Rheological property and stability of nano-silica modified self-compacting concrete with manufactured sand

Abstract

Self-compacting concrete (SCC) of high fluidity may lead to the high tendency of segregation, especially when manufactured sand (MS) is used. In this work, the rheological properties of SCC are optimized by adding nano-silica (NS) and limestone powder (LP) at different water-to-binder ratios (W/B). The segregation tendency of SCC is evaluated by calculating the stability index (i.e., the degree of segregation of aggregate) through image analysis method. The result shows that MS greatly decreases the stability of SCC, and the static stability index increases from 10.3% to 29.13% when the amount of MS exceeds 20%, increasing risk of segregation. NS can improve the stability of SCC during vibration significantly, however, when the dosage exceeds 0.3%, the fluidity (slump flow) is significantly reduced by 30%. LP improves the stability of SCC by increasing the plastic viscosity. Furthermore, the relationship between the dynamic yield stress/plastic viscosity and the instability index are linearly fitted, the former of which shows a higher correlation coefficient. Finally, the workability and stability of SCC are comprehensively evaluated by the rheological interval box, that is, the SCC with MS owns the best workability when yield stress is (0 ∼ 15.72 Pa) and plastic viscosity is (76.8 ∼ 250.4 Pa·s).