The features of different mineral admixtures affecting the self-healing capacity of cementitious-based materials

Abstract

Using mineral admixtures to improve the self-healing capacity of cementitious-based materials is a valid and economical method. To achieve a better understanding of the characteristics of different mineral admixtures affecting the self-healing performance of matrix, this study evaluated the self-healing capacity of mortar specimens blended with different kinds of mineral admixtures through testing crack width and water permeability, and characterized the healing products in cracks with microanalysis tools. The results show that, with the increase of healing time, the healing degree of cracks increases while water permeability of specimens decreases, presenting a linear correlation. Moreover, as for improving the self-healing capacity of matrix, slag (SL) only works at age 28d; fly ash (FA) mainly functions after 28d; metakaolin (MK) and limestone (LS) are extraordinary within 28d, especially LS, its effect within 28d is the most significant; and silica fume (SF) works well in the whole 112d age. Furthermore, calcium silicate hydrate gel (C-S-H) and calcium carbonate (CaCO3) are the two major healing products, supplemented by some Al-contained compounds and Mg-contained compounds, which is closely related to the chemical composition of mineral admixtures. Therefore, to better improve the self-healing capacity of cementitious-based materials, it is suggested to come up with a rational and optimized mineral admixture composition based on the feature of every mineral admixture.