Rheological study of high-performance concrete composed of fly ash and silica fume using ICAR rheometer

Rheological study of binary and ternary blended high-performance concrete (HPC) is necessary to eliminate the uncertainties of traditional workability methods. In this study silica fume and fly ash along with high range water reducing admixture (HRWA) and viscosity modifying agents (VMA) were utilised to develop HPC. Static yield stress (τ_s), dynamic yield stress (τ_d) and plastic viscosity (µ) of HPC were obtained using ICAR rheometer. Increase in the fly ash content from 10 to 20% increased the τ_s values but the µ values show a decreasing trend in the binary mixes. Further increment up to 30% fly ash content reduced the τ_s and µ values. The compressive strength (C_S) values of all the mixes drop with the increase in fly ash dosages. In the ternary mixes, incorporation of 5% silica fume deteriorated the flowability but increased the strength parameter. HRWA dosage from 0.8% to 1% decreased τ_s and µ values but increased the C_S values. Increment in HRWA content up to 1.2% show similar trends but there is a decrease in C_S due to segregation. Addition of 0.5% VMA in mixes with 1.2% HRWA increased the C_S but there was increase in the resistance to flow as well. An inverse linear relation between the τ_d and slump values shows high R² values of 0.88. Elemental analysis using Energy Dispersive X-ray Spectroscopy data shows that with the increase in oxygen content in the hardened matrix, the strength of HPC also increases.