Effect of the Pretreatment of Ground Granulated Blast-furnace Slag on the Performance of Alkali-activated Carbonatite-slag Cementitious Material

Alkali-activated carbonatite cementitious material(AACCM) prepared at room temperature is a new kind of cementitious material with low environmental load.When ground granulated blast-furnace slag(GGBFS) is added to AACCM,high strength both at early and late ages and good impermeabiliy are achieved.But with the addition of GGBFS,the workability of the cementitious material,such as gel time and flowability,is greatly decreased.This problem can't be solved by the traditional retarding method,such as the retarding methods suitable to cement or alkali-activated slag cement.It was found that the problem could be well solved by pretreating the GGBFS to be added to AACCM with sodium silicate solution of low concentration for a certain time under room temperature.The results show that after the pretreatment both the gel time and flowability of AACCM with GGBFS addition can be significantly improved,but the strength of the materials at early ages is somewhat decreased in comparison to control samples.The extended gel time and flowability with the pretreating method are varied with GGBFS addition and the concentration of alkali-activator.