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/flocculation state of the particles [ 7 ], the type and amount of mineral addition used [ 8 , 9 ], the presence of chemical admixtures [ 10 ] and the curing temperature [ 11 ]. The production of Portland limestone cement (PLC) rises around the world due to
Abstract
To use flue gas desulfurization (FGD) gypsum and limestone as supplement of cement, conduction calorimetry was applied to investigate the early hydration of ternary binder of calcium aluminate cement (CAC), Portland-limestone cement (PLC), and FGD gypsum, supplemented with the determination of setting times and X-ray diffraction (XRD) analysis. Different exothermal profiles were presented in two groups of pastes, in which one group (group A) sets the mass ratio of FGD gypsum/CAC at 0.25 and the other group (group B) sets the mass ratio of PLC/CAC at 0.25. Besides the two common exothermal peaks in cement hydration, a third exothermal peak appears in the pastes with 5–15% FGD gypsum after gypsum is depleted. It is found that not PLC but FGD gypsum plays the key role in such ternary binder where the reaction of ettringite formation dominates the hydration process. PLC accelerates the hydration of ternary binder, which mainly attributes to the nucleating effect of fine limestone particles and PC clinker. The modified hydration process and mechanism in this case is well visualized by the means of calorimetry and it helps us to optimize such design of ternary cementitious material.
Abstract
The thaumasite form of sulphate attack (TSA) concerns cements and concretes containing limestone and is attributed to the formation of thaumasite. This work deals with the confirmation of thaumasite formation in cement mortars. Three types of cement were examined: Portland cement and Portland limestone cement containing 15 and 30% mass/mass limestone. The specimens were cured at 5C, for 12 months, in a 1.8% MgSO4 solution. The formation of thaumasite was checked and confirmed by XRD, TG and SEM. It was concluded that mortars containing limestone suffer from TSA at low temperature. The combination of XRD, TG and SEM leads to the positive identification of thaumasite and resolves the well known problem of thaumasite and ettringite confusion.
of calcium sulfate. Lou et al. [ 21 ] state that “the accelerating effect of Portland limestone cement on hydration is clearly visualized by the isothermal calorimetric analyses.” Kadri et al. [ 22 ] conclude that “semi-adiabatic calorimetry have
, G , Chaniotakis , E , Souvaridou , A 1998 A study on the hydration of Portland limestone cement by means of TG . J Therm Anal Calorim 52 : 863 – 870 10.1023/A:1010139312958 . 16
into early hydration of Portland limestone cement from infrared spectroscopy and isothermal calorimetry . Cem Concr Res . 40 10 1541 – 1546 10.1016/j.cemconres.2010.06.008 . 36. Gruyaert
. Tsivilis , S , Kakali , G , Chaniotakis , E , Souvaridou , A 1998 A study on the hydration of Portland limestone cement by means of TG . J Therm Anal Calorim 52 : 863 – 870 10.1023/A:1010139312958 . 15
aluminate cement, Portland-limestone cement and FGD gypsum . J Therm Anal Calorim . 2010 ; 101 : 1 119 – 127 . 10.1007/s10973-009-0542-1 .
-009-0158-5 . 23. Lou , W , Guan , B , Wu , Z 2010 Calorimetric study of ternary binder of calcium aluminate cement, Portland–limestone cement and FGD gypsum . J Therm Anal Calorim 101 1 119 – 127 10.1007/s10973
