Rheological Properties of Nanosilica-Modified Cement Paste at Different Temperatures and Hydration Times

This paper investigates the temperature-time evolution of the rheological properties of nanosilica (NS)-modified cement paste. A rheometer was used to determine the theology curves of the paste at 20 degrees C-40 degrees C within 2 h and fitted to the Bingham model. Fluidity, free water content, isothermal calorimetry, and thermogravimetric analysis were used to explain the temperature-time evolution. The results showed that the temperature-time evolution of theological parameters of NS-modified paste was linear. Both the yield stress and plastic viscosity of cement paste increased with increasing NS dosage and related to the free water content. On account of the flocculation of NS, the initial values of the rheological parameters became larger, and the higher the temperature, the larger the values. The evolution rate of yield stress over time was NS 40 degrees C > NS 30 degrees C > NS 20 degrees C. The initial value of the thixotropy with NS increased by orders of magnitude compared with the control group, while the development of thixotropy was very sensitive to temperature. There was a small initial thixotropic value and a fast increase rate at 30 degrees C, which was an ideal evaluation model. The dominant factor in the dormant period of evolution was the destruction and reconstruction of C-S-H bridges. (C) 2020 American Society of Civil Engineers.

Automated summary

This study investigated the temperature-time evolution of the rheological properties of nanosilica-modified cement paste, finding that the yield stress and plastic viscosity increased with NS dosage, free water content, and temperature. The initial values of rheological parameters were significantly larger due to NS flocculation, with evolution rate of yield stress highest at 40 degrees C. Thixotropy showed a small initial value and rapid increase at 30 degrees C, serving as an ideal evaluation model.