been studied by 27Al and 29Si MAS-NMR and found to be similar in both cements. However, the amount of C-S-H gel i...