Influence of nanolimestone on the hydration, mechanical strength, and autogenous shrinkage of ultrahigh-performance concrete

The influence of nanolimestone/nanoCaCo₃ (NC) on the properties of ultrahigh-performance concrete (UHPC) cured at standard and heat conditions was experimentally investigated. The NC was used at ratios of 1, 2, and 3% as partial mass replacement for cement. Incorporating NC accelerated the hydration reactions of UHPC because of the nucleation effect. On the mechanical properties aspect, a threshold value of the NC content was found so that the compressive, flexural strengths, and flexural to compressive strength ratio of the UHPC were found to increase as the NC content increased towards the threshold content, and then to decrease with the increase of NC contents when the threshold was surpassed. Conversely, replacing cement with NC decreased flowability and increased the amount of autogenous shrinkage of the UHPC. While the NC accelerated the cement hydration process, it also acted as an effective filling material, resulting in enhanced mechanical properties and denser microstructure compared with the control UHPC mixture. Thus, through the use of NC, more environmentally friendly UHPC can be produced by reducing its cement factor and achieving enhanced engineering properties.