Effect of several accelerators on setting time and thermo-mechanical properties of phase change energy storage cement paste

Polyethylene glycol (PEG) can delay the hydration process of cement, thereby restricting its application in phase change energy storage composite materials. This study evaluated seven accelerators: including alkaline accelerators (Li₂CO₃, Na₂CO₃, Na₂SO₄) and non-alkaline accelerators (Al₂(SO₄)₃, CaSO₄, Ca(HCOO)₂, triethanolamine, TEA) on the initial setting time and thermodynamic properties. The results showed that 6 wt% Na₂CO₃ performed the best, reducing the initial setting time and final setting time by 96.4% and 94.3% respectively, which met the construction standards. Among the non-alkaline accelerators, 2 wt% TEA shortened the initial setting time by 82.0% and the final setting time by 74.2% by selectively complexing with aluminosilicates. From a mechanistic perspective, alkaline accelerators are superior to non-alkaline accelerators because of a dual synergistic effect: the alkaline environment promotes PEG aggregation, weakening its protective effect on cement particles; while the released ions (Ca2⁺, SO₄2⁻, CO₃2⁻) accelerate the precipitation of hydration products. Crucially, unlike the trade-off in traditional methods, the accelerated treatment simultaneously enhances mechanical strength and latent heat. However, when the TEA content exceeds 6 wt%, it leads to uneven AFt precipitation and internal cracks, indicating the existence of a critical compatibility threshold. Overall, this study established a feasible multi-performance optimization paradigm and provided practical guidance for the application of high-performance phase change energy storage cement slurry on an engineering scale.