Analysis of the self-healing capacity of ECCs with high levels of cement replacement by limestone calcined clay cements (LC3), based on micro X-ray computed tomography (µXRCT)

TU Braunschweig, Institute for Applied Mechanics, Pockelsstraße 3, 38106 Braunschweig, Germany

^* Corresponding author: urs.buegger@tu-braunschweig.de

Abstract

Limestone calcined clay cements (LC3) have been implemented into engineered cementitious composites (ECCs) with the goal of reducing their environmental impact. Regarding their mechanical performance, this has been very successful. The effect of high-volume cement substitution on the material’s self-healing ability, however, has barely been investigated. Using µXRCT, this study analyzes and compares the self-healing capacity of a standard ECC to two LC3-based ECCs with 50 % and 70 % cement replacement. µXRCT allows for a comprehensive analysis of the porosity and healing products throughout the crack, providing better insight into the self-healing mechanisms of these new cementitious systems. Results show that the self-healing performance is notably reduced when 50 % of the cement is replaced. Higher replacement levels of 70 %, however, do not yield significantly lower self-healing when compared to 50 % replacement. Loss of self-healing performance is accompanied by a reduction in total porosity of 8 % and 40 %, respectively, as well as strong pore refinement indicated by an increase in the number of pores of 73 % and 152 % respectively. The observed change in microstructure likely plays a key role in facilitating self-healing despite lower cement contents.