Effect of curing time on binder development and steel corrosion in alkali activated slag mortars

Trabajo presentado al 15th International Congress on the Chemistry of Cement (ICCC), celebrado en Praga (República Checa) del 16 al 20 de septiembre de 2019.The microstructural development of alkali-activated slag cements, and the electrochemical conditions prevailing within these materials, depend on many synthesis parameters, in particular the curing conditions applied. The aim of this study is to evaluate the effect of curing time (28, 90 and 180 days of curing) on the mineralogical, physical and mechanical development, and resistance to chlorideinduced corrosion, in steel-reinforced alkali-activated blast furnace slag mortars. The compressive strengths and chloride migration coefficients of alkali activated blast slag mortars increase and decrease respectively, with longer curing, and the mineralogy evolves toward the formation of more hydrotalcite-group phases. Corrosion potential values decrease with time of immersion in an alkaline chloride-rich solution, and this reduction is independent of the curing time, which would usually be taken to indicate susceptibility to breakdown of the passive film on the rebar. However, the actual corrosion activity observed in embedded rebars indicated that corrosion initiation and propagation are not taking place. The presence of sulfide in the pore solution, supplied by the slag and/or ionexchanging between the pore solution and the layered hydration products, reduces the redox potential but does not induce steel corrosion.The research leading to these results received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement #335928