2022 Volume 76 Issue 1 Pages 101-107
In this study, the influence of calcium hydroxide on the reaction of blast furnace slag with sodium carbonate was investigated. And we also discussed the mechanism of acceleration mechanism of blast furnace slag reaction by calcium hydroxide additon. This study is considered to be important for promoting carbon recycling in cement-based materials and for establishing carbon neutral society.
The reaction of blast furnace slag with sodium carbonate was accelerated by addition of calcium hydroxide and the hydration heat liberation was largely increased. The acceleration or delay of blast furnace slag reaction was related to the formation or decomposition of Na2Ca（CO3）2・5H2O （gaylussite）. The pH in the liquid phase highly increased by adding of calcium hydroxide to the blast furnace slag-sodium carbonate system. The reaction of calcium hydroxide and sodium carbonate makes calcium carbonate and sodium hydroxide, therefore the pH in the liquid phase rapidly increased. And the fluidity of blast furnace-sodium hydroxide paste decreased due to the increase in pH and high reactivity of blast furnace slag. The relationship between the hydration heat liberation of paste and the compressive strength of mortar was also confirmed.
It is necessary to establish a method for controlling the initial reaction of blast furnace slag-sodium carbonate-calcium hydroxide system in order to use as a binder.
