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The effects of steel slag (SS) and fly ash (FA) on hydration heat, fluidity, setting time and rheological properties of alkali-activated slag (AAS) pastes with different silicate modulus (Ms) values were comparatively investigated. The results show that the incorporation of SS shortens the induction period, increases the cumulative hydration heat, improves the initial fluidity and decreases the setting time at low Ms, but the opposite trend is found at high Ms. FA significantly retards the reaction, reduces the hydration heat, increases the fluidity and prolongs the setting time. The addition of SS or FA reduces the yield stress and plastic viscosity of AAS paste. SS improves the rheological properties of AAS paste more significantly than that of FA at high Ms. The yield stress and plastic viscosity of AAS paste with SS or FA rise with the increasing Ms and decline with the increasing water/binder (w/b) ratio. [ABSTRACT FROM AUTHOR]

The effects of steel slag (SS) and fly ash (FA) on hydration heat, fluidity, setting time and rheological properties of alkali-activated slag (AAS) pastes with different silicate modulus (Ms) values were comparatively investigated. The results show that the incorporation of SS shortens the induction period, increases the cumulative hydration heat, improves the initial fluidity and decreases the setting time at low Ms, but the opposite trend is found at high Ms. FA significantly retards the reaction, reduces the hydration heat, increases the fluidity and prolongs the setting time. The addition of SS or FA reduces the yield stress and plastic viscosity of AAS paste. SS improves the rheological properties of AAS paste more significantly than that of FA at high Ms. The yield stress and plastic viscosity of AAS paste with SS or FA rise with the increasing Ms and decline with the increasing water/binder (w/b) ratio.

Alkali-activated slag (AAS) binders-based composites are considered potential alternatives to conventional cement-based composites. However, the quasi-brittle mechanical behavior of AAS binders-based composites limits their widespread application. In this study, a graphene oxide-SiO 2 (GO-SiO 2) composite was produced to address this issue. The experimental results showed that the flexural strength of an AAS paste increased by 133.2% with 1.5 wt% GO-SiO 2 composite, and its corresponding flexural-to-compressive strength ratio increased 95% i.e. from 0.063 to 0.123. To explore the strengthening mechanism, the stability of the GO-SiO 2 composite in alkaline solutions and the dispersion effect of GO-SiO 2 composite on the mechanical properties of AAS paste were investigated. The experimental results showed that the prepared GO-SiO 2 composite had stable C–O–Si chemical bonds connected GO with hydration products, thereby improving the strength of the AAS paste. The molecular dynamics study revealed the mechanism that the high-dispersed GO-SiO 2 composite could improve the mechanical properties of the AAS paste dramatically. • The prepared GO-SiO 2 composite exhibited excellent dispersibility in an alkaline solution. • The stability of the C–O–Si chemical bond in the GO-SiO 2 composite was investigated. • Flexural strength of alkali-activated slag paste increased by 133.2% for the GO-SiO 2 modification. • Mechanisms of AAS paste reinforced by the GO-SiO 2 composite were clarified. [ABSTRACT FROM AUTHOR]