Optimizing anti-freezing agent on the properties of Portland cement-calcium sulphoaluminate cement system based on Taguchi-GRA method

The investigate of novel cementitious system suitable for negative temperature concreting was the key way to solve the high energy consumption of traditional winter construction. In this study, the matching effects of anti-freezing agents (CaCl₂, NaNO₂ and Li₂CO₃) on the Portland cement-calcium sulphoaluminate cement blended system (PC-CSA system) based on Taguchi-Grey Relational Analysis (Taguchi-GRA method) were studied. The setting time, compressive strength and freezing point were tested, and the hydration products, pore structure and morphology were also analyzed to reveal the mechanism. The results showed that CaCl₂ was the main parameter influencing the initial and final setting time. Whether at the early stage of continuous negative temperature curing, or from negative to positive temperature curing, CaCl₂ had a dominant influence on the compressive strength of PC-CSA system, which promoted the increase of the early hydration products, resulting in the rapid formation of a network structure. At the later stage of continuous negative temperature curing, the influential parameter changed to NaNO₂. The basic condition for hydration was provided due to the lowering of the freezing point of the liquid phase by NaNO₂. The presence of Li₂CO₃ enhanced the promoting effect of CaCl₂ on early strength. The optimal parameter combination for PC-CSA system was 1.0 % CaCl₂, 2.0 % NaNO₂ and 0.4 % Li₂CO₃ based on Taguchi-GRA method.