Effect of nano-SiO2 on rheology and early hydration of cement containing high volume slag

Using nano-SiO2 particles is a viable approach for enhancing early performance of blended cement containing high volume slag. The present research aims to investigate the rheology and early hydration of cement incorporating high volume slag and nano-SiO2. The initial and time-varying rheology of blended cement have been evaluated by testing static/dynamic yield stress, plastic viscosity as well as apparent viscosity. Besides, early hydration of blended cement has also been studied through measuring the setting time and heat of hydration. Results show that nano-SiO2 significantly increases the initial and time-varying rheological value of blended cement, the enhancement effect becomes more obvious with the increased dosage of nano-SiO2. In addition, nano-SiO2 can shorten the setting time of blended cement, which is beneficial to rapid construction of concrete with high volume slag. Further, nano-SiO2 shortens induction period, promote C3S hydration, accelerate the transformation from ettringite (AFt) to monosulfate (AFm). Ultimately, nanosilica decreases the content of C3S+C2S in hardened cement paste, resulting in more hydration products. This paper will provide scientific support for revealing the rheology and early hydration of blended cement with high volume slag and nano-SiO2. •Blended cement with high volume slag and nano- SiO2 is prepared and studied.•Nano-SiO2 obviously increases the yield stress and viscosity of blended cement.•Nano-SiO2 can improve the early hydration of cement before 3 d.