Impact of accelerator on rheological properties of cement composites with cellulose microfibers: 3D printing perspective

Abstract

This study aimed to investigate the impact of accelerator on the rheological properties of 3D printed concrete (3DPC) containing cellulose microfibers (CMFs). While saturated CMFs can mitigate shrinkage and associated damage through internal curing, they tend to delay the setting time of concrete, potentially reducing the structuration rate and consequently the buildability of 3DPC. As a potential solution, accelerators may expedite the setting process and improve the buildability. In this study, we examined the dynamic yield stress, plastic viscosity, static yield stress, and structuration rate of 16 cement composites with varying amounts of CMFs (0-1.0 wt%) and accelerator (0-1.0 wt%) through two rheological tests. Test results showed that increasing the CMFs content led to an 18 % rise in dynamic yield stress and a 12 % increase in plastic viscosity, while its effect on static yield stress remained negligible. Notably, the influence of accelerator was more pronounced, as it significantly increased static yield stress by up to 290 % and structuration rate by 400 %. Stress growth test results reveal that both the static yield stress at a given rest time and the structuration rate were proportional to the accelerator ratio, but the structuration rate had a marginal inverse relationship with the CMF ratio. Therefore, the addition of accelerator is deemed an effective solution to enhance the buildability of 3DPC and fully counteract the buildability degradation caused by CMFs.