Effects of nano- and micro-limestone addition on early-age properties of ultra-high-performance concrete

In this study, the effects of micro- and nano-CaCO 3 addition on the early-age properties of ultra-high-performance concrete (UHPC) cured at simulated cold and normal field conditions were investigated. The micro-CaCO 3 was added at rates of 0, 2.5, 5, 10 and 15 %, while the nano-CaCO 3 was added at rates of 0, 2.5, and 5 %, both as partial volume replacement for cement. Results indicate that micro-CaCO 3 acted mainly as an inert filler, creating a denser microstructure and increasing the effective w/c ratio. In addition, nano-CaCO 3 accelerated the cement hydration process through nucleation, and also acted as an effective filling material. Mixtures combining both micro- and nano-CaCO 3 resulted in similar or enhanced mechanical properties compared to that of the control, while achieving cement replacement levels up to 20 %. Thus, through the use of micro- and nano-CaCO 3 , more environmentally friendly UHPC can be produced by reducing its cement factor, while achieving enhanced engineering properties.