Calorimetric determination of the effect of additives on cement hydration process

Abstract

Possibilities of a multicell isoperibolic-semiadiabatic calorimeter application for the measurement of hydration heat and maximum temperature reached in mixtures of various compositions during their setting and early stages of hardening are presented. Measurements were aimed to determine the impact of selected components’ content on the course of ordinary Portland cement (OPC) hydration. The following components were selected for the determination of the hydration behaviour in mixtures: very finely ground granulated blast furnace slag (GBFS), silica fume (microsilica, SF), finely ground quartz sand (FGQ), and calcined bauxite (CB). A commercial polycarboxylate type superplasticizer was also added to the selected mixtures. All maximum temperatures measured for selected mineral components were lower than that reached for cement. The maximum temperature increased with the decreasing amount of components in the mixture for all components except for silica fume. For all components, except for CB, the values of total released heat were higher than those for pure Portland cement samples.

Application of Isothermal and Isoperibolic Calorimetry to Assess the Effect of Zinc on Hydration of Cement Blended with Slag

“…The use of slag as 15% cement replacement (see Figure 1, Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6) caused partial decrease in the released heat and prolongation of the induction period, due to lower reactivity of the additive compared to cement (the dilution effect, when some of the reactive material is replaced by a less reactive substance) [37]. For the same reason, the maximum heat flow was reduced in the isoperibolic measurement.…”

“…The main physical effects are: (a) the dilution effect, where more reactive cement is replaced by a less reactive component; (b) the filler effect, where the space between the grains of cement is filled by smaller particles of secondary raw materials; (c) the stimulation effect, which is the creation of new nucleation sites, typically leading to acceleration of hydration. The chemical effects are: (a) initial slag reaction, wherein the slag reacts with alkali and calcium hydroxide formed during the hydration of the cement; (b) the auto-pozzolanic reaction [35,36,37,38]. It is generally accepted that pozzolanic materials reduce early heat evolution due to the dilution effect.…”

“…It is generally accepted that pozzolanic materials reduce early heat evolution due to the dilution effect. Pozzolan or slag incorporation is typically reported to retard and reduce the rate of hydration [36,37,38]. Some additives with pozzolanic or hydraulic properties, replacing part of the cement in the material, are proposed to reduce the hydrate conversion and, therefore, its negative effects [39].…”

Application of Ground Granulate Blast Furnace Slag-Steel Slag Composite Binder in a Massive Concrete Structure under Severe Sulphate Attack

“…Additionally, the hydration degrees of the GGBS and steel slag increase dramatically at higher temperatures [18][19][20]. Additionally, the hydration heat of the GGBS is so large that the hydration heat of the binder containing 17-40% fine GGBS is greater than that of plain cement at room temperature, and the hydration heat of the binder containing 30-50% GGBS is close to or even higher than that of plain cement at 60 ∘ C [20,21]. It is noteworthy that the exothermic rate of the composite binder is greater than that of plain cement after hydration for approximately 10 h. On the one hand, dense and thick C-S-H layers forms when the cement hydrates rapidly at high temperatures, hindering the hydration of the cement at later ages to some extent [22].…”

Possibilities of Use of Isothermal and Isoperibolic Calorimetry to Study the Effect of Zinc on Hydration of Cement Blended with Fly Ash

“…Isoperibolic calorimetry is a method which is often used for the monitoring of hydration of hydraulic binders, especialy cements [16,[24][25][26]. The principle is the measurement of temperature changes during hydration at constant ambient temperature.…”