Title:
New Insights into the Effects of Alkali-Free and Alkaline Accelerators on the Cement Hydration Process: An Analysis from the Core Components (Prepublished)
Author(s):
Jiahe Wang, Yu Gao, Bofang Zhang
Publication:
Materials Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
accelerator; aluminum sulfate; cement hydration; sodium aluminate; triethanolamine
DOI:
10.14359/51751741
Date:
5/21/2026
Abstract:
The influence of core components in alkali-free and alkaline accelerators on the hydration of cement was comparatively studied. The setting time, compressive strength, and autogenous shrinkage of cement paste with aluminum sulfate (AS)/ sodium aluminate (SA) alone or AS/SA+ Triethanolamine (TEA) were tested. The hydration process and products were analyzed by the methods including isothermal calorimetry, X-ray diffraction (XRD), thermogravimetry analysis (TGA), inductively coupled plasma (ICP), etc. The results indicate that the generation of ettringite (AFt) at an early age after using AS is the essential reason for cement setting and strength improvement. The use of AS will promote the hydration process of C3S and C3A in cement, thereby ensuring the long-term strength development compared to the use of SA. The rod-shaped AFt generated after using AS will reduce the shrinkage of cement paste. But it will also lead to increases in the pore content and pore size in cement. The generation of aluminate-ferrite-monosulfate (AFm) after using SA is the main reason for cement setting. But SA will significantly delay the hydration process of C3S and C3A in cement, resulting in a decrease in the early and later mechanical properties. The sheet-like hydration product AFm makes the pore size and porosity of cement smaller, but the shrinkage is greater. When TEA is used in combination with AS/SA, it will promote the hydration of C3S but inhibit the hydration process of C3A, which is different from the effect of TEA used alone.