Mechanism of accelerated self-healing behavior of cement mortars incorporating triethanolamine: Carbonation of portlandite

Abstract

Mechanism of accelerated self-healing behavior of cement mortars incorporating triethanolamine (TEA) was investigated. The crack width in cement mortar specimens and the healing efficiency of cracks during immersion in water were quantitatively measured according to the Poiseuille's law. To reveal the working mechanism of TEA in the accelerated self-healing of cracks in cement mortars during water immersion, multi-techniques including X-ray diffraction (XRD), thermogravimetry (TG), nitrogen sorption isotherm and scanning electron microscopy (SEM) were employed to determine the changes in composition and microstructure of hydration products in the presence of TEA before and after water immersion. In addition, carbonation process of synthesized CH powder was studied. Results show that self-healing of the cracks in cement mortars during water penetration is a result of the continuous formation of CaCO3 on the fractured surfaces. TEA addition visibly enhances the self-healing performance of cement mortars and a higher dosage of TEA leads to a higher self-healing efficiency, because of the accelerated precipitation of CaCO3 on the fractured surface in mortars. TEA addition results in great morphological changes and increasing the surface area of portlandite as the second major hydration product of cement. Thus the carbonation process is notably accelerated in the mortars containing TEA. Moreover, the TEA-Ca2+complexation may promote the decalcification of C-S-H.