Effect of alkaline solutions on engineering properties of alkali-activated GGBFS paste

Abstract

In this study, two kinds of alkaline solutions, sodium hydroxide (NaOH) and sodium silicate (Na 2SiO 3), with threedosages of 0.5, 1.0 and 1.5% by weight were used to produce the alkali-activated ground granulated blast furnace slag (GGBFS) paste at three different liquid-solid ratios by weight of 0.45, 0.5 and 0.55. Most engineering properties of the paste were examined at age of 3, 7, 14, 28 and 56 days. Experimental results show that a mixed alkaline solution of sodium hydroxide and sodium silicate is necessary to produce an alkaliactivated GGBFS paste with adequate workability and strength. Both the liquid-solid ratio and the amount of the alkaline solution affect the compressive strength in the range of 30.38 to 166.22 MPa at age of 28 days. After curing 28 days, alkali-activated GGBFS paste has the coefficient of thermal conductivity and volumetric heat capacity in range of 0.585-0.791 W/m K and 1.583-1.8 J/m 3 K, respectively, which are lower than/close to those of normal weight concrete andthus can be used as a proper material for heat insulation. The microstructural porosity of alkali-activated GGBFS paste is closely related to its engineering and thermal properties.