Welan gum retards the hydration of calcium sulfoaluminate

This paper illustrates the retarding effects of welan gum on the hydration of C₄A₃$ both in the absence and presence of gypsum. By using the methods of isothermal calorimetry, X-ray diffractometry, mercury instruction porosimetry, thermogravimetry and scanning electron microscopy, it reveals that the hydration of C₄A₃$ is significantly retarded and reduced in the presence of welan gum, while the total hydration heat of C₄A₃$ is reduced with the rise of dose of welan gum. The retarding effect of welan gum on the hydration of C₄A₃$ in the absence of gypsum is much stronger than that in the presence of gypsum. The hydration product of AFm is AFm-12 at curing time longer than 1 d at the w/c ratio of 1. As a whole, welan gum will not affect the composition of hydration products of C₄A₃$, even though the AFm phase grains grown well and are better shaped with addition of 0.50% welan gum.