Abstract
The influence of activator solution concentration on hydration kinetics of an alkaline activated blast furnace slag has been studied. The alkaline activator used was a mix of waterglass (Na 2 SiO 3 ∙nH 2 O) and NaOH solution (of variable concentration). Final activator concentrations were 3,4 and 5 % Na 2 O wt. with respect to the slag total weight. Degree of reaction (α) was determined from hydration heat values obtained through isothermal conduction calorimetry. From the results obtained it is deduced that a treshold value of 4 % Na 2 O wt. exists. For those concentrations and at test temperatures (except for 25oC and 3 % Na 2 O wt.), the mechanism controlling hydration reaction for a values higher than 0.5, is a diffusion process. This process is described by .Jander equation [D 3 =(1-(1-α) 1/3 ) 2 =(k/r 2 )t=0,0426(t/t 0,5 ]. The activation energy obtained for that process is of approximately 50-58 Kj/mol.
Highlights
The alkaline activation of slag is a complex process (1) in which the slag structure destruction is firstly produced followed by a poUcondensation and precipitation of the reaction products formed
Some authors (2-5) considered this process to occur through an heterogeneous reaction
The objective of the present work is to determine the influence of activator solution concentration on the mechanism controlling the alkaline activation of blast furnace slags at different temperatures
Summary
The alkaline activation of slag is a complex process (1) in which the slag structure destruction is firstly produced followed by a poUcondensation and precipitation of the reaction products formed. Some authors (2-5) considered this process to occur through an heterogeneous reaction. These type of reactions are MA'l'liRIAIJiS 1) i CONSTRUCCIÓN, vol 47,n"246, abril/mayo/junio 1997. En un trabajo anterior (6), los autores del presente artículo, utilizando datos calorimétricos, prepusieron para grados de reacción elevados (a > 0,5), el mecanismo que explica el proceso de activación alcalina de una escoria de alto horno. In a former work (6), the authors of the present work proposed, using calorimetric data, a mechanism explaining the slag alkaline activation for high reaction degrees (a >0.5)
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