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 (tau s), dynamic yield stress (tau d) and plastic viscosity (mu) of HPC were obtained using ICAR rheometer. Increase in the fly ash content from 10 to 20% increased the tau s values but the mu values show a decreasing trend in the binary mixes. Further increment up to 30% fly ash content reduced the tau s and mu values. The compressive strength (CS) 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 tau s and mu values but increased the CS values. Increment in HRWA content up to 1.2% show similar trends but there is a decrease in CS due to segregation. Addition of 0.5% VMA in mixes with 1.2% HRWA increased the CS but there was increase in the resistance to flow as well. An inverse linear relation between the tau 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.